Process Of Peripheral Nerve Regeneration Research Articles

Nanoparticle-Facilitated Therapy: Advancing Tools in Peripheral Nerve Regeneration.

Peripheral nerve injuries, arising from a diverse range of etiologies such as trauma and underlying medical conditions, pose substantial challenges in both clinical management and subsequent restoration of functional capacity. Addressing these challenges, nanoparticles have emerged as a promising therapeutic modality poised to augment the process of peripheral nerve regeneration. However, a comprehensive elucidation of the complicated mechanistic foundations responsible for the favorable effects of nanoparticle-based therapy on nerve regeneration remains imperative. This review aims to scrutinize the potential of nanoparticles as innovative therapeutic carriers for promoting peripheral nerve repair. This review encompasses an in-depth exploration of the classifications and synthesis methodologies associated with nanoparticles. Additionally, we discuss and summarize the multifaceted roles that nanoparticles play, including neuroprotection, facilitation of axonal growth, and efficient drug delivery mechanisms. Furthermore, we present essential considerations and highlight the potential synergies of integrating nanoparticles with emerging technologies. Through this comprehensive review, we highlight the indispensable role of nanoparticles in propelling advancements in peripheral nerve regeneration.

Grape seed-derived procyanidins decreases neuropathic pain and nerve regeneration by suppression of toll-like receptor 4-myeloid differentiation factor-88 signaling.

Background: Recent studies have shown that peripheral nerve regeneration process is closely related to neuropathic pain. Toll-like receptor 4 (TLR4) signaling was involved in different types of pain and nerve regeneration. TLR4 induced the recruitment of myeloid differentiation factor-88 adaptor protein (MyD88) and NF-κB-depended transcriptional process in sensory neurons and glial cells, which produced multiple cytokines and promoted the induction and persistence of pain. Our study aimed to investigate procyanidins's effect on pain and nerve regeneration via TLR4-Myd88 signaling. Methods: Spinal nerve ligation (SNL) model was established to measure the analgesic effect of procyanidins. Anatomical measurement of peripheral nerve regeneration was measured by microscopy and growth associated protein 43 (GAP43) staining. Western blotting and/or immunofluorescent staining were utilized to detect TLR4, myeloid differentiation factor-88 adaptor protein (MyD88), ionized calcium-binding adapter molecule 1 (IBA1) and nuclear factor kappa-B-p65 (NF-κB-p65) expression, as well as the activation of astrocyte and microglia. The antagonist of TLR4 (LPS-RS-Ultra, LRU) were intrathecally administrated to assess the behavioral effects of blocking TLR4 signaling on pain and nerve regeneration. Result: Procyanidins reduced mechanical allodynia, thermal hyperalgesia and significantly suppressed the number of nerve fibers regenerated and the degree of myelination in SNL model. Compared with sham group, TLR4, MyD88, IBA1 and phosphorylation of NF-κB-p65 were upregulated in SNL rats which were reversed by procyanidins administration. Additionally, procyanidins also suppressed activation of spinal astrocytes and glial cells. Conclusion: Suppression of TLR4-MyD88 signaling contributes to the alleviation of neuropathic pain and reduction of nerve regeneration by procyanidins.

Progress in methods for evaluating Schwann cell myelination and axonal growth in peripheral nerve regeneration via scaffolds.

