Combined treatment of human mesenchymal stem cells and green tea extract on retinal ganglion cell regeneration in rats after optic nerve injury

Retinal ganglion cell (RGC) death and axonal loss cause irreversible vision loss upon optic nerve (ON) injury. We have independently demonstrated that mesenchymal stem cells (MSCs) and green tea extract (GTE) promote RGC survival and axonal regeneration in rats with ON injury. Here we aimed to evaluate the combined treatment effect of human bone marrow-derived MSCs (hBM-MSCs) and GTE on RGC survival and axonal regeneration after ON injury. Combined treatment of hBM-MSCs and GTE promoted RGC survival and neurite outgrowth/axonal regeneration in ex vivo retinal explant culture and in rats after ON injury. GTE increased Stat3 activation in the retina after combined treatment, and enhanced brain-derived neurotrophic factor secretion from hBM-MSCs. Treatment of 10 μg/mL GTE would not induce hBM-MSC apoptosis, but inhibited their proliferation, migration, and adipogenic and osteogenic differentiation in vitro with reducing matrix metalloproteinase secretions. In summary, this study revealed that GTE can enhance RGC protective effect of hBM-MSCs, suggesting that stem cell priming could be a prospective strategy enhancing the properties of stem cells for ON injury treatment.

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.

Combination of stem cells and nerve guide conduit for the treatment of peripheral nerve injury: A meta-analysis

INTRODUCTION/AIMS

Many small-sized, single-center preclinical studies have investigated the benefits of introducing stem cells into the interior of nerve conduit. The aims of this meta-analysis are to review and contrast the effects of various types of stem cells in in vivo models used to reconstruct peripheral nerve injuries (PNIs) and to assess the reliability and stability of the available evidence.

METHODS

A systematic search was conducted using Cochrane Library, Embase, PubMed, and Web of Science to identify studies conducted from January 1, 2000, to September 21, 2022, and investigate stem cell therapy in peripheral nerve reconstruction animal models. Studies that met the relevant criteria were deemed eligible for this meta-analysis.

RESULTS

Fifty-five preclinical studies with a total of 1234 animals were incorporated. Stem cells demonstrated a positive impact on peripheral nerve regeneration at different follow-up times in the forest plots of five outcome indicators: compound muscle action potential (CMAP) amplitude, latency, muscle mass ratio, nerve conduction velocity, and sciatic functional index (SFI). In most comparisons, stem cell groups showed substantial differences compared with the control groups. The superior performance of adipose-derived stem cells (ADSCs) in terms of SFI, CMAP amplitude, and latency (p < .001) was identified.

DISCUSSION

The findings consistently demonstrated a favorable outcome in the reconstruction process when utilizing different groups of stem cells, as opposed to control groups where stem cells were not employed.

Chronic Spinal Cord Injury Regeneration with Combined Therapy Comprising Neural Stem/Progenitor Cell Transplantation, Rehabilitation, and Semaphorin 3A Inhibitor

Spinal cord injury (SCI) often results in various long-term sequelae, and chronically injured spinal cords exhibit a refractory feature, showing a limited response to cell transplantation therapies. To our knowledge, no preclinical studies have reported a treatment approach with results surpassing those of treatment comprising rehabilitation alone. In this study of rats with SCI, we propose a novel combined therapy involving a semaphorin 3A inhibitor (Sema3Ai), which enhances axonal regeneration, as the third treatment element in combination with neural stem/progenitor cell transplantation and rehabilitation. This comprehensive therapeutic strategy achieved significant improvements in host-derived neuronal and oligodendrocyte differentiation at the SCI epicenter and promoted axonal regeneration even in the chronically injured spinal cord. The elongated axons established functional electrical connections, contributing to significant enhancements in locomotor mobility when compared with animals treated with transplantation and rehabilitation. As a result, our combined transplantation, Sema3Ai, and rehabilitation treatment have the potential to serve as a critical step forward for chronic SCI patients, improving their ability to regain motor function.

