脊髓损伤大鼠远端神经元及骨骼肌变化的基础研究

Basic research of the changes in distal neurons and skeletal muscles in rats with spinal cord injury

目的观察脊髓损伤大鼠远端神经元及骨骼肌变化情况。方法 20只大鼠随机分为2组,每组10只,分别为假手术组和脊髓损伤组,假手术组行椎板切除术,脊髓损伤组行胸10完全脊髓损伤,在制成模型后1、2、4、12、24周观察大鼠坐骨神经-运动终板-内侧腓肠肌形态变化情况。结果脊髓损伤组电镜下坐骨神经术后12周有髓神经纤维髓鞘崩解,其板层结构清晰,有髓神经纤维髓鞘于术后24周模糊、碎裂髓鞘变多,12周后无髓神经纤维及薄髓增多;术后12周腓肠肌光镜下局部肌细胞多数模糊,但边界清楚,结缔组织增生明显,肌细胞核相对聚集;肌细胞于术后24周融合,融合细胞间有空隙,细胞核密集,结缔组织增生明显;术后12周电镜下运动终板突触前后及皱褶膜不可分辨,肌纤维明暗带清晰,突触结构紊乱,z线不连续,高倍镜下突触前后膜不可辨,突触皱褶未见,可见类圆形细小颗粒及突触小泡,肌板结构清晰。结论大鼠脊髓损伤后在损伤平面以下周围神经、运动终板、骨骼肌在形态上会发生规律性变化,12周后显著变化,24周后则毁损性改变。

Objective To investigate the changes in distal neurons and skeletal muscles in rats with spinal cord injury （SCI）. Methods 20 rats were randomly selected as the research objects and were divided into sham-operated group in which the rats received laminectomy and SCI group in which the rats suffered from 10th thoracic cord injury, 10 rats in each group. The chan- ges in sciatic nerve, motor end-plate and inside gastrocnemius muscle were observed in the lst,2nd,4th, 12th and 24th week after successful model. Results 12 weeks after sciatic nerve operation in spinal cord injury rats under the electron microscope,the myelin disintegration occurred in myelinated nerve fibers where the lamellar structure was clear, and 24 weeks after successful model the myelinated nerve fibers became indistinct and showed more cataclastic myelin sheaths. In addition, 12 weeks later, the unmyeli- hated nerve fibers and thin myelin sheaths were increased. 12 weeks after operation at the light microscopic level the most partial muscle cells turned into being blurred but the periphery was clear, connective tissues presented obvious hyperplasia and muscular cell nucleus aggregated. Furthermore, the muscle cells merged together and the lacuna appeared between them accompanied by hugely hyperplastic connective tissues and intensive cell nucleus. In the 12th week,it was difficult to distinguish presynaptic membrane and postsynaptic membrane of motor end-plate as well as ruffle membrane observed by electron microscope. Although synaptic structure disorder and z-line discontinuity were found, the parazone and diazone of muscle fiber were clear. Similarly, we couldn＇t make out the presynaptic membrane and postsynaptie membrane by using high-power microscope,found out no synapsis folds and clearly discovered round-like tiny particles and synaptic vesicles, but the muscular plate structure was distinct. Conclusion The peripheral nerves, motor end plates and skeletal muscles can change beneath the injured plane after spinal cord injury in rats,and the significant changes occur in the 12th week and completely damaged changes appear in the 24th week.