A newly synthesized neurotropic pyrimidine compound, MS-818, may activate migratory Schwann cells in peripheral nerve regeneration

Following transection of a peripheral nerve in mice, a newly synthesized neurotropic pyrimidine compound, MS-818 was administered intraperitoneally at a dose of 1 mg kg⁻¹ b.wt. day⁻¹. The film model experiments for analyzing the early growth of axonal regeneration suggested that MS-818 activated Schwann cells which migrate from the proximal stump, inducing axonal elongation in vivo.     

Number, size, and class of peripheral nerve fibers regenerating after crush, multiple crush, and graft

Morphometric characterization of fiber regeneration in a distal nerve after focal proximal nerve injury may provide useful clinical information and insights about underlying neurobiologic mechanisms. The myelinated (MF) and unmyelinated (UF) fibers of peroneal nerve of groups of mice were assessed 9 months after crush, graft, and multiple crush injury of the proximal sciatic nerve: number and size distribution of axon areas, myelin areas, and fiber diameters. After crush, number of regenerated MF and UF was almost identical to that of controls. Their size distribution had almost returned to normal. After graft and multiple crush, fiber number had returned to normal or was significantly increased beyond normal but there were only a few large fibers present. This may be explained by: (a) disproportionate regeneration of small-diameter compared to large-diameter classes of fibers; (b) misdirected regrowth of fibers, so that functional reinnervation was not established, resulting in failure of development or retrograde atrophy and degeneration; or (c) cellular alterations at the site of injury or in the distal nerve which inhibited neural outgrowth or elongation or did not inhibit outgrowth but retarded or prevented maturation. We conclude that explanation (b) is involved, and that there is some evidence favoring the roles of (a) and (c).     

The effect of neurotrophic pyrimidine heterocyclic compounds,MS-818 and MS-430, on the regeneration of injured peripheral nerves

The effects of pyrimidine heterocyclic compounds (MS-818 and MS-430) on nerve regeneration were evaluated using the cut-and-suture model of the right sciatic nerve of Wistar rats. After surgery, 1 or 5 mg/kg/day of MS-818 or MS-430 was intraperitoneally administered for 21 days. Control rats received the same surgery, but were administered saline instead of a drug. Each week from week 2, evoked muscle action potentials were recorded on the calf muscle to compare the ratio of latency and amplitude between tbe experimental and non-treated side. The specimens were taken from the tibial nerve for light microscopic observation; and the diameter, density and % axon area of myelinated axons were evaluated. Tbe results of EMG and histology suggest that administration of MS-818 is more effective than that of MS-430 and that administration of 5 mg/kg/day has a higher promoting effect than that of 1 mg/kg/day for sprouting and elongation of the severed nerve. These new neurotrophic pyrimidine compounds may be a group of possible substances effective in facilitating nerve regeneration.     

Selective regeneration of sensory fibers following nerve crush injury.

We investigated whether or not all classes of myelinated sensory fibers regenerate simultaneously after nerve crush injury and whether each parent fiber produces and maintains a regenerated branch. Electrophysiologic recordings were made from isolated lumbar dorsal root fibers in rats at various times after sciatic nerve crush injury. For all fibers that responded to electrical stimulation distal to the crush, the conduction velocity of the parent axon was established using the collision method. During the first few months following sciatic nerve injury, Aδ parent fibers were under-represented in the sample of successfully regenerated fibers. Only later did sprouts of the bulk of Aδ fibers grow out. In time, however, all fibers regenerated. Combined with histologic data indicating that fiber number was restored in the distal nerve stump, this finding indicated that after crush injury the majority of parent fibers maintained one, but only one, regenerated branch.     

