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Abstract
Progenitor cells in the subventricular zone of the lateral ventricle and in the dentate gyrus of the hippocampus can proliferate throughout the life of the animal. To examine the proliferation and fate of progenitor cells in the subventricular zone and dentate gyrus after focal cerebral ischemia, we measured the temporal and spatial profiles of proliferation of cells and the phenotypic fate of proliferating cells in ischemic brain in a model of embolic middle cerebral artery occlusion in the adult rat. Proliferating cells were labeled by injection of bromodeoxyuridine (BrdU) in a pulse or a cumulative protocol. To determine the temporal profile of proliferating cells, ischemic rats were injected with BrdU every 4 h for 12 h on the day preceding death. Rats were killed 2-14 days after ischemia. We observed significant increases in numbers of proliferating cells in the ipsilateral cortex and subventricular zone 2-14 days with a peak at 7 days after ischemia compared with the control group. To maximize labeling of proliferating cells, a single daily injection of BrdU was administered over a 14-day period starting the day after ischemia. Rats were killed either 2 h or 28 days after the last injection of BrdU. A significant increase in numbers of BrdU immunoreactive cells in the subventricular zone was coincident with a significant increase in numbers of BrdU immunoreactive cells in the olfactory bulb 14 days after ischemia and numbers of BrdU immunoreactive cells did not significantly increase in the dentate gyrus. However, 28 days after the last labeling, the number of BrdU labeled cells decreased by 90% compared with number at 14 days. Clusters of BrdU labeled cells were present in the cortex distal to the infarction. Numerous cells immunostained for the polysialylated form of the neuronal cell adhesion molecule were detected in the ipsilateral subventricular zone. Only 6% of BrdU labeled cells exhibited glial fibrillary acidic protein immunoreactivity in the cortex and subcortex and no BrdU labeled cells expressed neuronal protein markers (neural nuclear protein and microtubule associated protein-2). From these data we suggest that focal cerebral ischemia induces transient and regional specific increases in cell proliferation in the ipsilateral hemisphere and that proliferating progenitor cells may exist in the adult cortex.
... The enhancement of SVZ neurogenesis after global ischemia was first described in 1998 (Liu et al., 1998). After this initial work, many studies confirmed this finding in both rodents and humans (Eriksson et al., 1998;Jin et al., 2001;Zhang et al., 2001). Post-stroke SVZ neurogenesis has been widely studied in experimental models of cerebral ischemia with striatal affectation, such as the intraluminal middle cerebral artery occlusion (MCAO) in rodents, which shows a clear temporal profile of the different neurogenic steps (Parent et al., 2002;Parent, 2003;Kernie and Parent, 2010): in this model, the literature describes an increase in the proliferation of SVZ precursors that migrate to the lesion site and differentiate to functional neurons around the infarct (Jin et al., 2001;Zhang et al., 2001Zhang et al., , 2004aArvidsson et al., 2002;Parent et al., 2002;Parent, 2003;Thored et al., 2006;Kernie and Parent, 2010;Lindvall and Kokaia, 2015). ...
... After this initial work, many studies confirmed this finding in both rodents and humans (Eriksson et al., 1998;Jin et al., 2001;Zhang et al., 2001). Post-stroke SVZ neurogenesis has been widely studied in experimental models of cerebral ischemia with striatal affectation, such as the intraluminal middle cerebral artery occlusion (MCAO) in rodents, which shows a clear temporal profile of the different neurogenic steps (Parent et al., 2002;Parent, 2003;Kernie and Parent, 2010): in this model, the literature describes an increase in the proliferation of SVZ precursors that migrate to the lesion site and differentiate to functional neurons around the infarct (Jin et al., 2001;Zhang et al., 2001Zhang et al., , 2004aArvidsson et al., 2002;Parent et al., 2002;Parent, 2003;Thored et al., 2006;Kernie and Parent, 2010;Lindvall and Kokaia, 2015). This increase, produced by a shortening of the cell cycle, is transient, starts 2 days after stroke onset, reaches a maximum in 1-2 weeks after the beginning of the damage (Jin et al., 2001;Zhang et al., 2001Zhang et al., , 2004aArvidsson et al., 2002), recovering its basal levels over six weeks after the damage (Thored et al., 2006). ...
... Post-stroke SVZ neurogenesis has been widely studied in experimental models of cerebral ischemia with striatal affectation, such as the intraluminal middle cerebral artery occlusion (MCAO) in rodents, which shows a clear temporal profile of the different neurogenic steps (Parent et al., 2002;Parent, 2003;Kernie and Parent, 2010): in this model, the literature describes an increase in the proliferation of SVZ precursors that migrate to the lesion site and differentiate to functional neurons around the infarct (Jin et al., 2001;Zhang et al., 2001Zhang et al., , 2004aArvidsson et al., 2002;Parent et al., 2002;Parent, 2003;Thored et al., 2006;Kernie and Parent, 2010;Lindvall and Kokaia, 2015). This increase, produced by a shortening of the cell cycle, is transient, starts 2 days after stroke onset, reaches a maximum in 1-2 weeks after the beginning of the damage (Jin et al., 2001;Zhang et al., 2001Zhang et al., , 2004aArvidsson et al., 2002), recovering its basal levels over six weeks after the damage (Thored et al., 2006). In addition to changes in cell cycle, it has been reported that stroke transiently changes the division of neural stem cells (NSCs) from asymmetric to symmetric, thus increasing their stock in the SVZ (Zhang et al., 2004a,b). ...
The substantial clinical burden and disability after stroke injury urges the need to explore therapeutic solutions. Recent compelling evidence supports that neurogenesis persists in the adult mammalian brain and is amenable to regulation in both physiological and pathological situations. Its ability to generate new neurons implies a potential to contribute to recovery after brain injury. However, post-stroke neurogenic response may have different functional consequences. On the one hand, the capacity of newborn neurons to replenish the damaged tissue may be limited. In addition, aberrant forms of neurogenesis have been identified in several insult settings. All these data suggest that adult neurogenesis is at a crossroads between the physiological and the pathological regulation of the neurological function in the injured central nervous system (CNS). Given the complexity of the CNS together with its interaction with the periphery, we ultimately lack in-depth understanding of the key cell types, cell–cell interactions, and molecular pathways involved in the neurogenic response after brain damage and their positive or otherwise deleterious impact. Here we will review the evidence on the stroke-induced neurogenic response and on its potential repercussions on functional outcome. First, we will briefly describe subventricular zone (SVZ) neurogenesis after stroke beside the main evidence supporting its positive role on functional restoration after stroke. Then, we will focus on hippocampal subgranular zone (SGZ) neurogenesis due to the relevance of hippocampus in cognitive functions; we will outline compelling evidence that supports that, after stroke, SGZ neurogenesis may adopt a maladaptive plasticity response further contributing to the development of post-stroke cognitive impairment and dementia. Finally, we will discuss the therapeutic potential of specific steps in the neurogenic cascade that might ameliorate brain malfunctioning and the development of post-stroke cognitive impairment in the chronic phase.
... Adult NSCs, which are originally in a static state, begin to undergo a transformative biological process known as endogenous NSC activation under the state of injury or stress [11]. There is no doubt that the proliferation of NSCs is the basis of nerve tissue repair, and many studies have also reported that endogenous NSC proliferation occurs after ischemic stroke [14][15][16][17]. However, neural repair is a complex process that goes beyond normal proliferation. ...
... It has been reported that after cerebral ischemia-reperfusion injury, NSCs are endogenously activated and proliferate [14][15][16][17]. Undoubtedly, cell proliferation is a prerequisite for subsequent nerve repair. ...
Background
Ischemia–reperfusion injury to the central nervous system often causes severe complications. The activation of endogenous neural stem cells (NSCs) is considered a promising therapeutic strategy for nerve repair. However, the specific biological processes and molecular mechanisms of NSC activation remain unclear, and the role of N6-methyladenosine (m⁶A) methylation modification in this process has not been explored.
Methods
NSCs were subjected to hypoxia/reoxygenation (H/R) to simulate ischemia–reperfusion in vivo. m⁶A RNA methylation quantitative kit was used to measure the total RNA m⁶A methylation level. Quantitative real-time PCR was used to detect methyltransferase and demethylase mRNA expression levels. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were conducted for NSCs in control and H/R groups, and the sequencing results were analyzed using bioinformatics. Finally, the migration ability of NSCs was identified by wound healing assays, and the proliferative capacity of NSCs was assessed using the cell counting kit-8, EdU assays and cell spheroidization assays.
Results
Overall of m⁶A modification level and Mettl14 mRNA expression increased in NSCs after H/R treatment. The m⁶A methylation and expression profiles of mRNAs in NSCs after H/R are described for the first time. Through the joint analysis of MeRIP-seq and RNA-seq results, we verified the proliferation of NSCs after H/R, which was regulated by m⁶A methylation modification. Seven hub genes were identified to play key roles in the regulatory process. Knockdown of Mettl14 significantly inhibited the proliferation of NSCs. In addition, separate analysis of the MeRIP-seq results suggested that m⁶A methylation regulates cell migration and differentiation in ways other than affecting mRNA expression. Subsequent experiments confirmed the migration ability of NSCs was suppressed by knockdown of Mettl14.
Conclusion
The biological behaviors of NSCs after H/R are closely related to m⁶A methylation of mRNAs, and Mettl14 was confirmed to be involved in cell proliferation and migration.
... Endogenous neurogenesis in the adult brain is no longer a novel phenomenon, as neuronal stem cells can be driven from specific locations under peculiar conditions. Neurogenesis in at least two lesions, the subventricular zone (SVZ) of the lateral ventricle and the subgranular zone (SGZ) of the hippocampus, is now a familiar event that can be confirmed after focal brain ischemia, especially in cerebral arterial infarction (CAI) rat models (Arvidsson et al., 2002;Wang et al., 2011;Zhang et al., 2001). In addition, there are increasing reports suggesting that neural stem cells also exist in the cerebral cortex, caudate nucleus, and striatum (Bernier et al., 2002;Gould et al., 1999;Gu et al., 2000). ...
... Previous reports using the middle cerebral artery occlusion (MCAO) model, in which ischemia reaches the basal ganglia, have shown that ischemia-induced neuroblasts migrate from the SVZ, resulting in delayed expression of generated neurons (Arvidsson et al., 2002). This fact indicates that the pathogenesis of MCAO has the potential to induce neurogenesis from the SVZ or SGZ, which is supported by many other reports (Arvidsson et al., 2002;Wang et al., 2011;Zhang et al., 2001). In contrast, it remains unclear whether neurogenesis occurs in CVI, and whether it occurs through ischemia localized in the cerebral cortex far from the SVZ and SGZ. ...
Neurogenesis in the subventricular zone (SVZ), subgranular zone (SGZ), and cerebral cortex is now a familiar event to confirm by cerebral arterial ischemia in rat models. However, it remains unclear whether cerebral venous ischemia (CVI) alone causes neurogenesis, and where that neurogenesis occurs. After creating CVI rat models via a two-vein occlusion (2-VO) method, neurogenesis was immunohistochemically evaluated by double-labeling 5-bromo-2’-deoxyuridine (BrdU)-positive cells with neuronal nuclei (NeuN) or doublecortin (DCX) antibody. Fifty Wistar rats were divided into two major groups (BrdU-NeuN and BrdU-DCX) and then separated into two subgroups (2-VO or sham). The total number of double-positive cells expressed inside a predefined region of interest (ROI) covering the ischemic area was compared between the two subgroups. Then, we divided the ROI into six sections to evaluate and compare the distribution of double-positive cells generated in each section between the two subgroups. The 2-VO subgroup presented more double-positive cells than the sham group in both BrdU-NeuN and BrdU-DCX groups, while the BrdU-DCX+2-VO group showed a characteristic distribution of double-positive cells in ROI 2 and ROI 3, suggesting areas of the ischemic core and penumbra, with a significant difference compared to the BrdU-DCX+sham group. This study demonstrates that CVI has the potential to induce endogenous neurogenesis, with significant numbers of both newly generated neurons and precursors observed in the ischemic area. The distribution of these cells suggests that the cortex could be the main origin of neurogenesis after cortical CVI.
... This process occurs in three steps [206]: (1) neural stem cell proliferation, (2) migration of neuroblasts and immature neurons, and (3) differentiation into mature neurons and synaptogenesis. Following ischemic stroke, neural stem cells migrate into the peri-infarct region and differentiate into neurons [207]. However, in an inflammatory environment lacking trophic factors, many of these immature neurons will not survive [208], which is why the role of various neurotrophic factors and the possibility of their upregulation has been investigated as a means of enhancing post-stroke recovery. ...
... This process occurs in three steps [206]: (1) neural stem cell proliferation, (2) migration of neuroblasts and immature neurons, and (3) differentiation into mature neurons and synaptogenesis. Following ischemic stroke, neural stem cells migrate into the peri-infarct region and differentiate into neurons [207]. However, in an inflammatory environment lacking trophic factors, many of these immature neurons will not survive [208], which is why the role of various neurotrophic factors and the possibility of their upregulation has been investigated as a means of enhancing poststroke recovery. ...
Its increasing incidence has led stroke to be the second leading cause of death worldwide. Despite significant advances in recanalization strategies, patients are still at risk for ischemia/reperfusion injuries in this pathophysiology, in which neuroinflammation is significantly involved. Research has shown that in the acute phase, neuroinflammatory cascades lead to apoptosis, disruption of the blood–brain barrier, cerebral edema, and hemorrhagic transformation, while in later stages, these pathways support tissue repair and functional recovery. The present review discusses the various cell types and the mechanisms through which neuroinflammation contributes to parenchymal injury and tissue repair, as well as therapeutic attempts made in vitro, in animal experiments, and in clinical trials which target neuroinflammation, highlighting future therapeutic perspectives.
... In contrast, the microglia are macrophages resident in the brain and are of the mesodermal germ layer lineage [2]. Formation of new neurons throughout the life of the individual through the proliferation and differentiation of neuronal progenitor stem cells has been reported in the subventricular zone of the lateral ventricles and in the sub-granular zone of the dentate gyrus in the hippocampus [17][18][19][20][21][22]. Only dormant progenitor neural stem cells exist in the adult cerebral cortex [23]. ...
... Neurogenesis, activated by ischemic insult, has been shown in the subventricular zone of the lateral ventricles, in the dentate gyrus of the hippocampus and in the dormant neural stem cells in the cerebral cortex [17,23,26]. Current concepts in brain plasticity, enabling lifelong learning, suggest that there can be spontaneous recovery and that rehabilitative training may help modify and boost the neuronal plasticity processes [27,28]. ...
Carcinoembryonic antigen‐cell adhesion molecule‐1 (CEA‐CAM‐1) positive stem cells have been visualized in the white matter and gray matter in the cerebral cortex of adult rats. Similar cells have also been isolated and characterized from the skeletal muscle of and peripheral vasculature of adult mammals, including humans. The current study was undertaken to determine the location of these cells with respect to the brains of the adult pig. Adult pigs were euthanized following the guidelines of Fort Valley State University's IACUC. The heads were fixed by immersion fixation, the brains isolated, cryosectioned and stained with an antibody diagnostic for adult pluripotential stem cells, i.e. CEA‐CAM‐1. The current study will discuss the location with respect to the white and gray natter in the adult pig. Studies are ongoing to address their functional significance in neuronal injury and repair.
