纤溶酶原激活剂及其相关分子在小鼠视神经损伤再生中的变化

目的:检测细胞外基质(ECM)中各蛋白酶在视神经损伤后的变化,分析ECM蛋白酶活性的变化与小鼠视神经损伤和损伤后再生之间的关系。方法:本实验采用建立小鼠视神经钳夹伤的动物模型,用WesternBlot方法检测小鼠视神经损伤后不同时间点神经丝(NF)、金属基质蛋白酶-9(MMP-9)、IgG的表达变化。同时采用原位酶谱分析法检测纤溶酶原激活剂(PA)活性在视神经损伤后各阶段的变化,并分析这种变化与纤维蛋白(原)沉积、髓鞘碎片清除等影响神经再生的因素之间的关系。结果:小鼠视神经损伤后发生进行性Wallerian变性,血-神经屏障(BNB)修复迟缓,沉积的纤维蛋白(原)于损伤后第2d清除。MMP-9在损伤后2d达到高峰,以后仍呈现高水平的表达,且均以前体形式出现。PA活性在损伤后第7d达到高峰,并持续至第28d。结论:视神经损伤后,损伤部位BNB重建、PA激活、纤维蛋白(原)的清除以及MMP-9的表达与周围神经截然不同,正是由于微环境的迥然差异,导致了中枢神经系统(CNS)髓鞘碎片清除不利、轴突再生障碍。     

Quantification of the mononuclear phagocyte response to Wallerian degeneration of the optic nerve

Summary We investigated the numbers, origin and phenotype of mononuclear phagocytes (macrophages/microglia) responding to Wallerian degeneration of the mouse optic nerve in order to compare it with the response to Wallerian degeneration in the PNS, already described. We found macrophage/microglial numbers elevated nearly four fold in the distal segments of crushed optic nerves and their projection areas in the contralateral superior colliculus 1 week after unilateral optic nerve crush. This relative increase in mononuclear phagocyte numbers compared well with the four-to five-fold increases reported in the distal segments of transected saphenous or sciatic nerves. Moreover, maximum numbers are reached at 3, 5 and 7 days in the saphenous, sciatic and optic nerves respectively, suggesting that the very slow clearance of axonal debris and myelin in CNS undergoing Wallerian degeneration is not simply due to a slow or small mononuclear phagocyte response. The apparent delay in the response in the CNS occurs because the mononuclear phagocytes respond to the Wallerian degeneration of axons, which is slightly slower in the CNS than the PNS, rather than to events associated with the crush itself, such as the abolition of normal electrical activity in the distal segment. This was demonstrated by the protracted time course of the mononuclear phagocyte response in the distal segment following optic nerve crush in mice carrying theWld ^smutation which dramatically slows the rate at which the axons undergo Wallerian degeneration. By³H-Thymidine labelling or by blocking microglial proliferation by X-irradiation of the head prior to optic nerve crush, we showed that the majority of macrophages/microglia initiating the response to Wallerian degeneration were of local, CNS origin but these cells rapidly (from 3 days post crush) upregulate endocytic and phagocytic functional markers although they do not resemble rounded myelin-phagocytosing macrophages observed in degenerating peripheral nerves. We speculate that the poor clearance of myelin in CNS fibre tracts undergoing Wallerian degeneration compared to the PNS, in the face of a mononuclear phagocyte response which is similar in relative magnitude and time course, is because Schwann cells in degenerating peripheral nerves promptly modify their myelin sheaths such that they can be recognized and phagocytosed by macrophages, whilst in the CNS oligodendrocytes do not.     

