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Partnership of Schwann cells and axons during regeneration. Neurofilament (NF; green), S100β (S100; red) and Hoechst (blue) labelling of axons and Schwann cells at times shown after sciatic nerve transection. A-E: the front edges of the regenerating axons are covered by Schwann cell processes at 4, 5 and 7 days (d). At days 4 and 5, Schwann cell processes (red) form a ‘ball-like’ structure at the tip of axon bundles (A, B and E) whereas at 7d (C and D), fine Schwann cell processes appear to proceed in front of the axons. D: higher magnification of boxed area shown in panel C to show Schwann cell leading processes proceeding in front of axons and guiding axons across the nerve bridge. E and F: higher magnification from the boxed area of panel B. G: higher magnification of boxed area in panel F showing the axonal bundles, white arrows in panel G indicate apparent individual axons. Red arrows in D and H show elongated Schwann cell bodies held by axons crossing the nerve bridge. Upon further axon growth in panel H at 10d, elongated Schwann cell bodies can clearly be seen held by axons in the nerve bridge. In all the panels, the proximal side is up and distal to the bottom of the picture.
Source publication
Peripheral nerve trauma triggers a well characterised sequence of events both proximal and distal to the site of injury. Axons distal to the injury degenerate, Schwann cells convert to a repair supportive phenotype and macrophages enter the nerve to clear myelin and axonal debris. Following these events, axons must regrow through the distal part of...
Citations
... Termed "digital pathology", this innovation streamlines the extraction, management, and interpretation of patient histopathological data. Its primary objective is to tackle the common challenges faced by traditional pathologists by providing the capability to access and share scanned slide images, which facilitates remote clinical case diagnosis [4,5]. ...
Simple Summary
This review highlights the profound impact of digital pathology (DP) and artificial intelligence (AI) on advancing cancer diagnosis and treatment. DP enables pathologists to access, analyze, and share high-resolution images, enhancing diagnostic accuracy and fostering remote collaboration. AI further refines cancer diagnosis by automating tasks and facilitating spatial analysis of the tumor microenvironment (TME), leading to the discovery of novel biomarkers. Immunoscore (IS), an AI-assisted immune assay, exhibits robust potential in improving cancer diagnosis, prognosis, and treatment selection, surpassing traditional staging systems. Integrating DP and AI, particularly the IS biomarker, into clinical practice promises to enhance personalized cancer therapy. The research underscores a pivotal leap forward in pathology, stressing the imperative of incorporating AI-driven technologies for improved cancer patient care and outcomes. This exploration aims to provide insights into the transformative potential of DP in cancer management, influencing the clinical community towards more effective diagnostic and therapeutic strategies.
Abstract
(1) Background: Digital pathology (DP) is transforming the landscape of clinical practice, offering a revolutionary approach to traditional pathology analysis and diagnosis. (2) Methods: This innovative technology involves the digitization of traditional glass slides which enables pathologists to access, analyze, and share high-resolution whole-slide images (WSI) of tissue specimens in a digital format. By integrating cutting-edge imaging technology with advanced software, DP promises to enhance clinical practice in numerous ways. DP not only improves quality assurance and standardization but also allows remote collaboration among experts for a more accurate diagnosis. Artificial intelligence (AI) in pathology significantly improves cancer diagnosis, classification, and prognosis by automating various tasks. It also enhances the spatial analysis of tumor microenvironment (TME) and enables the discovery of new biomarkers, advancing their translation for therapeutic applications. (3) Results: The AI-driven immune assays, Immunoscore (IS) and Immunoscore-Immune Checkpoint (IS-IC), have emerged as powerful tools for improving cancer diagnosis, prognosis, and treatment selection by assessing the tumor immune contexture in cancer patients. Digital IS quantitative assessment performed on hematoxylin–eosin (H&E) and CD3+/CD8+ stained slides from colon cancer patients has proven to be more reproducible, concordant, and reliable than expert pathologists’ evaluation of immune response. Outperforming traditional staging systems, IS demonstrated robust potential to enhance treatment efficiency in clinical practice, ultimately advancing cancer patient care. Certainly, addressing the challenges DP has encountered is essential to ensure its successful integration into clinical guidelines and its implementation into clinical use. (4) Conclusion: The ongoing progress in DP holds the potential to revolutionize pathology practices, emphasizing the need to incorporate powerful AI technologies, including IS, into clinical settings to enhance personalized cancer therapy.