The effectiveness of acellular nerve allografts compared to autografts in animal models: A systematic review and meta-analysis

BACKGROUND

Treatment of nerve injuries proves to be a worldwide clinical challenge. Acellular nerve allografts are suggested to be a promising alternative for bridging a nerve gap to the current gold standard, an autologous nerve graft.

OBJECTIVE

To systematically review the efficacy of the acellular nerve allograft, its difference from the gold standard (the nerve autograft) and to discuss its possible indications.

MATERIAL AND METHODS

PubMed, Embase and Web of Science were systematically searched until the 4th of January 2022. Original peer reviewed paper that presented 1) distinctive data; 2) a clear comparison between not immunologically processed acellular allografts and autologous nerve transfers; 3) was performed in laboratory animals of all species and sex. Meta analyses and subgroup analyses (for graft length and species) were conducted for muscle weight, sciatic function index, ankle angle, nerve conduction velocity, axon count diameter, tetanic contraction and amplitude using a Random effects model. Subgroup analyses were conducted on graft length and species.

RESULTS

Fifty articles were included in this review and all were included in the meta-analyses. An acellular allograft resulted in a significantly lower muscle weight, sciatic function index, ankle angle, nerve conduction velocity, axon count and smaller diameter, tetanic contraction compared to an autologous nerve graft. No difference was found in amplitude between acellular allografts and autologous nerve transfers. Post hoc subgroup analyses of graft length showed a significant reduced muscle weight in long grafts versus small and medium length grafts. All included studies showed a large variance in methodological design.

CONCLUSION

Our review shows that the included studies, investigating the use of acellular allografts, showed a large variance in methodological design and are as a consequence difficult to compare. Nevertheless, our results indicate that treating a nerve gap with an allograft results in an inferior nerve recovery compared to an autograft in seven out of eight outcomes assessed in experimental animals. In addition, based on our preliminary post hoc subgroup analyses we suggest that when an allograft is being used an allograft in short and medium (0-1cm, > 1-2cm) nerve gaps is preferred over an allograft in long (> 2cm) nerve gaps.

14-3-3 protein augments the protein stability of phosphorylated spastin and promotes the recovery of spinal cord injury through its agonist intervention

Axon regeneration is abortive in the central nervous system following injury. Orchestrating microtubule dynamics has emerged as a promising approach to improve axonal regeneration. The microtubule severing enzyme spastin is essential for axonal development and regeneration through remodeling of microtubule arrangement. To date, however, little is known regarding the mechanisms underlying spastin action in neural regeneration after spinal cord injury. Here, we use glutathione transferase pulldown and immunoprecipitation assays to demonstrate that 14-3-3 interacts with spastin, both in vivo and in vitro, via spastin Ser233 phosphorylation. Moreover, we show that 14-3-3 protects spastin from degradation by inhibiting the ubiquitination pathway and upregulates the spastin-dependent severing ability. Furthermore, the 14-3-3 agonist Fusicoccin (FC-A) promotes neurite outgrowth and regeneration in vitro which needs spastin activation. Western blot and immunofluorescence results revealed that 14-3-3 protein is upregulated in the neuronal compartment after spinal cord injury in vivo. In addition, administration of FC-A not only promotes locomotor recovery, but also nerve regeneration following spinal cord injury in both contusion and lateral hemisection models; however, the application of spastin inhibitor spastazoline successfully reverses these phenomena. Taken together, these results indicate that 14-3-3 is a molecular switch that regulates spastin protein levels, and the small molecule 14-3-3 agonist FC-A effectively mediates the recovery of spinal cord injury in mice which requires spastin participation.

Guiding axon regeneration: Instructions from blood vessels

In this issue of Neuron, Bhat et al.1 unveil the temporary reawakening of an embryonic guidance program, which facilitates the alignment of blood neovessels, creating a supportive "bridge" microenvironment for axon regrowth and tissue regeneration after peripheral nervous system (PNS) injury.

