Regeneration Of Myelinated Fibers Research Articles

Blockade of Rho-associated kinase prevents inhibition of axon regeneration of peripheral nerves induced by anti-ganglioside antibodies.

Anti-ganglioside antibodies are associated with delayed/poor clinical recovery in Guillain-Barrè syndrome, mostly related to halted axon regeneration. Cross-linking of cell surface gangliosides by anti-ganglioside antibodies triggers inhibition of nerve repair in in vitro and in vivo paradigms of axon regeneration. These effects involve the activation of the small GTPase RhoA/ROCK signaling pathways, which negatively modulate growth cone cytoskeleton, similarly to well stablished inhibitors of axon regeneration described so far. The aim of this work was to perform a proof of concept study to demonstrate the effectiveness of Y-27632, a selective pharmacological inhibitor of ROCK, in a mouse model of axon regeneration of peripheral nerves, where the passive immunization with a monoclonal antibody targeting gangliosides GD1a and GT1b was previously reported to exert a potent inhibitory effect on regeneration of both myelinated and unmyelinated fibers. Our results demonstrate a differential sensitivity of myelinated and unmyelinated axons to the pro-regenerative effect of Y-27632. Treatment with a total dosage of 9 mg/kg of Y-27632 resulted in a complete prevention of anti-GD1a/GT1b monoclonal antibody-mediated inhibition of axon regeneration of unmyelinated fibers to skin and the functional recovery of mechanical cutaneous sensitivity. In contrast, the same dose showed toxic effects on the regeneration of myelinated fibers. Interestingly, scale down of the dosage of Y-27632 to 5 mg/kg resulted in a significant although not complete recovery of regenerated myelinated axons exposed to anti-GD1a/GT1b monoclonal antibody in the absence of toxicity in animals exposed to only Y-27632. Overall, these findings confirm the in vivo participation of RhoA/ROCK signaling pathways in the molecular mechanisms associated with the inhibition of axon regeneration induced by anti-GD1a/GT1b monoclonal antibody. Our findings open the possibility of therapeutic pharmacological intervention targeting RhoA/Rock pathway in immune neuropathies associated with the presence of anti-ganglioside antibodies and delayed or incomplete clinical recovery after injury in the peripheral nervous system.

3D-bioprinted GelMA nerve guidance conduits promoted peripheral nerve regeneration by inducing trans-differentiation of MSCs into SCLCs via PIEZO1/YAP axis

Schwann cells (SCs)-based nerve guidance conduits (NGCs) is a promising strategy for repairing long-gap peripheral nerve injury (PNI). But the number of SCs is limited as terminally differentiated cells. Matrix stiffness is able to direct cell fate of stem cells. And nerve-special stiffness (NSS) may contribute to stem cells converting into SCs. However, the potential mechanisms remain uncertain. The present study aimed to elucidate whether the given NSS was able to promote mesenchymal stem cells (MSCs) trans-differentiating into Schwann cell-like cells (SCLCs), facilitating cell-based NGCs repairing PNI. Gelatin methacryloylate (GelMA) hydrogels with different stiffness were manufactured, and their roles in the trans-differentiation of MSCs into SCLCs were investigated in vitro study. The most favorable stiffness (0.9–2.9 kPa) for trans-differentiation and neurotrophic factors expression was confirmed by western blot and immunofluorescence assays. The reason might lie in softer stiffness stretched cell morphology, leading to up-regulation of PIEZO1 and then activating YAP nuclear translocation. As for in vivo study, multi-channel NGCs containing SCLCs were fabricated with extrusion-based bioprinting and then filled a 5 mm gap in sciatic nerve defect of SD rats. It turned out that GelMA-made NGCs with stiffness of 2.9 kPa achieved promising neurogenerative capacity, not only promoting recovering sensory and motor functions, but also improving myelinated nerve fiber regeneration. Our findings demonstrated that 0.9–2.9 kPa might be the desired mechanical strength inducing trans-differentiation into SCLCs via PIEZO1/YAP axis, and the 3D-printed GelMA NGCs combined with SCLCs could be a potential candidate for long-gap peripheral nerve injury.

