脊神经根撕脱后脊髓前后运动神经元死亡的机制

脊神经根撕脱可引起脊髓前角运动神经元死亡。本文介绍近几年来脊神经根撕脱后脊髓前角运动神经元死亡的病理形态,病理机制及分子机制的研究,并对脊神经根撕脱后的运动神经元死亡的可能机制作一简要论述。     

银杏叶提取物减轻臂丛根性撕脱后脊髓运动神经元超微结构的损伤

目的：研究银杏叶提取物(EGb761)对臂丛撕脱后运动神经元超微结构的保护作用。方法：显微镜下撕脱大鼠臂丛 C_5～T_(?)神经根,术后实验大鼠腹腔注射100 mg·kg~(-1)·d~(-1)EGb761,透射电镜观察损伤 C_7节段运动神经元的超微结构。结果：神经根撕脱6～8周,运动神经元胞体体积缩小、胞核染色质裂解、浓缩异染色质增多;粗面内质网和游离核糖体减少、线粒体减少、嵴肿胀;神经髓鞘不完整、呈空泡状变性。EGb761治疗后,胞体体积基本正常,偶见浓缩异染色质;粗面内质网减少不显著;游离核糖体数量明显增多;线粒体形态正常;髓鞘完整呈同心圆包绕在轴索周围。结论：EGb761能减轻运动神经元超微结构的损伤,减少臂丛根性撕脱诱导的运动神经元凋亡。     

RNA干扰技术抑制nNOS基因对根性撕脱伤脊髓运动神经元的影响

目的研究神经元型一氧化氮合酶(neuronal nitric oxide synthase,nNOS)基因在臂丛神经根撕脱伤中的作用地位。方法设计、筛选并构建针对nNOS基因的siRNA表达载体,建立C5～T1神经根撕脱伤SD雄性大鼠模型,于撕脱后14d脊髓鞘内给予nNOS的siRNA干预,3d后用NADPH-d酶组化反应结合中性红染色评估撕脱伤脊髓运动神经元的nNOS基因表达水平和创伤神经元的存活率。结果臂丛C5～T1根性撕脱伤17d后,C7节段损伤侧前角运动神经元的存活率在siRNA组、siRNA序列对照组和生理盐水组分别为(80.51±9.16)%、(88.26±2.95)%和(89.13±3.47)%;C7节段损伤侧前角运动神经元的nNOS阳性率为(18.10±6.63)%、(42.21±2.29)%和(39.46±2.41)%。nNOS的siRNA能显著减低撕脱伤诱导的nNOS蛋白在前角运动神经元内的表达水平。虽然与对照组相比,nNOS-siRNA组撕脱伤后运动神经元存活率有下降趋势,nNOS的siRNA但并未对撕脱伤导致的运功神经元的死亡造成显著影响。结论鞘内应用siRNA技术能下调撕脱伤后大鼠脊髓运动神经元内nNOS蛋白的表达,nNOS基因有可能发挥维持撕脱伤后运动神经元存活的作用。     

成年臂丛神经根性撕脱伤后脊髓前角运动神经元的死亡表型及其机制

正人类臂丛神经根性撕脱伤是临床上常见的一种周围神经损伤,但目前这类损伤尚缺乏有效的治疗手段。臂丛神经根性撕脱伤不仅导致损伤远侧段周围神经变性和相应靶器官的失神经支配,更为重要的是还造成了脊神经腹根和背根与脊髓的脱离~[1]。目前的外科手术修复虽然可以将撕脱的脊神经腹根和背根重新植入脊髓,但伤者的运动和感觉功能     