... In contrast, the microglia are macrophages resident in the brain and are of the mesodermal germ layer lineage [2]. Formation of new neurons throughout the life of the individual through the proliferation and differentiation of neuronal progenitor stem cells has been reported in the subventricular zone of the lateral ventricles and in the sub-granular zone of the dentate gyrus in the hippocampus [17][18][19][20][21][22]. Only dormant progenitor neural stem cells exist in the adult cerebral cortex [23]. ...
... Neurogenesis, activated by ischemic insult, has been shown in the subventricular zone of the lateral ventricles, in the dentate gyrus of the hippocampus and in the dormant neural stem cells in the cerebral cortex [17,23,26]. Current concepts in brain plasticity, enabling lifelong learning, suggest that there can be spontaneous recovery and that rehabilitative training may help modify and boost the neuronal plasticity processes [27,28]. ...
... recovery and repair of the damaged brain region [8][9][10]. In general, this involves the migration of neural stem cells to the infarct and peri-infarct region, followed by their differentiation into functional neurons [11][12][13]. This process is schematically depicted in Fig. 1, based on information derived from research in rodents and other model systems. ...
... In early studies, newborn neurons were detected in gerbil brains after cerebral ischemia, 26 days after ischemic insult and persisted for 7 months [89]. More recent studies, however, showed that in mice and rats, neural stem cell proliferation in the SVZ was significantly enhanced in as early as the first 7-14 days after MCAO [11,13,90,91]. Thored and colleagues reported the presence of neuroblasts from 1 week up to 16 weeks after insult, in the striatum [7]. ...
Stroke is a major cause of death and disability worldwide. Yet therapeutic strategies available to treat stroke are very limited. There is an urgent need to develop novel therapeutics that can effectively facilitate functional recovery. The injury that results from stroke is known to induce neurogenesis in penumbra of the infarct region. There is considerable interest in harnessing this response for therapeutic purposes. This review summarizes what is currently known about stroke-induced neurogenesis and the factors that have been identified to regulate it. Additionally, some key studies in this field have been highlighted and their implications on future of stroke therapy have been discussed. There is a complex interplay between neuroinflammation and neurogenesis that dictates stroke outcome and possibly recovery. This highlights the need for a better understanding of the neuroinflammatory process and how it affects neurogenesis, as well as the need to identify new mechanisms and potential modulators. Neuroinflammatory processes and their impact on post-stroke repair have therefore also been discussed.
... The rats were anesthetized with 10% chloral hydrate (0.36 ml/100 g, i. p.). Rat middle cerebral artery occlusion was performed as described previously (Zhang et al., 2001). Briefly, a 6-0 coated with silicon nylon monofilament suture (Beijing Cinontech Co. Ltd, Beijing, China) was inserted into the middle cerebral artery. ...
... Exo- some derived from ECs is highly beneficial for neural repair and remodeling through enriching angiogenesis and supporting vessel formation (Vissapragada et al., 2014). In addition, stroke increases neurogenesis and newly generated neuroblasts in the SVZ migrated to the ischemic boundary region (Zhang et al., 2001;Jin et al., 2001;Arvidsson et al., 2002), which strongly suggest that neovascular ECs after ischemic brain injury promote the endogenous NPCs proliferation and migration. Exosomes are associated with the message delivery of the CNS and could be involved in the pathogenesis of many neuroinflammatory and neurodegenerative disorders (Gupta and Pulliam, 2014). ...
Vascular endothelial cells were activated during acute ischemic brain injury, which could induce neural progenitor cell proliferation and migration. However, the mechanism was still unknown. In the current study, we explored whether vascular endothelial cells promoted neural progenitor cell proliferation and whether migration occurs via exosome communication. The acute middle cerebral artery occlusion (MCAO) model was prepared, and exosomes were isolated from bEnd.3 cells by ultracentrifugation. In the exosome injection (Exos) group and PBS injection (control) group, exosomes or PBS were injected intraventricularly into rats’ brains 2 hours after MCAO surgery, respectively. Sham group rats received the same surgical but did not cause middle cerebral artery occlusion. The infarct volume was reduced on day 21 after ischemic brain injury by MRI, and neurobehavioral outcomes were improved on day 7, 14, and 21 by exosome injection compared with the control (p<0.05). On the 21st day after MCAO, the animals were euthanized, and the number of BrdU/nestin-positive cells was measured by immunofluorescence. BrdU/nestin-positive cells in Exos group rats were significantly increased (p<0.05) in the peri infarct area, the ipsilateral DG zone of the hippocampus, and the ventral sub-regions of SVZ when compared with the rats in the control group. Further, in vitro study demonstrated that neural progenitor cell proliferation and migration were activated after exosomes treatment, and cell apoptosis was attenuated compared to the control (p<0.05). Our study suggested that exosomes should be essential for the reconstruction of neuronal vascular units and brain protection in an acute ischemic injured brain.
... In most adult mammals, including humans, proliferating neural stem cells and neural progenitor cells (NPCs) are localized in the subventricular zone (SVZ) of the lateral ventricle wall and the subgranular zone (SGZ) of the hippocampal dentate gyrus [1][2][3][4][5]. Focal cerebral ischemia increases the proliferation of NPCs in both the SVZ and SGZ of rodents from the first four days to two weeks after stroke onset, which can persist for months [6][7][8][9][10]. ...
Background:
Ischemic stroke may trigger neuroplastic changes via proliferation, migration towards the lesion, and differentiation of neuroprogenitor cells into mature neurons. Repetitive Transcranial Magnetic Stimulation (rTMS) may promote brain plasticity. This study aimed to assess rTMS's effect on post-stroke endogenous neuroplasticity by dosing plasma miRs 17~92, Netrin-1, Sema3A, and BDNF.
Methods:
In this case-controlled study, we randomized 19 ischemic stroke patients within five days from symptoms onset (T0) to neuronavigated-rTMS or sham stimulation. Stimulation was applied on the stroke hemisphere daily between the 7th and 14th day from stroke onset. Blood samples were collected at T0, before the first rTMS section (T7), and at the end of the last rTMS session (T14). Five healthy controls were also enrolled in this study.
Results:
Of 19 patients, 10 received rTMS and 9 sham stimulation. Compared with the sham group, in the rTMS group, plasma levels of miRs17~92 and Ntn-1 significantly increased whereas Sema3A levels tended to decrease. In multivariate linear regression analyses, rTMS was independently related to Ntn-1 and miR-25 levels at T14.
Conclusions:
We found an association between rTMS and neurogenesis/axonogenesis biomarker enhancement. Our preliminary data suggest that rTMS may positively interfere with natural endogenous plasticity phenomena of the post-ischemic human brain.
... Endogenous NPCs in the periventricular stem cell niche (SVZ) have been shown to migrate to the stroke lesion site within days following stroke [9,12]. However, the vast majority of NPCs do not survive and integrate in the parenchyma but rather die en route or within the lesion site [9,[29][30][31]. We first asked whether NWL283 was able to improve NPC survival using an in vitro assay. ...
Stroke results in neuronal cell death, which causes long-term disabilities in adults. Treatment options are limited and rely on a narrow window of opportunity. Apoptosis inhibitors demonstrate efficacy in improving neuronal cell survival in animal models of stroke. However, many inhibitors non-specifically target apoptosis pathways and high doses are needed for treatment. We explored the use of a novel caspase-3/7 inhibitor, New World Laboratories (NWL) 283, with a lower IC50 than current caspase-3/7 inhibitors. We performed in vitro and in vivo assays to determine the efficacy of NWL283 in modulating cell death in a preclinical model of stroke. In vitro and in vivo assays show that NWL283 enhances cell survival of neural precursor cells. Delivery of NWL283 following stroke enhances endogenous NPC migration and leads to increased neurogenesis in the stroke-injured cortex. Furthermore, acute NWL283 administration is neuroprotective at the stroke injury site, decreasing neuronal cell death and reducing microglia activation. Coincident with NWL283 delivery for 8 days, stroke-injured mice exhibited improved functional outcomes that persisted following cessation of the drug. Therefore, we propose that NWL283 is a promising therapeutic warranting further investigation to enhance stroke recovery.
... Previous research has indicated that stem cell-based therapy is an effective method for promoting neural function recovery after ischemic stroke. Zhang et al. demonstrated that the proliferation of neural precursor cells (NPCs) in the subventricular zone (SVZ) was observed within 2 weeks after focal ischemic stroke, and that the number of NPCs decreased substantially after 4 weeks [7]. The transient increase of NPCs implies an endogenous window of neuroplasticity, which offers an opportunity to improve the prognosis of ischemic stroke. ...
Background: Ischemic stroke is a common cerebrovascular accident with a high risk of neurological deficits. Stem cell therapy has progressively attracted the interest of scientists and clinicians due to the benefits of promoting neural regeneration and regulating the microenvironment surrounding the lesion after ischemic stroke. Our study aimed to evaluate the development trends and research hotspots in the field of stem cells and ischemic stroke.
Materials and methods: Publications related to stem cells and ischemic stroke were retrieved from the Web of Science from 2001 to 2022. Data analysis and mapping were performed using VOSviewer, Citespace and ImageGP.
Results: In total, 1932 papers were included in the analysis. Publications have steadily increased over the past 22 years. China has contributed the maximum number of publications, whereas the USA ranked first in the total number of citations and was considered the center of the international collaboration network. University of South Florida, Henry Ford Hospital, and Oakland University were the most influential institutions. Stroke, Brain Research, and Neural Regeneration Research were the most productive journals. The research in this field was primarily focused on the effects of stem cells on neurogenesis, inflammation, and angiogenesis following ischemic stroke, as well as their therapeutic potential for the disease. In addition, neural stem cells and mesenchymal stem cells are the most commonly utilized stem cells. The topics related to miRNA, extracellular vesicles, exosomes, mesenchymal stem cells, neuroinflammation, and autophagy are current research hotspots.
Conclusion: Our bibliometric study provides a novel perspective on the research trends in the field of stem cells and ischemic stroke. The outcome of this study may benefit scientists to identify research hotspots and development directions, thereby advancing the application of stem cell-based therapy for ischemic stroke.
... Research has demonstrated that adult neural stem cells located in the subventricular zone and the subgranular zone of the hippocampal dentate gyrus can be activated and generate neuroblasts. These neuroblasts are recruited to the ischemic area and participate in the repair of ischemic brain tissue [161][162][163]. Zhao and colleagues found that SIRT1 and SIRT2 contribute to NSC proliferation, whereas SIRT1, SIRT2, and SIRT6 contribute to NSC differentiation [164]. ...
Stroke is a major cause of mortality and disability globally, with ischemic stroke (IS) accounting for over 80% of all stroke cases. The pathological process of IS involves numerous signal molecules, among which are the highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent enzymes known as sirtuins (SIRTs). SIRTs modulate various biological processes, including cell differentiation, energy metabolism, DNA repair, inflammation, and oxidative stress. Importantly, several studies have reported a correlation between SIRTs and IS. This review introduces the general aspects of SIRTs, including their distribution, subcellular location, enzyme activity, and substrate. We also discuss their regulatory roles and potential mechanisms in IS. Finally, we describe the current therapeutic methods based on SIRTs, such as pharmacotherapy, non-pharmacological therapeutic/rehabilitative interventions, epigenetic regulators, potential molecules, and stem cell-derived exosome therapy. The data collected in this study will potentially contribute to both clinical and fundamental research on SIRTs, geared towards developing effective therapeutic candidates for future treatment of IS.
... Neurogenesis in the subventricular zone (SVZ) is greatly enhanced after cerebral ischemia, which promotes the proliferation of neural stem cells (NSCs) in the SVZ and induces NSC-derived neuroblast migration from SVZ toward the damaged brain region. [1][2][3][4][5][6][7][8][9][10] However, only a fraction of NSC-derived neuroblasts are found to migrate from SVZ to the damaged brain region, 1 which is a critical barrier to prevent the potential of endogenous neurogenesisbased brain repair. While much investigations have been focused on the development of exogenous stem cellbased stroke therapy, little effort has been made toward the development of therapeutic approaches that utilize the regenerative potential of endogenous neurogenesis in ischemic stroke. ...
Abstract Ischemic insult stimulates proliferation of neural stem cells (NSCs) in the subventricular zone (SVZ) after stroke. However, only a fraction of NSC‐derived neuroblasts from SVZ migrate toward poststroke brain region. We have previously reported that direct‐current stimulation guides NSC migration toward the cathode in vitro. Accordingly, we set up a new method of transcranial direct‐current stimulation (tDCS), in which the cathodal electrode is placed on the ischemic hemisphere and anodal electrode on the contralateral hemisphere of rats subjected to ischemia–reperfusion injury. We show that the application of this bilateral tDCS (BtDCS) promotes the migration of NSC‐derived neuroblasts from SVZ toward the cathode direction into poststroke striatum. Reversing the position of the electrodes blocks the effect of BtDCS on the migration of neuroblasts from SVZ. BtDCS protects against neuronal death and improves the functional recovery of stroke animals. Thus, the migration of NSC‐derived neuroblasts from SVZ toward poststroke brain region contributes to the effect of BtDCS against ischemia‐induced neuronal death, supporting a potential development of noninvasive BtDCS as an endogenous neurogenesis‐based stroke therapy.
... The proliferation of NSCs is greatly increased in both the SVZ and SGZ 2-5 days after a stroke, peaks on days 7-8 after ischemia, and continues for approximately 30 days [56,57]. By analyzing brain specimens from patients who had a stroke, it was also confirmed that proliferating neoblasts or new neurons were found in the penumbra area of the ischemic cortex after a stroke, some of which appeared to migrate 30 days after the stroke [51,58]. ...
Strokes are a leading cause of morbidity and mortality in adults worldwide. Extensive preclinical studies have shown that neural-stem-cell-based treatments have great therapeutic potential for stroke. Several studies have confirmed that the effective components of traditional Chinese medicine can protect and maintain the survival, proliferation, and differentiation of endogenous neural stem cells through different targets and mechanisms. Therefore, the use of Chinese medicines to activate and promote endogenous nerve regeneration and repair is a potential treatment option for stroke patients. Here, we summarize the current knowledge regarding neural stem cell strategies for ischemic strokes and the potential effects of these Chinese medicines on neuronal regeneration.
... Cell proliferation and migration occurs after a stroke occurs in the SVZ and SGZ (Jin et al. 2001;Parent et al. 2002;Yagita et al. 2001;Bravo-Ferrer et al. 2017;Palma-Tortosa et al. 2017). In a study, the proliferation of NSCs in the SVZ and SGZ regions began 2-5 days after stroke, peaked at 7-8 days, and lasted for approximately 30 days (Yagita et al. 2001;Zhang et al. 2001). Stroke can also lead to the transformation of the NSC differentiation pattern from asymmetric to symmetric (Zhang et al. 2004). ...
Normoxia is defined as an oxygen concentration of 20.9%, as in room air, whereas hypoxia refers to any oxygen concentration less than this. Any physiological oxygen deficiency or tissue oxygen deficiency relative to demand is called hypoxia. Neural stem cells (NSCs) are multipotent stem cells that can differentiate into multiple cell lines such as neurons, oligodendrocytes, and astrocytes. Under hypoxic conditions, the apoptosis rate of NSCs increases remarkably in vitro or in vivo. However, some hypoxia promotes the proliferation and differentiation of NSCs. The difference is related to the oxygen concentration, the duration of hypoxia, the hypoxia tolerance threshold of the NSCs, and the tissue source of the NSCs. The main mechanism of hypoxia-induced proliferation and differentiation involves an increase in cyclin and erythropoietin concentrations, and hypoxia-inducible factors play a key role. Multiple molecular pathways are activated during hypoxia, including Notch, Wnt/β-catenin, PI3K/Akt, and altered microRNA expression. In addition, we review the protective effect of exogenous NSCs transplantation on ischemic or anoxic organs, the therapeutic potential of hypoxic preconditioning on exogenous NSCs and clinical application of NSCs.