Correlation analysis of electroneuromyographic, functional-anatomical and morphometric indicators of regeneration of the injured sciatic nerve

Objective. To study the electrophysiological, functional-anatomical and morphometric indicators of the sciatic nerve regeneration after complete transection and connection of the nerve stumps with epineural sutures and adhesives. Materials and methods. The experiments were carried out on white outbred male rats. The efficiency of sciatic nerve regeneration was investigated with the standard 4-6 epineural sutures and the use of polyethylene glycol hydrogel Duraseal or Tisseel fibrin glue with 2 fixation sutures. On the 14th, 30th and 60th days after the complete transection of the sciatic nerve and subsequent connection of the nerve stumps with epineural sutures, hydrogel or fibrin glue, limb function was assessed using SFI test and ENMG. The distal segment of the nerve was sampled for electron microscopic and morphometric studies. The density of the regenerated myelinated nerve fibers was studied and a correlation analysis was performed with the results of SFI test and ENMG. Results. The use of adhesives provides a similar result of connecting the transected sciatic nerve, as in standard neurorrhaphy, and regeneration of myelinated nerve fibers in the distal nerve. The regeneration density of myelinated nerve fibers significantly increased on the 30 th and 60th days in the groups in which Duraseal hydrogel and Tisseel fibrin glue were used, without a statistically significant difference in ENMG parameters (M-response amplitude, nerve conduction velocity, latency period) and the result of SFI test. The amplitude of M-response on the 30th day was statistically significantly lower after the connection of nerve stumps with Tisseel fibrin glue in comparison with the Duraseal hydrogel, whereas on the 60th day there was no difference according to the results of electrophysiological studies. Conclusions. The efficiency of sciatic nerve regeneration after the combined connection exceeds the standard technique, and the results of pathophysiological assessments are more often correlated with morphometry data on the 30th day.

Green Tea Polyphenols Promote Functional Recovery from Peripheral Nerve Injury in Rats.

BackgroundPeripheral nerve injury (PNI) is a common and progressive disorder with sensory and motor deficits in the peripheral nervous system (PNS). Treatment is difficult, with unfavorable prognosis. Green tea polyphenols (GTPs) exert neuroprotective effects on regeneration of the central nervous system (CNS). However, the effects of GTPs on functional recovery of the PNS have not been fully characterized. Consequently, the present study investigated the effects of GTPs on nerve regeneration of rats with PNI.Material/MethodsThe model of PNI was established in rats by sciatic nerve injury (SNI). Adult male Wistar rats with SNI were randomly divided into a vehicle group and a GTPs group. The compound muscle action potential (CMAP) of rat sciatic nerves (SN) was measured using the CM6240 physiological signal acquisition and processing system. The wet weight of the triceps muscle was determined using an analytical balance. The number of myelinated nerve fibers was counted under an optical microscope. Ultrastructure of the regenerated nerves in SN was observed by transmission electron microscopy. The mRNA and protein expression of nerve growth factor (NGF), growth-associated protein-43 (GAP-43), neurofilament 200 (NF200), and myelin-associated glycoprotein (MAG) in SN stumps were measured by real-time quantification PCR (RT-qPCR) and Western blot, respectively.ResultsIn rats with SNI, GTPs relieved the adhesion between nerve anastomosis and surrounding tissues, and significantly increased nerve conduction velocity, wet weight of the triceps muscle, and development and axonal regeneration of myelinated nerve fibers. Moreover, GTPs promoted the mRNA and protein expressions of NGF, GAP-43, NF200, and MAG in SN stumps.ConclusionsGTPs promotes nerve regeneration in rats with SNI.

A Model to Study Myelinated Fiber Degeneration and Regeneration in Human Skin.