Structured wound angiogenesis instructs mesenchymal barrier compartments in the regenerating nerve

Organ injury stimulates the formation of new capillaries to restore blood supply raising questions about the potential contribution of neoangiogenic vessel architecture to the healing process. Using single-cell mapping, we resolved the properties of endothelial cells that organize a polarized scaffold at the repair site of lesioned peripheral nerves. Transient reactivation of an embryonic guidance program is required to orient neovessels across the wound. Manipulation of this structured angiogenic response through genetic and pharmacological targeting of Plexin-D1/VEGF pathways within an early window of repair has long-term impact on configuration of the nerve stroma. Neovessels direct nerve-resident mesenchymal cells to mold a provisionary fibrotic scar by assembling an orderly system of stable barrier compartments that channel regenerating nerve fibers and shield them from the persistently leaky vasculature. Thus, guided and balanced repair angiogenesis enables the construction of a "bridge" microenvironment conducive for axon regrowth and homeostasis of the regenerated tissue.

Ciliary neurotrophic factor mediated growth of retinal ganglion cell axons on PGS/PCL scaffolds

Ciliary neurotrophic factor (CNTF) promotes survival and/or differentiation of a variety of neuronal cells including retinal ganglion cells (RGCs). Delivery of CNTF requires a suitable medium capable of mediating diffusion and premature release of CNTF within the target tissue. Polymeric tissue-engineered scaffolds have been readily used as substrates for cell transplantation, expansion, and differentiation and, as carriers of cell growth factors. Their functions to CNTF release for RGC proliferation have remained so far unexplored, especially to CNTF affinity to the scaffold and subsequent RGC fate. Electrospunpoly(glycerol sebacate)/poly(ϵ-caprolactone) (PGS/PCL) biopolymer scaffolds have recently shown promising results in terms of supporting regeneration of RGC neurites. This work explores covalent immobilization of CNTF on PGS/PCL scaffold and the way immobilised CNTF mediates growth of RGC axons on the scaffold. Anex-vivothree-dimensional model of rodent optic nerve on PGS/PCL revealed that RGC explants cultured in CNTF mediated environment increased their neurite extensions after 20 d of cell culture employing neurite outgrowth measurements. The CNTF secretion on PGS/PCL scaffold was found bio-mimicking natural extracellular matrix of the cell target tissue and, consequently, has shown a potential to improve the overall efficacy of the RGC regeneration process.

Exogenous GDNF promotes peripheral facial nerve regeneration in rats through the PI3K/AKT/mTOR signaling pathway

Facial nerve regeneration still lacks a well-defined and practical clinical intervention. The survival of central facial motoneuron is a critical component in the successful peripheral facial nerve regeneration. Endogenous GDNF is vital for facial nerve regeneration according to earlier investigations. Nevertheless, the low endogenous GDNF level makes it challenging to achieve therapeutic benefits. Thus, we crushed the main trunk of facial nerve in SD rats to provide a model of peripheral facial paralysis, and we administered exogenous GDNF and Rapa treatments. We observed changes in the animal behavior scores, the morphology of facial nerve and buccinator muscle, the electrophysiological of facial nerve, and the expression of GDNF, GAP-43, and PI3K/AKT/mTOR signaling pathway-related molecules in the facial motoneurons. We discovered that GDNF could boost axon regeneration, hasten the recovery of facial paralysis symptoms and nerve conduction function, and increase the expression of GDNF, GAP-43, and PI3K/AKT/mTOR signaling pathway-related molecules in the central facial motoneurons. Therefore, exogenous GDNF injection into the buccinator muscle can enhance facial nerve regeneration following crushing injury and protect facial neurons via the PI3K/AKT/mTOR signaling pathway. This will offer a fresh perspective and theoretical foundation for the management of clinical facial nerve regeneration.

