后根轴突再生重建感觉传入通路的实验研究

目的 将后根分别与脊神经节中枢突支(后根)和周围突支(脊神经)吻合,为通过后根再生重建感觉传入通路奠定组织学基础.方法 SD大鼠74只随机分为三组,左侧为正常对照侧,右侧为手术侧.A组将L4后根近断端L6后根远断端吻合;B组将L4脊神经出椎间孔2 mm处切断,近断端与L6后根远断端吻合;C组手术操作同B组,但不吻合作为假手术组.术后3个月以逆行神经示踪、脊髓后根入口(dorsal root entry zone,DREZ)降钙素基因相关肽(calcitonin gene-related peptide,CGRP)阳性轴突分布、脊神经节和脊髓后角神经元存活率、光镜和透射电镜评价轴突再生效果.结果 逆行神经示踪证实B组再生轴突轴浆运输功能恢复良好.A组和B组均可见轴突再生通过吻合口,神经纤维数量和髓鞘厚度与正常对照侧比较差异无统计学意义;但A组轴突再生停止于DREZ,脊髓后角CGRP阳性纤维分布密度低于B组和正常对照侧,差异有统计学意义.三组L6脊神经节神经元存活率与正常对照侧比较差异无统计学意义;A组和C组L4脊髓后角神经元存活率低于B组和正常对照侧,差异有统计学意义.结论 后根与脊神经吻合后不影响脊髓后角神经元存活,神经纤维再生、轴浆运输能通过DREZ进入脊髓,是一种理想的修复感觉传导通路的方式.

Abstract：

Objective To provide the morphological evidence for sensory pathway by the repair of dorsal root (DR) in which received transected and anastomosed with central processes (DR) and peripheral processes (spinal nerve) respectively. Methods 74 SD rats were divided into three groups randomly. Group A: the distal ending of L6 DR was sutured to the proximal ending of the L4 DR in right side. Group B: the postganglionic spinal nerve of L4 was cut at a point 2 mm to intervertebral foramen and its proximal stump was reconnected to the distal ending of L6 DR in right side. Group C: under the same operative manipulation on group B, but no anastomosis was performed to serve as the sham operation group. The left side was kept intact and served as a normal control in all groups. The repairing results of DR axonal regeneration were evaluated at 3 months after operation by retrograde tracing, the density of positive Calcitonin gene-related peptide (CGRP) axon in dorsal root entry zone (DREZ), survival rate of neurons in DR ganglia and posterior horn, light and transmission electron microscope. Results HRP retrograde tracing demonstrated axonal axoplasmic transport of regenerative nerve recovered well in group B. Regenerative fibers were found. There was no difference between group A or B and normal control with regard to the number of myelinated axons and the thickness of myelin. Regenerating axon stop at the DREZ in group A and the density of positive CGRP were lower than those in group B and normal control. Survival rate of neurons in L6 DR ganglia had no difference among all groups. However, in posterior horn, a significant increase in death was seen in group A and sham group. Conclusion The ability of axonal regeneration was effective and with no disservice to neurons in posterior horn following anastomosis of postganglionic spinal nerve and dorsal root, by which axoplasmic transport across the DREZ into the spinal cord.     