条件性损伤的时间与频次对神经根撕脱伤后脊髓前角运动神经元死亡及NOS表达的影响

目的　探索条件性损伤 (CL)的时间和频次对神经根撕脱 (TL)后脊髓前角运动神经元一氧化氮合酶 (NOS)表达及细胞死亡的影响。方法　成年SD雌性大鼠 116只 ,体重 2 0 0～ 30 0g ,以钳夹神经干为CL ,分为两个系列。时间系列 :在CL后 1d、3d、1w、2w后进行TL ,频次系列分别在 1w和 2w内行 1次、2次、6次钳夹 ,术后不同时间点处死动物 ,以单纯撕脱臂丛为对照 ,取C5～C8节段脊髓 ,行NADPH d组化染色 ,中性红复染。定量观察前角运动神经元NOS表达及神经元数目。结果　单纯撕脱组术后第 5d脊髓前角运动神经元开始表达NOS ,术后 3wNOS阳性神经元数达到高峰 ,随后逐渐下降并伴有神经元丢失。时间系列 :撕脱后 3d和 2w ,CL与TL间隔 1d组的NOS表达和神经元数目与对照组无显著性差异 ,但 3d、1w、2w组的NOS细胞数及神经元的丢失均较对照组明显 (P <0 0 5P <0 0 1) ,但在撕脱后 4w各CL时间的NOS表达和神经元存活均较对照组减少 (P <0 0 5 )。频次系列 :在 1w和 2w内增加CL次数可使NOS的表达水平和神经细胞的死亡数目有显著增加 ,在撕脱后 2w和 4w等较后的时间点更为明显 ;但在一定时间内 2次与 6次钳夹之间则无显著性差异。结论　条件性损伤与二次损伤之间的间隔影响撕脱后神经元NOS表达和神经元的死亡 ,以间隔时间     

小动物PET-CT在大鼠臂丛根性撕脱脊髓损伤的应用研究

目的探究使用小动物正电子放射断层扫描(PET)/计算机断层成像(CT)技术诊断大鼠神经根撕脱导致的脊髓损伤的程度。方法对正常SD大鼠,通过尾静脉或腹腔注射不同剂量18F-FDG,筛选最优注射方式及剂量;随后,建立SD大鼠右侧全臂丛根性撕脱模型(BPRA组)并以假手术大鼠为对照组,对术后2周大鼠进行18F-FDG-micro-PET-CT成像检测,计算脊髓节段每克组织放射性占注入量的百分比(%ID/g),比较BPRA和假手术组大鼠C5~T1脊髓组织18F-FDG摄取差异。结果尾静脉注射1μCi/g的示踪剂18F-FDG,40 min后进行micro-PET-CT扫描其效果最佳;假手术组大鼠下颈段脊髓节段18F-FDG摄取均匀,而右全臂丛根性撕脱伤术后2周,BPRA模型组颈段脊髓18F-FDG摄取高亮范围增大,脊髓C5~C8、T1节段18F-FDG摄取率(%ID/g)为0.69±0.04与假手术组(0.60±0.02)比显著增加(P0.05)。结论尾静脉注射18F-FDG 1μCi/g联合micro-PET-CT成像技术能够监测臂丛撕脱伤后在体的脊髓组织的病理反应所引起的局部神经元和胶质细胞的代谢变化,为该病的基础研究提供工具及临床病程诊断提供了新思路。     

EGb761增强c-jun表达减少轴突撕脱后运动神经元的死亡

目的:观察EGb761对脊神经根撕脱后前角运动神经元c-jun表达和存活的影响。方法:成年Sprague-Dawley雌性大鼠180只,行脊髓C5-T1节段神经根撕脱术后,每日给予腹腔注射1mLEGb761(25mg·kg^-1),对照组注射同容积的生理盐水。治疗后4h、12h、1d、3d、5d、1周、2周、4周和6周9个时点分别处死动物,取C7脊髓节段行c-jun免疫细胞化学和中性红染色。定量比较两组c-jun阳性和存活的运动神经元数目。结果:对照组损伤侧运动神经元4h开始表达c-jun,1d达高峰,以后逐渐下降至术后2周。术后2周运动神经元开始死亡,4周-6周达高峰。EGb761组各时点c-jun阳性和存活的运动神经元数目都多于对照组。结论:EGb761能有效地减少神经根撕脱后运动神经元的死亡,机制可能与c-jun基因的上调有关。     