... In addition, several researches showed that neurogenesis is improved in dentate gyrus (DG) and SVZ in the injured brain, at both in diffuse and in focal ischemic lesions. [51][52] Even, in experimental animal models, it has been shown that intraventricular infusion of Epidermal Growth Factor (EGF) and Erythropoietin, but none of them alone, has been reported to induce new cortical tissue including neurons after small frontal cortical devascularization lesions in rats. 53 We utilized a tachistoscope as a stimulation method of both visual hemifields and we intended to maximize the cell activating effect in the striate cortex of both hemispheres. ...
A common problem in children affected by cerebral palsy, independently of its etiology, is the existence of visual impairment. In this retrospective study we analyzed the effects of Growth hormone (GH) administration (0,04 mg/kg/day, 5 days/week) together with visual stimulation with a tachistoscope in 42 children with cerebral palsy (22 boys, 20 girls, aged 2,48 ± 1,5 years [mean ± SD) in whom there was an evident lesion of the visual pathway. In 17 of these cases, prematurity was the responsible factor, while in the other 25 children, ischemic encephalopathy due to pre/perinatal problems was the origin of visual impairment. In addition, we analyzed three other children (1, 2 months and 1 year of age) in whom multicystic encephalopathy (due to severe hypoxia-ischemia at delivery) mainly affecting the occipital lobes was the responsible factor. Visual evoked potentials were recorded before beginning and after treatment, assessing the latency in ms of the N75, P100 and N140 waves, as well as the amplitude of the waves (µV). Treatment duration (mean ± SD) was 5.20 + 2.05 months. Completion of treatment was established by clinical criteria. The statistical significance of the data was carried out using the Wilcoxon test. The treatment induced a significant decrease in the latency of N75, P100 and N140 (p < 0.001), as well as a clear tendency to increase the amplitude of the waves (p < 0.05). Of special interest is the case of a child affected by Multicystic Encephalopathy in which the cystic cavities in the occipital lobes detected by MRI before starting treatment (15 days of age) completely disappeared in a new MRI performed 1 year later. That child is now totally independent for activities of daily living. GH treatment did not produce any adverse effects. In summary, from our results we can conclude that the administration of GH added to visual stimulation with a tachistoscope is an effective and safe method for the repair of visual deficiencies in children with cerebral palsy, regardless of the existence or not of GH deficiency.
... Quiescent and activated NSPCs within these two distinct regions function to generate new neurons within the adult brain. Ischemic stroke in rodents leads to an increase in neurogenesis within the SVZ, consequently triggering the migration of NSPC-derived neuroblasts from the SVZ to the boundary of the ischemic injury [77][78][79][80]. Notably, stroke-induced neurogenesis has also been demonstrated within the human brain [81][82][83]. ...
Recent studies have shed light on the diverse and complex roles of G-protein coupled receptors (GPCRs) in the pathophysiology of stroke. These receptors constitute a large family of seven transmembrane-spanning proteins that play an intricate role in cellular communication mechanisms which drive both tissue injury and repair following ischemic stroke. Orphan GPCRs represent a unique sub-class of GPCRs for which no natural ligands have been found. Interestingly, the majority of these receptors are expressed within the central nervous system where they represent a largely untapped resource for the treatment of neurological diseases. The focus of this review will thus be on the emerging roles of two brain-expressed orphan GPCRs, GPR37 and GPR37 L1, in regulating various cellular and molecular processes underlying ischemic stroke.
... The neurogenesis of the hippocampus includes different steps from a stem cell similar to a radial glia (a cell with a bipolar shape that spans the entire width of the cortex in the developing central nervous system [CNS]) and that serves as a primary progenitor capable of generating neurons, astrocytes, and oligodendrocytes presumably bipotent with properties astrocytic to transient amplifying progenitor cells determined according to its function, to mature neurons and post-mitotic (those that are not renewed, such as neurons) early 11 . The newly generated cells mature into functional neurons, which are structurally integrated into a pre-existing network; they receive synaptic information from local interneurons and the entorhinal cortex (located in the middle temporal lobe and functions as a hub in an extended network for memory and orientation) and extend axons to target cells in the CA3 region 12 . The structural integration of neurons generated in the adult brain is the prerequisite for functional synaptic integration. ...
Hypoxia-induced factor 1 (HIF-1) plays a fundamental role in the response to low oxygen tension, since it regulates the expression of a wide variety of genes, whose products participate in processes such as angiogenesis, energy metabolism, erythropoiesis, and cell proliferation as well as in the process of neurogenesis, which involves various stages, such as proliferation of neuronal stem cells, migration, differentiation, survival of new neurons, and integration of the same. Among the many intrinsic and extrinsic molecular signals that regulate the production of new neurons from progenitor cells in the adult in the central nervous system (CNS), hypoxic damage plays an important role in the maintenance and function of stem cells in development and disease.
... Due to the decreased viability of cell transplantation, endogenous NSCs are a good resource to utilize. Ischemic injury drastically increases neurogenesis in the rodent SVZ, and NSCs in the SVZ can generate many neuroblasts and migrate to the ischemic penumbra, improving neurological functional recovery [23,24]. However, self-repair from endogenous NSCs is very limited due to a nonpermissive environment for migration and neuronal differentiation [25,26]. ...
Scaffold materials, neurotrophic factors, and seed cells are three elements of neural tissue engineering. As well-known self-assembling peptide-based hydrogels, RADA16-I and modified peptides are attractive matrices for neural tissue engineering. In addition to its neuroprotective effects, cerebral dopamine neurotrophic factor (CDNF) has been reported to promote the proliferation, migration, and differentiation of neural stem cells (NSCs). However, the role of RADA16-I combined with CDNF on NSCs remains unknown. First, the effect of RADA16-I hydrogel and CDNF on the proliferation and differentiation of cultured NSCs was investigated. Next, RADA16-I hydrogel and CDNF were microinjected into the lateral ventricle (LV) of middle cerebral artery occlusion (MCAO) rats to activate endogenous NSCs. CDNF promoted the proliferation of NSCs, while RADA16-I induced the neural differentiation of NSCs in vitro. Importantly, both RADA16-I and CDNF promoted the proliferation, migration, and differentiation of endogenous NSCs by activating the ERK1/2 and STAT3 pathways, and CDNF exerted an obvious neuroprotective effect on brain ischemia-reperfusion injury. These findings provide new information regarding the application of the scaffold material RADA16-I hydrogel and the neurotrophic factor CDNF in neural tissue engineering and suggest that RADA16-I hydrogel and CDNF microinjection may represent a novel therapeutic strategy for the treatment of stroke.
... Additionally, changes in the migration behaviour of NSCs have also been reported after ischemia. Here, studies using various experimental rodent stroke models, including focal cerebral ischemia and MCAO, have reported that chains of migrating NSCs are rerouted from the SVZ or rostral migratory stream into the ischemic zone (Arvidsson et al. 2002;Jin et al. 2003;Parent et al. 2002;Zhang et al. 2004Zhang et al. , 2001. Interestingly, experiments performed in a mouse model of cortical ischemia have revealed that migrating NSCs default to a glial lineage and contribute to glial scar formation through a notch-dependent signalling mechanism (Benner et al. 2013). ...
Glial scars are a common pathological occurrence in a variety of central nervous system (CNS) diseases and injuries. They are caused after severe damage and consist of reactive glia that form a barrier around the damaged tissue that leads to a non-permissive microenvironment which prevents proper endogenous regeneration. While there are a number of therapies that are able to address some components of disease, there are none that provide regenerative properties. Within the past decade, neural stem cells (NSCs) have been heavily studied due to their potent anti-inflammatory and reparative capabilities in disease and injury. Exogenously applied NSCs have been found to aid in glial scar healing by reducing inflammation and providing cell replacement. However, endogenous NSCs have also been found to contribute to the reactive environment by different means. Further understanding how NSCs can be leveraged to aid in the resolution of the glial scar is imperative in the use of these cells as regenerative therapies. To do so, humanised 3D model systems have been developed to study the development and maintenance of the glial scar. Herein, we explore the current work on endogenous and exogenous NSCs in the glial scar as well as the novel 3D stem cell–based technologies being used to model this pathology in a dish.
... However, adult neurogenesis has been detected to occur throughout the lifetime of various mammals (59). adult neural stem cells in the subventricular zone of the lateral ventricle and the dentate gyrus of the hippocampus can be activated following stroke, to then proliferate and produce neuroblasts for the repair of damaged neurons (60,61). a number of studies have investigated the role of autophagy in embryonic and adult neural stem cells. in the adult mammalian brain, the most studied neural stem cells, such as those located in the subventricular zone of the lateral ventricle and the subgranular zone of the hippocampal dentate gyrus, are located in a relatively hypoxic environment, which is a necessary condition for stem cells (62,63). ...
Stroke is one of the main causes of disease‑related mortality worldwide. Buyang Huanwu Decoction (BHD) has been used to protect against stroke and stroke‑induced disability for several years in China. Studies have shown that BHD can relieve neuronal damage in rats with cerebral ischemia/reperfusion (I/R) injury. However, the mechanism remains unclear. A middle cerebral artery occlusion and reperfusion (MCAO‑R) model was used in the present study. The animals were treated with BHD (5, 10 and 20 g/kg) or rapamycin. Infarct size and modified neurological severity score were calculated on day 5 following MCAO‑R surgery. Cellular changes around the ischemic penumbra were revealed by hematoxylin and eosin and Nissl staining. The protein expression levels of nestin, brain‑derived neurotrophic factor (BDNF), doublecortin on the X chromosome (DCX) and autophagy‑related proteins (beclin 1, LC3‑II and p62) in the peri‑ischemic area of the brain were detected. The results demonstrated that post‑surgical treatment with BHD reduced the brain infarct size and improved neurological deficits in MCAO‑R rats. BHD protected against MCAO‑R‑induced neuronal impairment and promoted neurogenesis, increased the protein expression of nestin, BDNF and DCX and markedly enhanced autophagy by increasing beclin 1 and LC3‑II and decreasing p62. Meanwhile, BHD promoted the expression of sirtuin 1 (SIRT1), an important regulator of autophagy. In conclusion, the present study suggested that post‑surgical treatment with BHD could protect rat brains from I/R injury, potentially through the SIRT1/autophagy pathway.
... Neural precursor cells in the subventricular zone can contribute to recovery in tests of general motor function following stroke, [81,82,85]. Proliferation of these precursor cells in the subventricular zone begins by day 2 but increases greatly over the next 2 weeks [81,86,87]. The delayed development of most of this proliferation suggests limited opportunities for modification by the early olomoucine treatment. ...
Background
Following stroke, changes in neuronal connectivity in tissue surrounding the infarct play an important role in both spontaneous recovery of neurological function and in treatment-induced improvements in function. Microglia and astrocytes influence this process through direct interactions with the neurons and as major determinants of the local tissue environment. Subpopulations of peri-infarct glia proliferate early after stroke providing a possible target to modify recovery. Treatment with cell cycle inhibitors can reduce infarct volume and improve functional recovery. However, it is not known whether these inhibitors can influence neurological function or alter the responses of peri-infarct glia without reducing infarction. The present study aimed to address these issues by testing the effects of the cell cycle inhibitor, olomoucine, on recovery and peri-infarct changes following photothrombotic stroke.
Methods
Stroke was induced by photothrombosis in the forelimb sensorimotor cortex in Sprague-Dawley rats. Olomoucine was administered at 1 h and 24 h after stroke induction. Forelimb function was monitored up to 29 days. The effects of olomoucine on glial cell responses in peri-infarct tissue were evaluated using immunohistochemistry and Western blotting.
Results
Olomoucine treatment did not significantly affect maximal infarct volume. Recovery of the affected forelimb on a placing test was impaired in olomoucine-treated rats, whereas recovery in a skilled reaching test was substantially improved. Olomoucine treatment produced small changes in aspects of Iba1 immunolabelling and in the number of CD68-positive cells in cerebral cortex but did not selectively modify responses in peri-infarct tissue. The content of the astrocytic protein, vimentin, was reduced by 30% in the region of the lesion in olomoucine-treated rats.
Conclusions
Olomoucine treatment modified functional recovery in the absence of significant changes in infarct volume. The effects on recovery were markedly test dependent, adding to evidence that skilled tasks requiring specific training and general measures of motor function can be differentially modified by some interventions. The altered recovery was not associated with specific changes in key responses of peri-infarct microglia, even though these cells were considered a likely target for early olomoucine treatment. Changes detected in peri-infarct reactive astrogliosis could contribute to the altered patterns of functional recovery.
... Normally, neural progenitors from the SVZ migrate along the rostral migratory stream into the olfactory bulb, where they differentiate into interneurons (Lois and Alvarez-Buylla, 1993;Luskin, 1993). However, after injury, some of these cells migrate toward damaged areas and differentiate into both neurons and glias (Arvidsson et al., 2003;Ong et al., 2005;Zhang et al., 2001).The SVZ of rats is known to expand in size during acute recovery from neonatal HI with an increase in tripotential neural progenitors, followed later by an increase in the production of new neuroblasts, neurons, astrocytes, oligodendrocyte precursors, and oligodendrocytes (Alagappan et al., 2013;Back et al., 2001;Bain et al., 2010;Dizon et al., 2010;Felling et al., 2006;Ong et al., 2005;Plane et al., 2004;Zaidi et al., 2004). ...
Brain damage during early life is the main factor in the development of cerebral palsy (CP), which is one of the leading neurodevelopmental disorders in childhood. Few studies, however, have focused on the mechanisms of cell proliferation, migration, and differentiation in the brain of individuals with CP. We thus conducted a systematic review of preclinical evidence of structural neurogenesis in early brain damage and the underlying mechanisms involved in the pathogenesis of CP. Studies were obtained from Embase, Pubmed, Scopus, and Web of Science. After screening 2329 studies, 29 studies, covering a total of 751 animals, were included. Prenatal models based on oxygen deprivation, inflammatory response and infection, postnatal models based on oxygen deprivation or hypoxic-ischemia, and intraventricular hemorrhage models showed varying neurogenesis responses according to the nature of the brain damage, the time period during which the brain injury occurred, proliferative capacity, pattern of migration, and differentiation profile in neurogenic niches. Results mainly from rodent studies suggest that prenatal brain damage impacts neurogenesis and curbs generation of neural stem cells, while postnatal models show increased proliferation of neural precursor cells, improper migration, and reduced survival of new neurons.
Keywords: Animal models; Cerebral palsy; Neurogenesis.
... Normally, neural progenitors from the SVZ migrate along the rostral migratory stream into the olfactory bulb, where they differentiate into interneurons (Lois and Alvarez-Buylla, 1993;Luskin, 1993). However, after injury, some of these cells migrate toward damaged areas and differentiate into both neurons and glias (Arvidsson et al., 2003;Ong et al., 2005;Zhang et al., 2001).The SVZ of rats is known to expand in size during acute recovery from neonatal HI with an increase in tripotential neural progenitors, followed later by an increase in the production of new neuroblasts, neurons, astrocytes, oligodendrocyte precursors, and oligodendrocytes (Alagappan et al., 2013;Back et al., 2001;Bain et al., 2010;Dizon et al., 2010;Felling et al., 2006;Ong et al., 2005;Plane et al., 2004;Zaidi et al., 2004). ...
