Endothelial Regulation of Astrocyte Trans-differentiation in Stroke

神经发生在卒中康复中起着重要作用。在脑缺血模型中，神经发生是 在脑室下区(SVZ)和颗粒下区(SGZ)放大。除了这些回应外， 标准的神经源性生态位，一些报告表明实质星形胶质细胞可能转化为神经元 中风后。在SVZ和SGZ的神经源性生态位中，脑内皮细胞通过分泌 支持神经干细胞的营养因子。有没有可能脑内皮细胞也有助于调节 星形胶质细胞转分化？在这个方案中，我们将研究这一想法，即脑内皮细胞充当 一种意想不到的信号来源，可以将星形胶质细胞转化为神经元，从而改善中风后的预后。 我们的初步数据表明：(I)缺氧-葡萄糖剥夺(OGD)刺激的脑内皮细胞将 星形胶质细胞体外分化为神经前体细胞(NPC)--(II)低氧诱导的微泡移植 脑内皮细胞培养在体外将星形胶质细胞重新编程为鼻咽癌，(Iii)OGD来源的微泡- 刺激的脑内皮细胞也可在体内将星形胶质细胞转化为NPC，并促进小鼠的恢复 局灶性脑缺血，(Iv)脑内皮细胞内神经原转录因子Ascl1可能参与 星形胶质细胞转分化，(V)分析这些机制的方法(小鼠遗传学，脑内皮细胞 细胞特异性病毒感染、谱系追踪、单核RNA序列、成像等)在我们的实验室是可行的。 根据我们的实验数据，我们假设脑内皮细胞中Ascl1的上调源于 微泡诱导星形胶质细胞的转分化，从而促进神经发生、组织修复和 中风后的康复。 我们有三个具体目标。在目标1中，我们将比较主要神经血管单位细胞对星形胶质细胞反式-星形胶质细胞生长的影响。 差异化。在目标2中，我们将剖析脑内皮细胞介导的星形胶质细胞转导的机制。 分化，并使用功能增减实验来操纵大脑中Ascl1的表达 并追踪星形胶质细胞在局灶性脑缺血后的转分化。在目标3中，我们将调查 Ascl1过表达的脑内皮细胞来源的微囊对星形胶质细胞反式作用的影响 分化，并评估神经发生、组织修复和感觉运动/认知结果 局灶性脑缺血后雄性或雌性小鼠。我们的实验将利用小鼠的遗传和分子工具 包括AAV诱导的脑内皮细胞特异性基因表达(Tie2-Cre或CDH5-Cre)的组合 小鼠)，用他莫昔芬诱导的ALDH1L1-CreERT2进行星形胶质细胞的谱系追踪；R26R-YFP小鼠，scRNA- SEQ或SnRNA-SEQ以完整地定位卒中后接受微泡治疗的小鼠的星形胶质细胞的转录。 翻译相关性将通过体内光学成像和卒中后的长期结果进行评估。这 项目应定义卒中血管内皮细胞信号的新形式，确定独特的血管调节 神经可塑性的机制，并有望为大脑修复带来新的治疗机会。

Neurogenesis plays an important role in stroke recovery. In models of cerebral ischemia, neurogenesis is amplified in the sub-ventricular zone (SVZ) and the sub-granular zone (SGZ). In addition to these responses in the standard neurogenic niches, some reports suggest that parenchymal astrocytes may convert into neurons after stroke. Within neurogenic niches in SVZ and SGZ, brain endothelial cells play a vital role by secreting trophic factors to support neural stem cells. Is it possible that brain endothelium may also help regulate astrocyte trans-differentiation? In this proposal, we will investigate this idea, i.e. brain endothelial cells act as an unexpected source of signals to convert astrocytes into neurons, thus improving outcomes after stroke. Our pilot data suggest that (i) oxygen-glucose deprivation (OGD)-stimulated brain endothelial cells convert astrocytes into neural progenitor cells (NPC) in vitro, (ii) transfer of microvesicles derived from OGD-stimulated brain endothelial cultures reprogram astrocytes into NPC in vitro, (iii) microvesicles derived from OGD- stimulated brain endothelial cells also convert astrocytes into NPC in vivo, and promote recovery in mouse focal cerebral ischemia, (iv) pro-neural transcription factor Ascl1 in brain endothelial cells may be involved in astrocyte trans-differentiation, (v) methods to dissect these mechanisms (mouse genetics, brain endothelial cell-specific viral infection, lineage tracing, single-nuclei RNA-seq, imaging etc) are feasible in our labs. Based on our pilot data, we hypothesize that up-regulation of Ascl1 in brain endothelial cell-derived microvesicles induces astrocyte trans-differentiation, thus contributing to neurogenesis, tissue repair, and recovery after stroke. We have 3 specific aims. In Aim 1, we will compare effects of major neurovascular unit cells on astrocyte trans- differentiation. In Aim 2, we will dissect mechanisms of brain endothelial cell-mediated astrocyte trans- differentiation, and use gain- and loss-of-function experiments to manipulate Ascl1 expression in brain endothelial cells, and track astrocyte trans-differentiation after focal ischemia. In Aim 3, we will investigate the effect of microvesicles derived from Ascl1-overexpressed brain endothelial cells on astrocyte trans- differentiation, and assess neurogenesis, tissue repair, and sensorimotor/cognitive outcomes in young, older, male or female mice after focal ischemia. Our experiments will utilize mouse genetic and molecular tools including a combination of AAV-induced brain endothelial cell-specific gene expression (Tie2-Cre or Cdh5-Cre mice), lineage tracing of astrocytes by using tamoxifen-inducible Aldh1l1-CreERT2;R26R-YFP mice, scRNA- seq or snRNA-seq to fully map transcriptomes of astrocytes in mice treated with microvesicles post stroke. Translational relevance will be assessed with in vivo optical imaging and long-term outcomes post-stroke. This project should define a new form of endothelial signaling in stroke, identify a unique vascular-regulated mechanism of neuroplasticity, and hopefully may lead to novel therapeutic opportunities for brain repair.