Hallmarks of peripheral nerve injury and regeneration

Peripheral nerves are functional networks in the body. Disruption of these networks induces varied functional consequences depending on the types of nerves and organs affected. Despite the advances in microsurgical repair and understanding of nerve regeneration biology, restoring full functions after severe traumatic nerve injuries is still far from achieved. While a blunted growth response from axons and errors in axon guidance due to physical barriers may surface as the major hurdles in repairing nerves, critical additional cellular and molecular aspects challenge the orderly healing of injured nerves. Understanding the systematic reprogramming of injured nerves at the cellular and molecular levels, referred to here as "hallmarks of nerve injury regeneration," will offer better ideas. This chapter discusses the hallmarks of nerve injury and regeneration and critical points of failures in the natural healing process. Potential pharmacological and nonpharmacological intervention points for repairing nerves are also discussed.

Non degradation of chitosan and initial degradation of collagen nerve conduits used for protection of nerve coaptations

BACKGROUND

Nerve conduits are either used to bridge nerve gaps of up to 3 cm or to protect nerve coaptations. Biodegradable nerve conduits, which are currently commercially available, include Chitosan or collagen-based ones. As histological aspects of their degradation are highly relevant for the progress of neuronal regeneration, the aim of this study was to report the histopathological signs of such nerve conduits, which were removed during revision surgery.

MATERIALS AND METHODS

Either Chitosan (n = 2) or collagen (n = 2) nerve conduits were implanted after neuroma resection and nerve grafting (n = 2) or traumatic nerve lesion after cut (n = 1) or crush injury (n = 1) in two females and two men, aged between 17 and 57 years. Revision surgery with removal of the nerve conduits was indicated due to persisting neuropathic pain and sensorimotor deficits, limited joint motion, or neurolysis with hardware removal at a median time of 17 months (range: 5.5-48 months). Histopathological analyses of all removed nerve conduits were performed.

RESULTS

A scar neuroma was diagnosed in one out of four patients. Mechanical complication occurred in one patient after nerve conduit implantation bridged over finger joints. Intraoperatively no or only initial signs of degradation of the nerve conduits were observed. Chitosan conduits revealed largely unchanged shape and structure of chitosan, and coating of the conduit by a vascularized fibrous membrane. The latter contained deposits taken up by macrophages, most likely representing dissolved chitosan. Characteristic histopathologic features of the degradation of collagen conduits were a disintegration of the compact collagen into separate fine circular strands, No foreign body reaction was observed in all removed nerve conduits.

CONCLUSIONS

Both Chitosan nerve conduits have not been degraded. The collagen nerve conduits showed a beginning degradation process. Furthermore, wrapping the repaired nerve with a nerve conduit did neither prevent adhesions nor improved nerve gliding. Therefore, biodegradation in time should be particularly addressed in further developments of nerve conduits.

LKB1 and CRMP1 cooperatively promote the repair of the sciatic nerve injury

After peripheral nervous system injury, Schwann cells (SCs) can repair axons by providing a growth-promoting microenvironment. The aim of this study is to explore the effects and mechanisms of LKB1 and CRMP1 on the repair of sciatic nerve injury (SNI). The expressions of LKB1 and CRMP1 were changed in rats with SNI from 12 h to 4 weeks by hematoxylin-eosin staining, RT-PCR assay, immunohistochemical staining, and western blotting. Immunofluorescence results show that LKB1 and CRMP1 are co-localized in the regenerated axons of the sciatic nerve tissue of SNI rats. Co-immunoprecipitation indicates that LKB1 interacts with CRMP1. LKB1 interference suppresses the phosphorylation level of CRMP1. Overexpression of LKB1 and CRMP1 promotes the invasion and migration of SCs, and nerve cell protuberance extends. The structure of the myelin sheath in the sciatic nerve of the model group was found to be loose and disordered. Rats in the model group had higher pain thresholds and heat sensitivity response times than those in the control group. Nerve conduction velocity, the latency of action potential, and the peak value of compound muscle action potential in the SNI group were significantly lower than those in the control group, and the muscle atrophy was severe. Overexpression of LKB1 may significantly improve the above conditions. However, the function of LKB1 to improve SNI is abolished by the interference of CRMP1. In summary, the interaction between LKB1 and CRMP promotes the migration and differentiation of SCs and the extension of neurons, thereby improving the repair of nerve injury.

