不同部位骨骼肌失神经支配后超微结构变化的实验研究

ULTRASTRUCTURAL CHANGES AFTER DENERVATION OF DIFFERENT MUSCLES

目的 探讨长期失神经支配后萎缩骨骼肌神经修复手术疗效欠佳的机制。方法 12例臂丛神经损伤后 1、2、3、6、12和 18个月患者 ,术中切取小指展肌和肱二头肌的失神经骨骼肌 ,以相同部位的正常骨骼肌作对照 ,观察失神经骨骼肌超微结构和计数肌卫星细胞数量变化。结果 失神经支配后 2个月 ,骨骼肌细胞的超微结构基本正常 ,肌纤维周围无明显增生的胶原纤维 ,可见到运动终板 ,肌卫星细胞数量增多 ;6个月 ,肌丝断裂 ,排列紊乱现象明显增多 ,细胞核体积变小 ,染色加深 ,细胞核固缩 ,肌纤维周边出现较多的成纤维细胞和脂肪细胞以及增生的胶原纤维 ;12个月后 ,未见类似运动终板的结构 ,肌卫星细胞体积缩小 ,数量减少。小指展肌较肱二头肌中肌卫星细胞含量下降速度快。结论 失神经支配晚期骨骼肌纤维中运动终板消失和胶原增生以及肌卫星细胞含量的迅速下降可能是影响疗效的主要因素之一。

Objective To observe the ultrastructural changes and number of satellite cells in different muscles with different denervation interval and investigate the mechanism of denervation atrophy. Methods Muscles of different denervation interval were harvested, which were 6 biceps brachii and 6 abductor digiti minimi. The ultrastructure of the samples were observed under transmission electron microscope. The number of nucleus and satellite cells were counted to calculate the percentage content of satellite cells. Results In early stage of denervation, the myofilament and sarcomere of the majority were well oriented. The nucleoli of some muscle cell nucleus were enlarged and pale. Vacuolarization was also seen in some mitochondria. There was no obvious proliferation of collagen fiber around myofibers. After denervation of half a year, rupture and disorientation of myofilament was seen. The nucleus became smaller, dark stained, and some of them were condensed. There was proliferation of fibroblasts, adipose cells and collagen fibers around myofibers. Motor endplate was not recognized one year after denervation. In the early stage of denervation, satellite cell percentage of the two muscles was relatively high. It then declined with time. One year after denervation, satellite cells were scarcely detected. Comparison of the curves for satellite cell declination in two muscles revealed that the declination of the abductor digiti minimi was faster than that of biceps brachii. Decrease of the former started 3 months after denervation, while the latter started after 6 months. Conclusion Disappearing of motor endplate and proliferation of collagen fibers are main factors that affect the treatment outcome in late cases. Decrease of satellite cell number is another cause. The correlation of less satellite cell in abductor digiti minimi and poorer recovery of hand intrinsic muscles indicates that increment of satellite cells in long term denervated muscles may be one of the effective measures to improve treatment outcome.