Functional Nerve Regeneration Research Articles

Transplantation of Neural Progenitor Cells Derived from Stem Cells from Apical Papilla Through Small-Molecule Induction in a Rat Model of Sciatic Nerve Injury

Background:Stem cell-based transplantation therapy holds promise for peripheral nerve injury treatment, but adult availability is limited. A cell culture protocol utilizing a small-molecule cocktail effectively reprogrammed stem cells from apical papilla (SCAPs) into neural progenitor cells, subsequently differentiating into neuron-like cells. This study aims to evaluate neural-induced SCAPs, with and without small-molecule cocktail, for sciatic nerve repair potential.Methods:A scaffold-free cell sheet technique was used to construct a three-dimensional cell sheet. Subsequently, this cell sheet was carefully rolled into a tube and seamlessly inserted into a collagen conduit, which was then transplanted into a 5 mm sciatic nerve injury rat model. Functional sciatic nerve regeneration was evaluated via toe spread test, walking track analysis and gastrocnemius muscle weight. Additionally, degree of sciatic nerve regeneration was determined based on total amount of myelinated fibers.Results:Small-molecule cocktail induced SCAPs enhanced motor function recovery, evident in improved sciatic function index and gastrocnemius muscle retention. We also observed better host myelinated fiber retention than undifferentiated SCAPs or neural-induced SCAPs without small-molecule cocktail. However, clusters of neuron-like cell bodies (surrounded by sparse myelinated fibers) were found in all cell sheet-implanted groups in the implantation region. This suggests that while the implanted cells likely survived transplantation, integration was poor and would likely hinder long-term recovery by occupying the space needed for host nerve fibers to project through.Conclusion:Neural-induced SCAPs with small-molecule cocktail demonstrated promising benefits for nerve repair; further research is needed to improve its integration and optimize its potential for long-term recovery.

Autophagy-targeting modulation to promote peripheral nerve regeneration

Abstract Nerve regeneration following traumatic peripheral nerve injuries and neuropathies is a complex process modulated by diverse factors and intricate molecular mechanisms. Past studies have focused on factors that stimulate axonal outgrowth and myelin regeneration. However, recent studies have highlighted the pivotal role of autophagy in peripheral nerve regeneration, particularly in the context of traumatic injuries. Consequently, autophagy-targeting modulation has emerged as a promising therapeutic approach to enhancing peripheral nerve regeneration. Our current understanding suggests that activating autophagy facilitates the rapid clearance of damaged axons and myelin sheaths, thereby enhancing neuronal survival and mitigating injury-induced oxidative stress and inflammation. These actions collectively contribute to creating a favorable microenvironment for structural and functional nerve regeneration. A range of autophagy- inducing drugs and interventions have demonstrated beneficial effects in alleviating peripheral neuropathy and promoting nerve regeneration in preclinical models of traumatic peripheral nerve injuries. This review delves into the regulation of autophagy in cell types involved in peripheral nerve regeneration, summarizing the potential drugs and interventions that can be harnessed to promote this process. We hope that our review will offer novel insights and perspectives on the exploitation of autophagy pathways in the treatment of peripheral nerve injuries and neuropathies.

Cnicin promotes functional nerve regeneration

BackgroundThe limited regenerative capacity of injured axons hinders functional recovery after nerve injury. Although no drugs are currently available in the clinic to accelerate axon regeneration, recent studies show the potential of vasohibin inhibition by parthenolide, produced in Tanacetum parthenium, to accelerate axon regeneration. However, due to its poor oral bioavailability, parthenolide is limited to parenteral administration. PurposeThis study investigates another sesquiterpene lactone, cnicin, produced in Cnicus benedictus for promoting axon regeneration. ResultsCnicin is equally potent and effective in facilitating nerve regeneration as parthenolide. In culture, cnicin promotes axon growth of sensory and CNS neurons from various species, including humans. Neuronal overexpression of vasohibin increases the effective concentrations comparable to parthenolide, suggesting an interaction between cnicin and vasohibin. Remarkably, intravenous administration of cnicin significantly accelerates functional recovery after severe nerve injury in various species, including the anastomosis of severed nerves. Pharmacokinetic analysis of intravenously applied cnicin shows a blood half-life of 12.7 min and an oral bioavailability of 84.7 % in rats. Oral drug administration promotes axon regeneration and recovery after nerve injury in mice. ConclusionThese results highlight the potential of cnicin as a promising drug to treat axonal insults and improve recovery.

