脑缺血区pH值下降抑制室管膜下区干细胞向损伤区聚集的分子机制研究

Brain ischemic stroke activates subventricular zone neural stem cell to proliferate and aggregation to injury area. However, most of the proliferating stem cells retain in the vicinity of sbuventricular zone. Therefore, it is attractive to study the mechanism modulating the directional migratinon of neural stem cell after brain ischemic stroke. Lower pH value occurs in the ischemic zone.We found that stem cells located in the subventricular zone expresses ASIC1a channels,and that pH lowering stimulates intracellular Ca2+ elevation via ASIC1a homomeric channels thereafter inhibits migration of stem cells. These fingdings suggest that niche pH value induced by ischemic stroke plays an important role in the migration of neural stem cell via activating ASIC1a channels. Based on cultured eNSC,brain slice and ischemic stroke animal model, we investigate the role and mechanisms of lower pH in the directional migration of neural stem cell through morphological methods, patch clamp, RNA interference, knock-out mice and transgenic mice. We will focus on the signalling pathway in which ischemia-induced pH lowering activates Rho GTPase via ASIC1a channels to reorganize cytoskeleton protein actin to modulate the migration of stem cell. This study will not only help to elucidate the mechanisms controlling the directional migration of stem cell, but also provide evidence for the development of therapeutic strategy targeting it after ischemic stroke.

脑缺血后室管膜下区神经干细胞可活化增殖并向损伤区迁移聚集，但增殖的干细胞大量滞留在生发区周围附近，故神经干细胞向损伤区迁移聚集的调控机制是该领域研究热点。脑缺血后损伤区及其周围pH值下降明显，我们前期发现：室管膜下区神经干细胞表达酸敏感离子通道1a（ASIC1a），pH下降激活ASIC1a通道促发干细胞内钙升高，明显抑制干细胞迁移。提示：缺血区及其周围pH下降可激活干细胞上ASIC1a通道调控神经干细胞的迁移。本项目拟通过形态学、膜片钳、RNAi、基因敲除与转基因小鼠等方法从细胞、脑片、动物模型等层次，系统研究pH下降在神经干细胞迁移调控中的作用，阐明"pH下降通过ASIC1a通道活化Rho GTPase引起骨架肌动蛋白actin重排进而调控神经干细胞迁移"这一信号机制。通过本项目的研究，不仅有助于深入阐明干细胞定向迁移的调控机制,而且为设计以其为干预靶点的治疗新措施奠定基础。

脑缺血后室管膜下区神经干细胞可活化增殖并向损伤区迁移聚集，但增殖的干细胞大量滞留在生发区周围附近，故神经干细胞向损伤区迁移聚集的调控机制是该领域研究热点。本研究主要从pH下降对神经干细胞迁移的影响和内在机制2方面着手进行研究，发现：室管膜下区神经干细胞表达酸敏感离子通道1a（ASIC1a）和2a（ASIC2a），酸化可激活ASIC1a通道的开放，明显抑制干细胞迁移，给予ASICs抑制剂Amiloride\PcTx1可以有效抑制酸化对干细胞的迁移抑制效应，使用分子生物学技术和基因konck out技术发现抑制ASIC1a的表达可以明显挽回酸化对干细胞的迁移抑制效应。这些研究结果提示干细胞表达功能性ASIC1a通道，ASIC1a介导了酸化抑制干细胞的迁移的分子机制，以ASIC1a为靶点设计干预措施有望成为缺血性脑卒中的新治疗措施。