Miconazole enhances nerve regeneration and functional recovery after sciatic nerve crush injury

Introduction: Improving axonal outgrowth and remyelination is crucial for peripheral nerve regeneration. Miconazole appears to enhance remyelination in the central nervous system. In this study we assess the effect of miconazole on axonal regeneration using a sciatic nerve crush injury model in rats. Methods: Fifty Sprague‐Dawley rats were divided into control and miconazole groups. Nerve regeneration and myelination were determined using histological and electrophysiological assessment. Evaluation of sensory and motor recovery was performed using the pinprick assay and sciatic functional index. The Cell Counting Kit‐8 assay and Western blotting were used to assess the proliferation and neurotrophic expression of RSC 96 Schwann cells. Results: Miconazole promoted axonal regrowth, increased myelinated nerve fibers, improved sensory recovery and walking behavior, enhanced stimulated amplitude and nerve conduction velocity, and elevated proliferation and neurotrophic expression of RSC 96 Schwann cells. Discussion: Miconazole was beneficial for nerve regeneration and functional recovery after peripheral nerve injury. Muscle Nerve 57 : 821–828, 2018     

Platelet-rich plasma promotes peripheral nerve regeneration after sciatic nerve injury

The effect of platelet-rich plasma on nerve regeneration remains controversial.In this study,we established a rabbit model of sciatic nerve small-gap defects with preserved epineurium and then filled the gaps with platelet-rich plasma.Twenty-eight rabbits were divided into the following groups(7 rabbits/group):model,low-concentrati on PRP(2.5-3.5-fold concentration of whole blood platelets),medium-concentration PRP(4.5-6.5-fold concentration of whole blood platelets),and high-concentration PRP(7...     

Bacterial melanin promotes recovery after sciatic nerve injury in rats

Bacterial melanin, obtained from the mutant strain of Bacillus Thuringiensis, has been shown to promote recovery after central nervous system injury. It is hypothesized, in this study, that bacterial melanin can promote structural and functional recovery after peripheral nerve injury. Rats subjected to sciatic nerve transection were intramuscularly administered bacterial melanin. The sciatic nerve transected rats that did not receive intramuscular administration of bacterial melanin served as controls. Behavior tests showed that compared to control rats, the time taken for instrumental conditioned reflex recovery was significantly shorter and the ability to keep the balance on the rotating bar was significantly better in bacterial melanin-treated rats. Histomorphological tests showed that bacterial melanin promoted axon regeneration after sciatic nerve injury. These findings suggest that bacterial melanin exhibits neuroprotective effects on injured sciatic nerve, contributes to limb motor function recovery, and therefore can be used for rehabilitation treatment of peripheral nerve injury.     

PEMF fails to enhance nerve regeneration after sciatic nerve crush lesion

Abstract The use of electromagnetic fields has been reported to enhance peripheral nerve regeneration. This study aimed to identify the effects of a prolonged protocol of low‐frequency pulsed electromagnetic field (PEMF) on peripheral nerve regeneration. Thirty‐four male Swiss mice (Mus musculus) were divided into PEMF (n = 17) and control (n = 17) groups. All animals underwent a unilateral sciatic‐crush lesion, and the PEMF group was exposed to a 72‐Hz, 2‐G electromagnetic field for 30 min, five days a week, for three weeks. Functional analysis was carried out weekly. After three weeks, the animals were euthanized, and histological, morphometric, oxidative stress, and TGF‐β1 analyses were performed. Functional analysis showed no differences between the groups. Histological appearance was similar between PEMF and control nerves. Morphometric assessment showed that the PEMF nerves trended toward decreased regeneration. The levels of free radicals were more pronounced in PEMF nerves, but were not associated with an increase in the content of the TGF‐β1/Smad signaling pathway. Prolonged PEMF regimen leads to delayed histological peripheral nerve regeneration and increased oxidative stress but no loss of function recovery.     

