Endothelial Regulation of Astrocyte Trans-differentiation in Stroke

神经发生在中风恢复中起着重要作用。在脑缺血模型中，神经发生是 在脑室下区（SVZ）和颗粒下区（SGZ）中被放大。除了这些答复之外， 标准的神经原性小生境，一些报告表明，实质星形胶质细胞可以转化为神经元， 中风后在SVZ和SGZ的神经原性小生境中，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建议中，我们将研究这个想法，即脑内皮细胞作为 一个意想不到的信号源，将星形胶质细胞转化为神经元，从而改善中风后的结果。 我们的初步数据表明：（i）氧-葡萄糖剥夺（OGD）刺激的脑内皮细胞转化为 （ii）将来自OGD刺激的星形胶质细胞的微囊泡转移到体外的神经祖细胞（NPC）， 脑内皮细胞培养物在体外将星形胶质细胞重编程为NPC，（iii）来自OGD- 刺激脑内皮细胞在体内也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）脑内皮细胞中的前神经转录因子Ascl 1可能参与 星形胶质细胞转分化，（v）剖析这些机制的方法（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-seq、成像等）在我们的实验室中是可行的。 基于我们的初步数据，我们假设Ascl 1在脑内皮细胞源性 微泡诱导星形胶质细胞转分化，从而有助于神经发生、组织修复和 中风后的康复 我们有三个具体目标。在目的1中，我们将比较主要神经血管单位细胞对星形胶质细胞trans-mitting的影响。 分化在目标2中，我们将剖析脑内皮细胞介导的星形胶质细胞跨膜转运的机制。 分化，并使用功能获得和丧失实验来操纵脑中Ascl 1的表达。 内皮细胞，并跟踪局灶性缺血后星形胶质细胞的转分化。在目标3中，我们将研究 来源于Ascl 1过表达脑内皮细胞的微泡对星形胶质细胞转基因的影响 分化，并评估年轻人，老年人， 局灶性缺血后的雄性或雌性小鼠。我们的实验将利用小鼠遗传和分子工具 包括AAV诱导的脑内皮细胞特异性基因表达（Tie 2-Cre或Cdh 5-Cre）的组合 小鼠），通过使用他莫昔芬诱导的Aldh 1 l1-CreERT 2; R26 R-YFP小鼠，scRNA- seq或snRNA-seq来完全绘制中风后用微泡处理的小鼠中星形胶质细胞的转录组。 将通过体内光学成像和卒中后长期结局评估平移相关性。这 该项目应该定义一种新的中风内皮信号形式，确定一种独特的血管调节因子， 神经可塑性机制，并希望可能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.