臂丛神经根性撕脱伤后神经根回植的实验研究

目的探讨臂丛神经根性撕脱伤后，神经根回植脊髓对前角运动神经元的挽救效应及作用机制，观察回植后神经根的生长情况。方法成年Wistar大鼠30只，随机分两组，每组15只。取两组大鼠左侧为正常对照侧，不作任何处理；右侧进行模型制备。进行C4-6右侧椎板减压，于椎管内硬膜外撕脱C5、6神经根。实验组将C5神经前根回植入脊髓前角，用11—0无创缝线缝合2针，后根旷置，C5神经根埋入周围肌肉；对照组将撕脱的C5、6神经根埋入肌肉。术后2、4、6、8及12周取材，C6脊髓HE染色，观察脊髓前角运动神经元的形态和数量的变化；C6神经根作硝酸银染色，观察神经纤维的再生情况。结果两组大鼠术后均表现为右上肢上干瘫痪，余肢体活动正常。对照组撕脱的神经根与周围肌肉粘连；实验组神经根植入脊髓处有较多瘢痕组织粘连，未见神经根从脊髓上脱落。各时间点HE染色显示，实验组运动神经元胞体萎缩，部分运动神经元水肿，尼氏体减少或消失；对照组神经细胞胞体缩小。术后各时间点对照组脊髓前角运动神经元成活率分别为60．9％±5．8％、42．3％±3．5％、30．6％±6．1％、27．5％±7．9％及20．4％±6．8％，实验组为67．1％±7．4％、56．3％土4．6％、48．7％±8．8％、44．2％±5．5％及42．5％±8，3％，差异有统计学意义（P〈0．01）。硝酸银染色显示，实验组C6神经根硝酸银染色显示前角运动神经元能通过轴突再生进入回植的神经根内；对照组显示为神经纤维的退变，有髓神经纤维数目减少。结论臂丛神经根性撕脱伤后前根回植脊髓后，能够明显减少前角运动神经元的变性死亡。神经根回植后，运动神经元能通过轴突再生进入回植的神经根内，并有新生的有髓神经纤维生长。     

纳米银-胶原蛋白-明胶支架材料对兔坐骨神经缺损修复的实验研究

目的 探讨含纳米银的胶原蛋白-明胶支架材料通过静电吸附层黏连蛋白对周围神经缺损修复的效果.方法 制备纳米银-胶原蛋白支架材料,作为实验组,以不含纳米银的胶原蛋白支架为对照组.将雄性新西兰兔40只随机分为两组,每组20只.将实验组材料和对照组材料分别与层黏连蛋白复合后分组修复兔坐骨神经10 mm缺损.术后30 d通过电生理学、形态学观察和荧光金逆行示踪实验对修复效果进行评估.结果 层黏连蛋白通过静电吸附作用均匀地贴附在实验组支架内表面.兔坐骨神经桥接术后30 d,甲苯胺蓝及透射电镜显示实验组在再生神经纤维数量、神经髓鞘厚度以及被荧光金逆行标记的神经元数量方面均优于对照组.电生理结果:实验组和对照组坐骨神经电位波幅分别为(0.70±0.44)、(0.58±0.37)mV,差异有统计学意义(t=2.803,P=0.012);神经传导速度分别为(40.7±2.1)、(36.6±4.8)m/s,差异有统计学意义(t=2.427,P=0.031).结论 纳米银-胶原蛋白-明胶通过静电引力对层黏连蛋白具有较好的吸附作用,而吸附层黏连蛋白的纳米银-胶原蛋白-明胶支架对成年兔坐骨神经10 mm缺损具有较快的修复作用.     

The use of coaxially aligned freeze-thawed skeletal muscle autografts in the repair of the cauda equina — in the sheep

Summary The aim was to develop a model for study of nerve regeneration in nerve roots above the level of the dorsal root ganglion and to investigate the use of freeze-thawed muscle autografts for repair of nerve roots at this level.Four adult sheep were used for the experiment. A laminectomy was performed at the lumbosacral junction and the S2 root identified. Both the dorsal and ventral S2 roots were divided unilaterally within the dura and a freeze-thawed muscle graft was inserted into the nerve gap.When assessed at 6 months an action potential was recordable from the ventral root in one sheep. Histological examination of the nerve roots showed evidence of regeneration across the graft in the ventral roots of all the sheep and the dorsal roots of some.This preliminary work indicates a capacity for regeneration of the cauda equina and that freeze-thawed muscle can support this. It provides a useful model for further study of nerve root repair.     