... Accumulating evidence indicates that without the guidance of Schwann cells, regenerating axons cannot pass through the nerve gap (Dun & Parkinson, 2015;Torigoe et al., 1996). Researchers have reported that regenerating axons fail to cross the sciatic F I G U R E 6 Rap1 is involved in the Gastric inhibitory peptide (GIP)-dependent migration of Schwann cells. ...
Schwann cells play an essential role in peripheral nerve regeneration by generating a favorable microenvironment. Gastric inhibitory peptide/gastric inhibitory peptide receptor (GIP/GIPR) axis deficiency leads to failure of sciatic nerve repair. However, the underlying mechanism remains elusive. In this study, we surprisingly found that GIP treatment significantly enhances the migration of Schwann cells and the formation of Schwann cell cords during recovery from sciatic nerve injury in rats. We further revealed that GIP and GIPR levels in Schwann cells were low under normal conditions, and significantly increased after injury demonstrated by real‐time reverse transcription‐polymerase chain reaction (RT‐PCR) and Western blot. Wound healing and Transwell assays showed that GIP stimulation and GIPR silencing could affect Schwann cell migration. In vitro and in vivo mechanistic studies based on interference experiment revealed that GIP/GIPR might promote mechanistic target of rapamycin complex 2 (mTORC2) activity, thus facilitating cell migration; Rap1 activation might be involved in this process. Finally, we retrieved the stimulatory factors responsible for GIPR induction after injury. The results indicate that sonic hedgehog (SHH) is a potential candidate whose expression increased upon injury. Luciferase and chromatin immunoprecipitation (ChIP) assays showed that Gli3, the target transcription factor of the SHH pathway, dramatically augmented GIPR expression. Additionally, in vivo inhibition of SHH could effectively reduce GIPR expression after sciatic nerve injury. Collectively, our study reveals the importance of GIP/GIPR signaling in Schwann cell migration, providing a therapeutic avenue toward peripheral nerve injury. image
... As previously described, sciatic nerves were processed for the whole mount staining procedure (Dun and Parkinson, 2015). Briefly, after fixation, nerves were washed three times in PTX (1% Triton X-100 (Sigma, T9284) in phosphate-buffered saline (PBS)) for 10 min each time after the fixation. ...
... Mounting nerves in CitiFluor (Agar Scientific, AGR1320) were performed for confocal imaging following the clearance. Images were taken using Zeiss LSM 700 confocal microscope (Dun and Parkinson, 2015). ...
... The site of the nerve crush injury can be easily distinguished by fluorescent microscopy using a ×4 magnifying objective (crush point marked by the square). The Hoechst stain may also identify the crush site, where the proliferation of SCs can be seen at the crush point (Dun and Parkinson, 2015). Neurofilament was used to stain the regenerating axons through the sciatic nerve, while S100β was used to stain the cytoplasm of SCs. ...
Introduction: Crush injuries occur from acute traumatic nerve compression resulting in different degrees of neural damage leading to permanent functional deficits. Recently, we have shown that administration of Fraction B (FB) derived from catfish epidermal secretions accelerates healing of damaged nerve in a sciatic nerve crush injury, as it ameliorates the neurobehavioral deficits and enhances axonal regeneration, as well as protects spinal neurons and increases astrocytic activity and decreasing GAP-43 expression. The present study aimed to investigate the role of FB treatment on the apoptotic pathway in the neuroregeneration of the sciatic nerve crush injury.
Methods: Male Wistar rats were randomly assigned into five groups: (I) SHAM, (II) CRUSH, (III) CRUSH + (1.5 mg/kg) FB, (IV) CRUSH + (3 mg/kg) FB, and (V) CRUSH + (4.5 mg/kg) FB. Rats underwent sciatic nerve crush surgery, followed by treatment with FB administered intraperitoneally (IP) daily for two weeks and then sacrificed at the end of the fourth week.
