小鼠神经缺损管式修复后长时程功能恢复与再生评价

目的了解壳聚糖/聚乳酸-乙醇酸共聚体(PLGA)人工神经移植物修复小鼠神经缺损后神经功能长时程恢复水平与再生神经成熟度。方法采用人工神经移植物桥接修复小鼠坐骨神经缺损(n=6),以自体神经修复(n=6)和缺损组(n=6)为对照,术后1年采用热痛阈测定、电生理学、激光多普勒血流检测评定神经功能,采用靶肌湿重比、组织学和电子显微镜等技术综合评定神经重支配和再生神经成熟度。结果人工神经移植物组足底痛觉反应潜伏期、神经源性血管扩张程度、腓肠肌复合肌动作电位(CMAPs)波幅和潜伏期、靶肌湿重比、再生轴突数量等指标与自体神经修复组相近,但与健侧相比CMAPs潜伏期较长,髓鞘较薄,轴突直径分布滞后。结论人工神经移植物修复小鼠神经缺损术后1年感觉及自主神经功能、再生神经数量和靶肌重支配水平与自体神经修复相当,但再生神经纤维成熟度未达正常。

Long-term evaluation of functional recovery and nerve regeneration following tubulation repair of nerve defects in mice

Objective This study is to identify long-term functional recovery and maturity of regenerated nerve fibers after repairing mouse nerve defects with chitosan/polylactide-co-polyglycolide artificial nerve grafts (CPANGs). Methods Mouse sciatic nerve defects, 2mm in length, were bridged by CPANGs (n=6), with nerve autograft (n=6) and nerve defect (n=6) as controls. Plantar test, electrophysiological examination and laser Doppler perfusion imaging following nerve crush were carried out at 1 year after repair to assess nerve function recovery, while muscle wet weight ratio, histological assessment and transmission electron microscopy were performed to evaluate nerve re-innervation and maturity of regenerated nerve fibers. Results When compared to the autograft group, the CPANG group did not show statistically significant difference in functional recovery in terms of paw withdrawal latency, neurogenic vasodilatation, amplitude and latency of compound muscle action potentials (CMAPs), wet weight ratio of gastrocnemius and tibialis cranialis muscles, number of myelinated nerve fibers and density of unmyelinated axons. However, both these two repair groups exhibited significantly longer CMAPs latency, thinner myelin sheath and a lag behind shift of diameter distribution of myelinated axons as compared to the normal control. Conclusion At 1 year after the mouse sciatic nerve defect was repaired by CPANGs, sensory and autonomic nerve function, number of regenerated axons and muscle re-nnervation degree were recovered to the same extent as nerve autografting, but the regenerated nerve fibers were in a state of immaturity.