Urinary bladder reinnervation

The ability of mixed spinal nerve roots to regenerate and reinnervate the urinary bladder was examined in young adult female cats. Using microsurgical technique, a unilateral extradural spinal nerve root anastomosis of a lumbar (L7) to a sacral root (S1) either with or without a nerve graft was performed. Remaining ipsilateral sacral roots were transected. The contralateral normal sacral roots remained intact and allowed the animals adequate urination during the period necessary for axonal regeneration. At the time of restudy seven months later, stimulation of the anastomosed nerve root proximal to the anastomosis (isolated from the spinal cord) elicited a bladder contraction. Significant lumbar axonal regeneration was substantiated by compound action potentials recorded across the anastomosis. In addition, redirection of axons from a lumbar to a sacral distribution was demonstrated. The contralateral normal sacral roots provided control cystometric and electrophysiological data against which responses from the previously anastomosed nerve roots were compared. In conclusion, significant bladder reinnervation can occur after an anastomosis of a lumbar and sacral root with or without a nerve graft. This technique, or variations thereof, may have a clinical role in selected patients with neurogenic bladder dysfunction to reinnervate the bladder and restore central control.     

Schwann cells can induce collateral sprouting from intact axons: experimental study of end-to-side neurorrhaphy using a Y-chamber model.

Axonal regeneration across end-to-side neurorrhaphy has recently been reported; however, neither the mechanism by which collateral sprouting from intact axons is elicited, nor the origin of the regenerating axons are known. There has even been controversy over the presence of collateral axonal sprouting from intact axons altogether. This reported experimental study was designed to clarify these questions. A rat sciatic nerve model was used. To avoid any mechanical damage to the donor nerve during the procedure, a Y-shaped silicone chamber was employed instead of direct suture. Axonal regeneration from the intact tibial nerve across the gap into the peroneal nerve was assessed using a retrograde neurotracer and immunohistochemical staining. Axonal regeneration across the gap was observed in 66 percent of the animals. The neurotracer evaluation clearly showed that all regenerating axons were sensory axons from the dorsal root ganglia. The authors concluded that Schwann cells from the distal wallerian degeneration of nerve segments did elicit collateral axonal sprouting from intact sensory axons, but not from motor axons in end-to-side neurorrhaphy. Invasion of the Schwann cells into the epineurial layer was the crucial step for the initiation of collateral axonal sprouting from the intact axons.     

鼠腓总神经端侧缝合后脊髓内HRP阳性标记神经细胞出现的时间和数量

目的用辣根过氧化物酶（ｈｏｒｓｅｒａｄｉｓｈｐｅｒｏｘｉｄａｓｅ,ＨＲＰ）追踪法比较神经端侧缝合与对端缝合后脊髓内神经细胞出现的时间和数量。方法Ｗｉｓｔａｒ大鼠３６只,切断其右侧腓总神经后,按手术方法随机分为３组,每组１２只。（Ａ）端侧吻合组：腓神经远断端与胫神经侧方窗口缝合。（Ｂ）对端缝合组：腓总神经近、远端作对端缝合。（Ｃ）对照组：腓总神经不作缝合。术后２、４、６、８、１０及１２周,３组各取２只鼠,自腓总神经最远端注射０．１μｌＨＲＰ（３０％）,７２小时后取出大鼠Ｔ１２～Ｌ６脊髓节段和相应的后根神经节,作组织学观察。结果Ａ组：术后１２周时,同侧Ｌ２～５后根神经节,脊髓后角、前角出现典型的ＨＲＰ阳性标记细胞,比Ｂ组慢６周。细胞数量比Ｂ组少４５．７％（ｔ＝４．９２,Ｐ＜０．０１）。Ｃ组则一直未见ＨＲＰ阳性标记细胞。结论神经端侧缝合后可以再生,但其速度和阳性细胞数量均较对端缝合差。     

Morphological and functional evaluation of leg-muscle reinnervation after coupler coaptation of the divided rat sciatic nerve