To describe morphological changes associated with degeneration and regeneration of large fibers in the skin using a model of chronic compression of the median nerve. We studied cutaneous innervation in 30 patients with chronic compression of the median nerve at the wrist. Before surgery, we assessed the symptom severity and performed neurography, quantitative sensory testing, and analysis of nerve morphology and morphometry in skin biopsies from the third digit fingertip. Fifteen patients repeated all tests 12 months after the surgery. Thirty age- and sex-matched healthy subjects were included in the study. Clinical and neurophysiological basal assessment showed a moderate involvement of the median nerve. Quantitative sensory testing showed abnormal findings. The density of intraepidermal nerve fibers and intrapapillary myelinated endings was reduced. Myelinated fibers showed caliber reduction and nodal elongation. Meissner corpuscles had normal density but were located deeper in the dermis and their capsule appeared partially empty. During follow-up, patients exhibited a positive clinical and neurophysiological outcome. Quantitative sensory testing improved. Intraepidermal nerve fibers and intrapapillary myelinated endings remained unchanged, but the caliber of intrapapillary myelinated endings was increased. The neural component of the Meissner corpuscle filled the capsule of the mechanoreceptors that remained deeper in the dermis. The position of vasoactive intestinal peptide-immunoreactive fibers was more superficial compared to the basal assessment and controls. We recognized and quantified the pathological changes associated with nerve degeneration and regeneration in skin and proposed new parameters that may increase the diagnostic yield of skin biopsy in clinical practice. Ann Neurol 2020;87:456-465.

KLF7 overexpression in bone marrow stromal stem cells graft transplantation promotes sciatic nerve regeneration

Objective. Our previous study demonstrated that the transcription factor, Krüppel-like Factor 7 (KLF7), stimulates axon regeneration following peripheral nerve injury. In the present study, we used a gene therapy approach to overexpress KLF7 in bone marrow-derived stem/stromal cells (BMSCs) as support cells, combined with acellular nerve allografts (ANAs) and determined the potential therapeutic efficacy of a KLF7-transfected BMSC nerve graft transplantation in a rodent model for sciatic nerve injury and repair. Approach. We efficiently transfected BMSCs with adeno-associated virus (AAV)-KLF7, which were then seeded in ANAs for bridging sciatic nerve defects. Main results. KLF7 overexpression promotes proliferation, survival, and Schwann-like cell differentiation of BMSCs in vitro. In vivo, KLF7 overexpression promotes transplanted BMSCs survival and myelinated fiber regeneration in regenerating ANAs; however, KLF7 did not improve Schwann-like cell differentiation of BMSCs within in the nerve grafts. KLF7-BMSCs significantly upregulated expression and secretion of neurotrophic factors by BMSCs, including nerve growth factor, ciliary neurotrophic factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor in regenerating ANA. KLF7-BMSCs also improved motor axon regeneration, and subsequent neuromuscular innervation and prevention of muscle atrophy. These benefits were associated with increased motor functional recovery of regenerating ANAs. Significance. Our findings suggest that KLF7-BMSCs promoted peripheral nerve axon regeneration and myelination, and ultimately, motor functional recovery. The mechanism of KLF7 action may be related to its ability to enhance transplanted BMSCs survival and secrete neurotrophic factors rather than Schwann-like cell differentiation. This study provides novel foundational data connecting the benefits of KLF7 in neural injury and repair to BMSC biology and function, and demonstrates a potential combination approach for the treatment of injured peripheral nerve via nerve graft transplant.

Serum Brain‐derived neurotrophic factor promotes repair and regeneration of aged myelinated fibers via aerobic exercise

PurposeDegeneration of the distal peripheral nerve (DPN) with aging is associated with balance and gait disorders. Brain‐derived neurotrophic factor (BDNF) contributes to the repair and remodeling of myelinated fiber. However it is not obvious whether BDNF in the DPN increases with aerobic exercise (AE) in old age and promotes remodeling of MFs. We investigated morphological changes of MFs and BDNF expression levels of both serum and DPN via AE.MethodsEight male wistar rats (aged 95 weeks) were randomly divided into AE and control (Cont) groups. Rats in AE group performed running on the treadmill for 1 hour per day, 6 days per a week during 2 weeks. At 97 weeks of age, the bilateral tibial nerves of 2 groups were removed. To measure myelin thickness and axon diameter, semi‐thin sections of the unilateral specimens were stained with 0.5% Sudan Black B solution following double‐fixation. In addition, each expression level of serum and tissue BDNF in the contralateral specimens was analyzed with enzyme‐linked immunosorbent assay.ResultsMyelin thickness and axon diameter of AE group were significantly larger than those of Cont group (p<0.01). The serum BDNF level of AE group significantly decreased in comparison to that of Cont group (p<0.01). In contrast, BDNF level of AE group was significantly higher than that of Cont group (p<0.01).ConclusionIt was thought that serum BDNFs that were promoted by AE release into nerve fibers and contribute to the remodeling of myelinated fibers in aged DPNs.Support or Funding InformationThe present study was supported by a Grant‐in‐Aid for Scientific Research (C) from the Japan Society for the Promotion of Science (https://kaken.nii.ac.jp; 26350853).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Botulinum neurotoxin A promotes functional recovery after peripheral nerve injury by increasing regeneration of myelinated fibers