TEAD1 is crucial for developmental myelination, Remak bundles, and functional regeneration of peripheral nerves.

Previously we showed that the hippo pathway transcriptional effectors, YAP and TAZ, are essential for Schwann cells (SCs) to develop, maintain and regenerate myelin . Although TEAD1 has been implicated as a partner transcription factor, the mechanisms by which it mediates YAP/TAZ regulation of SC myelination are unclear. Here, using conditional and inducible knockout mice, we show that TEAD1 is crucial for SCs to develop and regenerate myelin. It promotes myelination by both positively and negatively regulating SC proliferation, enabling Krox20/Egr2 to upregulate myelin proteins, and upregulating the cholesterol biosynthetic enzymes FDPS and IDI1. We also show stage-dependent redundancy of TEAD1 and that non-myelinating SCs have a unique requirement for TEAD1 to enwrap nociceptive axons in Remak bundles. Our findings establish TEAD1 as a major partner of YAP/TAZ in developmental myelination and functional nerve regeneration and as a novel transcription factor regulating Remak bundle integrity.

Bredigite-Based Bioactive Nerve Guidance Conduit for Pro-Healing Macrophage Polarization and Peripheral Nerve Regeneration.

Structural and functional healing of peripheral nerves damaged by trauma or chronic disease remain major clinical challenges, requiring the development of an effective nerve guidance conduit (NGC). The present study investigates a NGC fabrication strategy based on bredigite (BRT, Ca7MgSi4O16) bioceramic for the treatment of peripheral nerve injury. Here, BRT bioceramic shows good biocompatibility and sustainable release of Ca2+, Mg2+, and Si4+ ions. Both BRT extracts and BRT-incorporating electrospun membranes promote the proliferation and myelination potential of RSC96 cells, as well as accelerate vascular formation by human umbilical vein endothelial cells. Notably, BRT facilitates RAW 264.7 cell polarization to the pro-healing phenotype under LPS-induced inflammatory stimulation. More importantly, the macrophages activated by BRT in turn promote RSC96 cell migration and remyelination. In a rat sciatic nerve defect model, improved electrophysiological performance and alleviated gastrocnemius muscle atrophy are observed at 12 weeks post-implantation. Further experiments verify that BRT-loaded NGC facilitates axonal regrowth and revascularization with high M2-like macrophage infiltration. These findings support the beneficial effects of BRT for creating a pro-healing immune microenvironment and orchestrating multicellular processes associated with functional nerve regeneration, indicating the potential of rationally engineered bioceramics as safe, effective, and economical materials for peripheral nerve repair.

The Effect of Adipose-Derived Mesenchymal Stem Cells on Peripheral Nerve Damage in a Rodent Model.

Peripheral nerve damage is a significant clinical problem with limited therapeutic options. Adipose-derived mesenchymal stem cells (ADSCs) have emerged as a promising therapeutic approach due to their regenerative potential. However, the underlying mechanisms by which ADSCs promote peripheral nerve regeneration remain unclear. In this study, we investigated the role of syndecan-1 and heat shock protein 70 (HSP-70) in mediating the regenerative effects of ADSCs on peripheral nerves. ADSCs were characterized and isolated from the adipose tissue of rats. In vitro experiments were conducted to evaluate the ability of ADSCs to secrete syndecan-1 and HSP-70 in response to stress conditions. To evaluate the therapeutic potential of ADSCs, rats with sciatic nerve injuries were treated with ADSCs and assessed for functional recovery, nerve regeneration, and changes in syndecan-1 and HSP-70 levels. Regeneration was evaluated with Electromyography (EMG) histology. The results showed that ADSCs could secrete syndecan-1 and HSP-70 in response to stress conditions. Furthermore, ADSC treatment significantly improved functional recovery and nerve regeneration and increased syndecan-1 and HSP-70 levels in the injured nerve. On the other hand, ADSCs make improvements histologically through the influence of Nerve growth factor (NGF), Malondialdehyde (MDA), and EMG.