Retrograde axonal transport in rat sciatic nerve after nerve crush injury

We investigated the quantitative alterations in retrograde transport of proteins following a nerve crush injury using the 3H N-succinimidyl propionate (3H NSP) method in rat sciatic nerve. After subepineurial injection of 3H NSP into the nerve the amount of radioactively labeled proteins accumulating in the cell bodies of the motor and sensory neurons was determined 1 day or 7 days later in nerves which had been crushed distal to the injection site 1, 3, 5, 7, or 33 days prior to 3H NSP labeling. One day accumulation in the DRG and spinal cord was not altered by nerve crush. Seven day accumulation in the DRG was initially slightly increased, then fell to 73% of control by 7 days, remaining reduced 33 days after crush. Seven day accumulation in the spinal cord was reduced to 25% of control 1 day after crush and remained at that low level except for 5 days post-crush when a normal amount of labeled protein was transported to the spinal cord. The time course of these changes suggests that quantitative alterations in retrograde transport may be involved in the long-term trophic interactions between the cell body and periphery, but are too slow to account for the earliest perikaryal responses to injury. In addition, the difference between the alterations of retrograde transport in motor and sensory neurons may reflect fundamental differences in the composition of retrograde transport in those different systems.     

Electrical stimulation influences satellite cell differentiation after sciatic nerve crush injury in rats

Introduction: Electrical stimulation is often used to prevent muscle atrophy and preserve contractile function, but its effects on the satellite cell population after nerve injury are not well understood. In this study we aimed to determine whether satellite cell differentiation is affected by electrical stimulation after nerve crush. Methods: The sciatic nerves of Sprague‐Dawley (SD) rats were crushed. Half of the injured rats received daily electrical stimulation of the gastrocnemius muscle, and the others did not. Tests for detecting paired box protein 7 (Pax7), myogenic differentiation antigen (MyoD), embryonic myosin heavy chain (eMyHC), and force production were performed 2, 4, and 6 weeks after injury. Results: More Pax7⁺/MyoD⁺ nuclei in stimulated muscles were observed than in non‐stimulated muscles. eMyHC expression was elevated in stimulated muscles and correlated positively with enhanced force production. Conclusions: Increased satellite cell differentiation is correlated with preserved muscle function in response to electrical stimulation after nerve injury. Muscle Nerve 51: 400–411, 2015     

Distribution of albumin-like immunoreactivity in rat sciatic nerve after nerve crush injury

To understand better the role of local factors in the response of peripheral nerve to crush injury, we studied the distribution of albumin-like immunoreactivity (A-LI) in the rat sciatic nerve from one day to eight weeks (wk) after a crushing injury; we used electron microscopic immunocytochemistry. In the nerve distal to the crush degenerating axons demonstrated intra-axonal A-LI, and by one wk most of the Schwann cells also showed A-LI. As regenerating sprouts entered the distal nerve, those Schwann cells in contact with sprouts lost their A-LI, while those cells not in contact with axons retained immunoreactivity up to eight wk after injury. Proximal to the nerve crush many axons showed intra-axonal A-LI from one to two wk after injury, despite appearing normal ultrastructurally. This immunoreactivity diminished as the distance from the crush site increased. Many Schwann cells proximal to the crush also showed A-LI from one to four wk after injury. These findings suggest that an albumin-like protein may play a role in the response of Schwann cells and axons to injury.     

Baseline effects of lysophosphatidylcholine and nerve growth factor in a rat model of sciatic nerve regeneration after crush injury