椎管内臂丛前后根的显微解剖及其临床意义

目的:研究臂丛椎管内前后根的显微解剖,为臂丛撕脱伤的诊治提供解剖学基础。方法:在15例防腐灌注红色乳胶的成人尸体的颈胸段标本上,对椎管内臂丛前后根的位置、形态和血供进行观察和测量。结果:臂丛前后根之间有齿状韧带相间隔;前根起始处与脊髓中线的距离从上至下由C5的2.2mm逐渐增大到T1的3.1mm,后根则从C5的4.2mm逐渐减小到T1的2.7mm;前后根与脊髓纵轴的夹角从C5的51.4°、54.8°逐渐减小到T1的21.7°、19.9°;前后根的长度从C5的14.9mm、13.9mm逐渐增大到T1的21.1mm、19.0mm;前后根的直径均以C6最为粗大,分别为2.1mm、3.3mm,后根比相应前根粗;前后根的血供来自椎动脉、颈深动脉和颈升动脉发出的节段性动脉。结论:熟悉臂丛椎管内前后根的显微解剖有助于临床臂丛根性撕脱伤的诊治。     

电针疗法对臂丛根性撕脱伤脊髓后角及中央管nNOS蛋白表达的影响

目的采用电针疗法干预大鼠臂丛神经撕脱伤模型,探索电针疗法对臂丛根性撕脱伤脊髓后角及中央管n NOS蛋白表达的影响。方法健康、雌性成年Sprague-Dawley(SD)大鼠共40只,行臂丛神经根性撕脱手术,随机分为撕脱伤组(AV组)和撕脱伤加电针治疗组(AV+EA组),AV+EA组动物隔日接受大椎(DU4)和手三里(LI10)电针治疗直至处死,每次治疗的输出脉冲波形为非对称双向疏密波,以20 Hz频率不间断治疗15 min。动物存活1周、2周、3周、6周处死,选取C7节段脊髓,行NADPH-d酶组织化学染色和中性红复染。结果脊髓后角,在AV组n NOS的微量表达;在AV+EA组2~3周n NOS在健侧的表达比伤侧增多,至6周脊髓后角n NOS阳性神经元表达AV组损伤侧;AV+EA组n NOS阳性神经元的表达与同时期的AV组。结论电针疗法导致脊髓后角及中央管n NOS阳性神经元的时空表达特异性。     

臂丛根性撕脱伤后神经根回植术的大鼠动物模型

目的：建立合理的臂丛根性撕脱伤后神经根回植术的大鼠动物模型。方法：在手术显微镜下，采用前入路，将C6神经根从脊髓上撕脱，咬除同侧C5椎体下外部分，显露脊髓；切断肌皮神经，切取长约30mm尺神经桥接肌皮神经与脊髓间的缺损，并将神经近端植入脊髓。术后观察手术侧前后肢的一般情况；6个月后，观察神经的解剖与组织学的连续性。结果：大鼠存活良好，手术侧前肢无坏死、溃疡、脱落，后肢无瘫痪；从脊髓到肱二头肌，神经的连续性完整；组织学检查见桥接神经段内有神经纤维再生。结论：该模型显露脊髓和切取桥接用神经方便，再植位置准确，便于直接观察神经根再植后神经再生及功能恢复情况，无明显的脊髓损伤并发症，较好模拟了臂丛根性撕脱伤后神经前根的回植。     

臂丛神经根性撕脱伤动物模型的研究

目的 研究臂丛神经根性撕脱伤实验动物模型。方法 选用Wistar大白鼠，取右下颌骨向下至胸大肌中部皮肤切口，显露胸大肌，分别切断胸大肌、胸小肌；暴露井剪断右锁骨，镜下解剖分离臂丛神经并紧贴近端根部将颈5至颈8剪断，造成臂丛神经根性撕脱伤模型，实验组用颈3、颈4神经修复臂丛中已损伤的颈5、颈6神经，对照组不做修复；用电生理及组织病理学观察神经肌肉组织变化，结果术后3个月病理检查发现，实验组中肌皮神经可见少量神经纤维长入，肱二共肌萎缩轻，失神经组之肌皮神经可见神经纤维变性、崩解、吸收，肱二头肌萎缩明显，电生理检查显示实验组与失神经组之诱发电位峰值电压与刺激电流比值及潜伏期时间与刺激电流强度之比值在统计学上有显著性差异（P〈0．05）。结论 该实验模型操作简单，科学，合理。为臂丛神经根性撕脱伤实验研究奠定了基础。     