Lesion-associated expression of transforming growth factor-beta-2 in the rat nervous system: evidence for down-regulating the phagocytic activity of microglia and macrophages

The mechanisms that control the phagocytic activities of microglia and macrophages during disorders of the nervous system are largely unknown. In the present investigation, we assessed the functional role of transforming growth factor (TGF)beta2 in vitro and studied TGFbeta-2mRNA and protein expression in two CNS lesion paradigms in vivo characterized by fundamental differences in microglia/macrophage behaviour: optic nerve crush exhibiting slow, and focal cerebral ischemia exhibiting rapid phagocytic transformation. Furthermore, we used sciatic nerve crush injury as a PNS lesion paradigm comparable to brain ischemia in its rapid phagocyte response. In normal and degenerating optic nerves, astrocytes strongly and continuously expressed TGF-beta2 immunoreactivity. In contrast, TGF-beta2 was downregulated in Schwann cells of degenerating sciatic nerves, and was not expressed by reactive astrocytes in the vicinity of focal ischemic brain lesions during the acute phagocytic phase. In line with its differential lesion-associated expression pattern, exogenous TGF-beta2 suppressed spontaneous myelin phagocytosis by microglia/macrophages in a mouse ex vivo assay of CNS and PNS Wallerian degeneration. In conclusion, we have identified TGF-beta2 as a nervous system intrinsic cytokine that could account for the differential regulation of phagocytic activities of microglia and macrophages during injury.     

大鼠坐骨神经压榨损伤后早期降钙素基因相关肽的变化

目的：研究大鼠坐骨神经压榨损伤后早期降钙素基因相关肽(CGRP)的动态变化及与神经再生的关系。方法：SD大鼠坐骨神经压榨损伤后分别存活1d到21d,免疫组化技术观察CGRP分布和含量的变化。结果：(1)1d组神经CGRP大量堆积,压榨近端明显多于远端,随即下降,21d组基本消失。(2)1d组背根节、脊髓后角和前角CGRP开始增高,并分别在3～5d、5～7d和7d组达峰值,随后渐降,21d组脊髓前角CGRP阳性运动神经元仍明显高于假手术组和对照侧。结论：神经压榨损伤后CGRP表达变化呈明显的时空模式,可能参与了神经元保护并介导了损伤信号的传导。     

The promotion of peripheral nerve regeneration by chitooligosaccharides in the rat nerve crush injury model

Chitooligosaccharides (COSs), the biodegradation product of chitosan, have shown many biological functions. In this study, we examined the possible benefits of treatment with COSs (M.W. 800) on regeneration of rat crushed sciatic nerves. The rats with sciatic nerve crush injury were administered intraperitoneally daily with 3 or 6 mg/kg body weight of COSs over a 3-week period. During and at the end of COSs treatment, a series of functional and histological examinations, including the measurement of withdrawal reflex latency (WRL) values, walking track analysis, electrophysiological assessments, morphometric analysis of gastrocnemius muscle, as well as immunohistochemistry and electromicroscopy to regenerated sciatic nerves, were performed to evaluate the therapeutic outcomes of COSs. The experimental data demonstrated that COSs promoted peripheral nerve regeneration with the desired functional recovery in the rat sciatic nerve crush injury model. This study raises a possibility of developing COSs as a potential neuroprotective agent for peripheral nerve repair applications.     

Histological and immunohistochemical study of the potential therapeutic impacts of bone marrow mesenchymal stem cells and exosomes for sciatic nerve crush injury model in rats

ABSTRACT

The aim was to evaluate the potential effect of bone marrow-derived mesenchymal stem cells (BMSC) and BMSC-EX in the sciatic nerve injury. Forty-five rats were divided into four groups, i.e. Group I control no surgery or treatment, Group II sciatic nerve crush surgery and 1 week post-surgery, Group III sciatic nerve crush injury was treated with BMSC, and Group IV sciatic nerve crush injury was treated with BMSC-EX. All animal groups were euthanized 2 weeks after treatment. Sciatic nerves were examined histologically and immunohistochemically. Group II showed various histological changes, i.e. vacuolation, degeneration and loss of nerve fibers. Group II showed a significant increase in collagen fibers, but with significant reduction in osmium tetroxide (OsO₄)-stained myelin sheaths and neurofilament immunostaining compared to Group I. Group II also revealed distortion and disruption of myelinated nerve fibers. Groups III and IV showed significant improvement of both histological and immunohistochemical changes in Group II. BMSC and BMSC-EX were shown to improve axonal regeneration.     