The injection of safe doses of botulinum neurotoxin A (BoNT/A) have been reported to be useful for the treatment of neuropathic pain, but it is still unknown how functional recovery is induced after peripheral nerve injury. We evaluated the effects of intranerve application of BoNT/A, on regeneration and sensorimotor functional recovery in partial and complete peripheral nerve injuries in the mouse. After sciatic nerve crush (SNC) and intranerve delivery of BoNT/A (15pg), axonal regeneration was measured by nerve pinch test at different days. Regeneration of myelinated and unmyelinated fibers was assessed by immunohistochemical double labeling for NF200/GAP43 and CGRP/GAP43. S100 was used as Schwann cells marker. Medial footpad skin reinnervation was assessed by PGP staining. Motor functions were assessed by means of nerve conduction tests. In other mice groups, nerve conduction tests were performed also after chronic constriction injury (CCI) of the sciatic nerve and intraplantar injection of BoNT/A (15pg). In SNC mice, BoNT/A increased the rate of axonal regeneration. The advantage of regrowing myelinated axons after BoNT/A injection was evidenced by longer NF200+ nerve profiles and confirmed by nerve histology. We observed also a higher expression of S100 in the distal portion of BoNT/A-injected regenerated nerves. In CCI mice, BoNT/A induced an increase in reinnervation of gastrocnemius and plantar muscles. These results show that a low dose of BoNT/A, insufficient to produce muscular dysfunction, conversely speeds up sensorimotor recovery by stimulating myelinated axonal regeneration, and points out its application as a multipotent treatment for peripheral neuropathies.

Oriented collagen tubes combined with basic fibroblast growth factor promote peripheral nerve regeneration in a 15mm sciatic nerve defect rat model.

We developed a new scaffold material-oriented collagen tubes (OCT)-and evaluated the potential of OCTs combined with basic fibroblast growth factor (bFGF) to repair of a 15mm sciatic nerve defect in rats. The treatment groups consisted of OCT with adsorbed bFGF (OCT/bFGF group), OCT in phosphate-buffered saline (PBS) (OCT/PBS group), and a no-treatment group (Defect group). Functional evaluation of nerve regeneration was performed using the CatWalk system, and histological analyses of the defect sites were also performed. In rats treated with either OCT/bFGF or OCT/PBS, the walking function parameter of max contact area returned to normal levels by 4 weeks after grafting, and the regeneration of myelinated fibers was detected after 8 weeks. However, more regenerated myelinated fibers were observed in the OCT/bFGF group compared with the OCT/PBS group at 4 weeks. In addition, the max contact area and swing speed in the OCT/bFGF group were significantly recovered compared to the OCT/PBS and Defect groups at 8 weeks. Although the combination of bFGF and OCT was superior to OCT alone for nerve regeneration and functional recovery, the present findings demonstrate that OCT alone or in combination with bFGF accelerates nerve repair in a large peripheral nerve defect in rats. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 8-14, 2017.

Trophic Effects of Dental Pulp Stem Cells on Schwann Cells in Peripheral Nerve Regeneration.