Delayed riluzole treatment is able to rescue injured rat spinal motoneurons

The effect of delayed 2-amino-6-trifluoromethoxy-benzothiazole (riluzole) treatment on injured motoneurons was studied. The L4 ventral root of adult rats was avulsed and reimplanted into the spinal cord. Immediately after the operation or with a delay of 5, 10, 14 or 16 days animals were treated with riluzole (n=5 in each group) while another four animals remained untreated. Three months after the operation the fluorescent dye Fast Blue was applied to the proximal end of the cut ventral ramus of the L4 spinal nerve to retrogradely label reinnervating neurons. Three days later the spinal cords were processed for counting the retrogradely labeled cells and choline acetyltransferase immunohistochemistry was performed to reveal the cholinergic cells in the spinal cords. In untreated animals there were 20.4+/-1.6 (+/-S.E.M.) retrogradely labeled neurons while in animals treated with riluzole immediately or 5 and 10 days after ventral root avulsion the number of labeled motoneurons ranged between 763+/-36 and 815+/-50 (S.E.M.). Riluzole treatment starting at 14 and 16 days after injury resulted in significantly lower number of reinnervating motoneurons (67+/-4 and 52+/-3 S.E.M., respectively). Thus, riluzole dramatically enhanced the survival and reinnervating capacity of injured motoneurons not only when treatment started immediately after injury but also in cases when riluzole treatment was delayed for up to 10 days. These results suggest that motoneurons destined to die after ventral root avulsion are programmed to survive for some time after injury and riluzole is able to rescue them during this period of time.     

Reactive changes in dorsal roots and dorsal root ganglia after C7 dorsal rhizotomy and ventral root avulsion/replantation in rabbits

Current surgical treatment of spinal root injuries aims at reconnecting ventral roots to the spinal cord while severed dorsal roots are generally left untreated. Reactive changes in dorsal root ganglia (DRGs) and in injured dorsal roots after such complex lesions have not been analysed in detail. We studied dorsal root remnants and lesioned DRGs 6 months after C7 dorsal rhizotomy, ventral root avulsion and immediate ventral root replantation in adult rabbits. Replanted ventral roots were fixed to the spinal cord with fibrin glue only or with glue containing ciliary neurotrophic factor and/or brain-derived neurotrophic factor. Varying degrees of degeneration were observed in the deafferented dorsal spinal cord in all experimental groups. In cases with well-preserved morphology, small myelinated axons extended into central tissue protrusions at the dorsal root entry zone, suggesting sprouting of spinal neuron processes into the central dorsal root remnant. In lesioned DRGs, the density of neurons and myelinated axons was not significantly altered, but a slight decrease in the relative frequency of large neurons and an increase of small myelinated axons was noted (significant for axons). Unexpectedly, differences in the degree of these changes were found between control and neurotrophic factor-treated animals. Central axons of DRG neurons formed dorsal root stumps of considerable length which were attached to fibrous tissue surrounding the replanted ventral root. In cases where gaps were apparent in dorsal root sheaths, a subgroup of dorsal root axons entered this fibrous tissue. Continuity of sensory axons with the spinal cord was never observed. Some axons coursed ventrally in the direction of the spinal nerve. Although the animal model does not fully represent the situation in human plexus injuries, the present findings provide a basis for devising further experimental approaches in the treatment of combined motor/sensory root lesions.     

Synaptic actions of the ventral root afferents on cat hindlimb motoneurons

Postsynaptic potentials (PSPs) with long latencies were evoked in cat hindlimb motoneurons by stimulation of the distal stump of a cut ventral root. Measurements of their latency and the threshold in the responsible afferent fibers showed that they were produced mainly by the activity of the unmyelinated fibers in the ventral root that enter the spinal cord through the dorsal root. Patterns of PSPs evoked in flexor and extensor motoneurons by ventral root stimulation were similar to those observed in the flexion reflex.     