Chemogenetic stimulation of intact corticospinal tract during rehabilitative training promotes circuit rewiring and functional recovery after stroke

BACKGROUND

Neuromodulatory techniques have been proven to enhance functional recovery after stroke in patients and animals, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). However, the success and feasibility of these approaches were often variable, largely due to a lack of target specificity.

OBJECTIVE

We explored the effects of specific chemogenetic stimulation of intact corticospinal tract during rehabilitative training on functional recovery after stroke in mice.

METHODS

We developed a viral-based intersectional targeting approach that allows specific chemogentic activation of contralateral hindlimb corticospinal neurons (CSNs) in a photothrombotic stroke model.

RESULTS

We demonstrated that specific chemogenetic activation of CSNs, when combined with daily rehabilitation training, leads to significant skilled motor functional recovery via promoting corticospinal tract (CST) axons midline crossing sprouting from intact to the denervated spinal hemicord, and rewiring new functional circuits by new synapse formation. Mechanistically, we revealed that combined chemogenetic stimulation of CSNs and daily rehabilitation training significantly enhanced the mTOR activity of CSNs.

CONCLUSIONS

Our findings highlight the great potential of specific neural activation protocols in combination with motor training for the recovery of skilled motor functions after stroke.

Unleashing Axonal Regeneration Capacities: Neuronal and Non-neuronal Changes After Injuries to Dorsal Root Ganglion Neuron Central and Peripheral Axonal Branches

Peripheral nerves obtain remarkable regenerative capacity while central nerves can hardly regenerate following nerve injury. Sensory neurons in the dorsal root ganglion (DRG) are widely used to decipher the dissimilarity between central and peripheral axonal regeneration as axons of DRG neurons bifurcate into the regeneration-incompetent central projections and the regeneration-competent peripheral projections. A conditioning peripheral branch injury facilitates central axonal regeneration and enables the growth and elongation of central axons. Peripheral axonal injury stimulates neuronal calcium influx, alters the start-point chromatin states, increases chromatin accessibility, upregulates the expressions of regeneration-promoting genes and the synthesis of proteins, and supports axonal regeneration. Following central axonal injury, the responses of DRG neurons are modest, resulting in poor intrinsic growth ability. Some non-neuronal cells in DRGs, for instance satellite glial cells, also exhibit diminished injury responses to central axon injury as compared with peripheral axon injury. Moreover, DRG central and peripheral axonal branches are respectively surrounded by inhibitory glial scars generated by central glial cells and a permissive microenvironment generated by Schwann cells and macrophages. The aim of this review is to look at changes of DRG neurons and non-neuronal cells after peripheral and central axon injuries and summarize the contributing roles of both neuronal intrinsic regenerative capacities and surrounding microenvironments in axonal regeneration.

Mesenchymal Stem Cell-Derived Mitochondria Enhance Extracellular Matrix-Derived Grafts for the Repair of Nerve Defect

Peripheral nerve injuries (PNI) can lead to mitochondrial dysfunction and energy depletion within the affected microenvironment. The objective is to investigate the potential of transplanting mitochondria to reshape the neural regeneration microenvironment. High-purity functional mitochondria with an intact structure are extracted from human umbilical cord-derived mesenchymal stem cells (hUCMSCs) using the Dounce homogenization combined with ultracentrifugation. Results show that when hUCMSC-derived mitochondria (hUCMSC-Mitos) are cocultured with Schwann cells (SCs), they promote the proliferation, migration, and respiratory capacity of SCs. Acellular nerve allografts (ANAs) have shown promise in nerve regeneration, however, their therapeutic effect is not satisfactory enough. The incorporation of hUCMSC-Mitos within ANAs has the potential to remodel the regenerative microenvironment. This approach demonstrates satisfactory outcomes in terms of tissue regeneration and functional recovery. Particularly, the use of metabolomics and bioenergetic profiling is used for the first time to analyze the energy metabolism microenvironment after PNI. This remodeling occurs through the enhancement of the tricarboxylic acid cycle and the regulation of associated metabolites, resulting in increased energy synthesis. Overall, the hUCMSC-Mito-loaded ANAs exhibit high functionality to promote nerve regeneration, providing a novel regenerative strategy based on improving energy metabolism for neural repair.

