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EGFR expression is increased and colocalized on astrocytes and progenitors at the lesion site after SCI. A, Western blots of naive (Ctl) and injured spinal cord tissues showing a single band of 175 kDa for EGFR, with-tubulin (50 kDa) as a loading control. B, EGFR expression is increased and remains high after spinal cord injury. ANOVA, p 0.001; *p 0.05, **p 0.01 versus Ctl (post hoc tests). C, Wide-field fluorescence image of uninjured spinal cord white matter showing EGFR expression predominately in gray matter, including the neuropil throughout the ventral horn (VH; C) and punctate staining in lateral white matter (LWM; C). D–D, Confocal microscopy shows EGFR expression in profiles throughout naive white matter (red; D, arrows) is colocalized with NF axons (D, blue; D, magenta profiles) but colocalization with astrocytes (GFAP, green) is rare. E, During the first week after injury, EGFR expression is upregulated primarily in the spared white matter, with minimal expression in the lesion core (*). E–E, High-power confocal image enlargement of white box in E shows profiles in register reflecting EGFR (E) and GFAP (E) astrocyte processes. F–F, Confocal micrograph at the lesion border at 3 DPI depicting EGFR profiles (F ) colocalized with BLBP cells of astrocyte lineage (F, F, white arrowheads). G, Confocal projection through a 10-m-thick slice showing BLBP/EGFR astrocytes at the lesion border; a colabeled cell (white arrow) projected along the right and bottom borders of the image (yellow arrows). H, Examples of BLBP/EGFR cells and z-stack from spared white matter at 3 DPI. I, J, Confocal micrographs of the central canal rostral to the injury epicenter with BLBP/EGFR cells at 3 and 7 DPI. Scale bars: C, E, 50 m; C, D, F, H, I, 10 m; C, G, H, I, 20 m.
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Astrocytes are both detrimental and beneficial for repair and recovery after spinal cord injury (SCI). These dynamic cells are primary contributors to the growth-inhibitory glial scar, yet they are also neuroprotective and can form growth-supportive bridges on which axons traverse. We have shown that intrathecal administration of transforming growt...
Citations
... The lack of significant difference in VAS scores between the groups before the treatment indicates that any observed post-treatment differences are likely due to the therapeutic effects of rhEGF rather than preexisting conditions. 16,17 The subsequent significant improvements in the VAS scores at all post-treatment timepoints in the observation group underline the sustained benefits of rhEGF over time. ...
Scarring following oral and maxillofacial trauma can have significant aesthetic and functional repercussions. Recombinant human epidermal growth factor (rhEGF) has emerged as a potential therapeutic agent to enhance wound healing and minimise scar formation. This retrospective study analysed data from March 2020 to June 2023 at a single institution. A total of 105 patients were divided into a control group ( n = 70) receiving standard treatment and an observation group ( n = 35) receiving standard treatment plus rhEGF. The primary outcomes were the incidence of scar hyperplasia and infection rates, with the secondary outcome being scar aesthetics measured by the visual analogue scale (VAS). No significant differences were found in baseline characteristics between the two groups. The observation group showed a significant reduction in scar hyperplasia (14.3% vs. 57.1%, χ ² = 20.98, p < 0.01) and infection rates (5.7% vs. 21.4%, χ ² = 4.246, p < 0.05) compared to the control group. VAS scores indicated a superior aesthetic outcome in the observation group at all post‐treatment timepoints ( p < 0.01). rhEGF treatment in oral and maxillofacial trauma patients resulted in favourable healing outcomes and reduced scar formation, improving aesthetic results. These findings highlight the therapeutic potential of rhEGF and underscore the need for larger‐scale trials to further investigate its benefits.