Spatiotemporal Expression of SSeCKS in Injured Rat Sciatic Nerve

SSeCKS (src suppressed C kinase substrate) functions in the control of cell signaling and cytoskeletal arrangement. It is expressed in brain and spinal cord, but little is known about its expression in peripheral nerves. In this study, in rats, real‐time polymerase chain reaction and Western blot analysis showed that expression of SSeCKS in crushed sciatic nerve reached its highest level 6 hr after crushing, whereas in a transection model, SSeCKS peaked at 2 days in the proximal stump and 12 hr in the distal stump. Immunohistochemical analysis demonstrated up‐regulation of SSeCKS protein surrounding the crush site and in the two stumps of the transected nerve. In addition, SSeCKS colocalized with growth‐associated protein 43 and with S100, which also changed with time after injury. These findings support the idea that SSeCKS participates in the adaptive response to peripheral nerve injury and may be associated with regeneration. Anat Rec, 291:527–537, 2008. © 2008 Wiley‐Liss, Inc.     

Acceleration of peripheral nerve regeneration after crush injury in rat

It the sciatic nerve of a rat is crushed in the thigh, axons from the proximal side of the crush will regenerate so that the toe-spreading reflex becomes observable again after 10.4 +/- 1.7 (mean +/- S.D.) days. If the nerve is electrically stimulated for 0.25-1.0 h at the crush site, just after the crush occurs, the toe-spreading reflex first becomes observable 4.14 +/- 1.6 (mean +/- S.D.) days after the crush. Stimulation is most effective if delivered immediately after the crush but can be delayed up to an hour and still cause significantly faster regeneration. This phenomenon could be useful in clinical management of crushed peripheral nerves.     

大鼠坐骨神经损伤后的生物力学研究

本文用Instron 1122型万能材料试验机,研究了大鼠坐骨神经钳夹伤后2、7、21、56天的生物力学性能,描绘出应力——应变曲线,发现损伤后早期最大应力和强度明显减弱;硬度在损伤后7天增强,到21天基本恢复,而到56天又明显增强,这与横断面积有关。神经的力学性能及损伤后的力学性能改变主要与神经外膜及束膜中胶原种类和组合方式有关,而损伤后神经外膜和束膜中的胶原是通过如何具体改变来影响生物力学性能改变的,还有待子进一步研究。     

用于中枢神经系统Waller变性研究的新型大鼠视神经夹伤模型

本实验旨在建立可用于中枢神经系统Waller变性研究的大鼠视神经(ON)损伤模型。成年SD大鼠12只,用夹持力为148g、镊端宽1mm的小号动脉阻血镊于球后2mm处夹持左侧视神经,致伤时间10s。术后随机分为两组(每组6只):一组动物术后立即于双侧上丘表面放置逆行荧光染料荧光金(FG),72h后处死。取视网膜铺片,ON冰冻连续切片。另一组动物术后72h常规灌注固定,取ON冰冻连续切片,分别行β-tubulin及NF-160免疫组化染色和HE染色。结果显示:左侧ON夹伤后3d,同侧视网膜内未见FG逆行标记的视网膜神经节细胞,ON夹伤部位形成一条宽达1mm的损伤带,ON基质连续,FG标记的神经纤维被阻断于损伤远侧,损伤远侧的β-tublin阳性纤维多已崩溃,NF-160阳性纤维数量较多,部分纤维末梢形成膨大的回缩球。上述结果表明ON夹伤后神经元轴突完全离断,中枢神经基质的连续性得以保持,损伤远侧段轴突发生典型的Waller变性,从而为中枢神经Waller变性及其药物治疗研究的筛选和评估提供了简单实用的实验模型。     

大鼠骶神经钳夹伤致神经源性膀胱模型的建立及评估

目的建立并评估大鼠骶神经钳夹伤后神经源性膀胱模型。方法将25只健康雌性大鼠随机分为对照组(n=10)和钳夹伤组(n=15)。钳夹伤组对大鼠双侧骶2神经进行钳夹伤,对照组仅暴露双侧骶2神经。造模后观察大鼠自主排尿情况,4周后检测尿流动力学指标,并对膀胱和骶神经进行组织形态学观察。结果造模48 h后钳夹伤组大鼠下腹部膀胱充盈,自主排尿受限,对照组大鼠可自主排尿。造模4周后钳夹伤组大鼠的最大膀胱容量大于对照组,差异具有统计学意义(P<0.05);钳夹伤组大鼠漏尿点压及膀胱内压高于对照组,差异具有统计学意义(P<0.05)。造模4周后钳夹伤组大鼠的膀胱明显胀大,HE染色膀胱壁肌层厚度小于对照组,差异具有统计学意义(P<0.05)。结论大鼠双侧骶2神经钳夹伤可建立神经源性膀胱模型,造模方法简单易行且模型稳定。     

