EphA4-RhoA/ROCK通路调控脑梗死后神经前体细胞增殖和迁移的作用及机制研究

Endogenous neurogenesis activated by ischemia is of great importance for repairing damaged tissue and restoring neurological function. Abnormal microenvironment induced by ischemia, which impede proliferation, survival and migration of neural progenitor cells, resulting in reduced efficiency of neurogenesis. Receptor tyrosine kinase EphA4 negatively regulate neurogenesis and cell migration during the embryonic stage. EphA4 receptor affect proliferation signaling pathway and cell skeleton through downstream RhoA/ROCK. EphA4 upregulate significantly after ischemia. Our previous study revealed that EphA4 blockage improved microenvironment through alleviating excitatory toxicity and inflammatory injury as well as promoting neurotrophic factor secretion during early stage after ischemia. Furthermore, our preliminary data found that EphA4 blockage increased numbers of newborn neural progenitor cells as well as mature neurons in infarcted border zone in the later stage ischemia, which was accompanied by down-regulated RhoA/ROCK expression. We assumed that EphA4 blockage could improve post-ischemia microenvironment and meantime promote neural progenitor cell proliferation and migration via RhoA/ROCK signaling. To verify the hypothesis, this project will aim to clarify the effect of EphA4-RhoA/ROCK signaling on neurovascular unit after ischemia and to elucidate the regulatory mechanism of EphA4-RhoA/ROCK signaling on neural progenitor cell proliferation and migration from animal，tissue， cellular and molecular levels. It would be valuable for developing a novel target for post-ischemia damage restoration.

脑梗死可激活内源性神经再生，修复损伤组织，促进神经功能恢复。但脑梗死后微环境紊乱限制了神经前体细胞增殖、存活和迁移，降低神经再生的效率。受体酪氨酸蛋白激酶EphA4是胚胎期神经发生和细胞迁移的负向调控因子，通过RhoA/ROCK调控增殖通路和细胞骨架，在脑缺血后明显上调。我们前期证实，阻断EphA4通过减轻缺血早期的谷氨酸兴奋性毒性和炎症反应、增加神经营养因子，改善局部微环境；还初步发现，EphA4阻断后，缺血后期新生神经前体细胞和缺血周边区成熟神经元的数目增加,RhoA/ROCK表达下调。我们假设，阻断EphA4可改善脑缺血后的微环境，并通过RhoA/ROCK促进神经前体细胞增殖和迁移。为验证该假设，本项目将从动物、组织、细胞及分子水平，明确EphA4-RhoA/ROCK通路对脑缺血后神经血管单元的作用，揭示其调控脑缺血后神经前体细胞增殖和迁移的机制，为促进脑梗死后的神经修复提供新靶点。

缺血性卒中后的神经修复有赖于神经血管单元的整体重塑。Eph-ephrin信号系统传导双向信号，同时作用于多细胞靶点，为整体调控神经血管单元提供新方向。EphA4是脑内表达最广泛的Eph受体，主要分布于神经元，阻断该受体能减轻缺血性脑损伤。申请人前期研究发现，EphA4在缺血后表达上调，参与缺血性脑损伤，机制不明。本项目分别通过药物和基因手段调控神经元EphA4受体，并检测缺血性脑损伤、运动和认知功能损伤、炎症、神经再生、NF-κb及Rho/ROCK通路等指标，发现阻断神经元EphA4受体后，调控RhoA/ROCK和NF-κb信号通路，促进小胶质细胞向抗炎型极化，神经营养因子分泌增加，炎性介质分泌减少，进而发挥神经保护和促进神经再生修复的作用，该研究阐明了神经元EphA4受体调控缺血性脑损伤的作用和可能机制，为缺血性卒中治疗提供新思路和新靶点。