Axonal regrowth downregulates the synthesis of glial cell line-derived neurotrophic factor in the lesioned rat sciatic nerve

The effect of axonal regeneration on de novo synthesis of glial cell line-derived neurotrophic factor (GDNF) in rat sciatic nerves was examined. Transection of the sciatic nerve caused a prominent increase in the GDNF content in the distal segments within 1 week. The high level was sustained until 4 weeks in the animal model in which the nerve ends were ligated with thread (non-regeneration group); however, it was reduced to the original level within 2 or 4 weeks after the transection only in the segments invaded by regenerating axons in the models in which the nerve ends were coaptated (regeneration group). Expression of both GDNF protein and mRNA was decreased with a reciprocal increase in the density of neurofilaments, used as a marker of axonal ingrowth in distal segments of the regeneration group, suggesting that axonal contact turned off the GDNF-mediated nerve regeneration activity.     

GDNF及dvHSV-GDNF对坐骨神经损伤大鼠脊髓前角运动神经元的影响

为了探讨胶质细胞源性神经营养因子及单纯疱疹病毒载体介导的胶质细胞源性神经营养因子 (dv HSV-GDNF)对坐骨神经损伤大鼠脊髓前角运动神经元的作用 ,本实验对成年大鼠造成双侧坐骨神经损伤后 ,于右侧损伤处分别施加胶质细胞源性神经营养因子和 dv HSV-GDNF;左侧损伤处施加生理盐水作为对照。分别取损伤后 4、7、14和 2 8d大鼠的脊髓 L4 ～ L6 节段 ,经石蜡包埋切片后行 Nissl染色 ,计数前角运动神经元数量并进行统计学分析。结果发现 :坐骨神经损伤后 4、7、14和 2 8d,右侧脊髓前角运动神经元的数量明显高于左侧。提示 :胶质细胞源性神经营养因子和 dv HSV-GDNF可减少坐骨神经损伤大鼠脊髓前角运动神经元的死亡     

Fibrin conduit supplemented with human mesenchymal stem cells and immunosuppressive treatment enhances regeneration after peripheral nerve injury

To address the need for the development of bioengineered replacement of a nerve graft, a novel two component fibrin glue conduit was combined with human mesenchymal stem cells (MSC) and immunosupressive treatment with cyclosporine A. The effects of MSC on axonal regeneration in the conduit and reaction of activated macrophages were investigated using sciatic nerve injury model. A 10mm gap in the sciatic nerve of a rat was created and repaired either with fibrin glue conduit containing diluted fibrin matrix or fibrin glue conduit containing fibrin matrix with MSC at concentration of 80×10(6) cells/ml. Cells were labeled with PKH26 prior to transplantation. The animals received daily injections of cyclosporine A. After 3 weeks the distance of regeneration and area occupied by regenerating axons and ED1 positives macrophages was measured. MSC survived in the conduit and enhanced axonal regeneration only when transplantation was combined with cyclosporine A treatment. Moreover, addition of cyclosporine A to the conduits with transplanted MSC significantly reduced the ED1 macrophage reaction.     

The effect of collagen-binding NGF-β on the promotion of sciatic nerve regeneration in a rat sciatic nerve crush injury model

Nerve growth factor plays a critical role in peripheral nerve regeneration. However, the lack of efficient NGF delivery approach limits its clinical application. It has demonstrated in our previous work that the native human NGF-β (NAT-NGF) fused with a collagen-binding domain (CBD) could bind to collagen specifically. Since collagen is the major component of nerve extracellular matrix, we speculated that the collagen-binding NGF would target to nerve cells and improve their regeneration. In this report, we found that the fusion protein could specifically bind to endogenous collagen of the rat sciatic nerves and maintain NGF activity both in vitro and in vivo. In the rat sciatic nerve crush injury model, we found that collagen-binding NGF could be retained and concentrated at the nerve injured site to promote nerve repair and enhance function recovery following nerve damage. Thus, the collagen-binding NGF could improve the repair of peripheral nerve injury.     