Induction of repulsive guidance molecule in neurons following sciatic nerve injury

Repulsive guidance molecule (RGM) is a protein implicated in both axonal guidance and neural tube closure. We examined the expression of RGMa in the spinal cord after the sciatic nerve crush by immunohistochemistry. Although there was no RGMa immunoreactivity under na?ve conditions in the dorsal horn, a weak signal for RGMa was found at 24 h after the nerve crush, and this signal was progressively increased in the NeuN-positive neurons in the ipsilateral dorsal horn from superficial to deep layers at 10 days after surgery. In the neurons of the ipsilateral ventral horn, RGMa was also induced at 10 days after surgery, whereas no RGMa signal could be observed in na?ve conditions or at 24 h after surgery. Thus, RGMa expression is upregulated both in the ipsilateral dorsal and ventral horns in response to the sciatic nerve injury. We next examined the effects of complete Freund's adjuvant (CFA)-induced inflammation on RGMa expression in the spinal cord. However, no RGMa expression was observed at 24 h and 10 days after the CFA injection in the dorsal horn, suggesting that RGMa is not involved in inflammation-induced gyperalgesia. Our present study demonstrates that induction of RGMa is associated with the peripheral nerve injury.     

Peripheral nerve explants grafted into the vitreous body of the eye promote the regeneration of retinal ganglion cell axons severed in the optic nerve

Summary We have conducted experiments in the adult rat visual system to assess the relative importance of an absence of trophic factors versus the presence of putative growth inhibitory molecules for the failure of regeneration of CNS axons after injury. The experiments comprised three groups of animals in which all optic nerves were crushed intra-orbitally: an optic nerve crush group had a sham implant-operation on the eye; the other two groups had peripheral nerve tissue introduced into the vitreous body; in an acellular peripheral nerve group, a frozen/thawed teased sciatic nerve segment was grafted, and in a cellular peripheral nerve group, a predegenerate teased segment of sciatic nerve was implanted. The rats were left for 20 days and their optic nerves and retinae prepared for immunohistochemical examination of both the reaction to injury of axons and glia in the nerve and also the viability of Schwann cells in the grafts. Anterograde axon tracing with rhodamine-B provided unequivocal qualitative evidence of regeneration in each group, and retrograde HRP tracing gave a measure of the numbers of axons growing across the lesion by counting HRP filled retinal ganglion cells in retinal whole mounts after HRP injection into the optic nerve distal to the lesion. No fibres crossed the lesion in the optic nerve crush group and dense scar tissue was formed in the wound site. GAP-43-positive and rhodamine-B filled axons in the acellular peripheral nerve and cellular peripheral nerve groups traversed the lesion and grew distally. There were greater numbers of regenerating fibres in the cellular peripheral nerve compared to the acellular peripheral nerve group. In the former, 0.6–10% of the retinal ganglion cell population regenerated axons at least 3–4 mm into the distal segment. In both the acellular peripheral nerve and cellular peripheral nerve groups, no basal lamina was deposited in the wound. Thus, although astrocyte processes were stacked around the lesion edge, a glia limitans was not formed. These observations suggest that regenerating fibres may interfere with scarring. Viable Schwann cells were found in the vitreal grafts in the cellular peripheral nerve group only, supporting the proposition that Schwann cell derived trophic molecules secreted into the vitreous stimulated retinal ganglion cell axon growth in the severed optic nerve. The regenerative response of acellular peripheral nerve-transplanted animals was probably promoted by residual amounts of these molecules present in the transplants after freezing and thawing. In the optic nerves of all groups the astrocyte, microglia and macrophage reactions were similar. Moreover, oligodendrocytes and myelin debris were also uniformly distributed throughout all nerves. Our results suggest either that none of the above elements inhibit CNS regeneration after perineuronal neurotrophin delivery, or that the latter, in addition to mobilising and maintaining regeneration, also down regulates the expression of axonal growth cone-located receptors, which normally mediate growth arrest by engaging putative growth inhibitory molecules of the CNS neuropil.     