... Astrocytes not only mount responses that protect the structure and function of neurons and synapses but also are involved in or are capable of ensuring the maintenance of oligodendrocytes and their myelin [132][133][134] through a variety of released factors in normal and pathological conditions, as well as of supporting oligodendrocyte precursor cells [nerve/glial antigen 2 (NG2)] in the face of several types of damage [135,136]. Accordingly, despite the neurite growth inhibitory properties of fully declared "glial scars" in severe injury, reactive astrocytes in milder forms of injury, whether scarring or non-scarring, actually can promote remyelination and de novo formation of oligodendrocytes [137][138][139]. This protective function can include enhancing the survival of NG2 cells against oxidative stress, starvation, or oxygen-glucose deprivation through mechanisms mediated by the mitogen-activated protein kinase (MAPK) kinase (MEK)/ extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Ak strain transforming factor (Akt) intracellular pathways [140], while other studies in vitro have shown that erythropoietin (EPO) released by astrocytes can protect NG2 cells subjected to hypoxia, by acting on EPO receptors expressed by NG2 cells [141]. ...
... Another pathway that may be relevant to the promotion of axon growth and myelination is the binding of TGF-α to EGF receptor (EGFR) in astrocytes, which leads to increased invasiveness of these cells while increasing penetration and axon outgrowth in the lesion [137][138][139]. Another factor which is also upregulated in dysfunctional or injured states CNTF, has been shown to promote myelination in vitro [144]. ...
Astrocytes not only support neuronal function with essential roles in synaptic neurotransmission, action potential propagation, metabolic support, or neuroplastic and developmental adaptations. They also respond to damage or dysfunction in surrounding neurons and oligodendrocytes by releasing neurotrophic factors and other molecules that increase the survival of the supported cells or contribute to mechanisms of structural and molecular restoration. The neuroprotective responsiveness of astrocytes is based on their ability to sense signals of degeneration, metabolic jeopardy, and structural damage, and on their aptitude to locally deliver specific molecules to remedy threats to the molecular and structural features of their cellular partners. To the extent that neuronal and other glial cell disturbances are known to occur in affective disorders, astrocyte responsiveness to those disturbances may help to better understand the roles astrocytes play in affective disorders. The astrocytic sensing apparatus supporting those responses involves receptors for neurotransmitters, purines, cell adhesion molecules, and growth factors. Astrocytes also share with the immune system the capacity to respond to cytokines released upon neuronal damage. In addition, in response to specific signals, astrocytes release unique factors such as clusterin or humanin that have been shown to exert potent neuroprotective effects. Astrocytes integrate the signals above to further deliver structural lipids, remove toxic metabolites, stabilize the osmotic environment, normalize neurotransmitters, provide antioxidant protection, facilitate synaptogenesis, and act as barriers to contain varied deleterious signals, some of which have been described in brain regions relevant to affective disorders and related animal models. Since various injurious signals that activate astrocytes have been implicated in different aspects of the etiopathology of affective disorders, particularly in relation to the diagnosis of depression, potentiating the corresponding astrocyte neuroprotective responses may provide additional opportunities to improve or complement available pharmacological and behavioral therapies for affective disorders.
... We found that IL-4/G-CSF polarized BMNΦ stimulate explanted neurons to grow neurites, in part, by an IGF-1R/ EGFR dependent pathway. Activation of the phosphatidylinositol-directly induced astrocytes to acquire a phenotype that supported axon regeneration 45 . ...
The adult central nervous system (CNS) possesses a limited capacity for self-repair. Severed CNS axons typically fail to regrow. There is an unmet need for treatments designed to enhance neuronal viability, facilitate axon regeneration, and ultimately restore lost neurological functions to individuals affected by traumatic CNS injury, multiple sclerosis, stroke, and other neurological disorders. Here we demonstrate that both mouse and human bone marrow (BM) neutrophils, when polarized with a combination of recombinant interleukin (IL)-4 and granulocyte-colony stimulating factor (G-CSF), upregulate alternative activation markers and produce an array of growth factors, thereby gaining the capacity to promote neurite outgrowth. Moreover, adoptive transfer of IL-4/G-CSF polarized BM neutrophils into experimental models of CNS injury triggered substantial axon regeneration within the optic nerve and spinal cord. These findings have far-reaching implications for the future development of autologous myeloid cell-based therapies that may bring us closer to effective solutions for reversing CNS damage.