Schwann cells play a major role in helping heal injured nerves. They help clear debris, produce neurotrophins, upregulate neurotrophin receptors, and form bands of Büngner to guide the healing nerve. But nerves do not always produce enough neurotrophins and neurotrophin receptors to repair themselves. Nerve growth factor(NGF) is an important neurotrophin for promoting nerve healing and lysophosphatidylcholine(LPC) has been shown to stimulate NGF receptors(NGFR). This study tested the administration of a single intraneural injection of LPC(1 mg/mL for single LPC injection and 10 mg/mL for multiple LPC injections) at day 0 and one(day 7), two(days 5 and 7), or three(days 5, 7, and 9) injections of NGF(160 ng/mL for single injections and 80 ng/mL for multiple injections) to determine baseline effects on crush ed sciatic nerves in rats. The rats were randomly divided into four groups: control, crush, crush-NGF, and crush-LPC-NGF. The healing of the nerves was measured weekly by monitoring gait; electrophysiological parameters: compound muscle action potential(CMAP) amplitudes; and morphological parameters: total fascicle areas, myelinated fiber counts, fiber densities, fiber packing, and mean g-ratio values at weeks 3 and 6. The crush, crush-NGF, and crush-LPC-NGF groups statistically differed from the control group for all six weeks for the electrophysiological parameters but only differed from the control group at week 3 for the morphological parameters. The crush, crush-NGF, and crush-LPC-NGF groups did not differ from each other over the course of the study. Single injections of LPC and NGF one week apart or multiple treatments of NGF at 5, 7 and 9 days post-injury did not alter the healing rate of the sciatic nerves during weeks 1-6 of the study. These findings are important to define the baseline effects of NGF and LPC injections, as part of a larger effort to determine the minimal dose regimen of NGF to regenerate peripheral nerves.     

Recombinant human fibroblast growth factor-2 promotes nerve regeneration and functional recovery after mental nerve crush injury

Several studies have shown that fibroblast growth factor-2(FGF2) can directly affect axon regeneration after peripheral nerve damage. In this study, we performed sensory tests and histological analyses to study the effect of recombinant human FGF-2(rh FGF2) treatment on damaged mental nerves. The mental nerves of 6-week-old male Sprague-Dawley rats were crush-injured for 1 minute and then treated with 10 or 50 μg/m L rh FGF2 or PBS in crush injury area with a mini Osmotic pump. Sensory test using von Frey filaments at 1 week revealed the presence of sensory degeneration based on decreased gap score and increased difference score. However, at 2 weeks, the gap score and difference score were significantly rebounded in the mental nerve crush group treated with 10 μg/m L rh FGF2. Interestingly, treatment with 10 μg/m L rh FGF had a more obviously positive effect on the gap score than treatment with 50 μg/m L rh FGF2. In addition, retrograde neuronal tracing with Dil revealed a significant increase in nerve regeneration in the trigeminal ganglion at 2 and 4 weeks in the rh FGF2 groups(10 μg/m L and 50 μg/m L) than in the PBS group. The 10 μg/m L rh FGF2 group also showed an obviously robust regeneration in axon density in the mental nerve at 4 weeks. Our results demonstrate that 10 μg/m L rh FGF induces mental nerve regeneration and sensory recovery after mental nerve crush injury.     

硫酸软骨素酶ABC(ch ABC)对大鼠坐骨神经损伤后神经再生功能的实验研究

目的观察硫酸软骨素酶ABC(chABC)对坐骨神经再生功能的影响。方法将72只SD大白鼠双侧坐骨神经切断造成0.8 cm缺损,用甲壳素导管桥接神经缺损后随机分为3组,每组24只。A组(实验组):管内注入聚乳酸-聚乙醇酸—chABC缓释微球(chABC-PLGA);B组(赋形剂组):管内注入聚乳酸-聚乙醇酸微球;C组(空白对照组):管内注入等渗盐水。术后4周、8周取材作神经电生理、神经组织学观察。结果术后4周、8周组织学观察见有再生神经通过再生室,其间有新生血管;神经电生理检查A组再生神经传导速度优于B、C组,差异有统计学意义(P<0.05),B、C组再生神经传导速度差别无统计学意义,组间比较(P>0.0167)组间多重比较行Bonferroni法检验,取校正α=0.0167)。S-100免疫组织化学及Loyez氏神经染色法显示:A组神经纤维数多于B、C组,差异有统计学意义(P<0.05),B、C组再生神经纤维数差别无统计学意义,组间比较(P>0.0167)。结论硫酸软骨素酶ABC(chABC)具有促进周围神经再生的作用。     

Nimodipine promotes regeneration and functional recovery after intracranial facial nerve crush

The calcium flow inhibitor, nimodipine, has been shown to promote motor neuron survival in the facial nucleus after intracranial facial nerve transection. However, it has not been known whether the neuroprotective effects primarily involve survival of nerve cell bodies or outgrowth and/or myelination of nerve fibers. Here, we studied the effects of nimodipine in a different injury model in which the facial nerve was unilaterally crushed intracranially. This lesion caused complete anterograde degeneration and partial retrograde degeneration that were studied with a combination of several stereological methods. Nimodipine did not attenuate the modest lesion-induced neuronal loss (13%) but accelerated the time course of functional recovery and axonal regrowth, inducing increased numbers and sizes of myelinated axons in the facial nerve. It is interesting to note that nimodipine also enlarged the axons and the myelin sheaths in the nonlesioned facial nerve, which points to the possibility of using this substance for new clinical applications to promote axonal growth and remyelination.     