Brain damage during early life is the main factor in the development of cerebral palsy (CP), which is one of the leading neurodevelopmental disorders in childhood. Few studies, however, have focused on the mechanisms of cell proliferation, migration, and differentiation in the brain of individuals with CP. We thus conducted a systematic review of preclinical evidence of structural neurogenesis in early brain damage and the underlying mechanisms involved in the pathogenesis of CP. Studies were obtained from Embase, Pubmed, Scopus, and Web of Science. After screening 2329 studies, 29 studies, covering a total of 751 animals, were included. Prenatal models based on oxygen deprivation, inflammatory response and infection, postnatal models based on oxygen deprivation or hypoxic-ischemia, and intraventricular hemorrhage models showed varying neurogenesis responses according to the nature of the brain damage, the time period during which the brain injury occurred, proliferative capacity, pattern of migration, and differentiation profile in neurogenic niches. Results mainly from rodent studies suggest that prenatal brain damage impacts neurogenesis and curbs generation of neural stem cells, while postnatal models show increased proliferation of neural precursor cells, improper migration, and reduced survival of new neurons.
... Adult male Sprague Dawley rats (250-270 g; Sippr-BK Laboratory Animal Co., Ltd., Shanghai, China) were anesthetized using 1% pentobarbital sodium (45 mg/kg). The middle cerebral artery (MCA) occlusion (MCAO) operation was performed as previously reported [18]. In short, 6-0 silicon-coated nylon monofilament suture (Beijing Cinontech Co. Ltd., Beijing, China) was incorporated into the MCA of rats. ...
Acute cerebral infarction (ACI) possesses high mortality. Exosomes present in serum have potential application value in ACI diagnosis. This study investigated the mechanism of serum exosomes in ACI. Serum exosomes isolated from ACI patients and normal people were identified and then injected into the established middle cerebral artery occlusion (MCAO) rat model to evaluate cerebral injury and inflammation. Exosomal microRNA (miR)-27-3p expression was detected and interfered to analyze rat cerebral inflammation. The binding relationship between miR-27-3p and PPARγ was predicted and verified. The lipopolysaccharide (LPS)-treated microglia model was established and intervened with miR-27-3p to detect PPARγ, Iba-1, and inflammation-related factor expressions. After overexpressing PPARγ, rat cerebral inflammation was evaluated. The clinical significance of serum exosomal miR-27-3p in ACI was evaluated. Serum exosomes from ACI patients caused exacerbated MCAO rat cerebral injury and poor behavior recovery, as well as promoted cerebral inflammation. Serum exosomal miR-27-3p deepened rat brain inflammation. miR-27-3p targeted PPARγ to promote microglia activation and inflammation-related factor expressions in MCAO rats, and overexpressing PPARγ attenuated MCAO rat cerebral inflammation. Serum exosomal miR-27-3p promised to be a biomarker for ACI. We proved that serum exosomes from ACI patients aggravated ACI patient cerebral inflammation via the miR-27-3p/PPARγ axis.
... Des analyses immunohistologiques révèlent une augmentation transitoire du nombre de cellules prolifératives (BrdU + ou pHis3 + ) dans la SVZ ipsilésionnelle chez les rongeurs après occlusion permanente ou transitoire de l'ACM (Palma-Tortosa et al., 2017;Zhang et al., 2001;Jin et al., 2001). ...
Malgré plus de deux décennies de recherches intensives, les accidents vasculaires cérébraux (AVC) demeurent l'une des principales causes de décès et d'invalidité dans le monde. À ce jour, les seules thérapies admises pour le traitement des AVC ischémiques sont les techniques de reperfusion,restreintes à une très courte fenêtre thérapeutique, puis ensuite la rééducation neurologique. Bien que ces interventions améliorent grandement le devenir des patients, le nombre de personnes éligibles à la reperfusion et la récupération fonctionnelle post-ischémique induite par des exercices de rééducation sont limités. Dans ce contexte de thérapies alternatives limitées, les cellules souches mésenchymateuses (MSC) réduisent de façon significative les déficits fonctionnels dans des modèles expérimentaux d’AVC ischémique, particulièrement celles purifiées du tissu adipeux. Chez l'homme, les MSC améliorent également la récupération fonctionnelle, même si l'effet apparait moins prononcé. Nous proposons donc d'essayer d’augmenter le potentiel thérapeutique de ces cellules MSC en utilisant le pituitary adenylate cyclase-activating polypeptide (PACAP) connu pour ses propriétés protectrices, neurotrophiques et immunomodulatrices dans le cadre de l’ischémie cérébrale. Au cours de cette étude, nous avons développé et évalué le potentiel thérapeutique de MSC purifiées du tissu adipeux (hADSC) et génétiquement modifiées pour exprimer le PACAP, en utilisant un baculovirus recombinant, permettant l’obtention des hADSC-PACAP. Dans un modèle d’occlusion permanente de l’artère cérébrale moyenne, la transplantation différée de hADSC-PACAP améliore, de façon rapide, la récupération fonctionnelle. Celle-ci est associée à une redirection efficace de la réponse inflammatoire microgliale vers un phénotype protecteur de type M2, susceptible de soutenir les mécanismes de réparation tissulaire. En complément de ces observations, une augmentation de la survie à long terme des neuroblastes et une réorganisation précoce des connexions corticales interhémisphériques est aussi observée. Parallèlement à la réduction globale des connexions interhémisphériques vers le cortex controlésionnel induite par la transplantation des hADSC-PACAP, une augmentation sélective de projections interhémisphériques provenant de la zone périlésionnelle et allant vers le cortex somatosensoriel dédié aux vibrisses, situé dans l’hémisphère controlésionnel, a été constatée. Ainsi, malgré l'absence de différences significatives entre les hADSC et les hADSC-PACAP, ces dernières en modulant la réponse inflammatoire vers un phénotype de type M2c/M2d renforcent la récupération fonctionnelle post-ischémique en créant un environnement propice aux mécanismes de réparation tissulaire et de neuroplasticité. Au regard de nos résultats, la transplantation de ces cellules semble favoriser l’établissement ou le réarrangement des connexions neuronales entre certaines aires cérébrales au détriment d’autres régions.
... Although our findings that CIMT promotes behavioural recovery are well-supported by clinical findings and animal studies, our findings are not consistent with previous reports that CIMT increases neurogenesis (Ishida et al., 2015;Rha et al., 2011;Zhang et al., 2001;Zhao et al., 2009 and enhances cell survival (Kim et al., 2018;Zhang et al., 2013b). Differences that could account for the discrepancies include the animal model of injury and duration of CIMT (plaster cast and for 2 continuous weeks), as well as the paradigm for labelling proliferating cells, the region analysed and functional outcome measured (rotarod, grip strength task, and the horizontal ladder rung) (Liu et al., 2019;Qu et al., 2015;Rha et al., 2011;Zhao et al., 2009;. ...
Neonatal stroke is a leading cause of long-term disability and currently available rehabilitation treatments are insufficient to promote recovery. Activating neural precursor cells (NPCs) in adult rodents, in combination with rehabilitation, can accelerate functional recovery following stroke. Here, we describe a novel method of constraint-induced movement therapy (CIMT) in a rodent model of neonatal stroke that leads to improved functional outcomes, and we asked whether the recovery was correlated with expansion of NPCs. A hypoxia/ischemia (H/I) injury was induced on postnatal day 8 (PND8) via unilateral carotid artery ligation followed by systemic hypoxia. One week and two weeks post-H/I, CIMT was administered in the form of 3 botulinum toxin (Botox) injections, which induced temporary paralysis in the unaffected limb. Functional recovery was assessed using the foot fault task. NPC proliferation was assessed using the neurosphere assay and EdU immunohistochemistry. We found that neonatal H/I injury alone expands the NPC pool by >2.5-fold relative to controls. We determined that using Botox injections as a method to provide CIMT results in significant functional motor recovery after H/I. However, CIMT does not lead to enhanced NPC activation or migration into the injured parenchyma in vivo. At the time of functional recovery, increased numbers of proliferating inflammatory cells were found within the injured motor cortex. Together, these findings suggest that NPC activation following CIMT does not account for the observed functional improvement and suggests that CIMT-mediated modification of the CNS inflammatory response may play a role in the motor recovery.
... In fact, neurogenesis in the cortex appears to be upregulated in response to ischemic stroke (Magavi et al., 2000;Jiang et al., 2001;Jin et al., 2006;Yang et al., 2007;Ohira et al., 2010). Similarly, the SVZ also appears to respond to cortical stroke with an upregulation of cell proliferation, which is then followed by the migration and the integration of new neurons into the damaged region of the cortex (Jin et al., 2001;Zhang et al., 2001Zhang et al., , 2004Bernier et al., 2002;Tonchev et al., 2005;Yamashita et al., 2006). Pharmacologic manipulation of molecular signals could serve to enhance this neuroprotective response and improve recovery (Marlier et al., 2015). ...
Convincing evidence has repeatedly shown that new neurons are produced in the mammalian brain into adulthood. Adult neurogenesis has been best described in the hippocampus and the subventricular zone (SVZ), in which a series of distinct stages of neuronal development has been well characterized. However, more recently, new neurons have also been found in other brain regions of the adult mammalian brain, including the hypothalamus, striatum, substantia nigra, cortex, and amygdala. While some studies have suggested that these new neurons originate from endogenous stem cell pools located within these brain regions, others have shown the migration of neurons from the SVZ to these regions. Notably, it has been shown that the generation of new neurons in these brain regions is impacted by neurologic processes such as stroke/ischemia and neurodegenerative disorders. Furthermore, numerous factors such as neurotrophic support, pharmacologic interventions, environmental exposures, and stem cell therapy can modulate this endogenous process. While the presence and significance of adult neurogenesis in the human brain (and particularly outside of the classical neurogenic regions) is still an area of debate, this intrinsic neurogenic potential and its possible regulation through therapeutic measures present an exciting alternative for the treatment of several neurologic conditions. This review summarizes evidence in support of the classic and novel neurogenic zones present within the mammalian brain and discusses the functional significance of these new neurons as well as the factors that regulate their production. Finally, it also discusses the potential clinical applications of promoting neurogenesis outside of the classical neurogenic niches, particularly in the hypothalamus, cortex, striatum, substantia nigra, and amygdala.
... The mechanisms underlying the beneficial effects of noninvasive brain electric stimulation are not fully understood. Numerous studies have revealed that brain stimulation of the ventromedial prefrontal cortex in middle aged rats, enhanced short-term memory in the novel-object recognition task (Liu et al., 2015), improved depressive behavior (Zhang et al., 2001) and restored the number of neuronal precursors after spinal cord injury (SCI) (Becker et al., 2010). Likewise, transcranial direct current stimulation also stimulates neurogenesis in mice (Pikhovych et al., 2016) and in a rat model of stroke along with oligodendrocyte precursors recruitment (Braun et al., 2016). ...
The major aim of stroke therapies is to stimulate brain repair and to improve behavioral recuperation after cerebral ischemia. Despite remarkable advances in cell therapy for stroke, stem cell-based tissue replacement has not been achieved yet stimulating the search for alternative strategies for brain self-repair using the neurogenic zones of the brain, the dentate gyrus and the subventricular zone (SVZ). However, during aging, the potential of the hippocampus and the SVZ to generate new neuronal precursors, declines. We hypothesized that electrically stimulation of endogenous neurogenesis in aged rats could increase the odds of brain self-repair and improve behavioral recuperation after focal ischemia. Following stroke in aged animals, the rats were subjected to two sessions of electrical non-convulsive stimulation using ear-clip electrodes, at 7- and 24 days after MCAO. Animal were sacrificed after 48 days. We report that electrical stimulation (ES) stimulation of post-stroke aged rats led to an improved functional recovery of spatial long-term memory (T-maze) but not on the rotating pole or the inclined plane, both tests requiring complex sensorimotor skills. Surprisingly, ES had a detrimental effect on the asymmetric sensorimotor deficit. Histologically, there was a robust increase in the number of doublecortin-positive cells in the dentate gyrus and SVZ of the infarcted hemisphere and the presence of a considerable number of neurons expressing tubulin beta III in the infarcted area. Among the gene that were unique to ES, we noted increases in the expression of seizure related 6 homolog like which is one of the physiological substrate of the β-secretase BACE1 involved in the pathophysiology of the Alzheimer’s disease and Igfbp3 and BDNF receptor mRNAs which has been shown to have a neuroprotective effect after cerebral ischemia. However, ES was associated with a long-term down regulation of cortical gene expression after stroke in aged rats suggesting that gene expression in the peri-infarcted cortical area may not be related to electrical stimulation induced-neurogenesis in the subventricular zone and hippocampus.
... The main angiogenic functions of VEGF-A (hereinafter VEGF) include promoting survival of endothelial cells [22], proliferation induction [23] and stimulation of migration and invasion of these cells [24]. Besides, VEGF is also involved in a number of other processes in the central nervous system, such as ontogenesis of the nervous system cells, including the processes of migration, differentiation, synaptogenesis, and myelination [25]; neuroprotection [26,27]; stimulation of neurogenesis in the adult organism [28,29]; post-ischemic reparation of the brain tissue [30] and blood vessels [31], stimulation of hippocampus-dependent memory formation [32]. VEGF is also involved in pathological processes such as atherogenesis [33] and cerebral edema [21,34,35]. ...
Stroke is an acute disorder of CNS being the leading factor of mortality and disability of the population. Dynamic assessment of trophic growth factors expression is a promising tool to predict the outcome of ischemic stroke. We investigated the concentration dynamics of the brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) in blood plasma of patients with acute ischemic stroke. 56 patients took part in the study. Venous blood was collected from all patients on the first, 7th and 21st day of their hospital stay. BDNF and VEGF plasma concentrations were measured using ELISA. Our study shows, that not single, but serial dynamic measures of BDNF plasma concentrations in the acute period of ischemic stroke have a prognostic significance. Increasing of the BDNF plasma concentration on day 7 in comparison to the concentration on day 1 was significantly associated with a better clinical outcome of acute ischemic stroke. Extremely high VEGF plasma concentrations (more than 260 pg/mL) on days 1 and 7 from the ischemic stroke onset were significantly associated with a worse clinical outcome on day 21 and a less favorable rehabilitation prognosis. Serial measurement of plasma concentrations of trophic growth factors in patients with ischemic stroke presents a rather simple, reliable and minimally invasive method of dynamic assessment of the clinical course of acute ischemic stroke and early outcome prediction.
... Although the mechanism(s) underlying the reduced OB neurogenesis remains to be determined, it should be noted that the deficiency in proliferation of stem cells in the SVZ of a CUMS mouse model of depression (Mineur et al., 2007) and a forced-swim model of stress in the mouse (Hitoshi et al., 2007), may provide additional explanations. A previous study showed that a significant increase in the number of proliferating cells in the subventricular zone coincided with a pronounced enlargement of newborn cells in the OB 2 weeks after ischemia in rats (Zhang et al., 2001). Contrarily, down-regulation of cell proliferation in the SVZ led to a decreased number of newborn cells in the OB 3 weeks after a short term treatment with estradiol in adult female C57B16/J mice (Brock et al., 2010). ...
