纤溶酶原激活剂及其相关分子在小鼠视神经损伤再生中的变化

目的:检测细胞外基质(ECM)中各蛋白酶在视神经损伤后的变化,分析ECM蛋白酶活性的变化与小鼠视神经损伤和损伤后再生之间的关系。方法:本实验采用建立小鼠视神经钳夹伤的动物模型,用WesternBlot方法检测小鼠视神经损伤后不同时间点神经丝(NF)、金属基质蛋白酶-9(MMP-9)、IgG的表达变化。同时采用原位酶谱分析法检测纤溶酶原激活剂(PA)活性在视神经损伤后各阶段的变化,并分析这种变化与纤维蛋白(原)沉积、髓鞘碎片清除等影响神经再生的因素之间的关系。结果:小鼠视神经损伤后发生进行性Wallerian变性,血-神经屏障(BNB)修复迟缓,沉积的纤维蛋白(原)于损伤后第2d清除。MMP-9在损伤后2d达到高峰,以后仍呈现高水平的表达,且均以前体形式出现。PA活性在损伤后第7d达到高峰,并持续至第28d。结论:视神经损伤后,损伤部位BNB重建、PA激活、纤维蛋白(原)的清除以及MMP-9的表达与周围神经截然不同,正是由于微环境的迥然差异,导致了中枢神经系统(CNS)髓鞘碎片清除不利、轴突再生障碍。

The changes of plasminogen activator and other molecules in regeneration and recovery after optic nerve injury

Objective:To study the changes of ECM proteinases after optic nerve injury as well as to find the relationship between the changes of proteinase activities and nerve injury and nerve regeneration.Methods:An optic nerve crush injury model is built on adult C57BL/6J male mice.The expressions of NF,MMP-9 and IgG at different time point after optic nerve crush injury were detected by Western Blot.PA(plasminogen activator)enzymatic activity at each stage after optic nerve injury was analyzed by in situ zymography.The relationship between PA activities and the deposition of fibrin and the clearance of fibrin and myelin debris were deduced.Results:The axon progressive Wallerian degeneration was detected after optic nerve crush injury,BNB repairment was so poor and slow,while the deposited fibrin were cleared at the 2nd day after optic nerve crush injury.MMP-9 expression was significantly elevated up to the peak at the 2nd day after optic nerve crush injury and lasted up to the 28th day on a considerable level.MMP-9 was only detected in its inactive pro-form(92 kDa)in degenerating optic nerves.PA enzymatic activity was significantly increased at the 7th day after crush and lasted up to the 28th day on a considerable level.Conclusion:These results showed that BNB recovery at the site of injury,activation of PA,fibrin(ogen)deposition and clearance,expression of MMP-9 in the central nervous system(CNS)following injury may be completely different comparing to that in the peripharal nervous system(PNS)following injury.Differences of the microenvironment between the PNS and CNS lead to a failure to clear CNS myelin debris and a poor axonal degeneration in the CNS.