Electroacupuncture Promotes Nerve Regeneration and Functional Recovery Through Regulating lncRNA GAS5 Targeting miR-21 After Sciatic Nerve Injury

Although the benefits of electroacupuncture (EA) for peripheral nerve injury (PNI) are well accepted in clinical practice, the underlying mechanism remains incompletely elucidated. In our study, we observed that EA intervention led to a reduction in the expression of the long non-coding RNA growth-arrest-specific transcript 5 (GAS5) and an increased in miR-21 levels within the injured nerve, effectively promoting functional recovery and nerve regeneration following sciatic nerve injury (SNI). In contrast, administration of adeno-associated virus expressing GAS5 (AAV-GAS5) weakened the therapeutic effect of EA. On the other hand, both silencing GAS5 and introducing a miR-21 mimic prominently enhanced the proliferation activity and migration ability of Schwann cells (SCs), while also inhibiting SCs apoptosis. On the contrary, inhibition of SCs apoptosis was found to be mediated by miR-21. Additionally, overexpression of GAS5 counteracted the effects of the miR-21 mimic on SCs. Moreover, SCs that transfected with the miR-21 mimic promoted neurite growth in hypoxia/reoxygenation-induced neurons, which might be prevented by overexpressing GAS5. Furthermore, GAS5 was found to be widely distributed in the cytoplasm and was negatively regulated by miR-21. Consequently, the targeting of GAS5 by miR-21 represents a potential mechanism through which EA enhances reinnervation and functional restoration following SNI. Mechanistically, the GAS5/miR-21 axis can modulate the proliferation, migration, and apoptosis of SCs while potentially influencing the neurite growth of neurons.

Effects of ECM proteins (laminin, fibronectin, and type IV collagen) on the biological behavior of Schwann cells and their roles in the process of remyelination after peripheral nerve injury.

Introduction: It is important to note that complete myelination and formation of myelinated fibers are essential for functional nerve regeneration after peripheral nerve injury (PNI). However, suboptimal myelin regeneration is common and can hinder ideal nerve regeneration. Therefore, it is important to closely monitor and support myelin regeneration in patients with PNI to achieve optimal outcomes. Methods: This study analyzed the effects of three extracellular matrix (ECM) proteins on Schwann cells (SCs) in the nerve regeneration environment, including their adhesion, proliferation, and migration. The study also explored the use of composite sodium alginate hydrogel neural scaffolds with ECM components and investigated the effects of ECM proteins on remyelination following peripheral nerve injury. Results: The results showed that laminin (LN), fibronectin (FN), and collagen Ⅳ (type IV Col) promoted the early adhesion of SCs in 2-dimensional culture but the ratios of early cell adhesion were quite different and the maintenance of cells' morphology by different ECM proteins were significantly different. In transwell experiment, the ability of LN and FN to induce the migration of SCs was obviously higher than that of type IV Col. An vitro co-culture model of SCs and dorsal root ganglia (DRG) neurons showed that LN promoted the transition of SCs to a myelinated state and the maturation of the myelin sheath, and increased the thickness of neurofilaments. Animal experiments showed that LN had superior effects in promoting myelin sheath formation, axon repair, and reaching an ideal G-ratio after injury compared to FN and Col IV. The situation of gastrocnemius atrophy was significantly better in the LN group. Notably, the thickness of the regenerated myelin sheaths in the type IV Col group was the thickest. Conclusion: In this experiment, we analyzed and compared the effects of LN, FN, and type IV Col on the biological behavior of SCs and their effects on remyelination after PNI and further clarified their unique roles in the process of remyelination. Further research is necessary to explore the underlying mechanisms.