Results: FB improved the recovery of neurobehavioral functions with a concomitant increase in axonal regeneration and neuroprotective effects on spinal cord neurons following crush injury. Further, FB enhanced Schwann cells (SCs) proliferation with a significant increase in myelin basic protein expression. FB-treated animals demonstrated higher numbers of neurons in the spinal cord, possibly through ameliorating oxidative DNA damage and alleviating the mitochondrial-dependent apoptotic pathway by inhibiting the release of cytochrome c and the activation of caspase-3 in the spinal cord neurons.
Conclusion: FB alleviates the neurodegenerative changes in the lumbar spinal cord neurons and recovers the decrease in the neuronal count through its anti-apoptotic and DNA antioxidative properties.
... In the distal injured nerve, Schwann cells deprived of axonal contact proliferate, upregulate the synthesis and release of a variety of neurotrophic factors and basal lamina components that create an appropriate microenvironment for regenerating axons . Accumulating evidence indicates that following injury, regenerating axons are unable to cross a peripheral nerve gap without Schwann cell guidance at their migrating growth front (Cattin et al., 2015;Dun and Parkinson, 2015;Chen et al., 2019). Napoli et al. (2012) indicated that Schwann cells dedifferentiate to a progenitor-like state and proliferate, forming bands of Büngner upon which axons can regrow with a growth factor after peripheral nerve injury. ...
We previously prepared nerve growth factor poly-lactide co-glycolid sustained-release microspheres to treat rat sciatic nerve injury using the small gap sleeve technique. Multiple growth factors play a synergistic role in promoting the repair of peripheral nerve injury; as a result, in this study, we added basic fibroblast growth factors to the microspheres to further promote nerve regeneration. First, in an in vitro biomimetic microenvironment, we developed and used a drug screening biomimetic microfluidic chip to screen the optimal combination of nerve growth factor/basic fibroblast growth factor to promote the regeneration of Schwann cells. We found that 22.56 ng/mL nerve growth factor combined with 4.29 ng/mL basic fibroblast growth factor exhibited optimal effects on the proliferation of primary rat Schwann cells. The successfully prepared nerve growth factor-basic fibroblast growth factor-poly-lactide-co-glycolid sustained-release microspheres were used to treat rat sciatic nerve transection injury using the small gap sleeve bridge technique. Compared with epithelium sutures and small gap sleeve bridging alone, the small gap sleeve bridging technique combined with drug-free sustained-release microspheres has a stronger effect on rat sciatic nerve transfection injury repair at the structural and functional level.
... Tiling and z-stack functions were used to image whole nerve. Maximum intensity projection was used to pull the data from all Z-stacks and represent it as a 2-D image [50,51]. ...
Background
Traumatic peripheral nerve injury (TPNI) is a major medical problem with no universally accepted pharmacologic treatment. We hypothesized that encapsulation of pro-angiogenic erythropoietin (EPO) in amphiphilic PLGA-PEG block copolymers could serve as a local controlled-release drug delivery system to enhance neurovascular regeneration after nerve injury.
Methods
In this study, we synthesized an EPO-PLGA-PEG block copolymer formulation. We characterized its physiochemical and release properties and examined its effects on functional recovery, neural regeneration, and blood vessel formation after sciatic nerve crush injury in mice.
Results
EPO-PLGA-PEG underwent solution-to-gel transition within the physiologically relevant temperature window and released stable EPO for up to 18 days. EPO-PLGA-PEG significantly enhanced sciatic function index (SFI), grip strength, and withdrawal reflex post-sciatic nerve crush injury. Furthermore, EPO-PLGA-PEG significantly increased blood vessel density, number of junctions, and myelinated nerve fibers after injury.
Conclusion
This study provides promising preclinical evidence for using EPO-PLGA-PEG as a local controlled-release treatment to enhance functional outcomes and neurovascular regeneration in TPNI.
... Successful nerve regeneration requires an orchestrated series of events that implies a switch of neurons to a pro-regenerative state and important changes at the distal stump, that lead to Wallerian degeneration and the creation of a permissive milieu for axonal regeneration, where Schwann cells, immune cells, endothelial cells, and fibroblasts play an important role supporting axonal regrowth (Mcdonald et al. 2006;Allodi et al. 2012;Kim et al. 2013;Dun and Parkinson 2015;Cattin and Lloyd 2016;Roballo and Bushman 2019). Despite the potential of peripheral nerves to regenerate, successful functional recovery is usually limited after severe nerve lesions (Navarro et al. 2007). ...