A variety of evidence has a connection with hip-pocampal neurogenesis in the pathophysiology of depression. However, whether other neurogenic regions in the adult central nervous system would likewise be involved is a highly interesting question. The olfactory bulb (OB) is one of the post-developmental neurogenesis areas in the adult mamma-lian brain. Clinical studies have shown a decreased olfactory sensitivity in depressed patients, and a recent study disclosed cases of reduced OB volume in acute major depression , indicating the OB may be also affected. Here, animal models are superior to human studies, which may provide further insight into such complex processes. We therefore investigated OB neurogenesis using a chronic unpredictable mild stress (CUMS) rat model of depression. Considering the functional analysis of adult neurogenesis which has been carried out at the synaptic level as well as animal behavior level, we detected pre-synaptic and olfactory function in the OB of rats after 4 weeks of chronic stress. Immunohisto-chemistry and Western blot analysis showed a dramatic reduction of immature neurons marked by polysialylated neural cell adhesion molecule and doublecortin as well as mature neurons labeled by neuronal nuclei. Moreover, chronic stress down-regulated the expression of synaptophsin but up-regulated syntaxin in the OB, as demonstrated by Western blot, whereas a significant variation at the mRNA level was lacking. Notably, in the rat model of depression, both a decreased OB volume and olfactory dysfunction were present at the same time, which is consistent with clinical findings in depressed patients. In summary, reduced OB neurogenesis and pre-synaptic dysfunction were observed in the rat model, which may at least in part correspond to the reduced OB volume and olfactory malfunction in patients suffering from depression.
... Despite that the subventricular zone (SVZ) is not the only neurogenic niche in the adult brain, it is the main source of precursors that reach the ischemic zone. The transient and spontaneous increase of parents is produced by a shortening of the cell cycle, beginning at 2 days and reaching the maximum in 2 weeks after the beginning of the damage returning to its basal levels at 6 weeks after it (Zhang et al., 2001;Thored et al., 2006;Zhao et al., 2008). ...
Ischemic stroke (IS) is the leading cause of disability in the western world, assuming a high socio-economic cost. One of the most used strategies in the last decade has been biomaterials, which have been initially used with a structural support function. They have been perfected, different compounds have been combined, and they have been used together with cell therapy or controlled release chemical compounds. This double function has driven them as potential candidates for the chronic treatment of IS. In fact, the most developed are in different phases of clinical trial. In this review, we will show the ischemic scenario and address the most important criteria to achieve a successful neuroreparation from the point of view of biomaterials. The spontaneous processes that are activated and how to enhance them is one of the keys that contribute to the success of the therapeutic approach. In addition, the different routes of administration and how they affect the design of biomaterials are analyzed. Future perspectives show where this broad scientific field is heading, which advances every day with the help of technology and advanced therapies.
... NSCs were isolated from non-ischemic rats and ischemic rats on day 7 after MCAO when stroke-increased neurogenesis reaches a peak, as previously described [33,34]. Briefly, the NSCs localized to the lateral walls of the lateral ventricles of the SVZ in sagittally dissected brain slices were isolated and digested in 0.05% Trypsin (MilliporeSigma, USA) at 37 C for 1 h and the digestion was stopped with an equal volume of 0.1% Trypsin inhibitor (MilliporeSigma). ...
Neurogenesis contributes to poststroke recovery. Long noncoding RNAs (lncRNAs) participate in the regulation of stem cell self-renewal and differentiation. However, the role of lncRNAs in stroke-induced neurogenesis remains unknown. In this study, we found that H19 was the most highly upregulated lncRNA in neural stem cells (NSCs) of the subventricular zone (SVZ) of rats subjected to focal cerebral ischemia. Deletion of H19 suppressed cell proliferation, promoted cell death, and blocked NSC differentiation. RNA sequencing analysis revealed that genes deregulated by H19 knockdown were those that are involved in transcription, apoptosis, proliferation, cell cycle, and response to hypoxia. H19 knockdown significantly increased the transcription of cell cycle-related genes including p27, whereas overexpression of H19 substantially reduced expression of these genes through the interaction with chromatin remodeling proteins EZH2 and SUZ12. Moreover, H19 regulated neurogenesis-related miRNAs. Inactivation of H19 in NSCs of ischemic rats attenuated spontaneous functional recovery after stroke. Collectively, our data provide novel insights into the epigenetic regulation of lncRNAs in stroke-induced neurogenesis.
Neural stem cells (NSCs) have the ability to proliferate and differentiate into neurons, astrocytes, oligodendrocytes and some other types of cells, which were used in therapies for multiple neural system disorders. However, the efficacy of NSCs is limited by their short lifespan. Therefore, promoting the proliferation of NSCs is one of the key bottlenecks in their use for transplantation and treatment. According to our research, β-hydroxybutyrate (BHB) promoted cell cycle progression, thereby enhancing the proliferation of both primary NSCs and neural progenitor cell line C17.2. The BHB receptors GPR41 and GPR109A were found to mediate this effect by activating the Erk1/2 pathway. Furthermore, the key transcription factors regulating NSC proliferation, Pax6 and Sox2, were also upregulated by BHB via increased histone trimethylation and acetylation levels in their promoters. In conclusion, BHB enhanced the proliferation of NSCs through a receptor-dependent pathway. At same time, epigenetic modification also plays a role in this process.
Mesenchymal stem/stromal cells (MSC)-derived small extracellular vesicles (sEVs) possess therapeutic potential for treatment of traumatic brain injury (TBI). The essential role of miRNAs underlying the beneficial effects of MSC-derived sEVs for treatment of TBI remains elusive. The present study was designed to investigate the role of microRNAs in sEVs from MSCs with argonaut 2 (Ago2) knockdown in neurological recovery, neuroinflammation, and neurovascular remodeling in TBI rats. Therapeutic effects of sEVs derived from naïve MSCs (naïve-sEV), MSCs transfected with a vector carrying scramble control shRNA (Vector-sEV), MSCs transfected with a lentiviral vector based shRNA against Ago2 to knock down Ago2 (Ago2-KD-sEV) were determined in adult male rats subjected to a moderate TBI induced by controlled cortical impact. sEVs (naïve-sEV, Vector-sEV, and Ago2-KD-sEV) or Vehicle (phosphate-buffered solution) were given intravenously one day post injury (PI). Multiple neurological functional tests were performed weekly PI for 5 weeks. The Morris water maze test was performed for spatial learning and memory 31-35 days PI. All animals were euthanized 5 weeks PI and the brains were collected for analyses of lesion volume, cell loss, neurovascular remodeling, and neuroinflammation. Ago2 knockdown reduced global sEV miRNA levels. Compared to the Vehicle treatment, both naïve-sEV and Vector-sEV treatments significantly improved functional recovery, reduced hippocampal neuronal cell loss, inhibited neuroinflammation, and promoted neurovascular remodeling (angiogenesis and neurogenesis). However, Ago2-KD-sEV treatment had a significantly less therapeutic effect on all the parameters measured above than did naïve-sEV and Vector-sEV treatments. The therapeutic effects of Ago2-KD-sEV were comparable to that of Vehicle treatment. Our findings demonstrate that attenuation of Ago2 protein in MSCs reduces miRNAs in MSC-derived sEVs and abolishes exosome treatment-induced beneficial effects in TBI recovery, suggesting that miRNAs in MSC-derived sEVs play an essential role in reducing neuronal cell loss, inhibiting neuroinflammation, augmenting angiogenesis and neurogenesis as well as improving functional recovery in TBI. The findings underscore the important role of miRNAs in MSC-derived sEVs in the treatment of TBI.
Background and AimsIn adult human brain, neurogenesis seems to persist throughout life and ischemic stroke was proved to stimulate this process. Using magnetic resonance spectroscopy (MRS), a 1.28-ppm peak, putative biomarker of neural progenitor cells (NPCs), was identified both in vitro and in vivo, i.e., in normal rat and healthy human brain. The aim of our study was to identify a 1.28-ppm peak in adult human ischemic brain by using 3.0 T multivoxel MRS.Methods
We studied 10 patients, six males, and four females, with a mean (± SD) age of 59.3 (± 17.3), at three different time points from ischemic stroke onset (T0: < 5 days; T14: 14 ± 2 days; T30: 30 ± 2 days).ResultsIn all patients except one, a 1.28-ppm peak at T14 was detected at the ischemic boundary (all p values < 0.05). MRS performed on six voluntary age-matched healthy subjects did not detect any 1.28-ppm peak.Conclusions
The nature of this 1.28-pm peak is uncertain; however, our data support the hypothesis that it might represent a marker of NPCs in post-stroke human brain.
One in four people over age 25 will have a stroke in their lifetime. Globally, an estimated 80 million people are currently living with stroke with many experiencing chronic disability and unmet needs. There is strong evidence demonstrating that the brain has a remarkable capacity for plasticity and reorganization into adulthood; however, application of this knowledge clinically is in its infancy. Adult neurogenesis is the generation of de novo neurons from neural stem cells and the integration of these immature neurons into established circuits in the adult brain. Therefore, neurogenesis is a really promising therapeutic for stroke patients, and we are going to highlight the ways it can be exploited to improve stroke outcome in this chapter. Briefly, we outline what is known about adult neurogenesis, and the techniques typically used to investigate it in humans and preclinical studies. We then provide evidence of post-stroke neurogenesis from both clinical and preclinical studies. Finally, we discuss some potential pharmacological and non-pharmacological approaches to enhance post-stroke neurogenesis to promote stroke recovery.KeywordsBrain plasticityBrain repairNeurogenesisNeuroplasticityStroke recovery
Stroke results in the formation of a cavity in the infarcted brain tissue. Angiogenesis and neurogenesis are poor in the cavity, preventing brain tissue regeneration for stroke therapy. To regenerate brain tissue in the cavity, we genetically engineered filamentous phages, the human‐safe nanofiber‐like bacteria‐specific viruses, to display many copies of RGD peptide on the sidewalls. The viral nanofibers, electrostatically coated on the biocompatible injectable silk protein microparticles, not only promoted the adhesion, proliferation, and infiltration of neural stem cells (NSCs), but also induced NSCs to differentiate preferentially into neurons in basal medium within 3 days. After the NSC‐loaded microparticles were injected into the stroke cavity of rat models, the phage nanofibers on the microparticles stimulated angiogenesis and neurogenesis in the stroke sites within 2 weeks for brain regeneration, leading to functional recovery of limb motor control of rats within 12 weeks. The viral nanofibers also brought about the desired outcomes for stroke therapy, such as reducing inflammatory response, decreasing thickness of astrocytes scars, and increasing neuroblasts response in the subventricular zone. Since virtually any functional peptide can be displayed on the phage by genetic means, the phage nanofibers hold promise as a unique and effective injectable biomaterial for stroke therapy. This article is protected by copyright. All rights reserved
Mesenchymal stem cell (MSC) transplantation is demonstrated to improve functional and pathological recovery in cerebral ischemia. To understand the underlying mechanism, we transplanted a MSC line (B10) in a rat middle cerebral artery occlusion (MCAO) model and checked the proliferation and migration of neuronal progenitor cells (NPCs). B10 transplantation increased NPCs in the subventricular zone and their migration towards the lesion area at an earlier time. Fourteen days after MCAO, some NPCs were differentiated to neurons and astrocytes. Although B10 transplantation increased total number of both astrocytes and neurons, it only increased the differentiation of NPC to astrocyte. The mRNA of polysialylation enzyme ST8SiaIV and a chemokine SDF-1 were persistently increased in B10-transplanted groups. SDF-1-positive cell number was increased in the core and penumbra area, which was expressed in macrophage/microglia and transplanted B10 cells at 3 days after MCAO. Furthermore, SDF-1 mRNA expression in cell culture was high in B10 compared to a microglia (HMO) or a neuronal (A1) cell line. B10 culture supernatant increased in vitro A1 cell migration, which was significantly inhibited by siRNA-mediated SDF-1 silencing in B10. Thus, our results suggested that MSC transplantation increased endogenous NPC migration in cerebral ischemic condition by increasing chemokine and polysialylation enzyme expression, which could be helpful for the restorative management of cerebral ischemia. In cerebral ischemic condition, sudden and severely compromised blood supply in a focal area causes necrotic death of brain tissue. Consequently, a neuroinflammatory process is initiated, leading to accumulation and activation of immune cells, and increased expression of several cytokines, chemokines, proteases and reactive oxygen species 1. Such activation of immune system results further cell death in the peri-infarct area that progresses at a slower pace 2,3. On the other hand, reparative processes including clearance of cell debris, expression of neuro-tropic factors and formation of glial scar to wall-off the infarct area from viable tissue are also observed 4-6. The balance of such inflammatory and reparative events ultimately determines the formation of a mature lesion. In addition to inflammatory and reparative processes, a regenerative process might also be attributed 7. For example, the proliferation of neural progenitor cells (NPCs) is increased in the sub-ventricular zone (SVZ) of human stroke patients as well as focal cerebral ischemia animal models; as evidenced by the presence of poly-sialylated neural cell adhesion molecule (PSA-NCAM) positive cells in the area 8,9. PSA-NCAM positive cells are considered as migrating NPCs 10,11. These newly proliferated NPCs are suggested to migrate toward the lesion areas 12 , and differentiate into mature neurons 13. However, such endogenous regenerative capacity of the brain seems to be insufficient to resolve the brain damage. Nevertheless, the strategy to boost up the regenerative
Neural stem cell therapy has been galvanized by the discovery of pluripotent stem cells. The possibility to generate specialized central nervous system-specific differentiated cells using human somatic cells engineered to become induced pluripotent stem cells (iPSCs) was a game changer. This technology has broad applications in the field of regenerative medicine, in vitro disease modeling, targeted drug discovery, and precision medicine. Currently, iPSCs are one of the most promising cell sources amenable for commercialization and off-the-shelf neural stem cell therapy products. iPSCs exhibit a strong self-renewable ability that supports the development of a virtually unlimited source of neural cells for structural repair in neurological disorders. However, along with this strong proliferative capacity of iPSCs comes the tumorigenic potential of these cells after transplantation. Thus, the isolation and purification of a homogeneous population of human neural stem cells (hNSCs) are of paramount importance to ensure consistency in the composition of the cellular product and to avoid tumor formation in the host brain. This chapter describes the isolation, neuralization, and long-term perpetuation of hNSCs derived from iPSCs through the use of specific growth medium and the preparation of hNSCs for transplantation in an experimental model of stroke. Additionally, we will describe methods to analyze the ischemic stroke and size of grafts using magnetic resonance imaging and OsiriX software and neuroanatomical tracing procedures to study axonal remodeling after ischemic stroke and cell transplantation.