Electrohydrodynamic Printing of Microfibrous Architectures with Cell-Scale Spacing for Improved Cellular Migration and Neurite Outgrowth.

Electrohydrodynamic (EHD) printing provides unparalleled opportunities in fabricating microfibrous architectures to direct cellular orientation. However, it faces great challenges in depositing orderly microfibers with cell-scale spacing due to inherent fiber-fiber electrostatic interactions. Here a finite element method is established to analyze the electrostatic forces induced on the EHD-printed microfibers and the relationship between the fiber diameter and spacing for parallel deposition of EHD-printed microfibers is revealed theoretically and experimentally. It is found that uniform fiber arrangement can be achieved when the fiber spacing is five times larger than the fiber diameter. This finding enables the successful printing of parallel fibrous architectures with a fiber diameter of 4.9 ± 0.1µm and a cell-scale fiber spacing of 25.6 ± 1.9µm. The resultant microfibrous architectures exhibit unique capability to direct cellular alignment and enhance cellular density and migration as the fiber spacing decreases from 100 to 25µm. The EHD-printed parallel microfibers with cell-scale spacing are found to improve the outgrowth length of neurites and accelerate the migration of Schwann cells from Dorsal Root Ganglion spheres, which facilitate the formation of densely-arranged and highly-aligned cellular constructs. The presented method is promising to produce biomimetic microfibrous architectures for functional nerve regeneration.

BMSCs Promote Differentiation of Enteric Neural Precursor Cells to Maintain Neuronal Homeostasis in Mice With Enteric Nerve Injury

Our previous study showed that transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) promoted functional enteric nerve regeneration in denervated mice but not through direct transdifferentiation. Homeostasis of the adult enteric nervous system (ENS) is maintained by enteric neural precursor cells (ENPCs). Whether ENPCs are a source of regenerated nerves in denervated mice remains unknown. Genetically engineered mice were used as recipients, and ENPCs were traced during enteric nerve regeneration. The mice were treated with benzalkonium chloride to establish a denervation model and then transplanted with BMSCs 3 days later. After 28 days, the gastric motility and ENS regeneration were analyzed. The interaction between BMSCs and ENPCs invitro was further assessed. Twenty-eight days after transplantation, gastric motility recovery (gastric emptying capacity, P < .01; gastric contractility, P < .01) and ENS regeneration (neurons, P < .01; glial cells, P < .001) were promoted in BMSCs transplantation groups compared with non-transplanted groups in denervated mice. More importantly, we found that ENPCs could differentiate into enteric neurons and glial cells in denervated mice after BMSCs transplantation, and the proportion of Nestin+/Ngfr+ cells differentiated into neurons was significantly higher than that of Nestin+ cells. A small number of BMSCs located in the myenteric plexus differentiated into glial cells. Invitro, glial cell-derived neurotrophic factor (GDNF) from BMSCs promotes the migration, proliferation, and differentiation of ENPCs. In the case of enteric nerve injury, ENPCs can differentiate into enteric neurons and glial cells to promote ENS repair and gastric motility recovery after BMSCs transplantation. BMSCs expressing GDNF enhance the migration, proliferation, and differentiation of ENPCs.

Modulation of Specific Sphingosine-1-Phosphate Receptors Augments a Repair Mediating Schwann Cell Phenotype.