Peripheral nerve regeneration by bioabsorbable nerve conduits filled with platelet-rich fibrin

PURPOSE

To repair peripheral nerve defects and seek alternatives for autografts, nerve conduits with various growth factors and cells have been invented. Few pieces of literature report the effect of nerve conduits plus platelet-rich fibrin (PRF). This study aimed to investigate the effectiveness of nerve conduits filled with PRF.

METHODS

The model of a 10 mm sciatic nerve gap in a rat was used to evaluate peripheral nerve regeneration. The thirty rats were randomly divided into one of the following three groups (n = 10 per group). Autogenous nerve grafts (autograft group), conduits filled with phosphate-buffered saline (PBS) (PBS group), or conduits filled with PRF group (PRF group). We assessed motor and sensory functions for the three groups at 4, 8, and 12 weeks postoperatively. In addition, axon numbers were measured 12 weeks after repair of the peripheral nerve gaps.

RESULTS

Significant differences in motor function were observed between the autograft group and the other two groups at 12 weeks postoperatively. In the test to evaluate the recovery of sensory function, there were significant differences between the PBS group and the other two groups at all time points. The most axon number was found in the autograft group. The axon number of the PRF group was significantly more extensive than that of the PBS group.

CONCLUSIONS

The nerve conduit filled with PRF promoted the axon regeneration of the sciatic nerve and improved sensory function.

Trigeminal or peripheral nerve stimulation improves functional outcomes of nerve recovery in a rodent forelimb gap repair model

BACKGROUND

The hypothesis of this study was that trigeminal nerve stimulation (TNS) or peripheral nerve stimulation (PNS) could improve functional outcomes of peripheral nerve injury in a rat forelimb model when compared to control rats not receiving electrical stimulation (ES). While PNS is known to improve outcomes after nerve surgery, the role of TNS has not been explored.

METHODS

Lewis rats were trained to perform a reach and grasp task before receiving a 2 mm gap repair of the ulnar and median nerves and randomized into four treatment groups: (1) sham injury, (2) nerve injury with sham ES, (3) nerve injury with PNS, and (4) nerve injury with TNS. Functional motor (median pull force and percent success in motor task) and sensory metrics (forelimb paw withdrawal thresholds) were collected both pre-injury and throughout rehabilitation. Nerves stained using Gomori's trichrome were assessed quantitatively and qualitatively.

RESULTS

The sham ES group did not recover their pre-injury baseline functional outcomes. In contrast, the TNS and PNS groups fully recovered following injury, with no difference in functional outcomes between the pre-injury baseline and the final week of rehabilitation (P > 0.05, all). Histomorphology results demonstrated no quantitative difference, but qualitative differences in architecture were evident.

CONCLUSIONS

Electrical stimulation of the trigeminal nerve or the injured nerve improved the functional outcomes of nerve regeneration in rodents. Histomorphology results of nerves from the TNS group support the proposed central mechanisms. This is an important step in translating this therapy as an adjunct, non-invasive treatment for high, mixed nerve injuries in humans.

Surface topologized ovalbumin scaffolds containing YIGSR peptides for modulating Schwann cell behavior

Peripheral nerve injuries (PNI) currently have limited therapeutic efficacy, and functional scaffolds have been shown to be effective for treating PNI. Ovalbumin (OVA) is widely used as a natural biomaterial for repairing damaged tissues due to its excellent biocompatibility and the presence of various bioactive components. However, there are few reports on the repair of PNI by ovalbumin. In this study, a novel bionic functionalized topological scaffold based on ovalbumin and grafted with tyrosine-isoleucine-glycine-serine-arginine (YIGSR) peptide was constructed by micro-molding method and surface-biomodification technology. The scaffolds were subjected to a series of evaluations in terms of morphology, mechanics, hydrophilicity, and biocompatibility, and the related molecular mechanisms were further penetrated. The results showed that the scaffolds prepared in this study had aligned ridge/groove structure, good mechanical properties and biocompatibility, and could be used as carriers to slowly release YIGSR, which effectively promoted the proliferation, migration and elongation of Schwann Cells (SCs), and significantly up-regulated the gene expression related to proliferation, apoptosis, migration and axon regeneration. Therefore, the bionic functional topological scaffold has significant application potential for promoting peripheral nerve regeneration and provides a new therapeutic option for repairing PNI.