... TGF-a exhibits neurotropic properties that protect neurons from various neurotoxic insults. 54 In this study, TGF-a peaked early and showed a steady decrease, which could reflect an immediate protective response to the primary brain injury. ...
Cerebral protein profiling in traumatic brain injury (TBI) is needed to better comprehend secondary injury pathways. Cerebral microdialysis (CMD), in combination with the proximity extension assay (PEA) technique, has great potential in this field. By using PEA, we have previously screened >500 proteins from CMD samples collected from TBI patients. In this study, we customized a PEA panel prototype of 21 selected candidate protein biomarkers, involved in inflammation (13), neuroplasticity/-repair (six), and axonal injury (two). The aim was to study their temporal dynamics and relation to age, structural injury, and clinical outcome. Ten patients with severe TBI and CMD monitoring, who were treated in the Neurointensive Care Unit, Uppsala University Hospital, Sweden, were included. Hourly CMD samples were collected for up to 7 days after trauma and analyzed with the 21-plex PEA panel. Seventeen of the 21 proteins from the CMD sample analyses showed significantly different mean levels between days. Early peaks (within 48 h) were noted with interleukin (IL)-1β, IL-6, IL-8, granulocyte colony-stimulating factor, transforming growth factor alpha, brevican, junctional adhesion molecule B, and neurocan. C-X-C motif chemokine ligand 10 peaked after 3 days. Late peaks (>5 days) were noted with interleukin-1 receptor antagonist (IL-1ra), monocyte chemoattractant protein (MCP)-2, MCP-3, urokinase-type plasminogen activator, Dickkopf-related protein 1, and DRAXIN. IL-8, neurofilament heavy chain, and TAU were biphasic. Age (above/below 22 years) interacted with the temporal dynamics of IL-6, IL-1ra, vascular endothelial growth factor, MCP-3, and TAU. There was no association between radiological injury (Marshall grade) or clinical outcome (Extended Glasgow Outcome Scale) with the protein expression pattern. The PEA method is a highly sensitive molecular tool for protein profiling from cerebral tissue in TBI. The novel TBI dedicated 21-plex panel showed marked regulation of proteins belonging to the inflammation, plasticity/repair, and axonal injury families. The method may enable important insights into complex injury processes on a molecular level that may be of value in future efforts to tailor pharmacological TBI trials to better address specific disease processes and optimize timing of treatments.
... Consistent with these findings, stimulation of astrocyte migration at the lesion site by TGFα administration enhanced axon growth into the lesion core following spinal cord contusion at T9 (White et al., 2008(White et al., , 2011. Axons within the lesion were found to associate with astrocytes that expressed high levels of both growth-supportive laminin and the growthinhibitory CSPG neurocan (White et al., 2008). ...
... A substantial number of NG2 cells differentiate into scar-forming astrocytes after spinal cord contusion (Hackett et al., 2016(Hackett et al., , 2018, raising the possibility that NG2 cell-derived astrocytes at the lesion may have a higher capacity to facilitate axon regeneration (Hackett et al., 2018). Finally, after spinal cord injury, axons that grow into the lesion often associate with astrocytes that express laminin, an extracellular matrix molecule known to promote axon growth (Frisen et al., 1995;Ma et al., 2004;White et al., 2008White et al., , 2011. Fibronectin produced by astrocytes can also enhance axon regeneration in mature white matter (Tom et al., 2004). ...
Understanding the regulation of axon growth after injury to the adult central nervous system (CNS) is crucial to improve neural repair. Following acute focal CNS injury, astrocytes are one cellular component of the scar tissue at the primary lesion that is traditionally associated with inhibition of axon regeneration. Advances in genetic models and experimental approaches have broadened knowledge of the capacity of astrocytes to facilitate injury-induced axon growth. This review summarizes findings that support a positive role of astrocytes in axon regeneration and axon sprouting in the mature mammalian CNS, along with potential underlying mechanisms. It is important to recognize that astrocytic functions, including modulation of axon growth, are context-dependent. Evidence suggests that the local injury environment, neuron-intrinsic regenerative potential, and astrocytes’ reactive states determine the astrocytic capacity to support axon growth. An integrated understanding of these factors will optimize therapeutic potential of astrocyte-targeted strategies for neural repair.