Progranulin (PGRN), a secreted glycosylated protein, has been reported to attenuate ischemia-induced cerebral injury through anti-inflammation, attenuation of blood-brain barrier disruption and neuroprotection. However, the effect of PGRN on neurogenesis in the subventricular zone (SVZ) after cerebral ischemia remains unclear. In this study, adult C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO), and different doses of recombinant mouse PGRN (r-PGRN, 0.3 ng, 1 ng, 5 ng) were intracerebroventricularly administered 30 min after pMCAO. Results showed that 1 ng r-PGRN markedly reduced infarct volume and rescued functional deficits 24 h after pMCAO. Meanwhile, 1 ng r-PGRN increased SVZ cell proliferation, as shown by a high number of bromodeoxyuridine-positive (BrdU⁺) cells and Ki-67⁺ cells in the ischemic ipsilateral SVZ 7 d after pMCAO. Additionally, PGRN increased the percentage of BrdU⁺/Doublecortin (DCX)⁺ cells in the ipsilateral SVZ 14 d after pMCAO and increased the percentage of new neurons (BrdU⁺/NeuN⁺ cells) in the peri-infarct striatum 28 d after pMCAO, suggesting that PGRN promotes neuronal differentiation. PGRN also upregulated phosphorylation of ERK1/2 and Akt in the ipsilateral SVZ 3 d after pMCAO. Our data indicate that PGRN treatment promotes acute functional recovery; most importantly, it also stimulates neurogenesis in the SVZ, which could be beneficial for long-term recovery after cerebral ischemia. The increase in neurogenesis could be associated with activation of the MAPK/ERK and PI3K/Akt pathways. These results suggest a potential new strategy utilizing PGRN in ischemic stroke therapy.
Bone Marrow mesenchymal stem cell transplantation increases neuronal progenitor cell migration
Ischemic stroke is one of the main causes of mortality and disability worldwide. However, the efficient therapeutic strategies are still lacking. Stem/progenitor cell-based therapy, with its vigorous advantages, has emerged as a promising tool for the treatments of ischemic stroke. The mechanisms involve new neural cells and neuronal circuitry formation, antioxidation, inflammation alleviation, angiogenesis and neurogenesis promotion. In the past decades, in-depth studies have suggested that cell therapy could promote vascular stabilization and decrease blood-brain barrier (BBB) leakage after ischemic stroke. However, the effects and underlying mechanisms on BBB integrity induced by the engrafted cells in ischemic stroke have not been reviewed yet. Herein, we will update the progress in researches of the effects of cell therapy on BBB integrity after ischemic stroke and review the underlying mechanisms. First, we will present an overview of BBB dysfunction under ischemic condition and cells engraftment for ischemic treatment. Then we will summarize and discuss the current knowledge about the effects and underlying mechanisms of cell therapy on BBB integrity after ischemic stroke. In particular, we will review the most recent studies in regard to the relationship between cell therapy and BBB in tissue plasminogen activator (t-PA)-mediated therapy and diabetic stroke.
Stroke remains the leading cause of adult disability. Post-stroke neurogenesis contributes to functional recovery. As an intrinsic neurorestorative process, it is important to elucidate the molecular mechanism underlying stroke-induced neurogenesis and to develop therapies designed specifically to augment neurogenesis. Epigenetic mechanisms include DNA methylation, histone modification and its mediation by microRNAs and long-non-coding RNAs. In this review, we highlight how epigenetic factors including DNA methylation, histone modification, microRNAs and long-non-coding RNAs mediate stroke-induced neurogenesis including neural stem cell self-renewal and cell fate determination. We also summarize therapies targeting these mechanisms in the treatment of stroke.
Despite the fact that major depressive disorder (MDD) is expected to become the single largest cause of injury and illness in the world by 2020 little is known regarding the underlying cause of the disease or the mechanism of action of antidepressants although the HPA axis and neurogenesis may be of importance in both processess. In this thesis I have attempted to further elucidate the links between the mechanism of action of antidepressants, disruption of the HPA axis and neurogenesis with particular focus on members of the Bcl-2 family of pro- and anti-apoptotic proteins. Results showed that disruption of the HPA axis in mice by elevating corticosterone via a pellet implant method caused robust behavioural changes in the forced swim test (FST) (following acute and 7 day administration but not 14 or 21 day administration) and the light/dark box (following chronic but not acute administration which was normalised following corticosterone withdrawal) indicative of a "depressed phenotype". Chronic corticosterone treatment also significantly decreased hippocampal neurogenesis (attenuated by antidepressant treatment) but failed to alter expression of the anti- or pro-apoptotic proteins Bcl-2 and BAX respectively indicating a role for a disrupted HPA axis in reduced hippocampal neurogenesis but not in increased apoptosis via changes in Bcl-2 or BAX expression. Conversely, antidepressants increased hippocampal neurogenesis and selectively increased hippocampal Bcl-2 without a corresponding change in BAX. Treatment with receptor subtype selective 5-HT antagonists indicated the involvement of the 5-HT1A and 5-HT2C receptor subtypes in the effects on Bcl-2. Central administration of Bcl-2 and BAX peptide fragments modulated monoamine systems increasing 5-HT metabolism and produced an antidepressant effect in the FST. Taken together results suggest a potential involvement for the Bcl-2 family of proteins in the mechanism of action of antidepressants and further supports the suggestion that chronically disrupted HPA axis function influences hippocampal neurogenesis.
Forced limb use, which forces the use of the impaired arm following stroke, improves functional recovery. The study was designed to investigate the mechanisms of recovery underlying forced impaired limbuse. Furthermore, forced unimpaired arm use was also performed in order to explore its effect on functional behavior. We hypothesized that forced forelimb use could improve functional recovery in rats that have had an experimentally induced ischemic stroke, through promoting the recruitment and differentiation of the oligodendrocyte progenitor cells (OPCs). Indeed the proliferation of Olig2 and NG2 positive cells, as well as the expression of myelin basic protein (MBP)were increased in the perilesional striatum, whereas quantitative changes of Olig2+ and NG2+ oligodendrocyte progenitor cells was not observed in the subventricular zone. Through comparing rats forced to rely on affected or unaffected forelimb, the results demonstrated that forced impaired limb use boosted functional recovery. At the same time forced unimpaired limb use deteriorated limb movement of injured side. In addition, the expression of NogoA is reduced, when the injured limb was used more, suggesting that it played a role in the repair of white matter.
Once considered to be a structurally rigid organ, the adult mammalian brain has recently been the subject of a series of discoveries of constant remodeling at multiple levels, including synapses, dendrites, axons, and neuronal soma under physiological conditions (for example, see a recent review by Abraham, 2008). Continuous production of new neurons (neurogenesis) in the mature brain is among recent additions to such structural plasticity. Moreover, recent studies have revealed its previously unrecognized capacity for self-repair, i.e., supply of new neurons and glia after damage. Studies of injured brains have also revealed that endogenous neural stem/progenitor cells serve as sensitive responders to various injury signals and actively participate in tissue repair in many ways. This review summarizes the current understanding of this injury-induced neurogenesis/gliogenesis in the adult mammalian brain and critically evaluates its significance in the context of brain repair. Emphasis is on the comparison between persistent and injury-induced neurogenesis and regulators and outcomes of neuronal and glial production in damaged/diseased brains. Several important issues, in particular, those that remain controversial, as well as the recently emerging idea that consider stem/progenitor cells as injury sensors and responders are also highlighted. Finally, prospects of future research aiming at utilizing endogenous repair capacity for therapy for various neurological disorders are discussed.
The early development of the mammalian forebrain involves the massive proliferation of the ventricular zone cells lining the lateral ventricles. A remnant of this highly proliferative region persists into adult life, where it is known as the subependymal layer. We examined the proliferation kinetics and fates of the mitotically active cells in the subependyma of the adult mouse. The medial edge, the lateral edge, and the dorsolateral corner of the subependymal layer of the rostral portion of the lateral ventricle each contained mitotically active cells, but the dorsolateral region had the highest percentage of bromodeoxyuridine (BrdU)-labeled cells per unit area. Repeated injections of BrdU over 14 hr revealed a proliferation curve for the dorsolateral population with a growth fraction of 33%, indicating that 33% of the cells in this subependymal region make up the proliferating population. The total cell cycle time in this population was approximately 12.7 hr, with an S-phase of 4.2 hr. To examine the fate of these proliferating cells, we injected low concentrations of a replication-deficient, recombinant retrovirus directly into the lateral ventricles of adult mice for uptake by mitotically active subependymal cells. Regardless of the survival time postinjection (10 hr, 1 d, 2 d, or 8 d), the number of retrovirally labeled cells per clone remained the same (1 or 2 cells/clone). This suggests that one of the progeny from each cell division dies. Moreover, the clones remained confined to the subependyma and labeled cells were not seen in the surrounding brain tissue. Thus, while 33% of the dorsolateral subependymal cells continue to proliferate in adult life, the fate of the postmitotic progeny is death.
Several cell adhesion molecules involved in neuron-neuron and neuron-glia interactions have been identified in our laboratory and have been shown to undergo cell surface modulation. In the case of the neural cell adhesion molecule (N-CAM), it has been found that during development the molecule is converted from a microheterogeneous embryonic (E) form containing 30 gm of sialic acid/100 gm of polypeptide to several distinct adult (A) forms containing one third as much of this sugar. In vitro analyses indicate that this change is accompanied by a 4-fold increase in the rate of N-CAM homophilic binding. In the present study of the mouse and the chick, alterations of N-CAMs occurring as a result of E----A conversion, prevalence modulation, and changes in antigenic state during the development of different neural regions were analyzed by the use of highly specific polyclonal and monoclonal antibodies combined with anatomical dissection and several new quantitative assays. We made the following observations. The relative concentration of N-CAM changed during development, with the highest concentration (2.8 times the adult level) occurring around the perinatal period. Each brain region followed a similar pattern of change but according to a different time schedule. While conversion from the E to the A forms of N-CAM occurred mainly during the first 3 postnatal weeks in mice, the relative conversion rates were distinctly different in various neural tissues. The extreme examples are dorsal root ganglia, which already displayed the A forms at birth, and the diencephalon and tectal region, which still retained some E forms in the adult. A cephalocaudal maturation gradient of E----A conversion was observed in the spinal cord and dorsal root ganglia. Differences in the antigenic determinants of N-CAMs from different neural tissues were detected by two independent monoclonal antibodies. Finally, in some adult neural tissues, one of the three A forms was found to be dominant. These results establish that during development there are definite quantitative and qualitative differences among N-CAMs from various neural tissues. The data are consistent with the hypothesis that alterations in the relative amounts and forms of N-CAM play major roles in neural morphogenesis, possibly by altering the rates of adhesion among neurons and their processes.
The hippocampus is one of the few areas of the rodent brain that continues to produce neurons postnatally. Neurogenesis reportedly persists in rats up to 11 months of age. Using bromodeoxyuridine (BrdU) labeling, the present study confirms that in the adult rat brain, neuronal progenitor cells divide at the border between the hilus and the granule cell layer (GCL). In adult rats, the progeny of these cells migrate into the GCL and express the neuronal markers NeuN and calbindin-D28k. However, neurogenesis was drastically reduced in aged rats. Six-to 27-month-old Fischer rats were injected intraperitoneally with BrdU to detect newborn cells in vivo and to follow their fate in the dentate gyrus. When killed 4-6 weeks after BrdU labeling, 12- to 27-month-old rats exhibited a significant decline in the density of BrdU-positive cells in the granule cell layer compared with 6-month-old controls. Decreased neurogenesis in aging rats was accompanied by reduced immunoreactivity for poly-sialylated neural cell adhesion molecule, a molecule that is involved in migration and process elongation of developing neurons. When animals were killed immediately (12 hr) after BrdU injection, significantly fewer labeled cells were observed in the GCL and adjacent subgranular zone of aged rats, indicative of a decrease in mitotic activity of neuronal precursor cells. The reduced proliferation was not attributable to a general aged-related metabolic impairment, because the density of BrdU-positive cells was not altered in other brain regions with known mitotic activity (e.g., hilus and lateral ventricle wall). The decline in neurogenesis that occurs throughout the lifespan of an animal can thus be related to a decreasing proliferation of granule cell precursors.
The adult mammalian subventricular zone (SVZ) contains stem cells that give rise to neurons and glia. In vivo, SVZ progeny migrate 3-8 mm to the olfactory bulb, where they form neurons. We show here that the SVZ of the lateral wall of the lateral ventricles in adult mice is composed of neuroblasts, glial cells, and a novel putative precursor cell. The topographical organization of these cells suggests how neurogenesis and migration are integrated in this region. Type A cells had the ultrastructure of migrating neuronal precursors. These cells were arranged as chains parallel to the walls of the ventricle and were polysialylated neural adhesion cell molecule- (PSA-NCAM), TuJ1- (beta-tubulin), and nestin-positive but GFAP- and vimentin-negative. Chains of Type A cells were ensheathed by two ultrastructurally distinct astrocytes (Type B1 and B2) that were GFAP-, vimentin-, and nestin-positive but PSA-NCAM- and TuJ1-negative. Type A and B2 (but not B1) cells incorporated [3H]thymidine. The most actively dividing cell in the SVZ corresponded to Type C cells, which had immature ultrastructural characteristics and were nestin-positive but negative to the other markers. Type C cells formed focal clusters closely associated with chains of Type A cells. Whereas Type C cells were present throughout the SVZ, they were not found in the rostral migratory stream that links the SVZ with the olfactory bulb. These results suggest that chains of migrating neuroblasts in the SVZ may be derived from Type C cells. Our results provide a topographical model for the adult SVZ and should serve as a basis for the in vivo identification of stem cells in the adult mammalian brain.
Neurogenesis in the dentate gyrus of adult rodents is regulated by NMDA receptors, adrenal steroids, environmental stimuli, and seizures. To determine whether ischemia affects neurogenesis, newly divided cells in the dentate gyrus were examined after transient global ischemia in adult gerbils. 5-Bromo-2'-deoxyuridine-5'-monophosphate (BrdU) immunohistochemistry demonstrated a 12-fold increase in cell birth in the dentate subgranular zone 1-2 weeks after 10 min bilateral common carotid artery occlusions. Two minutes of ischemia did not significantly increase BrdU incorporation. Confocal microscopy demonstrated that BrdU immunoreactive cells in the granule cell layer colocalized with neuron-specific markers for neuronal nuclear antigen, microtubule-associated protein-2, and calbindin D28k, indicating that the newly divided cells migrated from the subgranular zone into the granule cell layer and matured into neurons. Newborn cells with a neuronal phenotype were first seen 26 d after ischemia, survived for at least 7 months, were located only in the granule cell layer, and comprised approximately 60% of BrdU-labeled cells in the granule cell layer 6 weeks after ischemia. The increased neurogenesis was not attributable to entorhinal cortical lesions, because no cell loss was detected in this region. Ischemic preconditioning for 2 min, which protects CA1 neurons against subsequent ischemic damage, did not prevent increased neurogenesis in the granule cell layer after a subsequent severe ischemic challenge. Thus, ischemia-induced dentate neurogenesis is not attributable to CA1 neuronal loss. Enhanced neurogenesis in the dentate gyrus may be a compensatory adaptive response to ischemia-associated injury and could promote functional recovery after ischemic hippocampal injury.
The adult derivatives of the embryonic forebrain germinal zones consist of two morphologically distinct cell layers surrounding the lateral ventricles: the ependyma and the subependyma. Cell cycle analyses have revealed that at least two proliferating populations exist in this region, one that is constitutively proliferating and one that is relatively quiescent and thought to include the endogenous adult neural stem cells. Earlier studies demonstrated that specific dissection of the region surrounding the lateral ventricles was necessary for the in vitro isolation of multipotent, self-renewing neural stem cells. However, in these studies, the ependymal layer was not physically separated from the subependymal layer to identify the specific adult laminar localization of the neural stem cells around the lateral ventricles. To determine which cellular compartment in the adult forebrain contained the neural stem cells, we isolated and cultured the ependyma separately from the subependyma and tested for the presence of neural stem cells using the in vitro neurosphere assay. We demonstrate that the ependymal cells can proliferate in vitro to form sphere-like structures. However, the ependymal cells generating spheres do not have the ability to self-renew (proliferate to form secondary spheres after dissociation) nor to produce neurons, but rather only seem to generate glial fibrillary acidic protein-positive ependymal cells when plated under differentiation conditions in culture. On the other hand, a subpopulation of subependymal cells do possess the self-renewing and multipotential characteristics of neural stem cells. Therefore, the adult forebrain neural stem cell resides within the subependymal compartment.