Enhancement of nerve regeneration through schwann cell-mediated healing in a 3D printed polyacrylonitrile conduit incorporating hydrogel and graphene quantum dots: a study on rat sciatic nerve injury model

Despite recent technological advancements, effective healing from sciatic nerve damage remains inadequate. Cell-based therapies offer a promising alternative to autograft restoration for peripheral nerve injuries, and 3D printing techniques can be used to manufacture conduits with controlled diameter and size. In this study, we investigated the potential of Wharton's jelly-derived mesenchymal stem cells (WJMSCs) differentiated into schwann cells, using a polyacrylonitrile (PAN) conduit filled with fibrin hydrogel and graphene quantum dots (GQDs) to promote nerve regeneration in a rat sciatic nerve injury model. We investigated the potential of WJMSCs, extracted from the umbilical cord, to differentiate into schwann cells and promote nerve regeneration in a rat sciatic nerve injury model. WJMSCs were 3D cultured and differentiated into schwann cells within fibrin gel for two weeks. A 3 mm defect was created in the sciatic nerve of the rat model, which was then regenerated using a conduit/fibrin, conduit covered with schwann cells in fibrin/GQDs, GQDs in fibrin, and a control group without any treatment (n= 6/group). At 10 weeks after transplantation, motor and sensory functions and histological improvement were assessed. The WJMSCs were extracted, identified, and differentiated. The differentiated cells expressed typical schwann cell markers, S100 and P75.In vivoinvestigations established the durability and efficacy of the conduit to resist the pressures over two months of implantation. Histological measurements showed conduit efficiency, schwann cell infiltration, and association within the fibrin gel and lumen. Rats treated with the composite hydrogel-filled PAN conduit with GQDs showed significantly higher sensorial recovery than the other groups. Histological results showed that this group had significantly more axon numbers and remyelination than others. Our findings suggest that the conduit/schwann approach has the potential to improve nerve regeneration in peripheral nerve injuries, with future therapeutic implications.

Genome-wide study reveals novel roles for formin-2 in axon regeneration as a microtubule dynamics regulator and therapeutic target for nerve repair

Peripheral nerves regenerate successfully; however, clinical outcome after injury is poor. We demonstrated that low-dose ionizing radiation (LDIR) promoted axon regeneration and function recovery after peripheral nerve injury (PNI). Genome-wide CpG methylation profiling identified LDIR-induced hypermethylation of the Fmn2 promoter, exhibiting injury-induced Fmn2 downregulation in dorsal root ganglia (DRGs). Constitutive knockout or neuronal Fmn2 knockdown accelerated nerve repair and function recovery. Mechanistically, increased microtubule dynamics at growth cones was observed in time-lapse imaging of Fmn2-deficient DRG neurons. Increased HDAC5 phosphorylation and rapid tubulin deacetylation were found in regenerating axons of neuronal Fmn2-knockdown mice after injury. Growth-promoting effect of neuronal Fmn2 knockdown was eliminated by pharmaceutical blockade of HDAC5 or neuronal Hdac5 knockdown, suggesting that Fmn2deletion promotes axon regeneration via microtubule post-translational modification. In silico screening of FDA-approved drugs identified metaxalone, administered either immediately or 24-h post-injury, accelerating function recovery. This work uncovers a novel axon regeneration function of Fmn2 and a small-molecule strategy for PNI.