Mechanical couplers are successfully used for microvascular venous anastomoses. The advantages include a simple and fast technique and a high patency rate. Couplers offer a secluded coaptation site, and might also be of use in peripheral nerve repair. The present study was designed to investigate coupler coaptation of the rat sciatic nerve, evaluating the number and locations of motor and sensory neurons projecting to the selected muscles as well as stimulation-induced muscle contraction force. Adult rats underwent either suture or coupler repair after left sciatic nerve transection. In all rats, the experimental side was compared to the healthy right side. Evaluation after 20 weeks included retrograde labeling of motoneurons and dorsal root ganglion neurons projecting to the tibial anterior muscle and to the tibial posterior muscle, histology, muscle contraction force (tibial anterior muscle and gastrocnemius muscle), and a pinch reflex test. The results show that the suture and the coupler groups did not differ significantly regarding the examined parameters, except for discrete signs of nerve compression at the coaptation site after coupler repair due to fibrous tissue ingrowth. However, this did not impair axonal regeneration. Importantly, axonal outgrowth from the repair site to the surrounding tissue was not observed after coupler coaptation, but it was observed after suture repair. These results suggest that couplers may be of value for repair of nerves in adjacency to avoid axonal crisscrossing between nerves during regeneration.     

Alterations in retrograde axonal transport in streptozocin-induced diabetic rats

Retrograde axonal transport in the sciatic nerve of rats with streptozocin-induced diabetes was studied by the [3H]N-succinimidyl propionate [( 3H]NSP) method. The accumulation of retrogradely transported labeled proteins in the dorsal root ganglia and the ventral horn of spinal cord 1 day after [3H]NSP injection was not statistically significantly different from controls in rats diabetic for 1 or 14 days at the time of [3H]NSP injection. However, accumulation of labeled proteins in the dorsal root ganglia 7 days after [3H]NSP injection was reduced by 35% and transport to the ventral horn of spinal cord 7 days after [3H]NSP injection was reduced by 70% at the same time points. Partial control of the diabetes with insulin resulted in a partial reversal of these deficits. The early occurrence of defects in retrograde transport suggests that such defects may play a role in the pathogenesis of the neuropathy.     

Artificial nerve graft using collagen as an extracellular matrix for nerve repair compared with sutured autograft in a rat model

A study was conducted to compare the regeneration of rat peroneal nerves across 0.5-cm gaps repaired with artificial nerve grafts versus sutured autografts. The artificial nerve graft model is composed of a synthetic biodegradable passive conduit made of polyglycolic acid filled with a collagen extracellular matrix (predominantly Type I collagen, derived from calf skin, and with the telopeptide ends left intact). Axonal regeneration was studied in 22 long-term animals (11 or 12 months). The nerves were studied by qualitative and quantitative histological and electrophysiological methods, and by functional analysis in 9 of the animals. The axonal regeneration of the artificial nerve graft is equal to sutured autografts as measured by axonal counts, and by physiological and functional methods, although the sutured autografts demonstrated statistically superior axonal diameters.     

ELECTRIC STIMULATION OF A TRANSSECTED NERVE DOES NOT SEEM TO PREVENT LOSS OF SENSORY NEURONS: AN EXPERIMENTAL STUDY IN CATS

Injury to a sensory nerve often results in a clinically poor long term outcome, possibly as a result of the extensive loss of neurons within the dorsal root ganglia (DRG), which has been shown in several experimental studies. This loss is possibly caused by interruption of the sensory input and axonal transport in the damaged afferent nerve. To investigate the importance of sensory afferent input into a nerve a pulsed electric stimulation was applied on the proximal part of the superficial radial nerve after transsection and microsurgical repair. The purpose was to simulate nerve impulses and thereby mask the severity of the injury. To test this hypothesis a pilot study was undertaken in eight cats. The neuronal tracer showed that the median neuronal loss was 38% of the neurons of the dorsal root ganglia that received afferents from the nerve investigated, which corresponds to the figure in a previous study in which electric stimulation was not used. Artificial sensory stimulation during regeneration in a transsected and repaired peripheral nerve therefore does not seem to reduce neuronal loss.     

