整合素ɑ5β1和Ang1对话对脑缺血后血管新生和血管完整性的调节作用及其机制

To promote the cerebral angiogenesis and reduce the blood-brain barrier (BBB) disruption concomitantly in the early stage after ischemic stroke is a promising target for stroke treatment. It has been showed that angiopoietin1 (ang1) could promote the angiogenesis as well as maintain the structural integrity of the BBB. Unfortunately, overexpression of ang1 in the cerebral ischemic zone alone is not sufficient to improve the angiogenesis and BBB integrity significantly after cerebral ischemia. We previously demonstrated that the α5β1 integrin plays a key role in promoting cerebral angiogenesis in response to hypoxia. We also observed that the α5β1 integrin colocalizes with Ang1 on brain endothelial cells (BECs) in the ischemic penumbra in response to cerebral ischemia, and the time course of BECs expression of α5 integrins is similar to that of ang1, which exactly coincides with the timing of angiogenesis. It is reported that α5β1 integrin has the potential of increasing the integrity of the BBB. Also, ɑ5β1 can react with Ang1 synergistically in vitro. Here, we hypothesize that cross-talks between integrin ɑ5β1 with Ang1 could synergistically promote the cerebral angiogenesis and enhance the structural integrity of the BBB after ischemic stroke. In the current study, we will observe the regulating effect of Ang1-Tie2 in promoting the angiogenesis and enhancing the structural integrity of the BBB after ischemia and reperfusion under the influence of integrin ɑ5β1 activity in vivo and in vitro. Meanwhile, we also evaluate whether integrin ɑ5β1 and Ang1-Tie2 share the common downstream effectors PI3K-FAK/Akt to promote the angiogenesis and enhance the structural integrity of the BBB. We first propose that molecules interact with each other to regulate the cerebral angiogenesis and structural integrity of the BBB after ischemic stroke by changing the local microenvironment, which provide a prospective idea and fundamental data for searching the more active and more effective treatment target in promoting the functional cerebral angiogenesis after ischemic stroke.

血管新生和血管壁完整是卒中修复的关键。过去研究主要集中在血管生成素1（Ang1）促血管新生或抗血管渗漏方面，但单纯调控Ang1表达不能有效改善脑缺血后的血管修复。我们剔除小鼠内皮细胞整合素α5导致脑缺氧后血管新生障碍；还发现α5β1与Ang1在缺血半暗带血管上呈时相相关性共表达，与血管新生时程一致。体外研究显示α5β1与Ang1有协同作用。提示整合素α5β1及其与Ang1交互对话可能在脑缺血后血管新生及血管完整性调节中发挥重要作用。本项目拟在动物和细胞上模拟脑缺血再灌注损伤模型，用共聚焦成像、电镜、Cre-Lox和腺相关病毒双基因共表达等技术，通过在血管内皮细胞和缺血脑区上调或下调α5β1和Ang1表达，从整体、细胞和分子水平探讨并综合评价α5β1及其与Ang1交互对话在脑缺血后血管新生及血管完整性维持中的作用和分子调控机制。该项目可能为卒中后血管修复提供新分子靶标，为临床治疗提供新思路。

血管新生和血管壁完整是卒中修复的关键。过去研究主要集中在血管生成素1（angiopoietin1, Ang1）促血管新生或抗血管渗漏方面，但单纯调控Ang1表达不能有效改善脑缺血后的血管修复。本项目在动物和细胞上模拟脑缺血再灌注损伤模型，用共聚焦成像、免疫印迹、腺相关病毒双基因共表达等技术，通过调控脑血管内皮细胞和缺血脑区α5β1和Ang1的表达，从整体、细胞和分子水平探讨并综合评价α5β1及其与Ang1交互对话在脑缺血后血管新生及血管完整性维持中的作用和机制。结果发现，脑缺血后血管上表达的Ang1、整合素ɑ5β1和紧密连接蛋白在脑内血管重塑中受紧密调控；脑缺血后，一方面，整合素α5β1可以调节缺血所诱导的脑内皮细胞上Tie2受体的激活，另一方面，Ang1通过调节E-26特异性转录因子信号通路可促进脑内皮细胞上整合素α5的表达。Ang1/Tie2系统与整合素α5β1交互对话有助于脑缺血后内源性的血管保护反应；我们还发现，整合素α5和Ang1的共同过表达显著减少了缺血脑区的血管渗漏，改善了脑血管结构的完整性，协同促进了缺血性卒中早期的血管新生反应，增加了晚期的血管形成，使脑梗死体积显著减小，从而显著改善了卒中后神经功能的缺损。该项目为卒中后脑血管的修复提供了新的分子靶标，为临床提供了新的治疗策略。