骨髓间充质干细胞在节段性神经损伤局部微环境中的迁移和转归

Migration and homing of bone marrow mesenchymal stem cells in segmental nerve injury

背景:面对周围神经损伤修复这一难题,大量研究已证实组织工程干细胞修复方法的可行性,但干细胞的修复作用机制尚不明确。目的:探索骨髓间充质干细胞在损伤神经局部的迁移过程及对损伤神经的修复效果,并着重观察骨髓间充质干细胞在神经局部微环境中的分化及转归。方法:选取8周龄雄性SD大鼠,使用液氮冰冻坐骨神经,制造节段性神经损伤模型。将36只成功造模的大鼠随机分成3组(n=12),每组按添加细胞的方式不同具体分组如下:单纯冰冻损伤神经组,损伤神经内部注射细胞组,损伤神经周围添加细胞组。造模前及植入细胞后4,8,12周测量坐骨神经功能指数;植入细胞后12周,分别对小腿三头肌进行电生理学、湿重恢复率、收缩力恢复率检测以及Masson染色,损伤段神经组织进行免疫荧光染色,损伤远端神经进行甲苯胺蓝染色。结果与结论:植入细胞后4,8,12周各组坐骨神经功能指数差异无显著性意义,但损伤神经内部注射细胞组和损伤神经周围添加细胞组均高于单纯损伤神经组,并且损伤神经内部注射细胞组略高于损伤神经周围添加细胞组;各组电生理检测结果显示,2个细胞治疗组复合肌肉动作电位的潜伏期和波幅差异无显著性意义,两组的潜伏期均值较单纯损伤神经组缩短、波幅均值较单纯损伤神经组显著升高(P<0.05);2个细胞治疗组肌纤维横截面积均高于单纯损伤神经组;免疫荧光染色结果显示,在植入细胞12周后,2个细胞治疗组均能观察到Nestin、S100、P0蛋白的表达。结果表明在节段性损伤的神经周围添加骨髓间充质干细胞不仅可以迁移到损伤神经内部参与神经修复,而且能够向许旺细胞和神经干细胞方向分化,达到与直接向神经内部注射干细胞类似的修复效果。

BACKGROUND：A large number of studies have confirmed that tissue-engineered stem cel therapy is feasible to repair peripheral nerve injury, but the repair mechanism is unclear. OBJECTIVE：To observe the differentiation and homing of bone marrow mesechnymal stem cel s under local nerve microenvironment by exploring the migration and effect of bone marrow mesenchymal stem cel s in the repair of damaged nerve. METHODS：Male SD rats, aged 8 weeks, were selected to establish segmental nerve injury models by freezing the sciatic nerve. Thirty-six model rats were randomized into three groups （n=12）：frozen nerve injury group, cel injection into the nerve group, cel injection around the nerve group. Before modeling and at 4, 8, 12 weeks after cel implantation, the sciatic nerve function index was measured. Electrophysiological test, contractility recoveryrate, wet weight recovery rate of the triceps surae were detected and Masson staining was performed;toluidine blue staining of the distal nerve injury and immunofluorescence staining of the damaged nerve were performed. RESULTS AND CONCLUSION：At 4, 8, 12 weeks after cel implantation, the sciatic nerve function index was ranked as fol ows：frozen nerve injury group〈cel injection around the nerve group〈cel injection into the nerve group, but no significant difference was found among the three groups. Electrophysiological results showed that there was no difference in the latency and amplitude of compound muscle action potential between two cel therapy groups, but compared with the frozen nerve injury group, the latency was shorter and the amplitude was higher in the two cel therapy groups （P〈0.05）. Cross-sectional area of the muscle fibers was lower in the frozen nerve injury group compared with the other two groups. Immunofluorescence staining showed that Nestin, S100 and P0 proteins were al expressed in the two cel therapy groups 12 weeks after cel implantation. These findings indicate that bone marrow mesenchymal stem cel s added into the surrounding tissues of segmental damaged nerve can migrate into the damaged nerve, and even differentiate into Schwann cel s and neural stem cel s, which has a similar effect to the cel injection into the damaged cel s.