Effects of neonatal injury of the inferior alveolar nerve on the development and regeneration of periodontal nerve fibers in the rat incisor

Our previous study showed that the migration of terminal Schwann cells occurred in the periodontal ligament of the rat lower incisor following transection of the inferior alveolar nerve (IAN) in the adult animals [Y. Atsumi, K. Matsumoto, M. Sakuda, T. Maeda, K. Kurisu, S. Wakisaka, Altered distribution of Schwann cells in the periodontal ligament of the rat incisor following resection of the inferior alveolar nerve: An immunohistochemical study on S-100 proteins, Brain Res. 849 (1999) 187-195]. The aim of the present study was to investigate the effects of neonatal transection of the IAN on the regeneration of axon elements and Schwann cells in the periodontal ligament of the rat lower incisor. Following transection of IAN at post-natal day 5 (PN 5d), when the numbers of both axon elements and the terminal Schwann cells were very small, regenerating nerve fibers appeared between post-injured days 7 (PO 7d) and PO 14d, and increased in number thereafter gradually. Although the terminal morphologies of regenerated Ruffini endings became identical to those of the adult animals by PO 54d, the number of regenerated PGP 9.5-IR nerve fibers did not recover the adult levels even by PO 56d. A small number of Schwann cells migrated into the shear zone, the border between the alveolus-related part (ARP) and the tooth-related part (TRP), but did not enter into the TRP. Following transection of the IAN at PN 14d or PN 28d, when clusters of apparent terminal Schwann cells could be recognized, axon regeneration started around PO 5d. Individual axon terminals of the regenerating Ruffini endings ramified and became identical to those of the adult animals around PO 28d, but the number of regenerated Ruffini endings was smaller than that of the adult animals. Similar to the adult animals, the migration of Schwann cells into the shear zone and TRP occurred, and disappeared prior to the completion of the axonal regeneration. The present results indicate that the migration of the Schwann cells into TRP during the regeneration of the periodontal nerve fibers following nerve injury to the IAN depends on the maturation of the terminal Schwann cells of the periodontal Ruffini endings, not on post-operative time.     

神经损伤自发放电编码的神经再生研究进展

神经损伤与修复是一道长期摆在基础与临床科研工作面前的难题．每年因中枢、外周神经损伤导致的功能瘫痪．给患、患家庭和社会都带来了巨大的痛苦和负担。解决神经损伤修复的一个最基本条件就是搞清神经再生的理论问题。由于其再生机制不清导致目前所有已发现的神经修复方法虽都有不同程度的效果，但均不能从根本上解决完全修复问题。无疑，进一步研究神经再生机制是目前解决神经修复最迫切的问题。人们早已发现外周感觉神经在受到损伤性刺激后会表现出兴奋性增强、静息膜电位不稳定、出现自发放电现象．在中枢结构重塑活跃区域会有节律性放电反应。[第一段]     

Afterdischarge and interactions among fibers in damaged peripheral nerve in the rat

Sensory fibers trapped in nerve-end neuromas become abnormally excitable, and produce an ectopic discharge which is believed to contribute to paresthesias and pain associated with chronic nerve injury in man. Here we report that stimulation of injured nerves can alter this discharge, directly by antidromic invasion of active neuroma fibers, and indirectly through interactions with neighboring fibers. Antidromic stimulation of spontaneously active fibers in experimental neuromas in the rat sciatic nerve, using single electrical stimulus pulses, produced time-locking of rhythmic spontaneous firing and of spontaneous impulse bursts. Some initially silent fibers generated a burst of rhythmic afterdischarge when stimulated in this way. Stimulation delivered in brief trains (tetani) produced more prolonged alterations in spontaneous neuroma discharge, including excitation, suppression and combinations of the two. In some cases initially silent fibers were activated for extended periods. These responses to tetanic stimulation occurred even when the active fibers were not themselves stimulated, and reflect a novel form of fiber-fiber interaction in neuromas that we term 'crossed afterdischarge'. This interaction probably results from the accumulation of potassium ions within the extracellular compartment adjacent to active neuroma fibers during activation of their neighbors. It differs fundamentally from the high safety factor ephaptic cross-talk seen in acutely cut nerves and in neuromas of 30 or more days standing.     