Peripheral nerve injury (PNI) is a neurological disorder caused by trauma that is frequently induced by accidents, war, and surgical complications, which is of global significance. The severity of the injury determines the potential for lifelong disability in patients. Artificial nerve scaffolds have been investigated as a powerful tool for promoting optimal regeneration of nerve defects. Over the past few decades, bionic scaffolds have been successfully developed to provide guidance and biological cues to facilitate Schwann cell myelination and orientated axonal growth. Numerous assessment techniques have been employed to investigate the therapeutic efficacy of nerve scaffolds in promoting the growth of Schwann cells and axons upon the bioactivities of distinct scaffolds, which have encouraged a greater understanding of the biological mechanisms involved in peripheral nerve development and regeneration. However, it is still difficult to compare the results from different labs due to the diversity of protocols and the availability of innovative technologies when evaluating the effectiveness of novel artificial scaffolds. Meanwhile, due to the complicated process of peripheral nerve regeneration, several evaluation methods are usually combined in studies on peripheral nerve repair. Herein, we have provided an overview of the evaluation methods used to study the outcomes of scaffold-based therapies for PNI in experimental animal models and especially focus on Schwann cell functions and axonal growth within the regenerated nerve.

Nicotine Decreases Nerve Regeneration and Pain Behaviors via PTEN and Downstream Inflammation-Related Pathway in Two Rat Nerve Injury Models.

Neuropathic pain is stubborn and associated with the peripheral nerve regeneration process. Nicotine has been found to reduce pain, but whether it is involved in the regulation of nerve regeneration and the underlying mechanism are unknown. In this study, we examined the mechanical allodynia thermal hyperalgesia together with the peripheral nerve regeneration after nicotine exposure in two rat neuropathic pain models. In the spinal nerve ligation model, in which anatomic nerve regeneration can be easily observed, nicotine reduced anatomic measures of regeneration as well as expression of regeneration marker growth-associated protein 43 (GAP43). In the tibial nerve crush model, nicotine treatment significantly suppressed GAP43 expression and functional reinnervation as measured by myelinated action potential and electromyography of gastrocnemius. In both models, nicotine treatment reduced macrophage density in the sensory ganglia and peripheral nerve. These effects of nicotine were reversed by the selective α7 nicotinic acetylcholine receptor (nAChR) blocker methyllycaconitine. In addition, nicotine significantly elevated expression of PTEN (the phosphatase and tensin homolog deleted on chromosome 10), a key player in both regeneration and pain. Pharmacological interference of PTEN could regulate GAP43 expression, pain-related behaviors, and macrophage infiltration in a nicotine-treated nerve crush model. Our results reveal that nicotine and its α7-nAChR regulate both peripheral nerve regeneration process and pain though PTEN and the downstream inflammation-related pathway.

Biocompatible Polyurethane Conduit Grafted with Vascular Endothelial Growth Factor-Loaded Hydrogel Repairs the Peripheral Nerve Defect in Rats.

Artificial nerve guidance conduits (NGCs) can be potentially used to address the problems of peripheral nerve defects. The biomaterial polyurethane (PU) has already been used to construct NGCs. However, the use of a combination of PU-based NGCs and other bioactive cues, such as extracellular matrix proteins and growth factors, has not been reported yet. A PU conduit grafted with a vascular endothelial growth factor (VEGF)-loaded hydrogel (abbreviated as PU/Gel/VEGF conduit) is fabricated. The leachate generated during the use of the PU/Gel/VEGF conduit could facilitate the proliferation, migration, and expression of the neural marker S100β in RSC96 cells (in vitro). The walking track and target muscle are analyzed, and it is observed that PU/Gel/VEGF conduits promote the functional recovery of the injured side. Various histological staining analyses are carried out, and the results reveal that the PU/Gel/VEGF conduit effectively improves the extent of nerve regeneration achieved. The number of blood vessels developed during the regeneration of the axons in the PU/Gel/VEGF group (attributable to the pro-angiogenic effect of the functional NGC) is higher than the number of blood vessels developed in the PU/Gel conduit. Overall, the results indicate that PU/Gel/VEGF conduits could promote the process of peripheral nerve regeneration.

Analysis of Influencing Factors of Repair Effect after Peripheral Nerve Injury.