... [12][13][14] Recent studies, however, have indicated that astrocytes are required for successful neuronal survival in the CNS. 4,9,12,[15][16][17] Therefore, achieving a proper balance, rather than completely suppressing the astrocytes, may be critical for appropriate neuronal repair. ...
Purpose:
The purpose of this study was to investigate the roles of ciliary neurotrophic factor (CNTF) on the protective effects of astrocytes on retinal ganglion cells (RGCs).
Methods:
Primary RGCs were isolated from neonatal rats. Oxidative stress was induced, and the effects of co-culture with astrocytes and CNTF treatment on RGCs were evaluated. The pathways commonly altered by astrocytes and CNTF were investigated. Effects of each pathway were investigated using pathway inhibitors against PI3K/AKT, JAK/STAT, and MAPK/ERK. RNA sequencing was performed to identify the genes upregulated and downregulated by CNTF treatment.
Results:
Astrocytes improved the viability and increased β3-tubulin expression in RGCs. The concentration of CNTF increased in the RGC-astrocyte co-culture medium. The protective effects of astrocytes were abolished by neutralization with the anti-CNTF antibody; thus, CNTF may play an important role in the effects mediated by astrocytes. Furthermore, CNTF treatment alone enhanced the viability and β3-tubulin expression of RGCs and increased the population of viable RGCs under oxidative stress. The PI3K/AKT pathway was associated with both RGC viability and β3-tubulin expression. However, the JAK/STAT pathway increased the viability of RGCs, whereas the MAPK/ERK pathway was associated with β3-tubulin expression. RNA sequencing revealed the CNTF-upregulated genes associated with response to DNA damage and downregulated genes associated with photoreceptor cell differentiation.
Conclusions:
Our data revealed protective effects of astrocyte-derived CNTF on RGCs. In addition, we showed that multiple pathways exert these protective effects and identified the novel genes involved. These results may be helpful in developing treatments for RGC injury.
... The primary injury consists of irreversible tissue damage and necrosis caused by external mechanical injury [3,4], after which secondary pathological processes such as oxidative stress, inflammation, excitotoxicity, edema, spinal cord ischemia, electrolyte imbalance, microglia activation, astrocyte proliferation and spinal cord ischemia can further exacerbate the initial injury [3][4][5][6]. These factors, together with reactive gliosis, ultimately drive dense astrocytic scar formation [7,8], which produces factors that inhibit functional recovery following SCI and impairs the plasticity and regeneration of spinal cord [9][10][11]. However, the mechanisms governing spinal cord injury and associated healing processes necessitate further clarification. ...
G protein-coupled receptors (GPCRs) are fundamental mediators of a wide array of processes including proliferation, immune cell function and neural signaling. GPR120 is a GPCR present within the spleen, lungs, adipose tissue and intestines that is stimulated by endogenous free fatty acids (FFAs). Whether GPR120 is expressed or functionally relevant in the central nervous system (CNS), however, has yet to be directly examined. Herein, a rat spinal cord injury (SCI) model was established and used to explore the expression of GPR120 in SCI. Western blotting and immunohistochemical staining revealed that GPR120 was detectable in the spinal tissues of healthy rats, and the levels rose following SCI and reached the peak on day 3, whereafter they declined to basal levels within two weeks post-SCI. Dual immunofluorescent staining revealed detectable GPR120 expression in astrocytes, microglia and a limited number of neurons. Following SCI, GPR120 upregulation was primarily evident in astrocytes. After injury, colocalization between GPR120 and the proliferative marker PCNA was also detected. Together, these results offer new insights regarding the dynamics of spinal cord GPR120 expression and suggest that it may play important roles in the CNS following SCI.
... TGFα has been reported to promote neuronal survival and enhance neurogenesis and angiogenesis in models of stroke and neurodegenerative diseases [28][29][30][31][32]. Moreover, TGFα stimulates astrocytes to polarize into a phenotype that supports neurite outgrowth after spinal cord injury [33]. Microglia-derived TGFα also regulates astrocyte activity and limits pathogenic glial actions during experimental autoimmune encephalomyelitis [34]. ...