神经生长因子治疗周围神经损伤的疗效观察

目的 观察神经生长因子治疗周围神经损伤的临床疗效.方法 纳入60例周围神经损伤患者,采用随机数字表法分为2组.试验组30例采用鼠NGF肌内注射治疗,对照组30例采用维生素B12治疗,治疗4周后观察疗效.观察指标包括疼痛(VAS)、麻木等临床症状和体征,同时观察单神经的神经电生理情况.结果 疼痛改善:试验组总有效率93.33％,对照组为53.33％;麻木改善:试验组总有效率86.67％,对照组为66.67％;2组比较差异均有统计学意义(P＜0.05).试验组恢复神经的感觉及运动电位的潜伏期时间均明显短于对照组,差异有统计学意义(P＜0.05);而波幅则均显著高于对照组,差异有显著性意义(P＜0.05).结论 神经生长因子能有效改善患者的疼痛、麻木症状,而且能对神经纤维的修复、电生理功能有促进作用.     

Motoneurotrophins derived from limb buds protect the motoneurons in anterior spinal cord after nerve injury and promote nerve regeneration

The effects of limb bud-derived motoneurotrophins (LBMNTs) as seen in the motoneurons in the anterior spinal cord and sciatic nerve regeneration of adult rats, were evaluated in the present study. A nerve regeneration chamber with a nerve gap of 9 mm was created by suturing the proximal and distal ends of a random sciatic nerve into a silicone tube after removal of a 5 mm piece of nerve in the distal end, The chamber of the experimental group was filled with 34.34 μg LBMNTs and PBS (0.01 mol/ml, pH 7.0),and the control group with PBS only. At 1 day, 4 days, 1 week, 2 weeks, 4 weeks and 6 weeks post surgery, the content of acetylcholine esterase (AchE) and acid phosphatase (ACP) of the anterior spinal cord (injured side) was quantified, and the corresponding motoneuron's ultrastructure and the existant ratio were also examined. Meanwhile, the regenerated nerve from within the silicone tube was examined at 2, 4 and 6 weeks post surgery for histological studies at both the light microscopic and ultrastructural levels. The experimental group showed a smaller decrease of AchE and an increase of ACP, a larger existant ratio of motoneurons, better ultrastructure and a more mature regenerated nerve based on a larger diameter of the regenerated nerve trunk, a greater number of axons and thicker myelin sheaths than the control group. So it was concluded that LBMNTs had a high activity of protecting motoneurons in the anterior spinal cord after nerve injury and promoting nerve regeneration, and it may be a new source of neurotrophic factors (NTFs).     

损伤神经周围注射自体PRP对周围神经损伤的修复效果观察

目的 探讨损伤神经周围注射自体富血小板血浆(platelet-rich plasma,PRP)对周围神经损伤的修复效果。方法 选取2017年1月-2018年7月于本院接受治疗的周围神经损伤患者130例,随机分为手术组、PRP联合组各65例,手术组患者进行显微外科手术,PRP联合组患者在手术基础上注射自体PRP进行治疗; 用酶联免疫吸附实验法检测血清C反应蛋白(CRP)、肿瘤坏死因子-α(TNF-α)水平,用Western blot法检测胰岛素样生长因子1(IGF-1)、血管内皮生长因子(VEGF)表达水平,并对2组患者神经传导速度、下肢运动功能、基本功能优良率以及肌电图疗效进行检测。结果 治疗1、3、6、12个月后PRP联合组患者CRP、TNF-α水平均低于手术组,IGF-1、VEGF表达水平均高于手术组(P<0.05); 治疗1、3、6、12个月后PRP联合组患者感觉、运动神经传导速度、下肢运动功能评分、基本功能恢复优良率、肌电图愈显率均高于手术组(P<0.05)。结论 在手术治疗的基础上注射自体PRP对周围神经损伤患者进行治疗,能够减轻患者炎性损伤程度,上调IGF-1、VEGF的表达水平,加快神经传导速度,促进患者下肢运动功能恢复     

The effect of hyperbaric oxygen treatment on early regeneration of sensory axons after nerve crush in the rat