Expression of myelin-associated glycoprotein isoforms after sciatic nerve crush injury in mice

The large myelin-associated glycoprotein isoform (L-MAG) protein and small myelin-associated glycoprotein isoform (S-MAG) protein were demonstrated after sciatic nerve crush injury in mice by an immunoblotting technique using specific antibodies to the L-MAG protein and the S-MAG protein, respectively. Immunoblots indicated a rapid decrease in expression of both isoform proteins in the crushed sciatic nerves to <10% of the control side. By 13 d after injury, L-MAG protein expression had quickly recovered to 100% of the control level. Following the increase in L-MAG protein expression, S-MAG protein expression recovered to 100% by 20 d after injury. It has been reported that the developmental maximum expression of L-MAG protein precedes that of S-MAG protein in both central and peripheral nervous system (CNS and PNS). Our previous work demonstrated that L-MAG mRNA was characteristically induced at the time of most active myelination, including remyelination in the CNS. We here have shown the expression of L-MAG protein precedes that of S-MAG protein during active remyelination in the PNS. This suggests that it plays an important role in the early stage of myelin formation.     

Ursolic acid induces neural regeneration after sciatic nerve injury

In this study,we aimed to explore the role of ursolic acid in the neural regeneration of the injured sciatic nerve.BALB/c mice were used to establish models of sciatic nerve injury through unilateral sciatic nerve complete transection and microscopic anastomosis at 0.5 cm below the ischial tuberosity.The successfully generated model mice were treated with 10,5,or 2.5 mg/kg ursolic acid via intraperitoneal injection.Enzyme-linked immunosorbent assay results showed that serum S100 protein expression level gradually increased at 1-4 weeks after sciatic nerve injury,and significantly decreased at 8 weeks.As such,ursolic acid has the capacity to significantly increase S100 protein expression levels.Real-time quantitative PCR showed that S100 mRNA expression in the L4-6 segments on the injury side was increased after ursolic acid treatment.In addition,the muscular mass index in the soleus muscle was also increased in mice treated with ursolic acid.Toluidine blue staining revealed that the quantity and average diameter of myelinated nerve fibers in the injured sciatic nerve were significantly increased after treatment with ursolic acid.10 and 5 mg/kg of ursolic acid produced stronger effects than 2.5 mg/kg of ursolic acid.Our findings indicate that ursolic acid can dose-dependently increase S100 expression and promote neural regeneration in BALB/c mice following sciatic nerve injury.     

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.     

Scaffoldless tissue-engineered nerve conduit promotes peripheral nerve regeneration and functional recovery after tibial nerve injury in rats

Damage to peripheral nerve tissue may cause loss of function in both the nerve and the targeted muscles it innervates. This study compared the repair capability of engineered nerve conduit (ENC), engineered fibroblast conduit (EFC), and autograft in a 10-mm tibial nerve gap. ENCs were fabricated utilizing primary fibroblasts and the nerve cells of rats on embryonic day 15 (E15). EFCs were fabricated utilizing primary fi-broblasts only. Following a 12-week recovery, nerve repair was assessed by measuring contractile properties in the medial gastrocnemius muscle, distal motor nerve conduction velocity in the lateral gastrocnemius, and histology of muscle and nerve. The autografts, ENCs and EFCs reestablished 96%, 87% and 84% of native distal motor nerve conduction velocity in the lateral gastrocnemius, 100%, 44% and 44% of native specific force of medical gastrocnemius, and 63%, 61% and 67% of native medial gastrocnemius mass, re-spectively. Histology of the repaired nerve revealed large axons in the autograft, larger but fewer axons in the ENC repair, and many smaller axons in the EFC repair. Muscle histology revealed similar muscle fiber cross-sectional areas among autograft, ENC and EFC repairs. In conclusion, both ENCs and EFCs promot-ed nerve regeneration in a 10-mm tibial nerve gap repair, suggesting that the E15 rat nerve cells may not be necessary for nerve regeneration, and EFC alone can suffice for peripheral nerve injury repair.     