Recently, mesenchymal stem cells have demonstrated a potential for neurotrophy and neurodifferentiation. We have recently isolated mobilized dental pulp stem cells (MDPSCs) using granulocyte-colony stimulating factor (G-CSF) gradient, which has high neurotrophic/angiogenic potential. The aim of this study is to investigate the effects of MDPSC transplantation on peripheral nerve regeneration. Effects of MDPSC transplantation were examined in a rat sciatic nerve defect model and compared with autografts and control conduits containing collagen scaffold. Effects of conditioned medium of MDPSCs were also evaluated in vitro. Transplantation of MDPSCs in the defect demonstrated regeneration of myelinated fibers, whose axons were significantly higher in density compared with those in autografts and control conduits only. Enhanced revascularization was also observed in the MDPSC transplants. The MDPSCs did not directly differentiate into Schwann cell phenotype; localization of these cells near Schwann cells induced several neurotrophic factors. Immunofluorescence labeling demonstrated reduced apoptosis and increased proliferation in resident Schwann cells in the MDPSC transplant compared with control conduits. These trophic effects of MDPSCs on proliferation, migration, and antiapoptosis in Schwann cells were further elucidated in vitro. The results demonstrate that MDPSCs promote axon regeneration through trophic functions, acting on Schwann cells, and promoting angiogenesis.

NKCC1 Activation Is Required for Myelinated Sensory Neurons Regeneration through JNK-Dependent Pathway.

After peripheral nerve injury, axons are able to regenerate, although specific sensory reinnervation and functional recovery are usually worse for large myelinated than for small sensory axons. The mechanisms that mediate the regeneration of different sensory neuron subpopulations are poorly known. The Na(+)-K(+)-Cl(-) cotransporter 1 (NKCC1) is particularly relevant in setting the intracellular chloride concentration. After axotomy, increased NKCC1 phosphorylation has been reported to be important for neurite outgrowth of sensory neurons; however, the mechanisms underlying its effects are still unknown. In the present study we used in vitro and in vivo models to assess the differential effects of blocking NKCC1 activity on the regeneration of different types of dorsal root ganglia (DRGs) neurons after sciatic nerve injury in the rat. We observed that blocking NKCC1 activity by bumetanide administration induces a selective effect on neurite outgrowth and regeneration of myelinated fibers without affecting unmyelinated DRG neurons. To further study the mechanism underlying NKCC1 effects, we also assessed the changes in mitogen-activated protein kinase (MAPK) signaling under NKCC1 modulation. The inhibition of NKCC1 activity in vitro and in vivo modified pJNK1/2/3 expression in DRG neurons. Together, our study identifies a mechanism selectively contributing to myelinated axon regeneration, and point out the role of Cl(-) modulation in DRG neuron regeneration and in the activation of MAPKs, particularly those belonging to the JNK family.

Sleeve bridging of the rhesus monkey ulnar nerve with muscular branches of the pronator teres: multiple amplification of axonal regeneration.

Multiple-bud regeneration, i.e., multiple amplification, has been shown to exist in peripheral nerve regeneration. Multiple buds grow towards the distal nerve stump during proximal nerve fiber regeneration. Our previous studies have verified the limit and validity of multiple amplification of peripheral nerve regeneration using small gap sleeve bridging of small donor nerves to repair large receptor nerves in rodents. The present study sought to observe multiple amplification of myelinated nerve fiber regeneration in the primate peripheral nerve. Rhesus monkey models of distal ulnar nerve defects were established and repaired using muscular branches of the right forearm pronator teres. Proximal muscular branches of the pronator teres were sutured into the distal ulnar nerve using the small gap sleeve bridging method. At 6 months after suture, two-finger flexion and mild wrist flexion were restored in the ulnar-sided injured limbs of rhesus monkey. Neurophysiological examination showed that motor nerve conduction velocity reached 22.63 ± 6.34 m/s on the affected side of rhesus monkey. Osmium tetroxide staining demonstrated that the number of myelinated nerve fibers was 1,657 ± 652 in the branches of pronator teres of donor, and 2,661 ± 843 in the repaired ulnar nerve. The rate of multiple amplification of regenerating myelinated nerve fibers was 1.61. These data showed that when muscular branches of the pronator teres were used to repair ulnar nerve in primates, effective regeneration was observed in regenerating nerve fibers, and functions of the injured ulnar nerve were restored to a certain extent. Moreover, multiple amplification was subsequently detected in ulnar nerve axons.

Efficacy of the end-to-side neurorrhaphies with epineural window and partial donor neurectomy in peripheral nerve repair: an experimental study in rats.

