犬脊髓挫伤后胶质瘢痕形成模型的建立

Establishment of glial scar models in dogs following spinal cord contusion

目的:利用犬脊髓挫伤模型,结合磁共振成像、体感诱发电位、运动诱发电位分析犬脊髓损伤后胶质瘢痕的形成。方法:实验于2002-05/2003-04在解放军第三军医大学新桥医院实验动物中心完成。选取成年健康杂种犬12只,随机分为正常对照组3只,脊髓损伤组9只。脊髓损伤组动物,俯卧固定,定位棘突后以T8为中心作行椎板切除,骨窗10mm×15mm,暴露脊髓背侧硬膜,参考Allen’s法自行设计打击装置。用冲击棒至脊髓损伤,致伤能量为450g·cm,形成重度脊髓损伤模型。正常对照组除不致伤外,其余操作同脊髓损伤组。脊髓损伤组分别于伤后1d,2周,8周各取材3只。术后进行犬后肢功能观察评价,测定犬双后肢体感诱发电位和运动诱发电位的变化,观察脊髓结构的影像学及组织学变化。结果:①犬脊髓损伤后运动功能的变化:脊髓损伤组动物在损伤后1d,2周,8周观察的时间范围内,后肢和尾巴均未见活动。②犬脊髓损伤前后的电生理变化:脊髓损伤组动物在损伤前体感诱发电位和运动诱发电位均正常,但伤后增加刺激强度均不能记录到体感诱发电位和运动诱发电位。③各组脊髓结构的影像学比较:脊髓损伤组动物伤后损伤部位表现为T1加权成像呈局部低信号,T2加权成像呈高信号,信号纵向为(10.0±0.13)mm,大约是砸伤长度的2倍,为椭圆形空洞形成,局部脊髓萎缩变细,蛛网膜下腔粘连、连续性中断。④犬脊髓损伤后脊髓组织学变化:伤后1d脊髓弥漫出血、渗出,脊髓中央管变形,神经元内氏体减少。伤后2周仍有出血、水肿,脊髓白质空泡样改变,脊髓中央灰质坏死、空洞形成。伤后8周空洞壁为大量胶质细胞形成的胶质瘢痕,并见炎细胞浸润。结论:450g·cm致伤能量可导致犬脊髓严重损伤,从而形成典型的空洞及胶质瘢痕,提示该模型有利于慢性时期损伤修复的分析。

AIM： To investigate the formation of glial sear after spinal cord injury in dogs by using spinal cord contusion model with nuclear magnetic resonance, somatosensery evoked potential and motor induced potential. METHODS： The study was conducted in the Center of Experimential Animal, Xinqiao Hospital, Third Military Medical University of Chinese PLA from May 2002 to April 2003. Twelve mongrel adult dogs were selected and randomly divided into： normal control group with 3 dogs and spinal cord injury group with 9 dogs. Laminectomies were performed in animals of spinal injured group, the dogs were fixed at prostration and taking T8 as center after localing spinous process, with bone window of 10 mm×15 mm to provide dural expoure. Coup equiqment was designed by oneself with Allen＇s method. Severe spinal cord contusion was produced with impacting stick with the injured enegy of 450 g·cm to make severe spinal injured models. The dogs in the normal control group were treated as the same with the spinal injured group except injury. Three dogs were obtained from spinal injured group at the 1^st day, the 2^nd week and 8^th week, respectively. Observational evaluation of hindlimb function of dogs was performed after operation. Changes of somatosensory evoked potential and motor induced potential of double hindlimb were detected. Changes of imaging and histology in spinal structure were observed. RESULTS： ①Change of motor function after spinal injury of dogs： There was no activity of hindlimb and tail at 1 day, 2 and 8 weeks after injury in the spinal injury group. ②Electrophysiological change before and after spinal injury of dogs＂ The somatosensory evoked potential and motor induced potential were normal before injury in the spinal injury group, but the somatosensery evoked potential and motor induced potential could not be recorded after the increase of stimulus intensity. ③Comparison of imaging of spinal structure of each group： The T1 weighted imaging at injured part showed low signal after injury in the spinal injury group, and T2 weight imaging showed high signal with the longitudinal signal of （10.0 ±0.13 ） mm, about 2 times of the length of crashing injury, which was oval-shape cavitation, and part of spine shrinked and became thin. Subaraehnoid space was adherent and the concatenation was interrupted. ④ Change of spinal histology after spinal injury of dogs： At the 1^st day after injury, the spinal cord filled with blood, bleeding, deformation of spinal cord central canal and the number of neuronal Nissl body decreased. Two weeks after injury there was still blood, edema, vacuole-change of spinal cord white matter, and the gray of eental spine was died and formed cavitation. Cavity, glial sear formed by a large number of glial cells and infiltration of imflammatory cell at the 8^th week after injury. CONCLUSION： The force of 450 g·cm leads significant spinal cord injury in dogs, so typical cavity and glial sear are formed, which suggests that the models are beneficial for repair of spinal injury in chronic period.