Remodeling and recovery in the neurovascular unit

描述(申请人提供)：脑缺血或创伤后，小胶质细胞最初被激活为一种破坏性的炎症表型。但最终，随着大脑试图恢复，它们可能会转换为有益的重塑表型。该项目剖析了一种新的机制，允许脑内皮细胞和反应性星形胶质细胞对小胶质细胞开关进行差异化调节。 我们的假设如下。正常情况下，脑小胶质细胞不能“看到”脑内皮细胞，因为它们位于血脑屏障的后面。在急性损伤期间，血脑屏障渗漏，小胶质细胞现在“看到”受损或发炎的脑内皮细胞释放的微粒。这会激活它们形成一种有害的表型(如高肿瘤坏死因子�和白介素1�)。在最初的损伤阶段消退后，血脑屏障(BBB)被修复，反应性星形胶质细胞出现，开始释放促进恢复的介质，如高迁移率族蛋白-1(HMGB1)、IL-4和IL-10。这会导致小胶质细胞转变为有益的表型(例如，高生长因子)。我们的项目将剖析小胶质细胞开关的这种胶质血管调节所涉及的细胞间和细胞内的机制。 在目标1中，我们使用细胞培养来显示内皮细胞与星形胶质细胞的条件培养液 对小胶质细胞的激活有相反的影响。然后我们证明了有害的和有益的小胶质细胞 当添加到初级神经元上时，会产生神经毒性或神经再生作用。在目标2中，我们将确认 内皮细胞和星形胶质细胞的不同作用是通过释放微粒子HMGB1、IL-4和IL-10来调节的。在目标3中，我们将关联小鼠局灶性脑缺血或创伤后血脑屏障渗漏、星形胶质细胞增多和双相小胶质细胞的时间分布。我们还将直接注射内皮微粒或通过光遗传学激活星形胶质细胞，看看能否在体内唤起预测的小胶质细胞表型。与项目2协作，我们也将尝试评估白质中的这些小胶质细胞通路。与项目3协同，我们将尝试操纵Rho-Kinase途径，将小胶质细胞切换到有益的模式，促进恢复。成像和光遗传学将得到Core A的支持，我们的小鼠模型的神经恢复将得到Core B的支持。 综上所述，我们的研究应该确定内皮细胞和星形胶质细胞调节重建神经血管单位中的小胶质细胞开关的机制。这些发现可能最终带来促进中风和神经变性后修复和恢复的治疗机会。

Description (provided by applicant): After cerebral ischemia or trauma, microglia are initially activated into a damaging inflammatory phenotype. But eventually, they may switch to a beneficial pro-remodeling phenotype as the brain tries to recover. This project dissects a novel mechanism that allows cerebral endothelium and reactive astrocytes todifferentially regulate the microglial switch. Our hypothesis is as follows. Normally, brain microglia cannot "see" cerebral endothelium because they reside behind the BBB. During acute injury, the BBB is leaky and microglia now "see" microparticles that are released by damaged or inflammed cerebral endothelium. This activates them into a deleterious phenotype (e.g. high TNF� and IL1�). After this initial injury stage subsides, the blood-brain barrier (BBB) is repaired and reactive astrocytes emerge that begin to release pro-recovery mediators such as high-mobility-groupbox-1 (HMGB1), IL-4 and IL-10. This causes microglia to switch to a beneficial phenotype (e.g. high growth factors). Our project will dissect the inter- and intra-cellular mechanisms involved in this gliovascular regulation of the microglial switch. In Aim 1, we use cell cultures to show that conditioned media from endothelium vs astrocytes have opposite effects on microglia activation. Then we show that harmful vs beneficial microglia have either neurotoxic or neuroplastic effects when added to primary neurons. In Aim 2, we will confirm that the differential effects of endothelium vs astrocytes is mediated by release of microparticles, HMGB1, IL-4 and IL-10. In Aim 3, we will correlate the temporal profiles of BBB leakage, astrocytosis and biphasic microglia after focal cerebral ischemia or trauma in mice. We will also directly inject endothelial microparticles oractivate astrocytes via optogenetics to see whether we can evoke the predicted microglial phenotypes in vivo. Synergizing with Project 2, we will try to asses these microglial pathways in white matter as well. And synergizing with Project 3, we will try to manipulate rho-kinase pathways to switch microglia into a beneficial mode and promote recovery. Imaging and optogenetics will be supported by Core A. Neurorecovery in our mouse models will be supported by Core B. Taken together, our studies should define a mechanism by which endothelium and astrocytes regulate the microglial switch in the remodeling neurovascular unit. These findings may eventually lead to therapeutic opportunities for promoting repair and recovery after stroke and neurodegeneration.