Decellularized nerve allografts are an alternative to autograft for repairing severe nerve injuries, since they have higher availability and do not induce rejection. In this study, we have assessed the regenerative potential of a novel decellularization protocol for human and rat nerves for repairing nerve resections, compared to the gold standard autograft. A 15-mm gap in the sciatic nerve was repaired with decellularized rat allograft (DC-RA), decellularized human xenograft (DC-HX), or fresh autograft (AG). Electrophysiology tests were performed monthly to evaluate muscle reinnervation, whereas histologi- cal and immunohistochemical analyses of the grafts were evaluated at 4 months. A short-term study was also performed to compare the differences between the two decellularized grafts (DC-RA and DC-HX) in early phases of regeneration. The decellularization process eliminated cellularity while preserving the ECM and endoneurial tubules of both rat and human nerves. Higher amount of reinnervation was observed in the AG group compared to the DC-RA group, while only half of the animals of the DC-HX showed distal muscle reinnervation. The number of regenerating myelinated axons in the mid- graft was similar between AG and DC-RA and lower in DC-HX graft, but significantly lower in both DC grafts distally. At short term, fibroblasts repopulated the DC-RA graft, supporting regenerated axons, whereas an important fibrotic reaction was observed around DC-HX grafts. In conclusion, the decellularized allograft sustained regeneration through a long gap in the rat although at a slower rate compared to the ideal autograft, whereas regeneration was limited or even failed when using a decellularized xenograft
... In modern clinical practice, the advancement of technology enables the development of highly efficient, high-throughput and high-resolution (up to 0.23-0.25 µm/pixel) WSI devices that can digitize traditional glass slides into whole-slide images (WSIs) that can be remotely viewed on a display monitor for remote diagnosis of cases [42,43]. This digital process is termed "digital pathology" and has additional benefits compared to traditional pathology, including the ease of quickly and securely sharing pathology WSIs worldwide with other pathologists for second opinions, as well as providing a better view of the tissue with additional annotation and measurement tools while allowing for rapid access to archived cases without loss of quality [44]. ...
The implementation of DP will revolutionize current practice by providing pathologists with additional tools and algorithms to improve workflow. Furthermore, DP will open up opportunities for development of AI-based tools for more precise and reproducible diagnosis through computational pathology. One of the key features of AI is its capability to generate perceptions and recognize patterns beyond the human senses. Thus, the incorporation of AI into DP can reveal additional morphological features and information. At the current rate of AI development and adoption of DP, the interest in computational pathology is expected to rise in tandem. There have already been promising developments related to AI-based solutions in prostate cancer detection; however, in the GI tract, development of more sophisticated algorithms is required to facilitate histological assessment of GI specimens for early and accurate diagnosis. In this review, we aim to provide an overview of the current histological practices in AP laboratories with respect to challenges faced in image preprocessing, present the existing AI-based algorithms, discuss their limitations and present clinical insight with respect to the application of AI in early detection and diagnosis of GI cancer.
... These transgenic mice have been used, in combination with markers specific for different cell types, to show that upon nerve damage, polarized blood vessels direct the migrating cords of SCs across the bridge (Cattin et al., 2015). Moreover, whole-mount staining of PLP-EGFP muscles provides a useful research model to follow the time course of peripheral nerve regeneration (Dun & Parkinson, 2015) (Figure 5a). Indeed, after nerve damage, sciatic nerves can be collected and stained with antibodies specific for axons (against neurofilaments) or growth marker such as GAP43 or SG10 to evaluate the rate of regeneration and how this rate correlates with SC activation. ...
... Sciatic nerve compression interrupts all axons while preserving connective tissue sheaths and SCs, allowing regeneration to occur in 3-4 weeks. Conversely, the complete transection of the nerve disrupts axons, connective sheaths and basal lamina: also in this case regeneration takes place, but the process is less efficient and functional recovery is generally poor (Dun & Parkinson, 2015;Nguyen et al., 2002). ...