In order to improve the repair effect after peripheral nerve injury, this paper analyzes the related influencing factors. The regeneration of peripheral nerve includes two continuous and overlapping processes: the acute wound healing period and the axon seeking target tissue period. The complete and effective process of peripheral nerve regeneration includes the sprouting, growth and extension of regenerated axons, and the reconstruction of synaptic connections (neuromuscular junctions) with target organs to realize the reinnervation of nerves and restore function. This process includes three indicators of success in regeneration: structural reconstruction, metabolic regeneration, and functional recovery. In order to improve the repair effect of peripheral nerve injury, relevant influencing factors can be analyzed, and effective improvement of these influencing factors can improve the recovery effect of peripheral nerve injury. Finally, this paper analyzes multiple factors to provide theoretical references for follow-up clinical diagnosis and treatment.

Peripheral Nerve Healing: So Near and Yet So Far.

Peripheral nerve injuries represent a considerable portion of chronic disability that especially affects the younger population. Prerequisites of proper peripheral nerve injury treatment include in-depth knowledge of the anatomy, pathophysiology, and options in surgical reconstruction. Our greater appreciation of nerve healing mechanisms and the development of different microsurgical techniques have significantly refined the outcomes in treatment for the past four decades. This work reviews the peripheral nerve regeneration process after an injury, provides an overview of various coaptation methods, and compares other available treatments such as autologous nerve graft, acellular nerve allograft, and synthetic nerve conduits. Furthermore, the formation of neuromas as well as their latest treatment options are discussed.

The Role of Dietary Nutrients in Peripheral Nerve Regeneration.

Peripheral nerves are highly susceptible to injuries induced from everyday activities such as falling or work and sport accidents as well as more severe incidents such as car and motorcycle accidents. Many efforts have been made to improve nerve regeneration, but a satisfactory outcome is still unachieved, highlighting the need for easy to apply supportive strategies for stimulating nerve growth and functional recovery. Recent focus has been made on the effect of the consumed diet and its relation to healthy and well-functioning body systems. Normally, a balanced, healthy daily diet should provide our body with all the needed nutritional elements for maintaining correct function. The health of the central and peripheral nervous system is largely dependent on balanced nutrients supply. While already addressed in many reviews with different focus, we comprehensively review here the possible role of different nutrients in maintaining a healthy peripheral nervous system and their possible role in supporting the process of peripheral nerve regeneration. In fact, many dietary supplements have already demonstrated an important role in peripheral nerve development and regeneration; thus, a tailored dietary plan supplied to a patient following nerve injury could play a non-negotiable role in accelerating and promoting the process of nerve regeneration.

Localized sympathectomy reduces peripheral nerve regeneration and pain behaviors in 2 rat neuropathic pain models.

Previous studies have shown that the peripheral nerve regeneration process is linked to pain in several neuropathic pain models. Other studies show that sympathetic blockade may relieve pain in some pain models and clinical conditions. This study examined reduction in peripheral nerve regeneration as one possible mechanism for relief of neuropathic pain by sympathetic blockade. A "microsympathectomy," consisting of cutting the gray rami containing sympathetic postganglionic axons where they enter the L4 and L5 spinal nerves, reduced mechanical hypersensitivity in 2 different rat neuropathic pain models. In the spinal nerve ligation model, in which some functional regeneration and reinnervation of the ligated spinal nerve can be observed, microsympathectomy reduced functional and anatomical measures of regeneration as well as expression of growth-associated protein 43 (GAP43), a regeneration-related protein. In the spared nerve injury model, in which functional reinnervation is not possible and the futile regeneration process results in formation of a neuroma, microsympathectomy reduced neuroma formation and GAP43 expression. In both models, microsympathectomy reduced macrophage density in the sensory ganglia and peripheral nerve. This corroborates previous work showing that sympathetic nerves may locally affect immune function. The results further highlight the challenge of improving pain in neuropathic conditions without inhibiting peripheral nerve regeneration that might otherwise be possible and desired.

Analysis of Schwann Cell Migration and Axon Regeneration Following Nerve Injury in the Sciatic Nerve Bridge.

