缺血皮质原位神经元新生的来源及机制：Wnt2/β-catenin诱导的Sox2+星形胶质细胞去分化

Adult cortex has long been thought as “non-neurogenic”. Recent studies have reported neurogenesis in cortex after ischemia. The post-ischemic new-born neurons were regarded by most researchers as the progenies of adult neural stem cells in the subventricular zone which migrated to the lesion site. Whether in situ neurogenesis could occur is still under controversial. We found a rapid neurognenesis in the adult cortex after focal ischemia. Our data suggest that new neurons are mainly derived from local Nestin-positive cells. However, the authentic identity of the neurogenic cells and underlying mechanisms for this neurogenesis remain unclear. Considering the expression of Sox2 in a sub-population of astoryctes, and the fact that Sox2-positive astrocytes are the major cell type of Nestin-positve cells, we propose here, based on literature and our preliminary study that : Sox2-positive astrocytes may be the major contributor of local neurogenesis after ischemia. Wnt2/β-catenin signaling induced dedifferentiation of Sox2-positive astrocytes may account for the ischemia-induced cortical neurogenesis. In the present project, we will testify this hypothesis by by Split-Cre mediated cell-fate tracing, progenitor ablation and cell culture, and investigate the mechanism of dedifferentiation through coordinate regulation of Mash1, a pro-neuronal transcription factor in Sox2-positive astrocytes. Thereby, we wish to identify the potential neurogenic cells in adult cortex of mice and reveal the mechanism of ischemia-induced neurogenesis, hoping to promote the recovery of ischemic stroke by enhancing cortical neurogenesis through Wnt signaling.

传统认为成年大脑皮质无神经元发生，近年发现缺血后可有新生神经元。主流观点认为新生神经元来自侧脑室下区，皮质原位能否产生神经元一直存有争议。我们发现成年小鼠皮质缺血后有快速的神经元新生，新生神经元主要来自损伤区局部的Nestin+细胞，但具体的细胞来源及发生机制仍不清楚。由于正常皮质部分星形胶质细胞表达Sox2，后者是缺血后皮质Nestin+细胞的主体，结合文献与初步结果，我们推测：Sox2+星形胶质细胞可能是新生神经元的主要来源，Wnt2/β-catenin信号诱导的Sox2+星形胶质细胞去分化可能是神经元发生的主要机制。本项目将采用基于Split-Cre的细胞谱系追踪、前体细胞剔除、细胞培养等方法验证上述推测，并从Sox2+星形胶质细胞中神经元前体细胞关键转录因子Mash1表达调控的角度探讨去分化的分子机制，以期阐明皮质缺血后原位神经元新生的来源与机制，为脑缺血的修复/治疗提供新的思路。

在本项目的支持下，主要开展了以下研究工作：.阐明小鼠脑缺血后皮质局部新生神经元的细胞来源，及皮质过表达Wnt2对神经元新生的促进作用。从DAP5参与的IRES介导的蛋白翻译的角度揭示了凋亡神经元上调Wnt2的机制。在猴、人脑缺血后，观察了Wnt2上调与星形胶质细胞去分化的现象，证明了本课题所发现的现象为物种保守。最后，采用微小脑缺血模型，进一步确认了皮质局部神经元发生。本项目的发现对于理解脑缺血后的组织自发性修复具有重要意义。.另外，还开展了以下研究：（1）慢性痛诱导的背根节神经元发生及Sox2+卫星细胞的作用；（1）脑缺血后神经元程序性坏死及其对巨噬小胶质细胞极化的调节作用；（3）Wnt介导的海马神经元发生在慢性痛诱导焦虑中的作用；（4）Wnt信号激活对于Olig1阳性的少突胶质前体细胞分化的作用。.共发表SCI论文10篇（影响因子5以上4篇），在投1篇（Science Advances）。发表非SCI英文论文1篇，中文核心3篇。获批国家实用新型专利1项，参加学术交流7次，辅导毕业博士研究生4名，硕士研究生2名。.项目预算按计划执行。