β-1,4半乳糖基转移酶-I在钳夹伤后大鼠坐骨神经中表达的变化

为了观察β-1,4-半乳糖基转移酶-I(β-1,4-galactosyltransferase-I,β-1,4-GalT-I)在正常和钳夹伤后大鼠坐骨神经中表达的变化,本研究采用RT-PCR方法,从小鼠坐骨神经中特异性地扩增β-1,4-GalT-I cDNA片段并将其克隆到pGEM-T载体。采用体外转录的方法合成地高辛标记的正、反义β-1,4-GalT-I RNA探针。通过原位杂交和图像分析的方法,观察β-1,4-GalT-I mRNA在正常和夹伤大鼠坐骨神经中的表达及其变化。结果表明:β-1,4-GalT-I mRNA在大鼠坐骨神经的髓鞘中表达,在夹伤坐骨神经后1~2d,β-1,4-GalT-I mRNA在坐骨神经的表达最高,于夹伤后1周开始下降,在夹伤后1个月恢复至正常水平。上述结果提示坐骨神经夹伤后β-1,4-GalT-I mRNA的表达发生变化,并且主要表达在坐骨神经的Schwann细胞。本研究结果为进一步分析β-1,4-GalT-I在周围神经再生中的调控机制奠定了基础。     

胶质细胞源性神经营养因子缓释微球及NogoA,ChABC缓释微球联合应用损伤脊髓再生的形态学变化

背景：促进轴突再生的原则是改善抑制再生的环境和提高轴突生长能力,措施主要有轴突生长抑制因子阻滞剂和神经营养因子应用。用可降解微球加载药物是一种在局部提供持续药物释放的方法。 目的：探讨胶质细胞源性神经营养因子、NogoA、ChABC 缓释微球联合应用促进大鼠损伤脊髓再生病理形态学修复的作用。 方法：建立SD大鼠T10 脊髓完全横断伤模型,分别在损伤局部给予生理盐水、胶质细胞源性神经营养因子、胶质细胞源性神经营养因子缓释微球、NogoA缓释微球、ChABC 缓释微球及3种微球联合治疗,并设立未造模的正常组及假手术组。损伤后10周,每组行四甲基若丹明葡聚糖胺顺行示踪,及神经丝蛋白200、生长相关蛋白43、胶质细胞源性神经营养因子免疫组化检查,并采用免疫组化图像分析系统进行定量分析。 结果与结论：胶质细胞源性神经营养因子、NogoA、ChABC 缓释微球联合能提高脊髓损伤局部神经丝蛋白200、生长相关蛋白43、胶质纤维酸性蛋白的表达水平,显示局部脊髓再生修复加强,其效果优于单用胶质细胞源性神经营养因子缓释微球。提示,胶质细胞源性神经营养因子缓释微球及NogoA,ChABC 缓释微球联合促大鼠损伤脊髓再生修复其效果优于单用胶质细胞源性神经营养因子缓释微球。     

兔坐骨神经急性损伤的高频超声影像学观察

目的用高频超声观察兔坐骨神经急性损伤的超声图像表现,评价其临床诊断价值。方法16只健康家兔随机分为4组,建立兔坐骨神经急性损伤模型,分别在损伤后第1、2、4、8周,应用高频超声在同部位上观察双侧坐骨神经的声像图变化。结果坐骨神经损伤后,在不同阶段,高频超声均可观察到相应变化图像改变与神经损伤后退变、再生及肢体功能在动态变化上相一致。结论高频超声可实时准确反映神经退变和再生的过程,为诊断外周神经损伤提供新方法,对临床判断和预后提供客观依据。     

Survival and regeneration of cutaneous and muscular afferent neurons after peripheral nerve injury in adult rats