End-to-side (ETS) neurorrhaphy was a useful tool in peripheral nerve repair and "baby-sitter" procedure. The study was designed to evaluate the long-term efficacy of ETS with epineurial window and 40% partial donor neurectomy in rats. A total of 60 Lewis rats were divided into three groups (n = 20, each group): following peroneal nerve transection, rats in Group A underwent end-to-end neurorrhaphy; rats in Group B underwent ETS neurorrhaphy of the distal peroneal nerve stump to an epineurial window on the tibial nerve; and rats in Group C underwent ETS neurorrhaphy of the distal peroneal nerve stump to the tibial nerve with 40% partial neurectomy. At 6, 12, 18, and 24 weeks after surgery, electrophysiology, muscle tension, myelinated fiber regeneration, cross-sectional area of muscular fiber, and muscle weight were analyzed. Histology exhibited apparently increased number and size of myelinated fibers in peroneal nerves in Group C, compared with those in Group B. More superior recovery was demonstrated in the electrophysiology and axon regeneration of the peroneal nerves, as well as the maintenance of muscle force, wet weight, and fiber size of the anterior tibial muscles in Group C than those in Group B. ETS neurorrhaphy with partial donor neurectomy can achieve higher efficacy in functional and structural recovery of the recipient system. This study provides the evidence of long-term follow-up for the further investigation of ETS neurorrhaphies with different modalities in peripheral nerve repair and in "baby-sitter" procedure.

Identification of Factors Associated With Sural Nerve Regeneration and Degeneration in Diabetic Neuropathy

OBJECTIVEPatients with diabetic neuropathy (DN) demonstrate variable degrees of nerve regeneration and degeneration. Our aim was to identify risk factors associated with sural nerve degeneration in patients with DN.RESEARCH DESIGN AND METHODSDemographic, anthropometric, biochemical, and anatomical data of subjects with DN from a 52-week trial of acetyl-L-carnitine were retrospectively examined. Based on the change in sural nerve myelinated fiber density (ΔMFD%), subjects were divided into three groups: regenerator (top 16 percentiles, n = 67), degenerator (bottom 16 percentiles, n = 67), and intermediate (n = 290), with dramatically increased, decreased, and steady ΔMFD%, respectively. ANOVA, Fisher exact test, and multifactorial logistic regression were used to evaluate statistical significance.RESULTSΔMFD%s were 35.6 ± 17.4 (regenerator), −4.8 ± 12.1 (intermediate), and −39.8 ± 11.0 (degenerator). HbA1c at baseline was the only factor significantly different across the three groups (P = 0.01). In multifactorial logistic regression, HbA1c at baseline was also the only risk factor significantly different between regenerator (8.3 ± 1.6%) and degenerator (9.2 ± 1.8%) (odds ratio 0.68 [95% CI 0.54–0.85]; P < 0.01). Support Vector Machine classifier using HbA1c demonstrated 62.4% accuracy of classifying subjects into regenerator or degenerator. A preliminary microarray experiment revealed that upregulated genes in the regenerator group are enriched with cell cycle and myelin sheath functions, while downregulated genes are enriched in immune/inflammatory responses.CONCLUSIONSThese data, based on the largest cohort with ΔMFD% information, suggest that HbA1c levels predict myelinated nerve fiber regeneration and degeneration in patients with DN. Therefore, maintaining optimal blood glucose control is likely essential in patients with DN to prevent continued nerve injury.

Implications of Olfactory Lamina Propria Transplantation on Hyperreflexia and Myelinated Fiber Regeneration in Rats with Complete Spinal Cord Transection

Transplantation with olfactory ensheathing cells (OECs) has been adopted after several models of spinal cord injury (SCI) with the purpose of creating a favorable environment for the re-growth of injured axons. However, a consensus on the efficacy of this cellular transplantation has yet to be reached. In order to explore alternative parameters that could demonstrate the possible restorative properties of such grafts, the present study investigated the effects of olfactory lamina propria (OLP) transplantation on hyperreflexia and myelinated fiber regeneration in adult rats with complete spinal cord transection. The efficacy of OLP (graft containing OECs) and respiratory lamina propria (RLP, graft without OECs) was tested at different post-injury times (acutely, 2- and 4-week delayed), to establish the optimum period for transplantation. In the therapeutic windows used, OLP and RLP grafts produced no considerable improvements in withdrawal reflex responses or on the low-frequency dependent depression of H-reflex. Both lamina propria grafts produced comparable results for the myelinated fiber density and for the estimated total number of myelinated fibers at the lesion site, indicating that the delayed transplantation approach does not seem to limit the regenerative effects. However, animals transplanted with OLP 2 or 4 weeks after injury exhibit smaller myelin sheath thickness and myelinated fiber area and diameter at the lesion site compared to their respective RLP groups. Despite the ongoing clinical use of OECs, it is important to emphasize the need for more experimental studies to clarify the exact nature of the repair capacity of these grafts in the treatment of SCI.

