神经细胞黏附分子在小鼠脊髓损伤中的表达

摘要

目的:探讨神经细胞黏附分子(NCAM120、NCAM 140和NCAM 180)在小鼠脊髓撞击伤后的表达.方法:采用改良NYU(纽约大学)Weight-Drop Impactor打击装置制备脊髓损伤(SCI)模型(打击面积为2mm×2 mm).SA小鼠随机分为实验组和假手术组.实验组按7个时间点分别进行实验,免疫组织化学和免疫印迹检测各时间段脊髓组织NCAMs,进行图像分析及统计学处理.结果:免疫组织化学显示,NCAMs主要分布在脊髓后角灰质的Ⅰ板层及其交界浅层Ⅱ板层.各节段背根节(DRG)内大部分神经细胞膜及脊神经后根可见NCAMs的强阳性表达,而脊神经前根的表达为阴性.免疫印迹显示损伤节段3种NCAMs的表达高峰出现在损伤后4h,表达量接近正常的2倍,之后急剧下降；邻近损伤区的头尾脊髓节段NCAMs的表达高峰分别出现在损伤后16h和14 d.结论:损伤区脊髓组织中NCAMs的表达下调可能与脊髓损伤后投射至脊髓后角Ⅰ/Ⅱ板层内的DRG轴突Waller's变性和再生困难密切相关.脊髓损伤后,NCAMs各亚型于脊髓损伤区及邻近损伤区头尾脊髓节段有明显的动态变化过程,提示NCAMs可能与脊髓可塑性密切相关.%Objective:To investigate expression levels of three neural cell adhesion molecules (NCAM120, NCAM140 and NCAM180) in spinal cord injury (SCI) of mice. Methods: SCI mice were obtained by improved NYU (New York University) Weight-Drop Impactor using 25 gcf (10 g weight free fall from height 25 mm) against 2 mm×2 mm area. The SA mice were randomly divided into two groups: SCI mice in each of 7 moments were prepared as an experimental group. The mice in the sham group were executed laminectomy, and the incisions were sewed up subsequently. NCAMs of the spinal cord in each moment were detected via immunohistochemistry and Western blotting. Images were photographed and statistical analysis was carried out. Results: Immunohistochemical data showed that NCAMs mainly existed in lamina I of the spinal dorsal horn gray matter and lamina Ⅱ in their junctions. NCAMs were strongly expressed in most of the nerve cell membranes of the dorsal root ganglion (DRG) and the spinal nerve posterior root, while they were negative in the spinal ventral root. Western blotting data showed that the expression peak of three NCAMs was found in 4 h after SCI, which was two times that of the sham group, and was decreased greatly thereafter in injury sites. The expression peaks of NCAMs were observed in 16 h and 14 d respectively in adjacent sites. Conclusion: The down-regulation of NCAMs in spinal cord injury areas is most closely related to Waller's degeneration and troubles in regeneration of DRG axons in lamina Ⅰ/Ⅱafter SCI. There are significant dynamic changes of three NCAMs expressions after SCI and its adjacent sites, suggesting that they are related to plasticity of the spinal cord.u0000o W