Peripheral nerve injury induces the retrograde degeneration of dorsal root ganglion (DRG) cells, which affects predominantly the small-diameter cutaneous afferent neurons. This study compares the time-course of retrograde cell death in cutaneous and muscular DRG cells after peripheral nerve transection as well as neuronal survival and axonal regeneration after primary repair or nerve grafting. For comparison, spinal motoneurons were also included in the study. Sural and medial gastrocnemius DRG neurons were retrogradely labeled with the fluorescent tracers Fast Blue (FB) or Fluoro-Gold (FG) from the homonymous transected nerves. Survival of labeled sural and gastrocnemius DRG cells was assessed at 3 days and 1–24 weeks after axotomy. To evaluate axonal regeneration, the sciatic nerve was transected proximally at 1 week after FB-labeling of the sural and medial gastrocnemius nerves and immediately reconstructed using primary repair or autologous nerve grafting. Twelve weeks later, the fluorescent tracer Fluoro-Ruby (FR) was applied 10 mm distal to the sciatic lesion in order to double-label sural and gastrocnemius neurons that had regenerated across the repair site. Counts of labeled gastrocnemius DRG neurons did not reveal any significant retrograde cell death after nerve transection. In contrast, sural axotomy induced a delayed loss of sural DRG cells, which amounted to 22% at 4 weeks and 43–48% at 8–24 weeks postoperatively. Proximal transection of the sciatic nerve at 1 week after injury to the sural or gastrocnemius nerves neither further increased retrograde DRG degeneration, nor did it affect survival of sural or gastrocnemius motoneurons. Primary repair or peripheral nerve grafting supported regeneration of 53–60% of the spinal motoneurons and 47–49% of the muscular DRG neurons at 13 weeks postoperatively. In the cutaneous DRG neurons, primary repair or peripheral nerve grafting increased survival by 19–30% and promoted regeneration of 46–66% of the cells. The present results suggest that cutaneous DRG neurons are more sensitive to peripheral nerve injury than muscular DRG cells, but that their regenerative capacity does not differ from that of the latter cells. However, the retrograde loss of cutaneous DRG cells taking place despite immediate nerve repair would still limit the recovery of cutaneous sensory functions.     

Expression of type I and III collagens and fibronectin after transection of rat sciatic nerve. Reinnervation compared with denervation.

BACKGROUND: The regeneration of transected peripheral nerve is thought to happen with the help of cell-cell and cell-extracellular matrix interactions. We studied the role of axon in controlling the expression of extracellular matrix genes in transected peripheral nerve. EXPERIMENTAL DESIGN: Left sciatic nerves were transected in a total of 132 rats. In half of the animals, regeneration was allowed to occur, while in the other half regeneration was prevented. The expression of type I and III collagen and fibronectin genes was studied proximally and distally to the site of transection up to 8 weeks after the injury both with and without axonal reinnervation. For Northern blotting, the endoneuriums of 10 animals from both groups were used at each time point. For in situ hybridization, transverse sections of the nerves were used to observe cellular source of the mRNA. In addition, immunohistochemistry was performed in sequential sections in order to identify the cells expressing the studied extracellular matrix genes. RESULTS: Northern hybridization showed the highest expression of type I and III collagens in the distal stumps of transected nerves 7 to 14 days after nerve transection both with and without axonal reinnervation. The proximal site of the injury showed strong expression of the extracellular matrix genes which lasted markedly longer than in the distal site. In situ hybridizations showed that epi-, peri-, and endoneurium are active for producing type I collagen. S-100 immunohistochemistry suggested that the cell type responsible for the production of type I collagen in the endoneurium during the peripheral nerve regeneration is endoneurial fibroblast. CONCLUSIONS: During peripheral nerve regeneration the expression of the extracellular matrix genes does not seem to be simply related to the presence of axons. Endoneurial fibroblasts contribute to the production of collagen type I and apparently to that of fibronectin, which thus is not totally derived from plasma.     

Interleukin-1 beta promotes sensory nerve regeneration after sciatic nerve injury

Nerve injury brings about axonal disconnection, and thus axonal extension is one of the important steps for nerve regeneration. Expression of the pro-inflammatory cytokine interleukin-1 beta (IL-1beta) is increased at the early stage of nervous system injury, and previously IL-1beta has been reported to promote neurite outgrowth by inhibiting RhoA activity in vitro. However, the effect of IL-1beta on axonal extension in vivo has not been obvious. Now we examine whether IL-1beta takes advantages on sciatic nerve regeneration. Sciatic nerves of rats are transected and sutured, and IL-1beta or PBS is locally administered for 2 weeks. Although IL-1beta does not influence on motor functional recovery, it promotes sensory functional recovery, estimated by toe pinch test, and increases the number and the area of neurofilament-positive axons at 12 weeks compared with PBS. Moreover IL-1beta, which promotes Schwann cell proliferation and thus may inhibit myelination, does not impair remyelination, estimated by myelin basic protein. These findings suggest that IL-1beta may contribute to sensory nerve regeneration following sciatic nerve injury by promoting axonal extension.     