Transplantation of Adipose Derived Stem Cells for Peripheral Nerve Regeneration in Sciatic Nerve Defects of the Rat

Tissue engineering approaches for promoting the repair of peripheral nerve injuries have focused on cell-based therapies involving Adipose-derived stem cells (ASCs). The authors evaluated the effects of undifferentiated ASCs and of neurally differentiated ASCs on the regenerating abilities of peripheral nerves. We hope that this would demonstrate the feasibility of using adipose derived stem cells for peripheral nerve regeneration and provide clues regarding the use of adipose- derived stem cells. ASCs were isolated and cultured. Then the cells were cultured with neuronal induction agents for neural differentiation. ASCs and neurally differentiated ASCs were transplanted into sciatic nerve defects. After 12 weeks, the number and diameter of the myelinated fibers were measured and nerve conduction study was done. The extent of regeneration of myelinated fibers in the neurally differentiated ASCs transplanted group was greater than that in the ASCs transplanted group or the control group. However, thickness of myelin sheath and diameter of nerve fibers in the ASCs transplanted group were greater than those in the neutrally differentiated ASCs transplanted group or the control group. Nerve conduction study showed good recovery in the neurally differentiated ASCs transplanted groups. Muscles can atrophy and contract if denervation has started. It would be difficult to recover muscle function even if the nerve was reinnervated. Therefore, although neurally differentiated ASCs were found to have a greater functional effect than non-differentiated ASCs, time constraint is important when considering a method of ASCs transplantation.

Experimetal research Dexamethasone and vitamin B12 synergistically promote peripheral nerve regeneration in rats by upregulating the expression of brain-derived neurotrophic factor

IntroductionDexamethasone and vitamin B12 are currently used in the clinic to treat peripheral nerve damage but their mechanisms of action remain incompletely understood. In this study we hypothesized that dexamethasone and vitamin B12 promote the production of endogenous neurotrophic factors, thereby enhancing peripheral nerve repair.Material and methodsNinety-six adult male Wistar rats were employed to establish a sciatic nerve injury model. They were then randomly divided into 4 groups to be subjected to different treatment: saline (group A), dexamethasone (group B), vitamin B12 (group C), and dexamethasone combined with vitamin B12 (group D). The walking behavior of rats was evaluated by footprint analysis, and the nerve regeneration was assessed by electrophysiological analysis and ultrastructural examination. The expression of brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor, NT-3 and IL-6 in the injured sciatic nerves was detected by immunohistochemical and RT-PCR analysis.ResultsDexamethasone and vitamin B12 promoted the regeneration of myelinated nerve fibers and the proliferation of Schwann cells. Furthermore, dexamethasone and vitamin B12 promoted the recovery of sciatic functional index and sensory nerve conduction velocity, and upregulated BDNF expression in the injured sciatic nerves.ConclusionsDexamethasone and vitamin B12 promote peripheral nerve repair in a rat model of sciatic nerve injury through the upregulation of BDNF expression. These findings provide new insight into the neurotrophic effects of dexamethasone and vitamin B12 and support the application of these agents in clinical treatment of peripheral nerve injury.