While it is proposed that interaction between Schwann cells and axons is key for successful nerve regeneration, the behavior of Schwann cells migrating into a nerve gap following a transection injury and how migrating Schwann cells interact with regenerating axons within the nerve bridge has not been studied in detail. In this study, we combine the use of our whole-mount sciatic nerve staining with the use of a proteolipid protein-green fluorescent protein (PLP-GFP) mouse model to mark Schwann cells and have examined the behavior of migrating Schwann cells and regenerating axons in the sciatic nerve gap following a nerve transection injury. We show here that Schwann cell migration from both nerve stumps starts later than the regrowth of axons from the proximal nerve stump. The first migrating Schwann cells are only observed 4 days following mouse sciatic nerve transection injury. Schwann cells migrating from the proximal nerve stump overtake regenerating axons on day 5 and form Schwann cell cords within the nerve bridge by 7 days post-transection injury. Regenerating axons begin to attach to migrating Schwann cells on day 6 and then follow their trajectory navigating across the nerve gap. We also observe that Schwann cell cords in the nerve bridge are not wide enough to guide all the regenerating axons across the nerve bridge, resulting in regenerating axons growing along the outside of both proximal and distal nerve stumps. From this analysis, we demonstrate that Schwann cells play a crucial role in controlling the directionality and speed of axon regeneration across the nerve gap. We also demonstrate that the use of the PLP-GFP mouse model labeling Schwann cells together with the whole sciatic nerve axon staining technique is a useful research model to study the process of peripheral nerve regeneration.

In vivo Evaluation of Nanostructured Fibrin-Agarose Hydrogels With Mesenchymal Stem Cells for Peripheral Nerve Repair.

The regenerative capability of peripheral nerves is very limited, and several strategies have been proposed to increase nerve regeneration. In the present work, we have analyzed the in vivo usefulness of a novel nanostructured fibrin-agarose bio-artificial nerve substitute (Nano) used alone or in combination with NeuraGen® collagen type I conduits (Coll-Nano) in laboratory rats with a 10-mm sciatic nerve defect. Control animals were subjected to the gold-standard autograft technique (Auto). Results first demonstrated that the percentage of self-amputations was lower in Nano and Coll-Nano groups as compared to the Auto group. Neurotrophic ulcers were more abundant in the Auto group (60%, with 66.6% of them being >2-mm) than Nano and Coll-Nano groups (0%) at 4 weeks, although Nano showed more ulcers after 12 weeks. Foot length was significantly altered in Auto animals due to neurogenic retraction, but not in Nano and Coll-Nano groups after 12 weeks. At the functional level, all animals showed a partial sensory recovery as determined by the pinch test, especially in Nano and Auto groups, but did not reach the levels of native animals. Toe-spread test revealed a partial motor function recovery only in Nano animals at 4 weeks and Auto and Nano at 12 weeks. Electromyography showed clear denervation signs in all experimental groups, with few differences between Auto and Nano animals. After 12 weeks, an important denervation decrease and an increase of the reinnervation process was found in Auto and Nano groups, with no differences between these groups. Histological analyses demonstrated an active peripheral nerve regeneration process with newly formed peripheral nerve fascicles showing S-100, GAP-43 and myelin in all experimental groups. The peripheral nerve regeneration process was more abundant in Auto group, followed by Nano group, and both were better than Coll-Nano group. Muscle histology confirmed the electromyography results and showed some atrophy and fibrosis signs and an important weight and volume loss in all groups, especially in the Coll-Nano group (56.8% weight and 60.4% volume loss). All these results suggest that the novel Nano substitutes used in in vivo were able to contribute to bridge a 10-mm peripheral nerve defect in rats.