Peripheral nerve tissue engineering: autologous Schwann cells vs. transdifferentiated mesenchymal stem cells

Mesenchymal stem cells (MSCs) were evaluated as an alternative source for tissue engineering of peripheral nerves. MSCs, transdifferentiated MSCs, or Schwann cells cultured from male rats were grafted into devitalized autologous muscle conduits bridging a 2-cm sciatic nerve gap in female rats. The differentiation potential of MSCs and transformed cultivated MSCs into Schwann cell-like cells was exploited using a cocktail of cytokines. Polymerase chain reaction of the SRY gene confirmed the presence of the implanted cells in the grafts. After 6 weeks, regeneration was monitored clinically, histologically, and morphometrically. Autologous nerves and cell-free muscle grafts were used as control. Revascularization studies suggested that transdifferentiated MSCs, in contrast to undifferentiated MSCs, facilitated neo-angiogenesis and did not influence macrophage recruitment. Autologous nerve grafts demonstrated the best results in all regenerative parameters. An appropriate regeneration was noted in the Schwann cell-groups and, albeit with restrictions, in the transdifferentiated MSC groups, whereas regeneration in the MSC group and in the cell-free group was impaired. The results indicate that transdifferentiated MSCs implanted into devitalized muscle grafts are able to support peripheral nerve regeneration to some extent, and offer a potential for new therapeutic strategies.     

A modular,plasmin-sensitive,clickable poly(ethylene glycol)-heparin-laminin microsphere system for establishing growth factor gradients in nerve guidance conduits

Peripheral nerve regeneration is a complex problem that, despite many advancements and innovations, still has sub-optimal outcomes. Compared to biologically derived acellular nerve grafts and autografts, completely synthetic nerve guidance conduits (NGC), which allow for precise engineering of their properties, are promising but still far from optimal. We have developed an almost entirely synthetic NGC that allows control of soluble growth factor delivery kinetics, cell-initiated degradability and cell attachment. We have focused on the spatial patterning of glial-cell derived human neurotrophic factor (GDNF), which promotes motor axon extension. The base scaffolds consisted of heparin-containing poly(ethylene glycol) (PEG) microspheres. The modular microsphere format greatly simplifies the formation of concentration gradients of reversibly bound GDNF. To facilitate axon extension, we engineered the microspheres with tunable plasmin degradability. ‘Click’ cross-linking chemistries were also added to allow scaffold formation without risk of covalently coupling the growth factor to the scaffold. Cell adhesion was promoted by covalently bound laminin. GDNF that was released from these microspheres was confirmed to retain its activity. Graded scaffolds were formed inside silicone conduits using 3D-printed holders. The fully formed NGC's contained plasmin-degradable PEG/heparin scaffolds that developed linear gradients in reversibly bound GDNF. The NGC's were implanted into rats with severed sciatic nerves to confirm in vivo degradability and lack of a major foreign body response. The NGC's also promoted robust axonal regeneration into the conduit.     

Mesenchymal stem cells in a polycaprolactone conduit promote sciatic nerve regeneration and sensory neuron survival after nerve injury