Hybrid Electrically Conductive Hydrogels with Local Nerve Growth Factor Release Facilitate Peripheral Nerve Regeneration

It is challenging to treat peripheral nerve injury (PNI) clinically. As the gold standard for peripheral nerve repair, autologous nerve grafting remains a critical limitation, including tissue availability, donor-site morbidity, immune rejection, etc. Recently, conductive hydrogels (CHs) have shown potential applications in neural bioengineering due to their good conductivity, biocompatibility, and low immunogenicity. Herein, a hybrid electrically conductive hydrogel composed of acrylic acid derivatives, gelatin, and heparin with sustained nerve growth factor (NGF) release property was developed. The rat sciatic nerve injury (SNI) model (10 mm long segment defect) was used to investigate the efficacy of these hydrogel conduits in facilitating peripheral nerve repair. The results showed that the hydrogel conduits had excellent conductivity, mechanical properties, and biocompatibility. In addition, NGF immobilized in the hydrogel conduits had good sustained release characteristics. Finally, functional recovery and electrophysiological evaluations, together with histological analysis, indicated that the hydrogel conduits immobilizing NGF had superior effects on motor recovery, axon growth, and remyelination, thereby significantly accelerating the repairing of the sciatic nerve. This study demonstrated that hybrid electrically conductive hydrogels with local NGF release could be effectively used for PNI repair.

Adoptive cell transfer of macrophages following peripheral nerve injury in mice

Macrophages are key innate immune cells involved in multiple biological processes, including peripheral nerve regeneration. Here, we describe a protocol for the adoptive cell transfer of bone-marrow-derived macrophages (BMDMs) following sciatic nerve crush injury (SNCI). This procedure involves isolating BMDMs from a donor mouse, potentially manipulating them ex vivo, and reintroducing them into an animal following SNCI. Preclinical studies show that BMDMs can infiltrate injured nerves and impact functional recovery, potentially providing a novel therapy for nerve injuries. For complete details on the use and execution of this protocol, please refer to Jha et al.1.

In toto imaging of glial JNK signaling during larval zebrafish spinal cord regeneration

Identification of signaling events that contribute to innate spinal cord regeneration in zebrafish can uncover new targets for modulating injury responses of the mammalian central nervous system. Using a chemical screen, we identify JNK signaling as a necessary regulator of glial cell cycling and tissue bridging during spinal cord regeneration in larval zebrafish. With a kinase translocation reporter, we visualize and quantify JNK signaling dynamics at single-cell resolution in glial cell populations in developing larvae and during injury-induced regeneration. Glial JNK signaling is patterned in time and space during development and regeneration, decreasing globally as the tissue matures and increasing in the rostral cord stump upon transection injury. Thus, dynamic and regional regulation of JNK signaling help to direct glial cell behaviors during innate spinal cord regeneration.

Zwitterionic Conductive Hydrogel-Based Nerve Guidance Conduit Promotes Peripheral Nerve Regeneration in Rats

In recent years, conductive biomaterials have been widely used to enhance peripheral nerve regeneration. However, most biomaterials use electronic conductors to increase the conductivity of materials. As information carriers, electronic conductors always transmit discontinuous electrical signals, while biological systems essentially transmit continuous signals through ions. Herein, an ion-based conductive hydrogel was fabricated by simple copolymerization of the zwitterionic monomer sulfobetin methacrylate and hydroxyethyl methacrylate. Benefiting from the excellent mechanical stability, suitable electrical conductivity, and good cytocompatibility of the zwitterionic hydrogel, the Schwann cells cultured on the hydrogel could grow and proliferate better, and dorsal root ganglian had an increased neurite length. The zwitterionic hydrogel-based nerve guidance conduits were then implanted into a 10 mm sciatic nerve defect model in rats. Morphological analysis and electrophysiological data showed that the grafts achieved a regeneration effect close to that of the autologous nerve. Overall, our developed zwitterionic hydrogel facilitates efficient and efficacious peripheral nerve regeneration by mimicking the electrical and mechanical properties of the extracellular matrix and creating a suitable regeneration microenvironment, providing a new material reserve for the repair of peripheral nerve injury.