Myelinated fiber regeneration after crush injury is retarded in sciatic nerves of aging mice

To compare nerve regeneration in young adult and aging mice, the right sciatic nerves of 6- and 24-month-old mice were crushed at the sciatic notch. Two weeks later, both groups of mice were perfused with an aldehyde solution, and, after additional fixation, the sciatic nerves were processed so that the transverse sections of each nerve subsequently studied by light and electron microscopy included the entire posterior tibial fascicle 5 mm distal to the crush site. The same level was sectioned in unoperated contralateral nerves; these nerves served as controls. Electron micrographs and the Bioquant Image Analysis System IV were used to measure areas of posterior tibial fascicles and count the number of myelinated axons, the number of unmyelinated axons, and their frequency in Schwann cell units. In aging mice, the total number of regenerating myelinated axons was significantly reduced, but totals of regenerating unmyelinated axons in aging and young adults did not differ significantly. In aging mice, the frequency of Schwann cells that contained a single unmyelinated axon was greater, suggesting that before myelination began, Schwann cell ensheathment of axons also was slowed. After axotomy by a crush injury, the area of the posterior tibial fascicle was less than that in young adults and the distal disintegration of myelin sheath remnants also appeared to be retarded. The results indicate that responses of neurons, axons, and Schwann cells could be important in slowing the regeneration of myelinated fibers found in sciatic nerves from aging mice.     

High- and low-frequency transcutaneous electrical nerve stimulation delay sciatic nerve regeneration after crush lesion in the mouse

Abstract   The stimulation of peripheral nerve regeneration has been studied in different ways, including the use of electrical fields. The capacity of this modality to enhance nerve regeneration is influenced by the parameters used, including current type, frequency, intensity, and means of administration. Transcutaneous electrical nerve stimulation (TENS) is a frequently used form of administering electrical current to the body, but its effects on peripheral nerve regeneration are not known. This study assessed the influence of TENS on sciatic nerve regeneration, using a model of crush lesion in the mouse. Mice were stimulated 30 min a day, 5 days a week, for 5 weeks with both high- (100 Hz) and low- (4 Hz) frequency TENS. Control animals had the sciatic nerve crushed but were not stimulated. Assessment was performed weekly by functional analysis using the Static Sciatic Index for the mouse and at the end of the experiment by light and electron microscopy. The results showed that although there were no differences between the groups regarding the Static Sciatic Index values, TENS led to nerves with morphological signs of impaired regeneration. At light microscopy level, TENS nerves presented more axons with dark axoplasm, signs of edema, and a less organized cytoarchitecture. Electronmicrographs showed fewer and thinner thick myelinated fibers and increased number of Schwann cell nuclei. Myelinated axon diameters and density and diameter of nonmyelinated fibers were not affected by TENS, leading to the conclusion that this regimen of electrical stimulation leads to a delayed regeneration after a crush lesion of the sciatic nerve in the mouse. All these effects were more pronounced on high-frequency TENS nerves.     

Exercise training and axonal regeneration after sciatic nerve injury.

In the present study, we aimed to investigate the relationship between exercise training and peripheral nerve regeneration after crush injury. For this purpose, HRP neurohistochemistry and modified Pal-Weigert methods were used to assess the axonal regeneration. In the 2nd and 3rd regeneration week groups, myelin debris was observed, and there was no significant difference between exercise trained and sedentary groups. In the 4th regeneration week group, it was seen that myelin debris was removed, and some myelinated fibers were observed in the exercise trained group. On the other hand, there was no myelinated fiber in the sedentary group, and there was a significant difference between exercise trained and sedentary groups. Consequently, we think that exercise is effective in the 4th regeneration week.