Despite the fact that the peripheral nervous system is able to regenerate after traumatic injury, the functional outcomes following damage are limited and poor. Bone marrow mesenchymal stem cells (MSCs) are multipotent cells that have been used in studies of peripheral nerve regeneration and have yielded promising results. The aim of this study was to evaluate sciatic nerve regeneration and neuronal survival in mice after nerve transection followed by MSC treatment into a polycaprolactone (PCL) nerve guide. The left sciatic nerve of C57BL/6 mice was transected and the nerve stumps were placed into a biodegradable PCL tube leaving a 3-mm gap between them; the tube was filled with MSCs obtained from GFP+ animals (MSC-treated group) or with a culture medium (Dulbecco's modified Eagle's medium group). Motor function was analyzed according to the sciatic functional index (SFI). After 6 weeks, animals were euthanized, and the regenerated sciatic nerve, the dorsal root ganglion (DRG), the spinal cord, and the gastrocnemius muscle were collected and processed for light and electron microscopy. A quantitative analysis of regenerated nerves showed a significant increase in the number of myelinated fibers in the group that received, within the nerve guide, stem cells. The number of neurons in the DRG was significantly higher in the MSC-treated group, while there was no difference in the number of motor neurons in the spinal cord. We also found higher values of trophic factors expression in MSC-treated groups, especially a nerve growth factor. The SFI revealed a significant improvement in the MSC-treated group. The gastrocnemius muscle showed an increase in weight and in the levels of creatine phosphokinase enzyme, suggesting an improvement of reinnervation and activity in animals that received MSCs. Immunohistochemistry documented that some GFP+ -transplanted cells assumed a Schwann-cell-like phenotype, as evidenced by their expression of the S-100 protein, a Schwann cell marker. Our findings suggest that using a PCL tube filled with MSCs is a good strategy to improve nerve regeneration after a nerve transection in mice.     

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

Introduction

Dexamethasone 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 methods

Ninety-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.

Results

Dexamethasone 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.

Conclusions

Dexamethasone 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.     

Erythropoietin promotes peripheral nerve regeneration in rats by upregulating expression of insulin-like growth factor-1

Introduction

Erythropoietin (EPO) has been shown to have beneficial effects on peripheral nerve damage, but its mechanism of action remains incompletely understood. In this study we hypothesized that EPO promotes peripheral nerve repair via neurotrophic factor upregulation.

Material and methods

Thirty adult male Wistar rats were employed to establish a sciatic nerve injury model. They were then randomly divided into two groups to be subjected to different treatment: 0.9% saline (group A) and 5000 U/kg EPO (group B). The walking behavior of rats was evaluated by footprint analysis, and the nerve regeneration was assessed by electron microscopy. The expression of insulin-like growth factor-1 (IGF-1) in the injured sciatic nerves was detected by immunohistochemical analysis.

Results

Compared to saline treatment, EPO treatment led to the growth of myelin sheath, the recovery of normal morphology of axons and Schwann cells, and higher density of myelinated nerve fibers. Erythropoietin treatment promoted the recovery of SFI in the injured sciatic nerves. In addition, EPO treatment led to increased IGF-1 expression in the injured sciatic nerves.

Conclusions

Erythropoietin may promote peripheral nerve repair in a rat model of sciatic nerve injury through the upregulation of IGF-1 expression. These findings reveal a novel mechanism underlying the neurotrophic effects of EPO.     

Morphometric and ultrastructural studies of the sciatic nerve regeneration in rats intoxicated with ethanol.

The aim of the study was to examine the process of sciatic nerve regeneration and changes in the dorsal root ganglia (from which sensory fibres of the sciatic nerve extend) in animals intoxicated with ethanol. The experiment used 20 rats, divided into two groups: control and treated. The treated animals were intragastrically given 2g/kg b.w. of ethanol in 25% aqueous solution. In both groups the right sciatic nerve was transected and then sutured. After 5 months the animals were anaesthetized. The left and the right spinal dorsal ganglia-L5 and sections from the non-operated and operated sciatic nerves were collected for analysis. Ultrastructural examinations and morphometric measurements were conducted. It was found that ethanol administrated to rats inhibited regeneration of the transected and then sutured sciatic nerve, impairing the growth of axons in the transected nerve and destroying the regenerating sensory ganglion cells. The mechanism of the changes described may be associated with axonal transport disorders or with the suppressed production of biologically active substances, which affect nerve regeneration.     