Background
As a sequel of ischemic stroke, selective neuronal loss (SNL) mediated by activated microglia and consequential neuroinflammation affects the salvageable peri-infarct area (PIA) and hampers the functional recovery following reperfusion therapy. Recent evidence indicates that inhibition of sulfonylurea receptor 1-transient receptor potential M4 (SUR1-TRPM4) exerts a robust protective effect against inflammation. Hence, we hypothesized that blocking SUR1-TRPM4 channels reduced SNL after brain ischemia in the PIA.
Methods
Mice subjected to temporary middle cerebral artery occlusion (tMCAO) for 1 h and reperfusion for 24 h were adopted to mimic the pathophysiological changes of ischemic stroke. Gene expression, neuronal apoptosis, and protein content were tested by RNA-sequencing, TUNEL staining, Western blot, respectively.
Results
After tMCAO, abundant neuronal apoptosis appeared in the PIA, with remarkable up-regulation and co-localization of SUR1 and TRPM4. Blocking the SUR1-TRPM4 channel by glibenclamide (GLB, a SUR inhibitor) and Trpm4 gene deletion (Trpm4−/−) distinctly alleviated apoptotic neurons in the PIA. To explore the potential mechanism of blocking SUR1-TRPM4, we compared gene expression in brain tissues of Trpm4−/− and wild-type mice after tMCAO modeling using RNA-sequencing and identified 217 differentially expressed genes. Among them, the expression of Tgfα was significantly higher in Trpm4−/− mice compared with that in wild-type mice after tMCAO. GLB treatment significantly increased the expression of TGFα in microglia, as validated by Western Blot and immunofluorescence staining. Moreover, intracerebroventricular injection of recombinant TGFα significantly alleviated the neuronal loss in the PIA and improved neurological outcome after tMCAO. In vitro, we subjected BV-2 microglia cells to oxygen-glucose deprivation or lipopolysaccharide stimulation and found significant up-regulation and co-localization of SUR1 and TRPM4, while blocking SUR1-TRPM4 with GLB and 9-phenanthrol (9-Phe, a TRPM4 inhibitor) increased the expression and release of TGFα by activating the CaMKII/CREB pathway. BV-2 microglia derived conditioned medium after oxygen-glucose deprivation or lipopolysaccharide stimulation induced apoptosis of SH-SY5Y cells, which could be inhibited by applying GLB and 9-Phe on BV-2. Furthermore, direct application of recombinant TGFα alleviated neuronal apoptosis mediated by BV-2 microglia conditioned medium.
Conclusions
Collectively, our findings indicate that blocking SUR1-TRPM4 in microglia alleviates SNL, probably by up-regulating the expression and release of TGFα.
... Astrocytes, therefore, have long been associated with the failure of axon regeneration in the CNS, and studies have attempted to eliminate or inhibit astrocytes to promote axon regeneration after CNS injury [16,[18][19][20]. However, accumulating evidence now supports the concept that astrocytes are required for successful neuronal survival and axon regeneration in the CNS [12,13,16,19,[21][22][23][24][25]. In this review, we will outline the evidence that reactive gliosis is required for successful neural repair in the CNS and suggest that harnessing the function of macroglia in the retina could promote survival and axon regeneration of RGCs. ...
... Considering the evidence that the activation of STAT3 and PI3K/Akt pathways may be involved in the generation of A2 astrocytes, pharmacological stimulation of these pathways may lead to the increased population of A2 astrocytes that can promote neuronal survival and axon regeneration after CNS injury. The members of epidermal growth factor (EGF) family are known to activate these pathways via activation of epidermal growth factor receptors (EGFRs), and there is growing evidence that EGFR signaling can harness astrocytes to promote neuronal survival and axon regeneration in the CNS [21,22,[66][67][68][69][70]. ...