TA9901配伍EGb761对神经根撕脱后脊髓运动神经元的影响

目的　观察植物抗氧化剂TA990 1配伍EGb76 1对臂丛神经根撕脱后C7前角运动神经元c jun、NOS表达和存活的影响。方法　成年SD雌性大鼠 12 0只 ,随机分为撕脱组和治疗组。行C5～T1神经根撕脱术后 ,两组动物每天分别给予腹腔注射 1ml生理盐水或 0 5 % (TA990 1配伍EGb76 1)溶液。治疗后 4h、12h、1d、3d、5d、1周、2周、4周和 6周处死动物 ,行c jun免疫细胞化学、NADPH d组织化学和中性红复染。比较两组动物c jun阳性、NOS阳性和存活的运动神经元的数目。结果　臂丛神经根撒脱 4h后c jun开始表达 ,1d达高峰 ,随后下降至 6周。nNOS表达从 5d开始 ,2周时达高峰 ,以后逐渐下降至 6周。运动神经元的死亡开始于 2周 ,以 4周和 6周最明显。TA990 1配伍EGb76 1提高c jun表达的效果随治疗时间延长而增强、其抑制NOS表达作用则以 2周点最强。结论　TA990 1配伍EGb76 1能增强神经根撕脱后运动神经元c jun的反应 ,抑制NOS的表达 ,提高受损运动神经元的再生能力     

Glatiramer acetate positively influences spinal motoneuron survival and synaptic plasticity after ventral root avulsion

Avulsion of ventral roots induces degeneration of most axotomized motoneurons. At present there are no effective strategies to prevent such neuronal loss and to preserve the affected spinal circuits. Interestingly, changes in the spinal cord network also occur during the course of the experimental model of multiple sclerosis (experimental autoimmune encephalomyelitis—EAE). Glatiramer acetate (GA) significantly reduces the seriousness of the symptoms during the exacerbation of EAE. However, little is known about its effects on motoneurons. In the present study, we investigated whether GA has an influence on synapse plasticity and glial reaction after ventral root avulsion (VRA). Lewis rats were subjected to the avulsion of lumbar ventral roots and treated with GA. The animals were sacrificed after 14 days of treatment and the spinal cords processed for immunohistochemistry. A correlation between the synaptic changes and glial activation was obtained by performing immunolabeling against synaptophysin, GFAP and Iba-1. GA treatment preserved synaptophysin labeling, and significantly reduced the glial reaction in the area surrounding the axotomized motoneurons. After ventral root avulsion, GA treatment was also neuroprotective. The present results indicate that the immunomodulator GA has an influence on the stability of nerve terminals in the spinal cord, which may in turn contribute to future treatment strategies after proximal lesions to spinal motoneurons.     

臂丛损伤脊髓运动神经元与神经根GAP-43 mRNA表达

目的：探讨臂丛根性撕脱伤后脊髓腹角运动神经元胞体及其神经根GAP-43 mRNA的表达变化及其影响因素,为臂丛损伤的修复治疗提供理论依据.方法：本实验创立三种臂丛根性撕脱伤模型：C7前根撕脱（Ⅰ组）;C7前根撕脱＋切断同侧C5～T1后根（Ⅱ组）;C7前根撕脱＋C5和C6之间作同侧脊髓半横断（Ⅲ组）.术后2周按CBS评分标准检查动物神经缺失症状,用SYBR Green荧光定量RT-PCR方法检测脊髓腹角运动神经元胞体及其神经根GAP-43 mRNA的表达改变.结果：根据CBS评分标准,对照组计为0分,Ⅰ组计分较低、Ⅲ组计分最高.对照组C7神经元胞体和C7神经根中GAP-43 mRNA表达量相近,但三种损伤组术后2周神经元胞体内GAP-43 mRNA表达均上调,而神经根内表达却下调.结论：（1）臂丛根性撕脱伤后脊髓腹角运动神经元胞体GAP-43 mRNA表达受突触前机制的调控;（2）臂丛损伤2周时神经元胞体内GAP-43 mRNA表达呈现高峰期,此时进行神经移位术将显著提高神经修复的效果.