Traumatic neuroma caused the post-amputation neuropathic pain: epidemiology, mechanisms and factors involved in pain generation

Loss of the integrity of the peripheral nerves as a result of the traumatic injury or due to lower limb amputations in case of advanced ischemic disease is leading to serious complications and impaired tissue regeneration. Patients who experiencedamputation procedure do not only suffer from physical limitations and psychological problems, but also from chronic neuropathic pain, referred to as post-amputation pain (PAP), which significant decrease their quality of life. One of the main reason of PAP is post-traumatic neuromas, which are form chaotic structures consisting of regenerative axons and connective tissue, as a results of excessive regeneration of axons. The process of peripheral nerve regeneration starts with Wallerian degeneration and its main role is to degenerate damaged axons in the distal end of the injured nerve and initiate repair processes. In the process of nerves regeneration are involved Schwann cells, which attract immunocompetent cells (mainly macrophages, neutrophils and T lymphocytes) and activate inflammation process, necessary to remove damaged tissues and cells. However, the coordination of the production of pro- and anti-inflammatory cytokines and the activity of neurotrophic factors is of key importance. During regeneration of peripheral nerves, in the microenvironment of the damaged tissues increase the activity of neurotrophic factors including: nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), and ciliary neurotrophic factor (CNTF) - proteins promoting survival and regeneration of axons. The activity of neurotrophic factors supports axonal regeneration from the proximal part into the distal direction and the final re-innervation of the tissue. In the case of amputation of the limb, the lack of distal stump of the nerve disturb proper regeneration of axons, and excessive activity of neurotrophic factors at the site of injury leads to uncontrolled axonal proliferation and neuroma formation. In addition, the increased activity of NGF enhances the expression of the protein associated with the calcitonin gene related protein (CGRP), which is one of the factors involved in the genesis of neuropathic pain. The protection of the proximal end of the damaged nerve from the regenerative signals coming from the microenvironment of damaged nerve can prevent excessive growth of axons and may inhibit the post-traumatic neuroma formation.

Hepatocyte Growth Factor (HGF) Promotes Peripheral Nerve Regeneration by Activating Repair Schwann Cells

During the peripheral nerve regeneration process, a variety of neurotrophic factors play roles in nerve repair by acting on neuronal or non-neuronal cells. In this report, we investigated the role(s) of hepatocyte growth factor (HGF) and its receptor, c-met, in peripheral nerve regeneration. When mice were subjected to sciatic nerve injury, the HGF protein level was highly increased at the injured and distal sites. The level of both total and phosphorylated c-met was also highly upregulated, but almost exclusively in Schwann cells (SCs) distal from the injury site. When mice were treated with a c-met inhibitor, PHA-665752, myelin thickness and axon regrowth were decreased indicating that re-myelination was hindered. HGF promoted the migration and proliferation of cultured SCs, and also induced the expression of various genes such as GDNF and LIF, presumably by activating ERK pathways. Furthermore, exogenous supply of HGF around the injury site, by intramuscular injection of a plasmid DNA expressing human HGF, enhanced the myelin thickness and axon diameter in injured nerves. Taken together, our results indicate that HGF and c-met play important roles in Schwann cell-mediated nerve repair, and also that HGF gene transfer may provide a useful tool for treating peripheral neuropathy.

Schwann cell durotaxis can be guided by physiologically relevant stiffness gradients