Electric stimulation of a transsected nerve does not seem to prevent loss of sensory neurons: an experimental study in cats.

Injury to a sensory nerve often results in a clinically poor long term outcome, possibly as a result of the extensive loss of neurons within the dorsal root ganglia (DRG), which has been shown in several experimental studies. This loss is possibly caused by interruption of the sensory input and axonal transport in the damaged afferent nerve. To investigate the importance of sensory afferent input into a nerve a pulsed electric stimulation was applied on the proximal part of the superficial radial nerve after transsection and microsurgical repair. The purpose was to simulate nerve impulses and thereby mask the severity of the injury. To test this hypothesis a pilot study was undertaken in eight cats. The neuronal tracer showed that the median neuronal loss was 38% of the neurons of the dorsal root ganglia that received afferents from the nerve investigated, which corresponds to the figure in a previous study in which electric stimulation was not used. Artificial sensory stimulation during regeneration in a transsected and repaired peripheral nerve therefore does not seem to reduce neuronal loss.     

人工膀胱反射弧的远期功能观察

目的 :建立犬人工膀胱反射通路 ,以恢复脊髓损伤后的膀胱功能 ,观察人工反射弧的远期功能状态。方法 :将右L5前根近端与右S2 前根远端在硬膜囊内吻合 ,经轴突再生后 ,建立膝腱—脊髓中枢—膀胱这一新的人工膀胱反射通路 ,通过刺激膝腱激发排尿。结果 :神经根吻合术后 18个月 ,T10 平面截瘫 48h后 ,通过电刺激传入神经 ,经新建的反射弧引出的膀胱收缩平均可达正常的 84% ,敲击膝腱引出的膀胱收缩平均达正常的 6 2 % ;电刺激右L5后根和右股神经 ,均可记录到膀胱逼尿肌肌电图 ,其形态和波幅与对照组相似。结论 :体神经的运动传出支通过轴突再生能够长入自主神经的副交感性纤维 ,并具有良好的传导运动兴奋的功能 ;利用截瘫平面以下健存的体反射 ,通过神经根吻合的方法 ,可建立人工膀胱反射弧 ,实现患者的控制性排尿。     

大鼠嘌呤P2Y2受体在神经系统分布的实验研究

目的探讨P2Y2受体在脊髓、背根神经节和坐骨神经的表达和具体分布，研究三磷酸腺苷（adenosine triphosphate．ATP）对神经再生的作用机制提供理论基础。方法将6只SD乳鼠的脊髓、背根神经节和坐骨神经标本置于含有0．1％二乙基焦碳酸的4%多聚甲醛液中快速固定、石蜡包埋、超薄切片。实验组：根据P2Y2受体mRNA的碱基序列，制作非放射性标记的核苷酸探针，原位杂交后将切片置于含有NBT溶液（50mg／ml硝基兰四唑溶于二甲基甲酰胺）、BCIP溶液（75mg／ml溴绿一吲哚磷酸溶于二甲基酰胺）的检测缓冲液中染色，镜下观察P2Y2受体的具体分布。对照组：切片刚不含探针的杂交缓冲液覆盖、染色观察。结果实验组：脊髓灰质前角神经元胞浆中可见P2Y2受体的表达，呈弱阳性；背根神经节雪旺细胞的胞浆和胞核中均可见P2Y2受体的表达，且呈强阳性；对照组：无P2Y2受体表达。实验组与对照组坐骨神经原位杂交尢P2Y2受体的表达。结论P2Y2受体主要分布在脊髓、背根神经节，细胞外ATP可以通过P2Y2受体作用于脊髓和背根神经节细胞。     