Transdifferentiation of Schwann cells is essential for functional peripheral nerve regeneration after injury. By activating a repair program, Schwann cells promote functional axonal regeneration and remyelination. However, chronic denervation, aging, metabolic diseases, or chronic inflammatory processes reduce the transdifferentiation capacity and thus diminish peripheral nerve repair. It was recently described that the sphingosine-1-phosphate receptor (S1PR) agonist Fingolimod enhances the Schwann cell repair phenotype by activation of dedifferentiation markers and concomitant release of trophic factors resulting in enhanced neurite growth. Since Fingolimod targets four out of five S1PRs (S1P1, S1P3-5) possibly leading to non-specific adverse effects, identification of the main receptor(s) responsible for the observed phenotypic changes is mandatory for future specific treatment approaches. Our experiments revealed that S1P3 dominates and that along with S1P1 acts as the responsible receptor for Schwann cell transdifferentiation as revealed by the combinatory application of specific agonists and antagonists. Targeting both receptors reduced the expression of myelin-associated genes, increased PDGF-BB representing enhanced trophic factor expression likely to result from c-Jun induction. Furthermore, we demonstrated that S1P4 and S1P5 play only a minor role in the adaptation of the repair phenotype. In conclusion, modulation of S1P1 and S1P3 could be effective to enhance the Schwann cell repair phenotype and thus stimulate proper nerve repair.

Nerve implants with bioactive interfaces enhance neurite outgrowth and nerve regeneration in vivo

Nerve implants functionalized with growth factors and stem cells are critical to promote neurite outgrowth, regulate neurodifferentiation, and facilitate nerve regeneration. In this study, human umbilical cord mesenchymal stem cells (hUCMSCs) and 3,4-hydroxyphenalyalanine (DOPA)-containing insulin-like growth factor 1 (DOPA-IGF-1) were simultaneously applied to enhance the bioactivity of poly(lactide-co-glycolide) (PLGA) substrates which will be potentially utilized as nerve implants. In vitro and in vivo evaluations indicated that hUCMSCs and DOPA-IGF-1 could synergistically regulate neurite outgrowth of PC12 cells, improve intravital recovery of motor functions, and promote conduction of nerve electrical signals in vivo. The enhanced functional and structural nerve regeneration of injured spinal cord might be mainly attributable to the synergistically enhanced biofunctionality of hUCMSCs and DOPA-IGF-1/PLGA on the bioactive interfaces. Findings from this study demonstrate the potential of hUCMSC-seeded, DOPA-IGF-1-modified PLGA implants as promising candidates for promoting axonal regeneration and motor functional recovery in spinal cord injury treatment.

MP49-11 FIDGETIN-LIKE 2 (FL2) DEPLETION AT THE SITE AND TIME OF CAVERNOUS NERVE INJURY IMPROVES BLADDER FUNCTIONAL OUTCOMES