During development of the mammalian brain, both neurons and glia are generated from multipotent neural stem cells. Although neurogenesis ceases in most areas at birth, stem cells continue to generate neurons within the subventricular zone and hippocampal dentate gyrus throughout adult life. In this work, we provide the first demonstration that precursors native to regions of the adult brain that generate only glia can also generate neurons after exposure to FGF-2 in vitro. When progenitors isolated from hippocampal tissue were directly compared with cells isolated from the neocortex, both populations were able to initiate a program of proliferative neurogenesis. Genetic marking and lineage analysis showed that a majority of the cells able to generate neurons were multipotent precursors; however, progeny from these precursors acquired the competence to differentiate into neurons only after exposure to FGF-2. The recruitment of similar FGF-2-responsive cells from the adult optic nerve, a structure well isolated from the neurogenic zones within the brain, confirmed that neuron-competent precursors naturally exist in widely divergent tissues of the adult brain.
The mechanisms underlying cerebral microvascular perfusion deficit resulting from occlusion of the middle cerebral artery (MCA) require elucidation. We, therefore, tested the hypothesis that intravascular fibrin deposition in situ directly obstructs cerebral microcirculation and that local changes in type 1 plasminogen activator inhibitor (PAI-1) gene expression contribute to intravascular fibrin deposition after embolic MCA occlusion. Using laser-scanning confocal microscopy (LSCM) in combination with immunofluorescent staining, we simultaneously measured in three dimensions the distribution of microvascular plasma perfusion deficit and fibrin(ogen) immunoreactivity in a rat model of focal cerebral embolic ischemia (n = 12). In addition, using in situ hybridization and immunostaining, we analyzed expression of PAI-1 in ischemic brain (n = 13). A significant (p < 0.05) reduction of cerebral microvascular plasma perfusion accompanied a significant (p < 0.05) increase of intravascular and extravascular fibrin deposition in the ischemic lesion. Microvascular plasma perfusion deficit and fibrin deposition expanded concomitantly from the subcortex to the cortex during 1 and 4 hr of embolic MCA occlusion. Three-dimensional analysis revealed that intravascular fibrin deposition directly blocks microvascular plasma perfusion. Vascular plugs contained erythrocytes, polymorphonuclear leukocytes, and platelets enmeshed in fibrin. In situ hybridization demonstrated induction of PAI-1 mRNA in vascular endothelial cells in the ischemic region at 1 hr of ischemia. PAI-1 mRNA significantly increased at 4 hr of ischemia. Immunohistochemical staining showed the same pattern of increased PAI-1 antigen in the endothelial cells. These data demonstrate, for the first time, that progressive intravascular fibrin deposition directly blocks cerebral microvascular plasma perfusion in the ischemic region during acute focal cerebral embolic ischemia, and upregulation of the PAI-1 gene in the ischemic lesion may foster fibrin deposition through suppression of fibrinolysis.
The existence of multipotent progenitor populations in the adult forebrain has been widely studied. To extend this knowledge to the adult spinal cord we have examined the proliferation, distribution, and phenotypic fate of dividing cells in the adult rat spinal cord. Bromodeoxyuridine (BrdU) was used to label dividing cells in 13- to 14-week-old, intact Fischer rats. Single daily injections of BrdU were administered over a 12 d period. Animals were killed either 1 d or 4 weeks after the last injection of BrdU. We observed frequent cell division throughout the adult rodent spinal cord, particularly in white matter tracts (5-7% of all nuclei). The majority of BrdU-labeled cells colocalized with markers of immature glial cells. At 4 weeks, 10% of dividing cells expressed mature astrocyte and oligodendroglial markers. These data predict that 0.75% of all astrocytes and 0.82% of all oligodendrocytes are derived from a dividing population over a 4 week period. To determine the migratory nature of dividing cells, a single BrdU injection was given to animals that were killed 1 hr after the injection. In these tissues, the distribution and incidence of BrdU labeling matched those of the 4 week post injection (pi) groups, suggesting that proliferating cells divide in situ rather than migrate from the ependymal zone. These data suggest a higher level of cellular plasticity for the intact spinal cord than has previously been observed and that glial progenitors exist in the outer circumference of the spinal cord that can give rise to both astrocytes and oligodendrocytes.
In the present study, we examined the temporal and spatial expression profiles of GFAP mRNA and protein in a focal cerebral ischemia model with ischemic injury confined to the cerebral cortex in the right middle cerebral artery (MCA) territory. Northern blot analysis showed a respective 5.5-fold and 7.2-fold increase in the GFAP mRNA in the ischemic right MCA cortex in rats subjected to 30-min (mild) or 60-min (severe) ischemia followed by 72-hr reperfusion. The GFAP mRNA signal remained elevated up to 2-week reperfusion. Interestingly, increased GFAP mRNA signal was clearly demonstrated for the first time in the left MCA cortex. A significant 1.5-fold and 5-fold increase was observed after 72-hr reperfusion following mild and severe ischemia, respectively. However, unlike the ischemic right MCA cortex, this induction was transient in the non-ischemic left MCA counterpart. In situ hybridization studies further revealed characteristic spatial induction profile following mild vs. severe ischemia. In mild ischemia, following 24-hr reperfusion, increase in GFAP mRNA was observed mainly within the ischemic right MCA cortex. Following 72-hr reperfusion, GFAP mRNA signal was observed in virtually the entire ischemic cortex, particularly the amygdala region, then gradually reduced and restricted to right MCA territory and subcortical thalamic nucleus following 2-week reperfusion. On the other hand, in severe ischemia, following 24-hr reperfusion increased GFAP mRNA signal was observed in area surrounding right MCA territory (infarct region) and outer cortical layers within the right MCA territory. Following 72-hr reperfusion, no signal was detected within right MCA cortex; however, increased GFAP signal was detected throughout the remaining ipsilateral cortex and subcortical region, as well as the contralateral cerebral cortex. GFAP mRNA signals then gradually reduced its intensity and was restricted to area surrounding necrosis and ipsilateral thalamic nucleus following 2-week reperfusion. GFAP-like immunoreactivity was also detected in area expressing GFAP mRNA. It is very likely that de novo synthesis was responsible for this increase. In summary, increased GFAP signal was noted in both ipsilateral and contralateral cerebral following mild and severe ischemia. Although the temporal induction profile for mild vs. severe ischemia was similar, the spatial induction profile was different. The mechanism leading to this differential induction and their physiological and functional significance are not clear at present. It is very likely that some local factors may involve, nevertheless, the detailed mechanisms remain to be fully explored.
The thin lamina between the hippocampal hilus and granule cell layer, or subgranule zone (SGZ), is an area of active proliferation within the adult hippocampus known to generate new neurons throughout adult life. Although the neuronal fate of many dividing cells is well documented, little information is available about the phenotypes of cells in S-phase or how the dividing cells might interact with neighboring cells in the process of neurogenesis. Here, we make the unexpected observation that dividing cells are found in dense clusters associated with the vasculature and roughly 37% of all dividing cells are immunoreactive for endothelial markers. Most of the newborn endothelial cells disappear over several weeks, suggesting that neurogenesis is intimately associated with a process of active vascular recruitment and subsequent remodeling. The present data provide the first evidence that adult neurogenesis occurs within an angiogenic niche. This environment may provide a novel interface where mesenchyme-derived cells and circulating factors influence plasticity in the adult central nervous system.
Neural stem cells are maintained in the subventricular zone (SVZ) of the adult mammalian brain. Here, we review the cellular organization of this germinal layer and propose lineage relationships of the three main cell types found in this area. The majority of cells in the adult SVZ are migrating neuroblasts (type A cells) that continue to proliferate. These cells form an extensive network of tangentially oriented pathways throughout the lateral wall of the lateral ventricle. Type A cells move long distances through this network at high speeds by means of chain migration. Cells in the SVZ network enter the rostral migratory stream (RMS) and migrate anteriorly into the olfactory bulb, where they differentiate into interneurons. The chains of type A cells are ensheathed by slowly proliferating astrocytes (type B cells), the second most common cell type in this germinal layer. The most actively proliferating cells in the SVZ, type C, form small clusters dispersed throughout the network. These foci of proliferating type C cells are in close proximity to chains of type A cells. We discuss possible lineage relationships among these cells and hypothesize which are the neural stem cells in the adult SVZ. In addition, we suggest that interactions between type A, B, and C cells may regulate proliferation and initial differentiation within this germinal layer. © 1998 John Wiley & Sons, Inc. J Neurobiol 36: 234–248, 1998
To determine whether fibrillary astrocytes proliferate in response to brain injury, cells identified as fibrillary astrocytes using immunoperoxidase technique for glial fibrillary acidic protein (GFAP) were examined for uptake of radiolabeled thymidine by autoradiography. In injured mouse brain, autoradiographic label was present over nuclei of immunoreactive fibrillary astrocytes in the lesion site 1 hr following injection of radiolabeled thymidine. The data suggest that fibrillary astrocytes which are sufficiently differentiated to accumulate GFAP retain the capacity to proliferate in response to injury.
The response of the brain to injury involves the accumulation of a large number of proliferating cells at the site of damage. Neither the identity nor the origin of these cells is unequivocally established. We have investigated this proliferative response after unilateral kainic acid lesions in the striatum of adult mice by labeling with tritiated thymidine (3H-thy) or bromodeoxyuridine (Brdu) to identify cells passing through S-phase. Labeled cells were seen only ipsilaterally in coronal section and extended laterally from the subependymal zone lining the lateral ventricle, through the striatal kainic acid injection site and into the cortex. The maximum proliferative response, after a single pulse of 3H-thy administered 4 h before sacrifice, was seen 6 days post-lesion close to the injection site. The proliferating cells were not astrocytes, as neither 3H-thy- nor Brdu-labeled cells were double-labeled with antisera to glial fibrillary acidic protein after the lesion. Animals given 3H-thy on day 3 post-lesion and then sacrificed on days 4, 5 or 6 post-lesion showed cumulative increases in the number of proliferating cells at the injection site with no increases in the surrounding tissue. We hypothesized that this reflected the presence of 2 sources of labeled cells: (1) an exogenous population of blood cells coming in through the broken blood-brain barrier and accumulating at the injection site and (2) endogenous cells (microglia) which are normally quiescent in the adult but proliferate in response to injury. By irradiating adult mice (900 rads) we attempted to selectively remove the blood stem cell precursors which gave rise to the proposed exogenous source of cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Cell number and proliferation of reactive astrocytes were studied quantitatively in the stabbed cerebral cortex of adult mice, using immunohistochemistry for glial fibrillary acidic protein (GFAP) and [3H]thymidine autoradiography. GFAP-positive astrocytes increased in cell number gradually from 24 to 96 h after stabbing, and their immunoreactivity became intense. The maximum number of GFAP-positive cells was about 4.5 times normal in the layers II-VI of the cortex, whereas it was only 1.5 times normal in the layer I (molecular layer). In contrast to the gradual increase in cell number, no GFAP-positive astrocytes were labeled with [3H]thymidine prior to 48 h after stabbing, in either the layer I or the layers II-VI. Then 3-5% of them were labeled at 72 and 96 h, but very few again after 6 days. By injecting [3H]thymidine successively for 6 days after stabbing, only 17% of GFAP-positive astrocytes of the layer I or the layers II-VI were labeled. These results reveal that, in the cortical layers II-VI, many GFAP-negative source cells initially express much more GFAP-antigen without proliferation and change into GFAP-positive reactive astrocytes. Proliferation of reactive astrocytes is not the major factor for the marked increase in number of them. The cortical layer I would have few GFAP-negative source cells for reactive astrocytes. These source cells may be protoplasmic astrocytes.
The proliferation of glial cells outside the subependymal layer of the lateral ventricle as well as of endothelial cells was studied autoradiographically in the brain of the adult and untreated mouse. The double labeling method with 3H- and 14C-thymidine was applied in order to show experimentally the existence of a DNA synthesis phase (S phase) and to measure its duration. Adult mice received a first injection of 14C-thymidine, two or four hours later a second injection of 3H-thymidine and were sacrificed one hour after the last injection by perfusion fixation. Double layer autoradiographs were made from serial sections of the region from the corpus callosum/commissura anterior up to the corpus callosum/commissura fornicis ventralis in order to register purely 3H-, doubly 3H- and 14C-, and purely 14C-labeled nuclei. From the ratio of all 3H-labeled cells with and without 14C to the purely 3H-labeled cells a DNA synthesis phase of 9.4 ± 0.5 hours for glial cells and one of 11.0 ± 2.2 hours for endothelial cells was obtained. Based on the first appearance of labeled mitoses and labeled pairs of glial cells after injections of labeled thymidine the G2 phase was estimated to be < three hours and G2 + M about five hours. The duration of the measured S phase as well as the appearance of labeled mitoses about three hours after application of labeled thymidine are very similar to these cycle parameters in many other somatic cells in different kinds of animals. This has led to the conclusion that a well-defined DNA synthesis phase with doubling of the DNA content and a successive mitosis also exists in glial and endothelial cells of the adult mouse brain.
It has long been thought that mature oligodendrocytes in the adult mammalian central nervous system (CNS) are post-mitotic and are unable to proliferate in response to injury. The implications of this have been profound, because it has been suggested that this failure of oligodendrocytes to undergo mitosis is perhaps one of the reasons for the failure of the human CNS to undergo remyelination after demyelinating disease. This is in contrast with the normal peripheral nervous system in which there is consistent remyelination, and brisk Schwann cell mitosis. Although it has recently been shown that oligodendrocytes can be regenerated following some specific instances of demyelination, it has long been accepted that unlike mature astrocytes and microglia (macrophages), oligodendrocytes do not proliferate in response to general conditions damaging the nervous system. Here we show that mature oligodendrocytes in adult animals, as well as astrocytes and microglia, are able to respond to damage in the CNS following trauma by incorporating tritiated thymidine into their nuclei.
This review summarizes the current scientific literature concerning the ependymal lining of the cerebral ventricles of the brain with an emphasis on selective barrier function and protective roles for the common ependymal cell. Topics covered include the development, morphology, protein and enzyme expression including reactive changes, and pathology. Some cells lining the neural tube are committed at an early stage to becoming ependymal cells. They serve a secretory function and perhaps act as a cellular/axonal guidance system, particularly during fetal development. In the mature mammalian brain ependymal cells possess the structural and enzymatic characteristics necessary for scavenging and detoxifying a wide variety of substances in the CSF, thus forming a metabolic barrier at the brain-CSF interface.