BackgroundSuccessful nerve regeneration depends upon directed migration of morphologically specialized repair state Schwann cells across a nerve defect. Although several groups have studied directed migration of Schwann cells in response to chemical or topographic cues, the current understanding of how the mechanical environment influences migration remains largely understudied and incomplete. Therefore, the focus of this study was to evaluate Schwann cell migration and morphodynamics in the presence of stiffness gradients, which revealed that Schwann cells can follow extracellular gradients of increasing stiffness, in a form of directed migration termed durotaxis.MethodsPolyacrylamide substrates were fabricated to mimic the range of stiffness found in peripheral nerve tissue. We assessed Schwann cell response to substrates that were either mechanically uniform or embedded with a shallow or steep stiffness gradient, respectively corresponding to the mechanical niche present during either the fluid phase or subsequent matrix phase of the peripheral nerve regeneration process. We examined cell migration (velocity and directionality) and morphology (elongation, spread area, nuclear aspect ratio, and cell process dynamics). We also characterized the surface morphology of Schwann cells by scanning electron microscopy.ResultsOn laminin-coated polyacrylamide substrates embedded with either a shallow (∼0.04 kPa/mm) or steep (∼0.95 kPa/mm) stiffness gradient, Schwann cells displayed durotaxis, increasing both their speed and directionality along the gradient materials, fabricated with elastic moduli in the range found in peripheral nerve tissue. Uniquely and unlike cell behavior reported in other cell types, the durotactic response of Schwann cells was not dependent upon the slope of the gradient. When we examined whether durotaxis behavior was accompanied by a pro-regenerative Schwann cell phenotype, we observed altered cell morphology, including increases in spread area and the number, elongation, and branching of the cellular processes, on the steep but not the shallow gradient materials. This phenotype emerged within hours of the cells adhering to the materials and was sustained throughout the 24 hour duration of the experiment. Control experiments also showed that unlike most adherent cells, Schwann cells did not alter their morphology in response to uniform substrates of different stiffnesses.ConclusionThis study is notable in its report of durotaxis of cells in response to a stiffness gradient slope, which is greater than an order of magnitude less than reported elsewhere in the literature, suggesting Schwann cells are highly sensitive detectors of mechanical heterogeneity. Altogether, this work identifies durotaxis as a new migratory modality in Schwann cells, and further shows that the presence of a steep stiffness gradient can support a pro-regenerative cell morphology.

Use of Stem Cells in the Regeneration of Peripheral Nerve Injuries: an Overview

Introduction: Peripheral nervous system has an innate regenerative ability that many factors are involved in its formation, such as Schwann cells, growth factors, and extracellular matrix. However, in severe injuries, peripheral nerve regeneration process is very weak and ineffective and therapeutic measures are needed for nerve regeneration. Current therapeutic methods have several limitations and low efficacy. In this regard, one of the most important research approaches is using stem cells in the regeneration of peripheral nerves. Stem cells have a potential to differentiate into Schwann cells. Stem cells modulate the immune system by secreting neurotrophic factors and help formation of myelin layer during peripheral nerve regeneration. Researches in this field also represent these capabilities and promise a bright future in the application of stem cells in the regeneration of peripheral nerve injuries. Conclusion: Regarding the importance of stem cells in the future of regenerative medicine and neurological tissue engineering, understanding of characteristics of stem cells as well as recognition of the extraction resource and their abilities in promoting the peripheral nerve regeneration are necessary. This paper is a review of the most important progress that has been achieved in this field.

Neural regeneration after peripheral nerve injury repair is a system remodelling process of interaction between nerves and terminal effector.