End-to-end versus peripheral nerve graft repair of the oculomotor nerve in rats: A comparative histological and morphometric study

A comparative study was undertaken to evaluate end-to-end versus peripheral nerve graft repair in cranial nerve reconstruction. In 14 rats, the oculomotor nerve was sharply transected in the cavernous sinus and repaired either by end-to-end coaptation (n = 7) or by interposition of a peripheral nerve graft (n = 7). The results were evaluated 16 weeks after surgery by light and transmission electron microsurgery and by morphometric analysis. The degree of neuroma formation, fibrosis, and axonal disorganisation at the repair site was the same for both groups. Histologically, both end-to-end and graft repair groups revealed various degrees of axonal regeneration with myelinated nerve fibres in the distal nerve segments. In both groups, the number of nerve fibres distal to the repair site was increased compared to proximal to the repair (P < 0.001) but myelinated axon diameter was significantly less than that of control nerves (P < 0.001). No difference existed between the two repair groups in terms of mean myelinated axonal diameter. However, the number and density of myelinated axons was statistically greater in the graft group (P < 0.05). In conclusion, despite the disadvantage of two repair sites, peripheral nerve grafting results in equal or slightly superior axonal regeneration compared to an end-to-end repair in the rodent model of intracranial oculomotor nerve reconstruction. We speculate that this may be due to the structure of the peripheral nerve graft.     

Nerve regeneration across an extended gap: A neurobiological view of nerve repair and the possible involvement of neuronotrophic factors

We have compared the anatomic and functional regeneration of a transected sciatic nerve following regrowth from its proximal stump through either preformed empty mesothelial chambers or autologous nerve grafts bridging a 10 mm gap. Within the mesothelial chambers an organized multifascicular nerve trunk forms between the proximal and distal stumps. After 3 months, distal segment cross sections from the mesothelial chamber and nerve graft groups did not differ with respect to axonal density or distribution of axonal diameters. Mean conduction velocities across the gaps were also similar, although the nerve graft group had a wider distribution of velocities. Little or no regeneration was evident when the gap between the nerve stumps was left empty. These results suggest that if the regrowing proximal stump is in an appropriate environment, it can form a well organized and oriented nerve trunk. In the mesothelial chambers, the regenerating nerve is surrounded by a loose cellular stroma and a small amount of interstitial fluid, which was found to contain trophic activity for cultured rodent sensory neurons. Such factors may also support nerve regeneration in vivo.     

Transmigration of donor cells involved in the sciatic nerve graft

INTRODUCTION: Recently, human hand transplantation in Europe has shown that motor function may be recovered in some cases. However, little is known about cell trafficking involved the graft nerve. We have succeeded to use green fluorescent protein transgenic (GFP-Tg) rats with various cells strongly expressing GFP in a model a long-term survival of limb graft. In this model, we found retrograde migration of GFP-positive donor cells through the sclatic nerve anastomosis. It is well known that cellular components in the peripheral nerve graft especially Schwann cells, play an important role in the axonal regeneration promoted by nerve grafting. However, it was difficult to distinguish the cellular component of the nerve graft from recipient cells. The purpose of this study was to evaluate the migration of donor origin cells to the recipient's nerve and to examine the contribution of these cells in axonal regeneration using a simplified model of sciatic grafting. METHODS: Nerve defects were created in recipient rats, using three experimental combinations: group 1: wild-type rats from GFP Tg rats; group 2: GFP Tg rats from wild-type rats; group 3: wild-type rats from GFP Tg rats whose nerve grafts had been pretreated by freeze-thawing cycles (representing an acellular graft). The sciatic nerve specimens were examined under excitation light at 1, 2, and 3 weeks after transplantation. RESULTS: GFP-positive area expanded clearly beyond the anastomosis both proximally and distally in group 1 and infiltrated into the middle of the null graft in group 2. On the contrary, freeze-thawing grafts donated GFP Tg rats lost GFP expression completely. Columns of GFP-positive cells were formed in the degenerated graft migrated into the recipient's nerve both ante- and retrograde. The S100-positive GFP-positive cells were considered to be graft-origin Schwann cells. The regenerating axons were accompanied with these double-positive cells in the recipient nerve. In conclusion, we have visualized the contribution of graft cells to axonal regeneration beyond a peripheral nerve anastomosis.     