Schwann cells (SCs) are fundamental components of the peripheral nervous system (PNS) of all vertebrates and play essential roles in development, maintenance, function, and regeneration of peripheral nerves. There are distinct populations of SCs including: (1) myelinating SCs that ensheath axons by a specialized plasma membrane, called myelin, which enhances the conduction of electric impulses; (2) non-myelinating SCs, including Remak SCs, which wrap bundles of multiple axons of small caliber, and perysinaptic SCs (PSCs), associated with motor axon terminals at the neuromuscular junction (NMJ). All types of SCs contribute to PNS regeneration through striking morphological and functional changes in response to nerve injury, are affected in peripheral neuropathies and show abnormalities and a diminished plasticity during aging. Therefore, methodological approaches to study and manipulate SCs in physiological and pathophysiological conditions are crucial to expand the present knowledge on SC biology and to devise new therapeutic strategies to counteract neurodegenerative conditions and age-derived denervation. We present here an updated overview of traditional and emerging methodologies for the study of SCs for scientists approaching this research field.
... As in spontaneous recovery, angiogenesis occurs in the transplant and conduit and supports the regeneration of nerve tissue. Inhibition of angiogenesis prevents invasion of Schwann cells into the conduit and axon regeneration [45][46][47], while implantation of a vascular nerve conduit, or cultured human umbilical vein endothelial cells with a tube-like structure in collagen hydrogel, promotes peripheral nerve regeneration [48,49]. ...
Endothelial cells acquire different phenotypes to establish functional vascular networks. Vascular endothelial growth factor (VEGF) signaling induces endothelial proliferation, migration, and survival to regulate vascular development, which leads to the construction of a vascular plexuses with a regular morphology. The spatiotemporal localization of angiogenic factors and the extracellular matrix play fundamental roles in ensuring the proper regulation of angiogenesis. This review article highlights how and what kinds of extracellular environmental molecules regulate angiogenesis. Close interactions between the vascular and neural systems involve shared molecular mechanisms to coordinate developmental and regenerative processes. This review article focuses on current knowledge about the roles of angiogenesis in peripheral nerve regeneration and the latest therapeutic strategies for the treatment of peripheral nerve injury.
... Accordingly, the axon is initially sprouting without directionality [19,22]. In 3 days post injury, SCs start the "repair" program and are converted to progenitor-like cells [23]. ...
... Of note, the axon elongation rate can be thus divided into double stages: the first slow stage (86 lm per day) without SCs and the second fast stage (433 lm per day) with SC guidance [18]. Researchers identified the Netrin1 signaling as a critical cue for regenerating axons to grow alongside migrating SCs [22,24,25]. In short, migrating SCs guide regenerating axons to travel across the nerve gap. ...
Neuronal microenvironment imbalance is associated with successive and irreversible pathophysiological changes and insufficient functional restoration after peripheral nerve injury. Conventional neural-supporting scaffolds result in unsatisfactory curative effects due to lack of biomimetic nanotechnology designs and biochemical or physicochemical modifications. Consequently, they fail in rational and facile remodeling of the imbalanced growth microenvironment, and cannot recover neural structure and function. In recent years, with the increasing knowledge in neuronal injury-associated microenvironment, a number of novel strategies are applied in enhancing the biochemical and physicochemical natures of biomimetic nanomaterial-based scaffolds for nerve tissue engineering. These nanoscale scaffolds can trigger growth factor secretion and aggregation through surface modification, regulate ATP synthesis and hydrolysis, switch between oxidation and reduction states, and activate ion channels and stimulate electrical signals under certain biophysical cues. Consequently, they can determine neuronal cell fate by modulating their viability, development and cell cycles during the regeneration process. In this review, we systematically summarize the studies on the biomimetic scaffold design of functional nanomaterials, their basic topological, biochemical and physical properties, and nanotechnology-based restoration of a balanced nutritional microenvironment regarding four key neural regeneration factors, including immune response, intraneural vascularization, bioenergetic metabolism and bioelectrical conduction in order to provide ideas and inspiration for the nanomedicine-based neuronal regeneration therapy.