You have accessJournal of UrologyCME1 May 2022MP49-11 FIDGETIN-LIKE 2 (FL2) DEPLETION AT THE SITE AND TIME OF CAVERNOUS NERVE INJURY IMPROVES BLADDER FUNCTIONAL OUTCOMES Yi Wang, Moses Tar, Marcia Urban-Maldonado, Lisa Baker, David Sharp, Sylvia Suadicani, and Kelvin Davies Yi WangYi Wang More articles by this author , Moses TarMoses Tar More articles by this author , Marcia Urban-MaldonadoMarcia Urban-Maldonado More articles by this author , Lisa BakerLisa Baker More articles by this author , David SharpDavid Sharp More articles by this author , Sylvia SuadicaniSylvia Suadicani More articles by this author , and Kelvin DaviesKelvin Davies More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002624.11AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Radical prostatectomy (RP) is the most common treatment for localized prostate cancer. Unfortunately, the procedure carries high risk for the development of lower urinary tract symptoms (LUTS). These urogenital complications are highly detrimental to the post-surgical well-being of men, for whom there are presently poor treatment options. We recently demonstrated in a rat model of nerve injury associated with RP, that Fidgetin-Like 2 (FL2) depletion through application of FL2-siRNA at the site and time of cavernous nerve injury (CNI), resulted in significantly enhanced functional nerve recovery, as determined by cavernosometry [1]. In the present studies, we determined if the same approach would also improve bladder function outcomes in the rat model of CNI. METHODS: Animals were submitted to bilateral CNI, or to CNI followed by treatment with either FL2-siRNA or control-siRNA at the time and site of injury (the nerve and major pelvic ganglia). Voiding function was evaluated 7-days post-injury using the voided stain on paper (VSOP) method. Changes in i) micturition frequency and ii) voided volume per micturition were compared to those of naïve (unoperated) rats. The decrease in micturition frequency and increase in voiding volume in the CNI, and CNI treatment groups (FL2-siRNA or control-siRNA groups) were compared to the naïve cohort. 6 rats were analyzed per group and significance determined by Student’s t-test. RESULTS: Voiding function was significantly altered following CNI injury; at 7-days post-CNI, when compared to naïve (unoperated) age-matched controls, CNI animals displayed significantly lower micturition frequency (0.4 versus 0.55 voids per hour, P=0.02), and more than 2-fold greater voided volume per micturition (P=0.055). Remarkably, FL2-siRNA treatment at the time and site of injury mitigated these side-effects of CNI on voiding function, whereas treatment with control-siRNA was ineffective. CONCLUSIONS: These findings indicate that in addition to promoting recovery of erectile function following CNI rats [1], FL2 depletion at the site and time of injury also leads to improved bladder function outcomes. However, given that our studies on the role of FL2 depletion in mitigating LUTS were conducted at 7-days rather than 2-weeks after injury (a time point too short for visible nerve regeneration), the primary mechanisms by which FL2 depletion improves these different urogenital conditions are likely to be different and are currently being investigated. 1] Baker, L., Tar, M., Villegas, G., Charafeddine, R.A., Kramer, A., Vafaeva, O., Nacharaju, P., Friedman, J., Davies, K.P., and Sharp, D.J. (2021) Fidgetin-like 2 is a novel negative regulator of axonal growth and can be targeted to promote functional nerve regeneration after injury. JCI Insight. 2021 May 10;6(9):138484. PMID: 33872220. Source of Funding: NIH R41 DK112476 (MPI: Baker, Davies, Sharp), NIH R01 DK109314 (MPI: Davies, Sharp) © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e857 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Yi Wang More articles by this author Moses Tar More articles by this author Marcia Urban-Maldonado More articles by this author Lisa Baker More articles by this author David Sharp More articles by this author Sylvia Suadicani More articles by this author Kelvin Davies More articles by this author Expand All Advertisement PDF DownloadLoading ...

Sutureless neurorrhaphy system using a macrophage-polarizing in situ visible light-crosslinkable adhesive protein hydrogel for functional nerve regeneration

Surgical intervention after traumatic peripheral nerve injury relies heavily on sutures. While the suture method often burdens functional nerve regeneration by causing secondary traumatic damage and eliciting prolonged inflammatory immune responses, replacing sutures has rarely been considered because secure anastomosis between severed nerve ends has been the utmost priority in neurorrhaphy. In the present work, a macrophage-polarizing sutureless neurorrhaphy system was proposed by using an in situ visible light-crosslinkable protein-based bioadhesive hydrogel containing a functional neurotransmitter peptide. The efficacy of the proposed bioadhesive hydrogel as a successful sutureless neurorrhaphy system was intensively evaluated in vitro and in vivo. Using a rat sciatic nerve defect model, our findings suggested that this macrophage-polarizing bioadhesive hydrogel offered effective sutureless anastomosis and the capability to induce M2 macrophage polarization for effective tissue remodeling, significantly enhancing functional nerve regeneration compared with conventional sutures. Taken together, these results suggest that our macrophage-polarizing functional bioadhesive hydrogel system can be utilized as a promising alternative to surgical sutures for nerve regenerative medicine applications.