In China, there are approximately 20 million people suffering from peripheral nerve injury and this number is increasing at a rate of 2 million per year. These patients cannot live or work independently and are a heavy responsibility on both family and society because of extreme disability and dysfunction caused by peripheral nerve injury (PNI). Thus, repair of PNI has become a major public health issue in China. Repair of PNI involves two processes, (i) the central nervous system remodels and innervates the target organs in an anterograde manner via the repaired peripheral nerve, and (ii) distal target organs induce retrograde remodelling of the central nervous system via the repaired peripheral nerve. Our team (the 973 program team) was the first to propose that “neural regeneration after PNI repair is a system remodelling process of interaction between nerves and terminal effector” (Jiang et al., 2007, 2014). It is based on regeneration, regulatory and remodelling mechanisms. The following six topics are the major concerns for discussion. Mechanisms underlying tissue inducing PNI The Institute of Orthopedics of the General Hospital of Chinese PLA assumed responsibility to investigate the mechanism by which tissue induces peripheral nerve regeneration using histological and electrophysiological methods in a PNI model repaired with slit-sleeve technique. Regulatory mechanisms underlying neuronal axon growth and myelination The Jiangsu Provincial Key Laboratory of Nerve Regeneration, Nantong University, China assumed responsibility to investigate axon degeneration, myelination and neuronal function change in the proximal injured peripheral nerve at molecular and cellular levels using biochip technique, and to reveal the regulatory mechanism underlying neuronal axon growth and myelination during the process of peripheral nerve regeneration. Regulatory mechanisms underlying denervated muscular atrophy after PNI The Department of Hand Surgery, Huashan Hospital of Fudan University, China assumed responsibility of using proteomic techniques to investigate the regulatory mechanism underlying denervated muscular atrophy, determining the interventional strategy for effectively preventing denervated muscular atrophy and determining mechanisms underlying further nerve bud regeneration and established appropriate surgical methods. Mechanisms underlying pain and paraesthesia after PNI and interventional strategies The Institute of Neuroscience, Beijing University, China assumed responsibility of investigating the neuronal ion channel change and its effect on pain sensitivity using patch clamp techniques, clarifying the central mechanism underlying the interaction between pain perception and emotional states, and determining effective interventional measures. Central structure remodelling and function repair after PNI The Jinan University in China assumed responsibility of investigating central structure and nerve circuit loop functional remodelling in the brain and spinal cord after PNI using a tracer technique, imaging, and gene knockout models. Terminal effector-induced system function remodelling during innovative repair of injured peripheral nerve The Peking University People's Hospital assumed responsibility to investigate terminal effector-induced system function remodelling and the possible underlying mechanisms of multiple innovative repair modes of PNI. The 973 program team has assembled many Chinese teams whose research focuses on the peripheral nerve, with members coming from eight institutions including: Peking University, Fudan University, The General Hospital of Chinese PLA, Sun Yat-sen University, Fourth Military Medical University of Chinese PLA, Nantong University, Jinan University, and Southern Medical University in China. Among these scholars, two are academicians of the Chinese Academy of Engineering, four have been awarded National Outstanding Youth Foundation, and three are new century excellent talents awarded by the Ministry of Education of China. The 973 program team enables to provide labs for neuroscience. These teams already have long-term collaborations and abundant case sources of their own. This program will, on the whole, elucidate the major mechanisms underlying regeneration after PNI and more importantly provide new solutions for the treatment of PNI. This study was supported by grants from the National Program on Key Basic Research Project of China (973 Program), No. 2014CB542200; Program for Innovative Research Team in University of Ministry of Education of China, No. IRT1201; the National Natural Science Foundation of China, No. 31271284, 31171150, 81171146, 30971526, 31100860, 31040043; and Program for New Century Excellent Talents in University of Ministry of Education of China, No. BMU20110270.

Granulocyte colony-stimulating factor (G-CSF) positive effects on muscle fiber degeneration and gait recovery after nerve lesion in MDX mice.

BackgroundG-CSF has been shown to decrease inflammatory processes and to act positively on the process of peripheral nerve regeneration during the course of muscular dystrophy.AimsThe aims of this study were to investigate the effects of treatment of G-CSF during sciatic nerve regeneration and histological analysis in the soleus muscle in MDX mice.MethodsSix-week-old male MDX mice underwent left sciatic nerve crush and were G-CSF treated at 7 days prior to and 21 days after crush. Ten and twenty-one days after surgery, the mice were euthanized, and the sciatic nerves were processed for immunohistochemistry (anti-p75NTR and anti-neurofilament) and transmission electron microscopy. The soleus muscles were dissected out and processed for H&E staining and subsequent morphologic analysis. Motor function analyses were performed at 7 days prior to and 21 days after sciatic crush using the CatWalk system and the sciatic nerve index.ResultsBoth groups treated with G-CSF showed increased p75NTR and neurofilament expression after sciatic crush. G-CSF treatment decreased the number of degenerated and regenerated muscle fibers, thereby increasing the number of normal muscle fibers.ConclusionsThe reduction in p75NTR and neurofilament indicates a decreased regenerative capacity in MDX mice following a lesion to a peripheral nerve. The reduction in motor function in the crushed group compared with the control groups may reflect the cycles of muscle degeneration/regeneration that occur postnatally. Thus, G-CSF treatment increases motor function in MDX mice. Nevertheless, the decrease in baseline motor function in these mice is not reversed completely by G-CSF.

