一种治疗脑卒中的生物物理方法及其作用机制

Although focal ischemia insult can stimulate proliferation and differentiation of neural stem/progenitor cells (NSPCs) in the subventricular zone (SVZ), and promote NSPC migration to the damaged brain region, only a fraction of the newly generated neurons are found to migrate to damaged brain regions, which is a critical barrier to prevent brain repair. However, little effort has been made towards identifying guidance cues that promote NSPC migration to the damaged brain area. We have recently provided evidence suggesting that the direct-current electrical field (EF) may be one such guidance cue (Li L, et al., Stem Cells.2008). As EF application has been proved potentially safe in human CNS, EF stimulation may be a practical approach to be developed as a biophysical brain repair therapy. Our study has demonstrated that EF stimulation guides and facilitates migration of NSPC-derived new neurons towards the cathode in cultured embryonic explants, and that this migration requires interaction of N-methyl-D-aspartate receptors (NMDARs) with Rho GTPase Rac1/actin cytoskeleton signaling. We also found that activation of NMDARs mediated the directionality of EF-induced NSPC migration. Importantly, using a rat focal ischemic stroke model we showed that a non-invasive EF stimulation promoted migration of SVZ NSPC-derived new neurons towards the cathode direction to the ischemic zone, and that EF stimulation reduced infarct volume of ischemic brain. In this study, we will continue to use the rat ischemic stroke model to test the hypothesis that EF stimulation guides and accelerates the migration of SVZ NSPC-derived new neurons to the damaged brain region and promotes functional recovery through NMDAR-dependent Rac1/actin signal pathway. The results from this study would provide critical evidence for the role of EF-directed NSPC migration in ischemic brain and thus support the ultimate development of EF as a novel biophysical brain repair therapy.

虽然脑卒中可引起室管膜下区(SVZ)神经干/祖细胞(NSPC)增殖和分化显著增强，但仅有小部分SVZ起源的新生神经元迁移至损伤区。甚少研究探讨如何促进新生神经元迁移至受损区并达到脑修复目的。我们的研究表明，直流电场（EF）可能成为这种治疗手段，我们首次证实EF刺激引导并加快离体NSPCs向阴极方向迁移，并需要NMDA受体（NMDAR）/Rho GTPase Rac1/actin信号通路介导。重要的是，在大鼠脑卒中缺血模型中无创性EF刺激促进SVZ起源的新生神经元向置放阴极的缺血区方向迁移，并减少缺血面积。本课题将釆用大鼠脑缺血模型集中探讨EF刺激如何通过NMDAR/Rac1/actin信号通路引导新生神经元向受损区迁移并促进脑功能恢复。与药物治疗策略相比，EF疗法毒副作用小，本研究结果为将EF这一生物物理手段发展成为有效、无创、安全、使用方便的脑卒中仪器治疗方法提供充分的理论和实验依据。

根据缺血性脑损伤后成人脑室管膜下区(SVZ)聚集大量增殖的神经干/祖细胞(NSPC)的变化，我们前期研究了体外直流电刺激对培养NSPC迁移的影响，我们发现直流电刺激引导NSPC向阴极方向迁移。因此，本项目提出在缺血再灌注损伤大鼠中观察双侧经颅直流电刺激(tDCS)对SⅤZ成体神经干细胞迁移的影响，取得了以下进展。我们的实验结果显示，当阴极电极置于缺血侧半球，阳极电极置于对侧半球时，tDCS会促使神经母细胞从SVZ向阴极方向迁移到损伤后的纹状体，而倒置电极的位置会阻碍tDCS的作用。tDCS治疗对脑卒中动物的神经细胞具有保护作用，并且改善脑卒中动物的神经行为学评分。当抑制SVZ神经干细胞的有丝分裂和随后的神经母细胞迁移则会减弱tDCS引起的神经保护作用。因此我们的结果提示，tDCS刺激作用导致NSPC衍生神经母细胞从SVZ迁移到脑卒中后的脑损伤区域，从而发挥神经保护作用。根据我们的研究发现，我们与企业合作研发了一种促神经干细胞脑损伤治疗仪，目前正进行二类仪器EMC检测，很快将进入临床试验阶段。我们的研究为缺血性脑卒中病人提供了一种全新的基于神经干细胞的生物物理治疗方法。