Expression of axon guidance ligands and their receptors in the cornea and trigeminal ganglia and their recovery after corneal epithelium injury

Axon guidance proteins are essential for axonal pathfinding during development. In adulthood, they have been described as pleiotropic proteins with multiple roles in different organs and tissues. While most studies on the roles of these proteins in the cornea have been performed on the Semaphorin family members, with few reports on Netrins or Ephrins, their function in corneal epithelium wound healing and functional nerve regeneration is largely unknown. Here, we studied the expression of ligands belonging to three distinct axon guidance families (Semaphorins, Ephrins, and Netrins) and their most commonly associated receptors in the cornea and trigeminal ganglia (TG) using immunofluorescence staining and RT-qPCR. We also evaluated how their expression recovers after corneal epithelium injury. We found that all ligands studied (Sema3A, Sema3F, EphrinB1, EphrinB2, Netrin-1, and Netrin-4) are abundantly expressed in both the TG and corneal epithelium. Similarly, their receptors (Neuropilin-1, Neuropilin-2, PlexinA1, PlexinA3, EphB2, EphB4, Neogenin, UNC5H1 and DCC) are also expressed in both tissues. Upon corneal epithelium injury, quick recovery of both ligands and receptors was observed at the protein and gene expression levels. While the timing and expression levels vary among these proteins, in general, most of them remained upregulated for several weeks after injury. We propose that the initial protein expression recovery may be related to corneal epithelium recovery since Sema3A, EphrinB2 and Netrin-4 accelerated corneal epithelial cells wound healing. The sustained high expression levels may be functionally related to nerve regeneration and/or patterning. Whilst further studies are required to test this hypothesis, this work contributes to unraveling their function in normal and injured cornea.

Conductive Nerve Guidance Conduits Based on Morpho Butterfly Wings for Peripheral Nerve Repair.

Peripheral nerve injury (PNI), causing loss of sensory and motor function, is a complex and challenging disease in the clinic due to the restricted regeneration capacity. Nerve guidance conduits (NGCs) have become a promising substitute for peripheral nerve regeneration, but their efficacy is often limited. Here, inspired by the physiological structures of peripheral nerves, we present a conductive topological scaffold for nerve repair by modifying Morpho butterfly wing with reduced graphene oxide (rGO) nanosheets and methacrylated gelatin (GelMA) hydrogel encapsulated brain-derived neurotrophic factor (BDNF). Benefiting from the biocompatibility of GelMA hydrogel, the conductivity of rGO and parallel nanoridge structures of wing scales, PC12 cells, and neural stem cells grown on the modified wing have an increased neurite length with guided cellular orientation. In addition, the NGCs are successfully obtained by manually rolling up the scaffolds and exhibited great performance in repairing 10 mm sciatic nerve defects in rats, and we believe that the NGCs can be applied in reparing longer nerve defects in the future by further optimization. We also demonstrate the feasibility of electrically conductive NGCs based on the rGO/BDNF/GelMA-integrated Morpho butterfly wing as functional nerve regeneration conduits, which may have potential value for application in repairing peripheral nerve injuries.

Transplanted neural lineage cells derived from dental pulp stem cells promote peripheral nerve regeneration.

Cell therapy for peripheral nerve injury is a promising strategy as regenerative medicine that restores neurological function. However, challenges remain in producing suitable and sufficient amounts of autologous cells for promoting nerve regeneration. This study aimed to identify the characteristics of neural lineage cells (NLCs) differentiated from dental pulp stem cells (DPSCs) and reveal their effect on functional recovery and nerve regeneration after cell transplantation into an immunodeficient rat using a nerve guide conduit. Here we report a protocol of neural induction in monolayer culture and characterize NLCs in vitro. Furthermore, NLCs were transplanted into an immunodeficient rat model with a 10-mm sciatic nerve defect, and cell survival and differentiation were investigated in vivo. Outcomes of nerve regeneration were also assessed using the remyelinated axon numbers, myelin sheath thickness, electrophysiological activities, and gastrocnemius muscle mass. NLCs comprised neuronal, astrocyte, oligodendrocyte, and neural crest lineage cells. NLCs enhanced the activities of endothelial cells, Schwann cells, and neurons in a paracrine-dependent manner in vitro. At 2weeks post-transplantation, numerous transplanted NLCs differentiated into platelet-derived growth factor receptor alpha (PDGFRα) + oligodendrocyte progenitor cells (OPCs) and a few PDGFRα + /p75 neurotrophin receptor + Schwann cell-like cells derived from OPCs were observed. At 12weeks post-transplantation, human Schwann cell-like cells survived, and axon growth, remyelination, electrophysiological activities, and muscle atrophy were improved. This study demonstrates the broad application of our protocol of neural induction of DPSCs and portrays the efficacy of transplantation of NLCs derived from human DPSCs as a promising strategy for peripheral nerve regeneration.