Supplementation of acellular nerve grafts with skin derived precursor cells promotes peripheral nerve regeneration

Introduction of autologous stem cells into the site of a nerve injury presents a promising therapy to promote axonal regeneration and remyelination following peripheral nerve damage. Given their documented ability to differentiate into Schwann cells (SCs) in vitro, we hypothesized that skin-derived precursor cells (SKPs) could represent a clinically-relevant source of transplantable cells that would enhance nerve regeneration following peripheral nerve injury. In this study, we examined the potential for SKP-derived Schwann cells (SKP–SCs) or nerve-derived SCs to improve nerve regeneration across a 12 mm gap created in the sciatic nerve of Lewis rats bridged by a freeze-thawed nerve graft. Immunohistology after 4 weeks showed survival of both cell types and early regeneration in SKP seeded grafts was comparable to those seeded with SCs. Histomorphometrical and electrophysiological measurements of cell-treated nerve segments after 8 weeks survival all showed significant improvement as compared to diluent controls. A possible mechanistic explanation for the observed results of improved regenerative outcomes lies in SKP–SCs' ability to secrete bioactive neurotrophins. We therefore conclude that SKPs represent an easily accessible, autologous source of stem cells for transplantation therapies which act as functional Schwann cells and show great promise in improving regeneration following nerve injury.     

Affinity-based release of glial-derived neurotrophic factor from fibrin matrices enhances sciatic nerve regeneration

Glial-derived neurotrophic factor (GDNF) promotes both sensory and motor neuron survival. The delivery of GDNF to the peripheral nervous system has been shown to enhance regeneration following injury. In this study, we evaluated the effect of affinity-based delivery of GDNF from a fibrin matrix in a nerve guidance conduit on nerve regeneration in a 13 mm rat sciatic nerve defect. Seven experimental groups were evaluated which received GDNF or nerve growth factor (NGF) with the delivery system within the conduit, control groups excluding one or more components of the delivery system, and nerve isografts. Nerves were harvested 6 weeks after treatment for analysis by histomorphometry and electron microscopy. The use of the delivery system (DS) with either GDNF or NGF resulted in a higher frequency of nerve regeneration vs. control groups, as evidenced by a neural structure spanning the 13 mm gap. The GDNF DS and NGF DS groups were also similar to the nerve isograft group in measures of nerve fiber density, percent neural tissue and myelinated area measurements, but not in terms of total fiber counts. In addition, both groups contained a significantly greater percentage of larger diameter fibers, with GDNF DS having the largest in comparison to all groups, suggesting more mature neural content. The delivery of GDNF via the affinity-based delivery system can enhance peripheral nerve regeneration through a silicone conduit across a critical nerve gap and offers insight into potential future alternatives to the treatment of peripheral nerve injuries.     

Neurite extension of DRG neurons by gicerin expression is enhanced by nerve growth factor

Gicerin, a cell adhesion molecule, is expressed in dorsal root ganglion (DRG) and sciatic nerves during chick development. This molecule re-appears in these tissues after an injury to the sciatic nerve. In the present study, we investigated the expression of nerve growth factor (NGF) in the regenerating sciatic nerve of chicks and the effects of NGF on the expression and neurite activities of gicerin in DRG. In the sciatic nerve after a crush injury, the expression of NGF and gicerin increased in the Schwann cells and in the nerve fibers, respectively. NGF promoted the neurite projections from in vitro DRG on the gicerin ligands, which were inhibited by anti-NGF antibody. The gicerin mRNA expression increased in the DRG with NGF, which was inhibited by the co-incubation with anti-NGF antibody. These results indicate that NGF might therefore enhance the expression of gicerin in DRG, thereby promoting the gicerin-dependent neurite extension during sciatic nerve regeneration.     

Regulatory expression of Neurensin-1 in the spinal motor neurons after mouse sciatic nerve injury

Axonal regeneration after crush injury of the sciatic nerve has been intensely studied for the elucidation of molecular and cellular mechanisms. Neurite extension factor1 (Nrsn1) is a unique membranous protein that has a microtubule-binding domain and is specifically expressed in neurons. Our studies have shown that Nrsn1 is localized particularly in actively extending neurites, thus playing a role in membrane transport to the growing distal ends of extending neurites. To elucidate the possible role of Nrsn1 during peripheral axonal regeneration, we examined the expression of Nrsn1 mRNA by in situ hybridization and Nrsn1 localization by immunocytochemistry, using a mouse model. The results revealed that during the early phase of axonal regeneration of motor nerves, Nrsn1 mRNA is upregulated in the injured motor neuron. Nrsn1 is localized in the cell bodies of motor neurons and at the growing distal ends of regenerating axons. These results indicate that Nrsn1 plays an active role in axonal regeneration as well as in embryonic development.