大鼠脊髓损伤后脱髓鞘病变及pEGFR的表达变化

The relationship between demyelinating lesion and expression of pEGFR after spinal cord Injury in rats

目的探讨大鼠脊髓损伤(SCI)后有髓神经纤维数量、超微结构与活化型表皮生长因子受体(pEGFR)及其下游蛋白少突胶质细胞系转录因子-2(Olig-2)的表达变化之间的关系。方法制备大鼠SCI模型,BBB(Basso Beattie&Bresnahan)评分观察大鼠后肢神经功能;勒克索尔固蓝(LFB)染色计数有髓神经纤维的数量;电子显微镜观察有髓神经纤维的超微结构;蛋白印迹(Wb)检测各组pEGFR、Olig-2的表达水平。结果SCI后,大鼠损伤平面以下的神经功能几乎完全丧失,随着时间的延长其神经功能有一定程度的恢复,BBB评分随着时间延长而逐渐升高、有髓神经纤维的数量随着时间的延长亦逐渐增加。电子显微镜显示,SCI后出现如下病理改变:轴突、髓鞘水肿及髓鞘结构紊乱、增厚甚至溃变、崩解;随着时间延长,轴突及髓鞘的肿胀程度较前减轻,髓鞘结构亦逐渐致密。pEGFR、Olig-2的表达随时间延长而逐渐增加并于14d达到高峰。腹腔注射选择性pEGFR抑制剂(PD153035)14d后,pEGFR、Olig-2的表达,大鼠BBB评分及有髓神经纤维数量均较模型14d组明显降低;抑制剂组的轴索肿胀程度明显加重,轴浆线粒体数量减少,髓鞘分层而呈重度脱髓鞘改变。结论pEGFR的表达与大鼠SCI后神经纤维的再髓鞘化有关,其机制可能在于pEGFR参与了Olig-2的上调。

Objective Investigating the relationship between the neural functions,the amout of myelinated nerve fibers,the ultrastructural changes of myelin sheath and the expression level of phosphorylated epidermal growth factor receptor(pEGFR),Olig-2 after spinal cord injury(SCI)in rats.Methods The SCI model was established.The neural functions were monitored by the Basso,Beattie Bresnahan(BBB)locomotor rating scale,and the number of myelinated nerve fibers was detected by Luxol fast blue(LFB)staining.The ultrastructural changes of myelinated nerve fibers were observed by electron microscope,and the expressions of pEGFR,Olig-2 were detected by western blotting(Wb).Results The neural functions was completely lost but recovered to some extent with the extension of time after SCI.The BBB scores and the number of myelinated nerve fibers increased gradually with time after SCI.Electron microscopy showed that the axons of spinal cord were swollen in varying degrees;the myelin sheath was edema,disordered,thickened and finally was degenerated,disintegrated;the swelling degree of myelin decreased and the structure of myelin sheath became denser gradually with time extension after SCI.The expression of pEGFR,Olig-2 increased gradually with time and reached a peak at 14 days after SCI.Compared with the day 14 group,significantly decreases in expression of pEGFR,Olig-2,BBB scores and number of myelinated nerve fibers were observed in rats which were injected intraperitoneally selective pEGFR inhibitor(PD153035)for 14 days.In the inhibitor group,the swelling degree of axons was obviously aggravated,the distance between axons was reduced,the mitochondria in axoplasm was decreased,the myelin sheath was stratified,and the myelin sheath was heavily demyelinated.Conclusion The expression of pEGFR is related to the remyelination of nerve fibers and the mechanism may be that pEGFR is up-regulates the expression of Olig-2 after SCI in rats.