In Situ Prevascularization Strategy with Three-Dimensional Porous Conduits for Neural Tissue Engineering.

Neovascularization is crucial for peripheral nerve regeneration and long-term functional restoration. Previous studies have emphasized strategies that enhance axonal repair over vascularization. Here, we describe the development and application of an in situ prevascularization strategy that uses 3D porous nerve guidance conduits (NGCs) to achieve angiogenesis-mediated neural regeneration. The optimal porosity of the NGC is a critical feature for achieving neovascularization and nerve growth patency. Hollow silk fibroin/poly(l-lactic acid-co-ε-caprolactone) NGCs with 3D sponge-like walls were fabricated using electrospinning and freeze-drying. In vitro results showed that 3D porous NGC favored cell biocompatibility had neuroregeneration potential and, most importantly, had angiogenic activity. Results from our mechanistic studies suggest that activation of HIF-1α signaling might be associated with this process. We also tested in situ prevascularized 3D porous NGCs in vivo by transplanting them into a 10 mm rat sciatic nerve defect model with the aim of regenerating the severed nerve. The prevascularized 3D porous NGCs greatly enhanced intraneural angiogenesis, resulting in demonstrable neurogenesis. Eight weeks after transplantation, the performance of the prevascularized 3D NGCs was similar to that of traditional autografts in terms of improved anatomical structure, morphology, and neural function. In conclusion, combining a reasonably fabricated 3D-pore conduit structure with in situ prevascularization promoted functional nerve regeneration, suggesting an alternative strategy for achieving functional recovery after peripheral nerve trauma.

Human Umbilical Cord Mesenchymal Stem Cell-Derived Extracellular Vesicles Promote the Proliferation of Schwann Cells by Regulating the PI3K/AKT Signaling Pathway via Transferring miR-21.

As an alternative mesenchymal stem cell- (MSC-) based therapy, MSC-derived extracellular vesicles (EVs) have shown promise in the field of regenerative medicine. We previously found that human umbilical cord mesenchymal stem cell-derived EVs (hUCMSC-EVs) improved functional recovery and nerve regeneration in a rat model of sciatic nerve transection. However, the underlying mechanisms are poorly understood. Here, we demonstrated for the first time that hUCMSC-EVs promoted the proliferation of Schwann cells by activating the PI3K/AKT signaling pathway. Furthermore, we showed that hUCMSC-EVs mediated Schwann cell proliferation via transfer of miR-21. Our findings highlight a novel mechanism of hUCMSC-EVs in treating peripheral nerve injury and suggest that hUCMSC-EVs may be an attractive option for clinical application in the treatment of peripheral nerve injury.

Retinal Ganglion Cell Transplantation: Approaches for Overcoming Challenges to Functional Integration.

As part of the central nervous system, mammalian retinal ganglion cells (RGCs) lack significant regenerative capacity. Glaucoma causes progressive and irreversible vision loss by damaging RGCs and their axons, which compose the optic nerve. To functionally restore vision, lost RGCs must be replaced. Despite tremendous advancements in experimental models of optic neuropathy that have elucidated pathways to induce endogenous RGC neuroprotection and axon regeneration, obstacles to achieving functional visual recovery through exogenous RGC transplantation remain. Key challenges include poor graft survival, low donor neuron localization to the host retina, and inadequate dendritogenesis and synaptogenesis with afferent amacrine and bipolar cells. In this review, we summarize the current state of experimental RGC transplantation, and we propose a set of standard approaches to quantifying and reporting experimental outcomes in order to guide a collective effort to advance the field toward functional RGC replacement and optic nerve regeneration.