Abstract The effect of hyperbaric oxygen treatment (HBO) on sensory axon regeneration was examined in the rat. The sciatic nerve was crushed in both legs. In addition, the distal stump of the sural nerve on one side was made acellular and its blood perfusion was compromised by freezing and thawing. Two experimental groups received hyperbaric exposures (2.5 ATA) to either compressed air (pO2 = 0.5 ATA) or 100% oxygen (pO2 = 2.5 ATA) 90 minutes per day for 6 days. Sensory axon regeneration in the sural nerve was thereafter assessed by the nerve pinch test and immunohistochemical reaction to neurofilament. HBO treatment increased the distances reached by the fastest regenerating sensory axons by about 15% in the distal nerve segments with preserved and with compromised blood perfusion. There was no significant difference between the rats treated with different oxygen tensions. The total number of regenerated axons in the distal sural nerve segments after a simple crush injury was not affected, whereas in the nerve segments with compromised blood perfusion treated by the higher pO2, the axon number was about 30% lower than that in the control group. It is concluded that the beneficial effect of HBO on sensory axon regeneration is not dose-dependent between 0.5 and 2.5 ATA pO2. Although the exposure to 2.5 ATA of pO2 moderately enhanced early regeneration of the fastest sensory axons, it decreased the number of regenerating axons in the injured nerves with compromised blood perfusion of the distal nerve stump.     

The effect of treatment with BRX-220, a co-inducer of heat shock proteins, on sensory fibers of the rat following peripheral nerve injury

In this study, we examined the effect BRX-220, a co-inducer of heat shock proteins, in injury-induced peripheral neuropathy. Following sciatic nerve injury in adult rats and treatment with BRX-220, the following features of the sensory system were studied: (a) expression of calcitonin gene-related peptide (CGRP); (b) binding of isolectin B4 (IB4) in dorsal root ganglia (DRG) and spinal cord; (c) stimulation-evoked release of substance P (SP) in an in vitro spinal cord preparation and (d) nociceptive responses of partially denervated rats. BRX-220 partially reverses axotomy-induced changes in the sensory system. In vehicle-treated rats there is a decrease in IB4 binding and CGRP expression in injured neurones, while in BRX-220-treated rats these markers were better preserved. Thus, 7.0 +/- 0.6% of injured DRG neurones bound IB4 in vehicle-treated rats compared to 14.4 +/- 0.9% in BRX-220-treated animals. Similarly, 4.5 +/- 0.5% of DRG neurones expressed CGRP in the vehicle-treated group, whereas 9.0 +/- 0.3% were positive in the BRX-220-treated group. BRX-220 also partially restored SP release from spinal cord sections to electrical stimulation of primary sensory neurones. Behavioural tests carried out on partially denervated animals showed that BRX-220 treatment did not prevent the emergence of mechanical or thermal hyperalgesia. However, oral treatment for 4 weeks lead to reduced pain-related behaviour suggesting either slowly developing analgesic actions or enhancement of recovery processes. Thus, the morphological improvement seen in sensory neurone markers was accompanied by restored functional activity. Therefore, treatment with BRX-220 promotes restoration of morphological and functional properties in the sensory system following peripheral nerve injury.     

The effect of extraction of the intrafascicular contents of peripheral nerve trunks on perineurial structure

Summary The intrafascicular contents have been extracted from the tibial nerve of the rabbit through perineurial incisions. Within 6–8 days following this procedure, the perineurial cells separate from one another, become dissociated from their basement membranes and assume a fibroblast-like appearance. The intrafascicular space becomes populated with endoneurial fibroblasts. With the ingrowth of regenerating axons, bundles of axons and associated Schwann cells become surrounded by cells of fibroblastic appearance which undergo perineurial transformation resulting in the development of multiple small fascicles. The cells of the surrounding perineurium appear to reassume a lamellar organization and to reestablish contacts with each other with the formation of junctional complexes. It is therefore suggested that neural structures may be responsible for the development and maintenance of the structural organization of the perineurium.     