几丁糖复合聚乙烯醇神经导管修复大鼠坐骨神经损

目的 径较粗,达到正常神经的直径。肌肉湿重和肌细胞截面积：A组和C组比较,差异无统计学意义(P＞0.05);A、C组明显优于B组,差异有统计学意义(P＜0.05)。组织学观察：A组和C组神经纤维数日多、大小均匀、成熟良好,B组神经纤维数目少、不均匀、髓鞘发育较差。神经示踪观察结果显示：A、B、C三组在L4～L6节段脊髓前角和背根节均可见到真蓝标记的神经元细胞,其中A组脊髓前角真蓝标记的神经元数目和C组相似,差异无统计学意义(P＞0.05),但明显优于B组,差异有统计学意义(P＜0.05)。 结论 几丁糖复合聚乙烯醇神经导管具有促进神经轴突再生的作用,有望成为自体神经的替代材料,应用于周围神经缺损的修复。     

Effects of topically administered nerve growth factor on axonal regeneration in peripheral nerve autografts implanted in the spinal cord of rats

The effect of exogenous nerve growth factor (NGF) on axonal regeneration into autologous peripheral nerve (PN) grafts implanted to the spinal cord (SC) of rats was assessed by retrograde labeling of the parent soma of the regenerating axons with horseradish peroxidase. NGF was delivered at the graft site over periods of 15 and 30 days by using indwelling osmotic minipumps. In control rats, the minipumps were filled with saline. At 15 days after grafting in the NGF-treated rats, the mean number of SC as well as dorsal root ganglion (DRG) neurons that regenerated their axons into the peripheral nerve grafts was increased 55.3 and 26.4 times, respectively, as compared to the control group values. At 30 days, SC and DRG neurons in the NGF-treated group were 10.9 and 3.1 times greater than in the control group. In the NGF-treated group, the regenerating SC neurons were located within a range of 7 to 13 mm from the graft site as compared to 1 to 7 mm in the control group. Finally, the analysis of the soma diameters of the regenerating neurons showed that NGF enhanced and maintained with time the regenerative response from small-sized DRG neurons. Therefore, NGF is thought to promote directly the regenerative potential of SC as well as DRG neurons and to exert an indirect glial cell-mediated effect at the SC-graft interface.     

Acellular muscle with Schwann-cell implantation: an alternative biologic nerve conduit

Denatured or acellular muscle grafts are known to support axonal regeneration. With increasing gap length, failure of regeneration is evident, due to the lack of viable Schwann cells in the graft. The authors created a biologic nerve conduit, in a rat sciatic nerve model, by implanting cultured Schwann cells into an acellular gracilis muscle. Autologous nerve grafts and acellular muscle grafts without Schwann cells served as controls. After 6 weeks, regeneration was assessed clinically, histologically, and morphometrically. Polymerase chain reaction (PCR) analysis showed that the implanted Schwann cells remained viable within the graft. Good regeneration was noted in the muscle-Schwann cell group, while regeneration in the muscle grafts without Schwann cells was significantly impaired. The muscle-Schwann cell graft demonstrated systematic and organized regeneration, including the proper orientation of regenerated fibers. The number of axons regenerating through the muscle-Schwann cell grafts was significantly increased, compared with the acellular muscle without Schwann cells. Implantation of Schwann cells into acellular muscle thus provided a biologic conduit with large basal lamina tubes, as a pathway for regenerating axons. The positive effects of Schwann cells, producing neurotrophic and neurotropic factors, supported axonal regeneration.