大鼠视神经损伤后大胶质细胞去分化及预变性腓总神经的诱导

目的研究视神经损伤后神经胶质细胞的去分化及其诱导。方法成年雄性SD大鼠,分为正常对照组、损伤组、移植组和压榨移植组,在视神经伤后3d、7d、14d和28d 4个不同时相点取视神经,用HE方法计数细胞数量,用免疫组织化学、免疫印迹、原位杂交组织化学结合计算机图像分析检测巢蛋白(Nestin)、胶质纤维酸性蛋白(GFAP)、髓鞘碱性蛋白(MBP)、神经丝(NF)、脑源性神经营养因子(BDNF)、Nogo-A及Nogo-A mRNA的表达,用免疫荧光双标组织化学法检测Nestin-GFAP和Nestin-MBP的共表达。结果损伤组细胞数量仅在伤后7d明显增多,Nestin、MBP、Nogo-A及其mRNA表达上调,GFAP、NF、BDNF下调,出现一些Nestin-GFAP双标细胞和少量Nestin-MBP双标细胞;与损伤组相比,移植组和压榨移植组一些时相点的细胞数量不同程度地增多,Nestin、GFAP、BDNF和NF表达上调,MBP、Nogo-A及其mRNA表达下调,Nestin-GFAP双标细胞有所增加,且28d组高于14d组。结论视神经损伤后,主要是星形胶质细胞发生去分化,大胶质细胞呈现一些不利于神经再生的基因表达变化;移植预变性周围神经能进一步诱导星形胶质细胞去分化,大胶质细胞的一些基因表达变化有利于神经再生。     

Interleukin-1β influences functional regeneration following nerve injury in mice through nuclear factor-κB signaling pathway

This study focuses on investigating the role of interleukin-1β (IL-1β) in functional regeneration following nerve injury in mice. A microarray-based mRNA profiling study was used to analyze the expression level of IL-1β in peripheral nerve regeneration. Quantitative real-time polymerase chain reaction and Western blot were applied to assess the IL-1β expressions of C57BL/6J-crush and C57BL/6J-crush+IL-1β mice at different post-injury time-points after the standard sciatic nerve crush injury. The outcomes of nerve regeneration were evaluated by behavioral tests. IL-1β was found to be up-regulated in peripheral nerve regeneration and significantly raised on the 3rd day and returned to normal levels on the 14th day after nerve injury. Compared with C57BL/6J-crush+IL-1β mice, the nerve regeneration of C57BL/6J-crush mice was worse after nerve crush injury. IL-1β increased mechanical sensitivity and stimulated amplitude. IL-1β could benefit the recovery of sciatic nerve crush injury by facilitating nerve regeneration.     

兔坐骨神经急性损伤的高频超声影像学观察

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

毛囊神经干细胞促进受损大鼠视神经大胶质细胞去分化

目的 培养毛囊神经干细胞,研究其对受损视神经大胶质细胞去分化的影响。 方法 取约90g雄性SD大鼠触须垫毛囊隆突区贴块,无血清培养或经15%胎牛血清诱导培养毛囊隆突区细胞,用免疫荧光细胞化学和PCR鉴定;以含增强型绿色荧光蛋白的腺相关病毒（rAAV2EGFP）稳定转染该细胞。成年雄性SD大鼠54只,分为正常对照组、损伤组、移植组,移植组为视神经损伤后移植上述毛囊神经干细胞。转染细胞移植组术后7d、14d、30d,取视神经荧光显微镜下观察;损伤组和未转染细胞移植组术后7d取术侧视神经行Affymetrix基因芯片及实时荧光定量PCR检测,术后7d、14d取术侧视神经行HE、免疫组织化学检测。 结果 成功培养出神经前体细胞标记分子阳性的毛囊神经干细胞,诱导后该细胞可表达成熟神经细胞标记分子。毛囊神经干细胞移植到受损视神经30 d后,仍能存活和迁移。与损伤组相比,移植组差异表达基因有240条,其中一些与去分化相关,如干细胞、凋亡、增殖、信号转导、转录、分化发育、细胞黏附等相关基因,实时荧光定量PCR与基因芯片结果基本相符。移植组视神经远侧段细胞数较损伤组明显增多,巢蛋白、髓鞘碱性蛋白(MBP)、细胞外信号调节激酶1/2(ERK1/2)表达增加,胶质纤维酸性蛋白(GFAP)表达减少,且视神经近侧段神经丝(NF)表达增加。 结论 毛囊神经干细胞通过调节受损视神经中的一些基因表达,促进了其大胶质细胞去分化并向有利于神经再生方向变化。     