Cavernous nerve injury elicits GAP-43 mRNA expression but not regeneration of injured pelvic ganglion neurons

Recovery of erectile dysfunction after cavernous nerve injury takes a long period. To elucidate this mechanism, unilateral cavernous nerve of male rat was cut, and the expression level of a nerve regeneration marker, the growth associated protein-43 (GAP-43) mRNA was evaluated by in situ hybridization and RT-PCR. While GAP-43 mRNA expression was transiently increased in the injured neurons of the major pelvic ganglion (MPG) at 7 days after nerve injury, continuous increase of GAP-43 mRNA was observed in the contralateral MPG from 7 days to 6 months after the nerve injury. Histochemical double-labeling studies for either neuronal NOS (nNOS) or tyrosine hydroxylase (TH) and the GAP-43 mRNA expression demonstrated that in injured MPG the transient up-regulation of GAP-43 mRNA was mainly seen in nNOS negative and/or TH positive neurons, suggesting non-parasympathetic post-ganglionic neurons, and also demonstrated that in contralateral MPG GAP-43 mRNA positive neurons were gradually increased in nNOS positive but TH negative neurons, suggesting parasympathetic post-ganglionic neurons. When a retrograde tracer Fluorogold (FG) was injected into the penile crus 7 days before histological experiments, FG-positive neurons were, if any, hardly seen in nNOS-positive neurons of the injured MPG for at least 6 months, whereas numerous FG-positive cells were seen in nNOS-positive neurons of the contralateral MPG. These results suggest that post-ganglionic projecting neurons of the intact side, which express increased GAP-43 mRNA, would be most likely to contribute to the recovery of the erectile function after unilateral cavernous nerve injury possibly by a plastic change such as nerve sprouting.     

Enhanced functional recovery from sciatic nerve crush injury through a combined treatment of cold-water swimming and mesenchymal stem cell transplantation

Abstract

Objective:

Although regimens of stem cell implantation can elicit functional recovery following peripheral nerve injury, the degree of outcome is still limited. This study evaluated the synergistic effects of cold-water swimming (CWS) and mesenchymal stem cell (MSC) transplantation on functional recovery of crushed sciatic nerve in rats.

Method:

Forty Sprague-Dawley rats that had their sciatic nerve crushed during surgery were randomly divided into four groups: MSCCWS group, treated with combination of MSC and CWS; MSC group, treated with MSC alone; CWS group, treated with CWS alone; and non-treated group, without any treatments. The sciatic function index (SFI), vertical activity (VA), ankle activity (AA) and electrophysiological study were examined before, immediately after surgery, after the treatment and after 4?weeks from treatment. Morphological and S100 immunohistochemical studies were also performed.

Results:

The MSCCWS group showed a greater improvement in SFI, VA, AA, peak amplitudes and onset latencies of compound muscle action potential (CMAP) in sciatic nerve and infiltration of immune cells with significant difference from the MSC, CWS and non-treated groups (P?<?0.05).

Conclusions:

MSC transplantation combined with CWS could achieve better results in functional recovery than a single treatment of MSC alone or CWS alone in nerve crush injury.     

Restorative effect and mechanism of mecobalamin on sciatic nerve crush injury in mice

Mecobalamin,a form of vitamin B12 containing a central metal element(cobalt),is one of the most important mediators of nervous system function.In the clinic,it is often used to accelerate recovery of peripheral nerves,but its molecular mechanism remains unclear.In the present study,we performed sciatic nerve crush injury in mice,followed by daily intraperitoneal administration of mecobalamin(65 μg/kg or 130 μg/kg) or saline(negative control).Walking track analysis,histomorphological examination,and quantitative real-time PCR showed that mecobalamin significantly improved functional recovery of the sciatic nerve,thickened the myelin sheath in myelinated nerve fibers,and increased the cross-sectional area of target muscle cells.Furthermore,mecobalamin upregulated m RNA expression of growth associated protein 43 in nerve tissue ipsilateral to the injury,and of neurotrophic factors(nerve growth factor,brain-derived nerve growth factor and ciliary neurotrophic factor) in the L4–6 dorsal root ganglia.Our findings indicate that the molecular mechanism underlying the therapeutic effect of mecobalamin after sciatic nerve injury involves the upregulation of multiple neurotrophic factor genes.     