Pathology and gene expression of the sciatic nerve after non-freezing cold injury

Objective To investigate the morphological changes in the sciatic nerve and the dorsal root ganglions (DRGs) and also gene expression in DRGs after non-freezing cold injury, and to explore the molecular mechanism of peripheral nerve cold injury and regeneration. Methods Twenty-four male Wistar rats were used. The sciatic nerve on one side was cooled to 4℃ for 2 h, and the sciatic nerve on the opposite side was exposed, but without cooling. Sciatic nerves and L4, L5 and L6 DRGs from both sides were harvested at the 1st, 2nd and 3rd week after cooling. Any pathological changes were observed using light and electron microscopy. Laser capture microdissection (LCM) was used to investigate the DRG neurons' gene expression. The array result was verified with RT-PCR for eight genes. Results Large fiber degeneration was obvious by the 7th day after cooling. Myelinated fiber regeneration had begun by the 14th day, so this time was chosen to explore the neurons' gene expression. Ninety-six genes and expressed sequence tags (ESTs) were up-regulated greater than 2 fold. Their proteins' functions were classified as adaptive response to external stimulus, apoptosis regulation, cell adhesion, immune and inflammation response,nerve regeneration, pain associated molecules, microtubule cytoskeleton, ion-channels, neurotransmitters and receptors, and neuropeptides. Conclusions A complex molecular mechanism is involved in cold injury and regeneration of the sciatic nerve, and many genes are involved. Large scale microarray analysis is a potent means to screen out related genes, thus suggesting future repair strategies. Key words: Cold injury; Peripheral nerves; Gene expression; Microarrays; Laser capture microdissection

Soluble Nogo Receptor Down-regulates Expression of Neuronal Nogo-A to Enhance Axonal Regeneration

Nogo-A, a member of the reticulon family, is present in neurons and oligodendrocytes. Nogo-A in central nervous system (CNS) myelin prevents axonal regeneration through interaction with Nogo receptor 1, but the function of Nogo-A in neurons is less known. We found that after axonal injury, Nogo-A is increased in dorsal root ganglion (DRG) neurons unable to regenerate following a dorsal root injury or a sciatic nerve ligation-cut injury and that exposure in vitro to CNS myelin dramatically enhanced neuronal Nogo-A mRNA and protein through activation of RhoA while inhibiting neurite growth. Knocking down neuronal Nogo-A by small interfering RNA results in a marked increase of neurite outgrowth. We constructed a nonreplicating herpes simplex virus vector (QHNgSR) to express a truncated soluble fragment of Nogo receptor 1 (NgSR). NgSR released from QHNgSR prevented myelin inhibition of neurite extension by hippocampal and DRG neurons in vitro. NgSR prevents RhoA activation by myelin and decreases neuronal Nogo-A. Subcutaneous inoculation of QHNgSR to transduce DRG neurons resulted in improved regeneration of myelinated fibers in both the dorsal root and the spinal dorsal root entry zone, with concomitant improvement in sensory behavior. The results indicate that neuronal Nogo-A is an important intermediate in neurite growth dynamics and its expression is regulated by signals related to axonal injury and regeneration, that CNS myelin appears to activate signaling events that mimic axonal injury, and that NgSR released from QHNgSR may be used to improve recovery after injury.

Effects of 4-Methylcatechol on Skin Reinnervation: Promotion of Cutaneous Nerve Regeneration After Crush Injury

We assessed the effects of treatment with 4-methylcatechol (4MC), a known inducer of nerve growth factor, on peripheral nerve regeneration by analyzing cutaneous and muscular reinnervation in mice after sciatic nerve crush injury. At 3 months postinjury, the skin innervation index was significantly higher in the 4MC group than the control group (p=0.0002); there was also increased unmyelinated fiber density (p=0.0042) and unmyelinated fibers/Remak bundle (p = 0.001) in sural nerves, indicating unmyelinated nerve fiber regeneration. These changes were accompanied by increases of transcripts for nerve growth factor (p = 0.0026) and glial cell line-derived neurotrophic factor (p=0.03) in the 4MC group. In contrast, muscle innervation indices were similar in both groups and were higher than the skin innervation index (p < 0.0001). The regeneration of myelinated nerve fibers, as assessed by fiber density, diameter and g ratio analyses in sural nerves, and amplitudes of muscle action potential in sciatic nerves, was similar in both groups. Taken together, these data suggest that 4MC specifically promoted the regeneration of unmyelinated nerve fibers and reinnervation of the skin by increasing the expression of nerve growth factor and glial cell line-derived neurotrophic factor.