... Currently, it is unclear whether EGFR signaling is involved in inhibition of axon regeneration. However, in support of the possibility that EGFR signaling could support axon regeneration in the CNS, a couple of studies have shown that TGF-α can promote axon regeneration after SCI [21,22]. Based on previous evidence that astrocytes can promote neuroprotection and may support axonal growth after injury, White et al. hypothesized that endogenous astrocytes could be harnessed to support axon regeneration with proper stimulation after SCI, and they intrathecally administered TGF-α in adult mice for two weeks following the injury [21]. ...
Astrocytes have been associated with the failure of axon regeneration in the central nervous system (CNS), as it undergoes reactive gliosis in response to damages to the CNS and functions as a chemical and physical barrier to axon regeneration. However, beneficial roles of astrocytes have been extensively studied in the spinal cord over the years, and a growing body of evidence now suggests that inducing astrocytes to become more growth-supportive can promote axon regeneration after spinal cord injury (SCI). In retina, astrocytes and Müller cells are known to undergo reactive gliosis after damage to retina and/or optic nerve and are hypothesized to be either detrimental or beneficial to survival and axon regeneration of retinal ganglion cells (RGCs). Whether they can be induced to become more growth-supportive after retinal and optic nerve injury has yet to be determined. In this review, we pinpoint the potential molecular pathways involved in the induction of growth-supportive astrocytes in the spinal cord and suggest that stimulating the activation of these pathways in the retina could represent a new therapeutic approach to promoting survival and axon regeneration of RGCs in retinal degenerative diseases.
... The non-neural woundhealing process involves epithelial cells that undergo a transition to a mesenchymal phenotype that includes extensive cytoskeletal remodeling, degrading cell-cell junctions, and altering of electron cryomicroscopy (ECM) (Haensel and Dai, 2018). This epithelial-to-mesenchymal transition (EMT) is promoted by signaling pathways, such as JAK/STAT, epidermal growth factor (EGF), and tumor necrosis factor alpha (TNF-a) (Jere et al., 2017;Stone et al., 2016;Yan et al., 2010), which also promote astrogliosis after injury (Li et al., 2011;Okada et al., 2006;Wanner et al., 2013;White et al., 2011). In addition to wound healing, EMT is a well-studied process in neural development and cancer metastasis (Nieto et al., 2016). ...
... The full effect of the targeted loss of astrocytic Zeb2 is likely underestimated in this study, because the knockout of Zeb2 in astrocytes was not complete. Previous studies that genetically modified astrocytes have typically used constitutive pro-moters, such as Gfap, to drive recombination, because the loss of the target genes did not noticeably disrupt neural development (Anderson et al., 2016;Brambilla et al., 2005;Okada et al., 2006;Sahni et al., 2010;Wanner et al., 2013;White et al., 2011). By contrast, Zeb2 has established developmental roles in the nervous system (Epifanova et al., 2019;Hegarty et al., 2015;McKinsey et al., 2013;Miquelajauregui et al., 2007;Van de Putte et al., 2003), and a previous study that deleted Zeb2 with constitutively active Cre recombinase expressed under the control of a Gfap promoter reported the onset of severe tremors and defects in balance control approximately two weeks after birth (He et al., 2018). ...
The astrocytic response to injury is characterized on the cellular level, but our understanding of the molecular mechanisms controlling the cellular processes is incomplete. The astrocytic response to injury is similar to wound-healing responses in non-neural tissues that involve epithelial-to-mesenchymal transitions (EMTs) and upregulation in ZEB transcription factors. Here we show that injury-induced astrogliosis increases EMT-related genes expression, including Zeb2, and long non-coding RNAs, including Zeb2os, which facilitates ZEB2 protein translation. In mouse models of either contusive spinal cord injury or transient ischemic stroke, the conditional knockout of Zeb2 in astrocytes attenuates astrogliosis, generates larger lesions, and delays the recovery of motor function. These findings reveal ZEB2 as an important regulator of the astrocytic response to injury and suggest that astrogliosis is an EMT-like process, which provides a conceptual connection for the molecular and cellular similarities between astrogliosis and wound-healing responses in non-neural tissue.