Electroacupuncture promotes peripheral nerve regeneration after facial nerve crush injury and upregulates the expression of glial cell-derived neurotrophic factor

The efficacy of electroacupuncture in the treatment of peripheral facial paralysis is known, but the specific mechanism has not been clarified. Glial cell-derived neurotrophic factor(GDNF) has been shown to protect neurons by binding to N-cadherin. Our previous results have shown that electroacupuncture could increase the expression of N-cadherin mRNA in facial neurons and promote facial nerve regeneration. In this study, the potential mechanisms by which electroacupuncture promotes nerve regeneration were elucidated through assessing the effects of electroacupuncture on GDNF and N-cadherin expression in facial motoneurons of rabbits with peripheral facial nerve crush injury. New Zealand rabbits were randomly divided into a normal group(normal control, n = 21), injury group(n = 45) and electroacupuncture group(n = 45). Model rabbits underwent facial nerve crush injury only. Rabbits in the electroacupuncture group received facial nerve injury, and then underwent electroacupuncture at Yifeng(TE17), Jiache(ST6), Sibai(ST2), Dicang(ST4), Yangbai(GB14), Quanliao(SI18), and Hegu(LI4; only acupuncture, no electrical stimulation). The results showed that in behavioral assessments, the total scores of blink reflex, vibrissae movement, and position of apex nasi, were markedly lower in the EA group than those in the injury group. Hematoxylin-eosin staining of the right buccinator muscle of each group showed that the cross-sectional area of buccinator was larger in the electroacupuncture group than in the injury group on days 1, 14 and 21 post-surgery. Toluidine blue staining of the right facial nerve tissue of each group revealed that on day 14 post-surgery, there was less axonal demyelination and fewer inflammatory cells in the electroacupuncture group compared with the injury group. Quantitative real time-polymerase chain reaction showed that compared with the injury group, N-cadherin mRNA levels on days 4, 7, 14 and 21 and GDNF mRNA levels on days 4, 7 and 14 were significantly higher in the electroacupuncture group. Western blot assay displayed that compared with the injury group, the expression of GDNF protein levels on days 7, 14 and 21 were significantly upregulated in the electroacupuncture group. The histology with hematoxylin-eosin staining and Nissl staining of brainstem tissues containing facial neurons in the middle and lower part of the pons exhibited that on day 7 post-surgery, there were significantly fewer apoptotic neurons in the electroacupuncture group than in the injury group. By day 21, there was no significantly difference in the number of neurons between the electroacupuncture and normal groups. Taken together, these results have confirmed that electroacupuncture promotes regeneration of peripheral facial nerve injury in rabbits, inhibits neuronal apoptosis, and reduces peripheral inflammatory response, resulting in the recovery of facial muscle function. This is achieved by up-regulating the expression of GDNF and N-cadherin in central facial neurons.     

The Achyranthes bidentata polypeptide k fraction enhances neuronal growth in vitro and promotes peripheral nerve regeneration after crush injury in vivo

We have previously shown that Achyranthes bidentata polypeptides （ABPP）, isolated from Achyranthes bidentata Blume （a medicinal herb）, exhibit neurotrophic and neuroprotective effects on the nervous system. To identify the major active component of ABPP, and thus optimize the use of ABPP, we used reverse-phase high performance liquid chromatography to separate ABPP. We obtained 12 fractions, among which the fraction of ABPPk demonstrated the strongest neuroactivity. Immunocytochemistry and western blot analysis showed that ABPPk promoted neurite growth in cultured dorsal root ganglion explant and dorsal root ganglion neurons, which might be associated with activation of Erk1/2. A combination of behavioral tests, electrophysiological assessment, and histomorphometric analysis indicated that ABPPk enhanced nerve regeneration and function restoration in a mouse model of crushed sciatic nerve. All the results suggest that ABPPk, as the key component of ABPP, can be used for peripheral nerve repair to yield better outcomes than ABPP.