β-1,4半乳糖基转移酶-I在钳夹伤后大鼠坐骨神经中表达的变化

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

Quantification of N-CAM and N-cadherin expression in axotomized and crushed rat sciatic nerve

Adhesion molecules are important in supporting axonal regeneration. Qualitative studies have described increased expression of neural cell adhesion molecule (NCAM) and N-cadherin in models of nerve injury allowing active regeneration. In this study we have used quantitative immunohistochemistry to compare expression of NCAM and N-cadherin after nerve injury either with active regeneration (crush) into the distal stump or without (axotomy and capping). Quantification was performed 15 days after axotomy in proximal and distal stumps. Quantification after crush either proximal, distal or within the crushed area was performed at 2, 7, 15 and 30 days after injury. Axotomy induced increases in expression in proximal stumps between two and three times those in uninjured nerves for both molecules. In distal stumps, N-cadherin levels increased seven-fold, yet NCAM levels did not exceed control values. After crush, NCAM immunoreactivity increased in the crushed area and distal stump in contrast to axotomy and NCAM-positive axons co-localized with PGP9.5. N-cadherin levels in the distal stump increased above control levels, but the magnitude of the increase seen after crush was different to those seen after axotomy. In conclusion, increased expression of adhesion molecules, particularly NCAM, in the distal stump of injured nerves is dependent upon the presence of regenerating axons.     

Glial cell proliferation in the spinal cord after dorsal rhizotomy or sciatic nerve transection in the adult rat

Proliferation of glial cells is one of the hallmarks of CNS responses to neural injury. These responses are likely to play important roles in neuronal survival and functional recovery after central or peripheral injury. The boundary between the peripheral nervous system (PNS) and CNS in the dorsal roots, the dorsal root transitional zone (DRTZ), marks a distinct barrier for growth by injured dorsal root axons. Regeneration occurs successfully in the PNS environment, but ceases at the PNS-CNS junction. In order to understand the role of different glial cells in this process, we analysed the proliferation pattern of glial cells in central (CNS) and peripheral (PNS) parts of the dorsal root and the segmental white and grey spinal cord matter after dorsal rhizotomy or sciatic nerve transection in adult rats 1-7 days after injury. Monoclonal antibody MIB-5 or antibodies to bromodeoxyuridine were used to identify proliferating cells. Polyclonal antibodies to laminin were used to distinguish the PNS and CNS compartments of the dorsal root. Dorsal root lesion induced glial cell proliferation in the CNS as well as PNS beginning at 1 day, with peaks from 2 to 4 days postoperatively. After sciatic nerve injury, cell proliferation occurred only in the CNS, was minimal at 1 day, and peaked from 2 to 4 days postoperatively. Double immunostaining with specific glial cell markers showed that after dorsal root transection 60% of the proliferating cells throughout the postoperative period examined were microglia, 30% astrocytes and 10% unidentified in the CNS, while in the PNS 40% were Schwann cells, 40% macrophages and 20% unidentified. After sciatic nerve injury virtually all proliferating cells were microglia. These findings indicate that non-neuronal cells in the CNS and PNS are extremely sensitive to the initial changes which occur in the degenerating dorsal root axons, and that extensive axonal degeneration is a prerequisite for astroglial and Schwann cell, but not microglial cell, proliferation.