N-CAM is abundantly expressed in the nervous system in the form of numerous structural variants with characteristic distribution patterns and functional properties. N-CAM-180, the variant having the largest cytoplasmic domain, is expressed by all neurons. The N-CAM-180-specific exon 18 has been deleted to generate homozygous mice unable to express this N-CAM form. The most conspicuous mutant phenotype was in the olfactory bulb, where granule cells were both reduced in number and disorganized. In addition, precursors of these cells were found to be accumulated at their origin in the subependymal zone at the lateral ventricle. Analysis of the mutant in this region suggests that the mutant phenotype involves a defect in cell migration, possibly through specific loss of the polysialylated form of N-CAM-180, which is expressed in the migration pathway. Subtle but distinct abnormalities also were observed in other regions of the brain.
Focal brain ischemia induced in rats by occlusion of an intracranial artery is a widely used paradigm of human brain infarct. Details of the structural changes that develop in either the human or the rat brain at various times after occlusion of an intracranial artery are incompletely characterized. We studied, in 48 adult Wistar rats, structural alterations involving the cerebral hemisphere ipsilateral to an arterial occlusion, at intervals ranging from 30 min to 7 days. Microscopic changes developed over time in separate areas of the corresponding cerebral hemisphere in a predictable pattern, appearing as small lesions in the preoptic area (30 minutes), enlarging to involve the striatum, and finally involving the cerebral cortex. Two types of neuronal responses were noted according to the time elapsed; acute changes (up to 6 hours) included scalloping, shrinkage, and swelling, whereas delayed changes (eosinophilia and karyolysis) appeared later (> or = 12 hours). Three types of astrocytic responses were noted. 1) Cytoplasmic disintegration occurred in the preoptic area at a time and in a place where neurons appeared minimally injured. 2) Nuclear and cytoplasmic swelling were prominent responses in the caudoputamen and cerebral cortex at a time when neurons showed minimal alterations. 3) Increased astrocytic glial fibrillary acidic protein reactivity was noted at the interface between the lesion and the surrounding brain tissue after 4 to 6 hours. The gross pattern of the brain lesion and the maturation of neuronal changes typical of a brain infarct have a predictable progression. Focal brain ischemia of up to 6-hour duration does not induce coagulation necrosis.
The developmental fates of subventricular zone (SVZ) cells of the postnatal rat forebrain were determined by retroviral-mediated gene transfer and immunolabeling for glial antigens. A beta-galactosidase-containing retrovirus injected stereotactically into the SVZ infected small, immature cells. By 28 days post-injection labeled cells had appeared in both gray and white matter of the ipsilateral hemisphere. White matter contained labeled oligodendrocytes, but few astrocytes, while neocortex and striatum contained both glial types, often appearing in tightly knit clusters. An analysis after simultaneously injecting alkaline phosphatase- and beta-galactosidase-containing retroviruses showed that cells in each cortical cluster were related. Most clusters contained a single cell type, but approximately 15% contained both astrocytes and oligodendrocytes. These observations strongly suggest that a single SVZ cell can differentiate into both glial types.
Transplantation studies have been used to show that tangential migration of olfactory bulb interneuron precursors is retarded in NCAM-mutant mice, and that this defect reflects loss of NCAM polysialic acid (PSA). In contrast, radial migration of cells within the bulb did not require PSA. Reciprocal transplantations between wild-type and mutant mice have revealed that the mutation affects the in vivo migration environment in the subventricular zone, and not movement of individual cells. However, in vitro migration of the cells into a PSA-negative collagen matrix environment was also PSA dependent. The surprisingly similar results obtained in the in vivo and in vitro environments is consistent with the observation that migration of subventricular cells occurs as streams of closely apposed cells in which the PSA-positive cells appear to serve as their own migration substrate.
The subventricular zone (SVZ) bordering the lateral ventricle is one of the few regions of adult brain that contains dividing cells. These cells can differentiate into neurons in vivo after migration into the olfactory bulb and in vitro in the presence of appropriate growth factors. Little is known, however, about the fate of these cells in vivo after brain injury in adults. We examined cell number and expression of differentiation markers in the SVZ of adult rats after cortical lesions. Aspiration lesions of the sensorimotor cortex in adult rats induced a transient doubling of the number of cells in the SVZ at the level of the striatum without consistent increases in bromodeoxyuridine-labeled cells. Immunoreactivity to the polysialylated neural cell adhesion molecule, expressed by the majority of cells of the SVZ during development, increased dramatically after lesion. In contrast, immunolabeling for molecules found in mature neurons and glia did not increase in the SVZ after lesion, and immunoreactivity for growth factors that induce differentiation of SVZ cells in vitro decreased or remained undetectable, suggesting that lack of appropriate growth factor expression may contribute to the lack of differentiation of the newly accumulated cells in vivo. The data reveal that cells of the SVZ are capable of plasticity in the adult rat after brain injury in vivo and that the newly accumulated cells retain characteristics seen during development.
This paper is a continuation of parts I (history, methods and cell kinetics) and II (clinical applications and carcinogenesis) published previously (Dolbeare, 1995 Histochem. J. 27, 339, 923). Incorporation of bromodeoxyuridine (BrdUrd) into DNA is used to measure proliferation in normal, diseased and injured tissue and to follow the effect of growth factors. Immunochemical detection of BrdUrd can be used to determine proliferative characteristics of differentiating tissues and to obtain birth dates for actual differentiation events. Studies are also described in which BrdUrd is used to follow the order of DNA replication in specific chromosomes, DNA replication sites in the nucleus and to monitor DNA repair. BrdUrd incorporation has been used as a tool for in situ hybridization experiments.
We developed a mouse model of embolic focal cerebral ischemia, in which a fibrin-rich clot was placed at the origin of the middle cerebral artery (MCA) in C57BL/6J mice (n = 31) and B6C3 mice (n = 10). An additional three non-embolized C57BL/6J mice were used as a control. Embolus induction, cerebral vascular perfusion deficit, and consequent ischemic cell damage were confirmed by histopathology, immunohistochemistry, laser confocal microscopy, and regional cerebral blood flow (rCBF) measurements. Reduction in rCBF and cerebral infarct were not detected in the control animals. An embolus was found in all C57BL/6J and B6C3 mice at 24 hours after injection of a clot. Regional CBF in the ipsilateral parietal cortex decreased to 23% (P < 0.05) and 17% (P < 0.05) of preembolization levels immediately and persisted for at least 1 hour in C57BL/6J mice (n = 6) and in B6C3 mice (n = 3), respectively. A significant decrease of rCBF was accompanied by a corresponding reduction of plasma perfusion in the ipsilateral MCA territory. Neurons exhibited marked reduction in microtubule-associated protein-2 immunostaining coincident with the area of perfusion deficit. The percent infarct volume was 30.3% +/- 13.4% for C57BL/6J mice (n = 17), and 38.3% +/- 15.3% for B6C3 mice (n = 7) at 24 hours after embolization. This model of embolic ischemia is relevant to thromboembolic stroke in humans and may be useful to investigate embolic cerebral ischemia in the genetically altered mouse and for evaluation of antiembolic therapies.
We developed a new model of embolic cerebral ischemia in the rat which provides a reproducible and predictable infarct volume within the territory supplied by the middle cerebral artery (MCA). The MCA was occluded by an embolus in Wistar rats (n = 71). An additional three non-embolized rats were used as a control. Cerebral blood flow (CBF) was measured by means of laser Doppler flowmetry (LDF) and perfusion weighted imaging (PWI) before and after embolization. The evolution of the lesion was monitored by diffusion weighted imaging (DWI). Cerebral vascular perfusion patterns were examined using laser scanning confocal microscopy. Infarct volumes were measured on hematoxylin and eosin (H&E) stained coronal sections. The lodgment of the clot at the origin of the MCA and the ischemic cell damage were examined using light microscopy. Regional CBF in the ipsilateral parietal cortex decreased to 43 +/- 4.1% (P < 0.05) of preischemic levels (n = 10). Confocal microscopic examination revealed a reduction of cerebral plasma perfusion in the ipsilateral MCA territory (n = 6). MRI measurements showed a reduction in CBF and a hyperintensity DWI encompassing the territory supplied by the MCA (n = 4). An embolus was found in all rats at 24 h after embolization. The infarct volume as a percentage of the contralateral hemisphere was 32.5 +/- 3.31% at 24 h (n = 20), 33.0 +/- 3.6% at 48 h (n = 13), and 34.5 +/- 4.74% at 168 h (n = 12) after embolization. This model of embolic focal cerebral ischemia results in ischemic cell damage and provides a reproducible and predictable infarct volume. This model is relevant to thromboembolic stroke in humans and may be useful in documenting the safety and efficacy of fibrinolytic intervention and in investigating therapies complementary to antithrombotic therapy.
New neurons are continuously added in specific regions of the adult mammalian central nervous system. These neurons are derived from multipotent stem cells whose identity has been enigmatic. In this work, we present evidence that ependymal cells are neural stem cells. Ependymal cells give rise to a rapidly proliferating cell type that generates neurons that migrate to the olfactory bulb. In response to spinal cord injury, ependymal cell proliferation increases dramatically to generate migratory cells that differentiate to astrocytes and participate in scar formation. These data demonstrate that ependymal cells are neural stem cells and identify a novel process in the response to central nervous system injury.
Bone marrow progenitor cells have been shown to contribute to a small proportion of cells in nonhematopoietic tissues including the brain. In the acute unilateral middle cerebral artery occlusion model in spontaneously hypertensive rats following male-to-female bone marrow transplantation, we present data suggesting that 55% more marrow-derived cells, in general, and 161% more GFAP-positive astrocytes, in particular, migrate preferentially to the ischemic cortex than to the contralateral non-ischemic hemisphere. In addition to their biological significance, our findings could have therapeutic implications. Marrow-derived progenitor cells could potentially be used as vehicles for ex vivo gene transfer to the brain.
In the developing postnatal cerebral cortex, protracted generation of glia and neurons occurs and precise matching of local cell types is needed for the functional organization of regional microdomains characteristic of complex CNS tissues. Recent studies have suggested that multipotent progenitors play an important role in neural lineage elaboration during neurogenesis and gliogenesis after migration from paramedian generative zones. The presence of a separate reservoir of cerebral cortical multipotent cells under strict local environmental regulation would provide an appropriate mechanism for terminal developmental sculpting and for reconstitution of regional cellular pools after injury. We have isolated distinct pools of EGF- and bFGF-responsive multipotent progenitors from the postnatal mammalian cerebral cortex independent of the subventricular zone. These progenitor populations are under tight environmental regulation by specific hierarchies of cytokine subclasses that program the progressive elaboration of intermediate lineage-restricted progenitors and differentiated type I and II astrocytes, myelinating oligodendrocytes and neuronal subtypes that express specific neuromodulatory proteins. Neural lineage development from these cortical multipotent progenitors is a graded developmental process involving sequential induction of specific cytokine receptors, acquisition of factor responsiveness and complex lineage interdependence. The cortical multipotent progenitor pathways program the elaboration of neural lineage species with distinct cellular response properties when compared with analogous species derived from subventricular zone progenitors, indicating that the cortical multipotent cells contribute to the establishment of lineage diversity within the developing cortical cortex. In addition, the cortical multipotent cells generate dynamic intermediate progenitor pools that utilize temporally-coded environmental cues to alter neural fate decisions. These cumulative observations suggest that postnatal cerebral cortical multipotent cells represent a novel set of progenitor pathways necessary for normal mammalian cortical maturation, and may have important implications for our understanding of a wide variety of neuropathological conditions and for the development of more effective regenerative strategies to combat these pervasive neurological disorders.
Neuronal connections and cortical maps are continuously remodeled by our experience. Knowledge of the potential capabilityof the brain to compensate for lesions is a prerequisite for optimal stroke rehabilitation strategies. Experimental focal cortical lesions induce changes in adjacent cortex and in the contralateral hemisphere. Neuroimaging studies in stroke patients indicate altered poststroke activation patterns, which suggest some functional reorganization. To what extent functional imaging data correspond to outcome data needs to be evaluated. Reorganization may be the principle process responsible for recovery of function after stroke, but what are the limits, and to what extent can postischemic intervention facilitate such changes? Postoperative housing of animals in an enriched environment can significantly enhance functional outcome and can also interact with other interventions, including neocortical grafting. What role will neuronal progenitor cells play in future rehabilitation-stimulated in situ or as neural replacement? And what is the future for blocking neural growth inhibitory factors? Better knowledge of postischemic molecular and neurophysiological events, and close interaction between basic and applied research, will hopefully enable us to design rehabilitation strategies based on neurobiological principles in a not-too-distant future.
Several studies support the hypothesis that after stroke, specific features of brain function revert to those seen at an early stage of development, with the subsequent process of recovery recapitulating ontogeny in many ways. Many clinical characteristics of stroke recovery resemble normal development, particularly in the motor system. Consistent with this, brain-mapping studies after an ischemic insult suggest re-emergence of childhood organizational patterns: recovery being associated with a return to adult patterns. Experimental animal studies demonstrate increased levels of developmental proteins, particularly in the area surrounding an infarct, suggesting an active process of reconditioning in response to cerebral ischemia. Understanding the patterns of similarity between normal development and stroke recovery might be of value in its treatment.
PSA-NCAM, polysialylated form of the neu-ronal cell adhesion molecule ; RMS, rostral migratory stream
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OB, olfactory bulb; PSA-NCAM, polysialylated form of the neu-ronal cell adhesion molecule ; RMS, rostral migratory stream ;
SVZ, subventricular zone ; VZ, ventric-ular zone. NSC 4962 16-7-01 Cyaan Magenta Geel Zwart www
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SGZ, subgranular zone; SVZ, subventricular zone ; VZ, ventric-ular zone. NSC 4962 16-7-01 Cyaan Magenta Geel Zwart www.elsevier.com/locate/neuroscience Neuroscience Vol. 105, No. 1, pp. 33^41, 2001 ß 2001 IBRO. Published by Elsevier Science Ltd Printed in Great Britain. All rights reserved. PII: S
Targeting of marrow-derived astrocytes to the ischemic brain Multipotent progenitor cells in the adult dentate gyrus Progression from ischemic injury to infarct following middle cerebral artery occlusion in the rat
- M A Eglitis
- D Dawson
- K W Park
- M M Mouradian
- F H Gage
- G Kempermann
- T D Palmer
- D A Peterson
- J Ray
- J H Garcia
- Y Yoshida
- H Chen
- Y Li
- Z G Zhang
- J Lian
- S Chen
- M Chopp
Eglitis, M.A., Dawson, D., Park, K.W., Mouradian, M.M., 1999. Targeting of marrow-derived astrocytes to the ischemic brain. NeuroReport 10, 1289^1292. Gage, F.H., Kempermann, G., Palmer, T.D., Peterson, D.A., Ray, J., 1998. Multipotent progenitor cells in the adult dentate gyrus. J. Neurobiol. 36, 249^266. Garcia, J.H., Yoshida, Y., Chen, H., Li, Y., Zhang, Z.G., Lian, J., Chen, S., Chopp, M., 1993. Progression from ischemic injury to infarct following middle cerebral artery occlusion in the rat. Am. J. Pathol. 142, 623^635. Garcia-Verdugo, J.M., Doetsch, F., Wichterle, H., Lim, D.A., Alvarez-Buylla, A., 1998. Architecture and cell types of the adult subventricular zone: in search of the stem cells. J. Neurobiol. 36, 234^248.
Progression from ischemic injury to infarct following middle cerebral artery occlusion in the rat
- Garcia
Vascular niche for adult hippocampal neurogenesis
- Palmer
Multipotent progenitor cells in the adult dentate gyrus
- Gage