Design and properties of a new braided poly lactic-co-glycolic acid catheter for peripheral nerve regeneration

A new braided poly lactic-co-glycolic acid (PLGA) (LA : GA = 10 : 90) catheter, consisting of an outside-tube and an inside-scaffold, was designed and fabricated to guide and support peripheral nerve regeneration. According to the process of peripheral nerve regeneration, the functional division of the outside-tube and the inside-scaffold was confirmed as follows: the major function of the outside-tube was support for the space of the nerve regeneration and the needed good compression performance and the major function of the inside-scaffold was simulation of the matrix bridge in the nerve regeneration process. Therefore, the outside-tube was braided for a higher density with PLGA ply yarns and coated with chitosan; the inside-scaffold was braided for a lower density with PLGA single filaments treated by H2O2. The arrangement and number of micro-tubes were designed and theoretically calculated. In this paper, the basic thickness and density performance of the new catheter was tested first. Then, the fibroblast cytocompatibility and the fiber tensile in degradation were assessed as indications of the performance change of the unmodified and modified materials. Finally, the compression performance of the new catheter was compared with two other catheters. The results showed that the new catheter had a uniform and stable structure. The modified inside-scaffold had a higher cytocompatibility and facilitation of fibroblast growth than the unmodified one; meanwhile, it maintained enough mechanical properties to support nerve regeneration in degradation. Furthermore, the elastic recovery and compressive resistance retention respectively reached 84% and 93%, which meant excellent compression performance. In summary, the performance of this new braided PLGA catheter attained the designed targets.

Visualization of peripheral nerve regeneration.

Peripheral nerve injuries are often caused by trauma and they may result in a partial or total loss of motor function or sensory perception. After nerve injuries, peripheral axons have the ability to regenerate and reconnect the proximal and distal ends of severed nerve axons if the nerve gap is small. For larger nerve gaps, surgical treatments are often required to repair the injured nerves.

Assessment of In vivo behavior of polymer tube nerve grafts simultaneously with the peripheral nerve regeneration process using scanning electron microscopy technique

In this study, scanning electron microscopy (SEM) has been applied for instantaneous assessment of processes occurring at the site of regenerating nerve. The technique proved to be especially useful when an artificial implant should have been observed but have not yet been extensively investigated before for assessment of nerve tissue. For in vivo studies, evaluation of implant's morphology and its neuroregenerative properties is of great importance when new prototype is developed. However, the usually applied histological techniques require separate and differently prepared samples, and therefore, the results are never a 100% comparable. In our research, we found SEM as a technique providing detailed data both on an implant behavior and the nerve regeneration process inside the implant. Observations were carried out during 12-week period on rat sciatic nerve injury model reconstructed with nerve autografts and different tube nerve grafts. Samples were analyzed with haematoxylin-eosin (HE), immunocytochemical staining for neurofillament and S-100 protein, SEM, TEM, and the results were compared. SEM studies enabled to obtain characteristic pictures of the regeneration process similarly to TEM and histological studies. Schwann cell transformation and communication as well as axonal outgrowth were identified, newly created and matured axons could be recognized. Concurrent analysis of biomaterial changes in the implant (degradation, collapsing of the tube wall, migration of alginate gel) was possible. This study provides the groundwork for further use of the described technique in the nerve regeneration studies.