Astrocyte-endothelial crosstalk after cerebral ischemia and hemorrhage

描述（申请人提供）：脑缺血出血后星形胶质细胞-内皮细胞串扰传统上认为反应性星形胶质细胞抑制中枢神经系统损伤后神经元的可塑性。但现在新出现的数据表明，反应性星形胶质细胞也可能有有益的作用。我们的前期数据表明：(1)反应性星形胶质细胞释放HMGB1促进血管生成，(2)下调反应性星形胶质细胞释放HMGB1可能会使小鼠局灶缺血后神经血管恢复恶化，(3)HMGB1可能上调脑内皮细胞上的RAGE受体，(4)内皮细胞RAGE的增加可能通过β -2整合素增强内皮祖细胞的靶向粘附，(5)HMGB1可能增加增殖。内皮祖细胞的成熟和血管生成，从而促进中风后的修复。基于这些初步数据，我们假设星形胶质细胞-内皮细胞串音对脑卒中后神经血管恢复至关重要：反应性星形胶质细胞释放HMGB1，上调脑内皮上的RAGE受体；RAGE与循环内皮祖细胞上的β -2整合素结合，从而将它们拉入恢复中的大脑；一旦内皮祖细胞到达，HMGB1促进其增殖、成熟和血管生成。重要的是，我们提出这一途径可以促进缺血性或出血性中风后的恢复。我们将用三个目标来检验这一假设。在Aim 1中，我们研究了来自受刺激星形胶质细胞的HMGB1如何上调脑内皮细胞上的RAGE并增强内皮祖细胞的靶向粘附。在目的2中，我们剖析了HMGB1促进内皮祖细胞增殖、成熟和血管生成能力的机制。在Aim 3中，我们将使用小鼠局灶性脑缺血和脑出血模型来证实这些星形胶质细胞-内皮- epc机制，并表明它们实际上介导了体内神经血管的恢复。为了测试我们的途径，我们将结合使用细胞培养、体内小鼠模型、药物抑制剂、包括siRNA在内的分子技术、长期神经学结果和体内成像。这项研究应该确定一种新的机制，其中反应性星形胶质细胞、脑内皮细胞和循环内皮祖细胞之间的串扰是脑缺血和出血后神经血管恢复的基础。解剖这些细胞-细胞信号通路可能为促进缺血性和出血性中风患者功能恢复提供新的治疗方法。

DESCRIPTION (provided by applicant): Astrocyte-endothelial crosstalk after cerebral ischemia and hemorrhage Reactive astrocytes were traditionally thought to inhibit neuronal plasticity after CNS injury. But emerging data now suggest that reactive astrocytes may also have beneficial actions. Our pilot data suggest that (i) reactive astrocytes release HMGB1 that can promote angiogenesis, (ii) downregulating the release of HMGB1 from reactive astrocytes may worsen neurovascular recovery after focal ischemia in mice, (iii) HMGB1 may upregulate RAGE receptors on cerebral endothelial cells, (iv) increased endothelial RAGE may enhance targeted adhesion of endothelial progenitor cells via beta-2 integrins, and (v) HMGB1 may increase proliferation, maturation and angiogenesis in endothelial progenitor cells, thus promoting repair after stroke. Based on these pilot data, we hypothesize that astrocyte-endothelial crosstalk is essential for neurovascular recovery after stroke: reactive astrocytes release HMGB1 that upregulates RAGE receptor on cerebral endothelium; RAGE binds beta-2 integrins on circulating endothelial progenitor cells thus pulling them into recovering brain; and once endothelial progenitors arrive, HMGB1 promotes their proliferation, maturation and angiogenesis. Importantly, we propose that this pathway can promote recovery after both ischemic or hemorrhagic strokes. We will test this hypothesis in three aims. In Aim 1, we ask how HMGB1 from stimulated astrocytes upregulate RAGE on cerebral endothelial cells and enhance the targeted adhesion of endothelial progenitor cells. In Aim 2, we dissect mechanisms that underlie the ability of HMGB1 to enhance proliferation, maturation and angiogenesis in endothelial progenitor cells. In Aim 3, we will use mouse models of focal cerebral ischemia and intracerebral hemorrhage to confirm these astrocyte-endothelium-EPC mechanisms and show that they actually mediate neurovascular recovery in vivo. To test our pathways, we will use a combination of cell culture, in vivo mouse models, pharmacologic inhibitors, molecular techniques including siRNA, long-term neurological outcomes, and in vivo imaging. This study should define a novel mechanism wherein crosstalk between reactive astrocytes, cerebral endothelium, and circulating endothelial progenitor cells underlie neurovascular recovery after cerebral ischemia and hemorrhage. Dissecting these cell-cell signaling pathways may lead to new therapeutic approaches for promoting functional recovery in patients after ischemic and hemorrhagic strokes.