原位末端标记检测重症肌无力大鼠中枢损害时脑改变

Brain change in experimental myasthenic model of central nervous system dysfunction by TUNEL method

目的 :探讨重症肌无力 (MG)中枢 (CNS)受损的可能机制 .方法 :将MG患者血中提取的AChRab经侧脑室注射到大鼠脑室系统 ,建立CNS受损的MG大鼠模型 .用原位末端标记 (TUNEL)的方法观察脑细胞凋亡具体情况及不同病程变化 ,并和用健康人血清提取的IgG注入大鼠侧脑室建立的对照组进行比较 .另一组不予任何处理作为空白对照 .结果 :模型大鼠表现出类似实验性自身免疫性重症肌无力(EAMG)动物模型样症状 .TUNEL结果示 :实验组大鼠脑组织切片标记后棕蓝混合染色的阳性细胞 (因行苏木素复染 )于注射后 2wk出现且随时间逐渐增多 ,至 3wk后数目最多 .脑内多部位都有凋亡细胞出现 ,以皮层和海马区较明显 .与对照组比较差别明显 .结论 :经侧脑室注入到大鼠脑室系统的MG患者AChRab可以引起大鼠CNS功能障碍 ,神经细胞发生凋亡 ,凋亡细胞数目随大鼠症状的加重而增加 ,提示细胞凋亡在MG。

AIM: To investigate the possible mechanism of central nervous system (CNS) dysfunction in myasthenia gravis (MG). METHODS: CNS dysfunction myasthenic model was established by injection of acetylcholine receptor antibody (AChRab) purified from MG patients sera into rats cerebral ventricular system. Brain tissues were removd at the end of 1 wk, 2 wk, 3 wk after injury. The number and position of apoptosis were observed by TdT mediated dVTP Nick end Labeling (TUNEL). These results were compared with normal controls which were injected with normal human IgG and with blank controls without receiving any treatment. RESULTS: Experimental rats presented the symptoms and signs which imitated experimental autoimmune myasthenia gravis (EAMG). TUNEL results showed that apoptosis occured in neurons in experimental models. In MG CNS dysfunction model rats brain tissue sections, the blue and brown dyeing positive neurons (after further hematein dyeing) appeared at the end of 2nd wk and the number increased with the development of disease symptoms, reaching its peak at the end of 3rd wk. Apoptotic cells appeared in many sites in brain, especially evident in cortex and hippocampus. Significant difference was found between MG group and the control groups ( P <0.01). CONCLUSION: Intraventricular administration of AChRab from human MG sera can cause CNS dysfunction in rats and establish the MG model with CNS dysfunction. Apoptosis may occur in nerve cells. The increase of apoptotic cell number was accompanied by the aggravation of muscle weakness. These suggest apoptosis may play an important role in MG CNS dysfunction.