Regulation of Stromal Derived Factor-1 Mediated Angiogenesis in Ischemic Brain

描述（由申请人提供）：中风是导致发病率和长期残疾的第三大原因。由于脑动脉闭塞，缺血性中风导致严重的血液供应减少，导致内皮完整性破坏和神经元细胞死亡。确实，脑血管密度越高的患者脑卒中后恢复和生存越好。许多炎症趋化因子支持血管血液供应的发展（血管生成）和祖细胞向损伤部位的迁移。特别是，趋化因子基质衍生因子（SDF1）通过其受体CXCR4发挥作用，在促进血管生成和祖细胞募集中发挥核心作用。然而，SDF1经常被蛋白水解裂解和失活。这一过程可能会阻碍脑损伤修复所必需的神经（NPC）和内皮祖细胞（EPC）的迁移和血管生成。因此防止SDF1失活具有重要的临床意义。虽然二肽基肽酶4 （DPPIV）被证明可以切割SDF1，但其在缺血性卒中中的作用尚不清楚。本提案的目的是为评估DPPIV抑制在增强SDF1活性以改善血管生成和脑损伤修复方面的功效建立基础工作。我们的研究表明，DPPIV缺失与SDF1水平升高之间存在相关性，导致神经嵴干细胞衍生的神经母细胞瘤细胞的迁移和血管生成潜力增加。我们进一步观察到DPPIV在缺血后脑中的表达明显增加。我们假设局灶性缺血后，DPPIV上调会抑制SDF1活性，从而阻碍祖细胞向缺血区域的迁移，抑制随后的血管生成和神经发生。我们进一步提出基因敲除或DPPIV的小分子抑制剂可增加缺血后SDF1水平，从而促进缺血脑中NPC和EPC的迁移和血管生成。在本提案中，我们将测试短暂性大脑中动脉闭塞（MCAO）后小鼠大脑和血清中DPPIV表达与SDF1和CXCR4水平的预测负相关（目的1）。我们将研究DPPIV基因缺失或DPPIV小分子抑制剂是否能促进体内缺血脑和体外缺氧缺血模型中EPC募集和血管生成。将表达NPC/EPC的荧光素酶移植到MCAO小鼠的对侧纹状体中，并使用生物发光成像跟踪迁移细胞（目的2）。重要的是，DPPIV抑制剂是FDA批准的抗糖尿病药物，可增加糖尿病患者的循环EPCs。我们的研究如果成功，可以转化为临床前和临床研究，以改善血管生成和神经发生。这些研究结果可能为更好地理解脑损伤修复的新靶点和机制提供坚实的基础，也可能为脑卒中治疗开辟新的方向。

DESCRIPTION (provided by applicant): Stroke is the third leading cause of morbidity and long-term disability. Due to cerebral artery occlusion, ischemic stroke causes a severe reduction in blood supply causing destruction of endothelial integrity and neuronal cell death. Indeed, patients with higher density of cerebral blood vessel show better recovery and survival after stroke. Many inflammatory chemokines support the development of vascular blood supply (angiogenesis) and progenitor cell migration to the site of injury. Particularly, the chemokine stromal derived factor (SDF1) acting via its receptor CXCR4 plays a central role in promoting angiogenesis and progenitor cell recruitment. However, SDF1 is often proteolytically cleaved and inactivated. This process may hinder neural (NPC) and endothelial progenitor cells (EPC) migration and angiogenesis necessary for brain injury repair. Thus preventing SDF1 inactivation is of clinical importance. Although the protease dipeptidyl peptidase 4 (DPPIV) is shown to cleave SDF1, its role in ischemic stroke is unknown. The goal of this proposal is to establish a ground work for evaluating the efficacy of the DPPIV inhibition in enhancing the activity of SDF1 for improved angiogenesis and brain injury repair. Our studies show a correlation between loss of DPPIV and increased levels of SDF1 resulting in increased migratory and angiogenic potential of neural crest stem cell derived neuroblastoma cells. We further observed significantly increased DPPIV expression in the post- ischemic brain. We hypothesize that following focal ischemia, DPPIV up regulation curtails SDF1 activity and thus hinders the migration of progenitor cells to the ischemic region and suppresses subsequent angiogenesis and neurogenesis. We further propose that genetic knockout or small molecule inhibitors of DPPIV increases post-ischemic SDF1 levels, which in turn enhances NPC and EPC migration and angiogenesis in ischemic brain. In this proposal, we will test the predicted inverse correlation between DPPIV expression and SDF1, and CXCR4 levels in mouse brain and serum following transient middle cerebral artery occlusion (MCAO) (Aim 1). We will examine whether genetic loss of DPPIV or small molecule inhibitor of DPPIV enhances EPC recruitment and angiogenesis in vivo ischemic brain and in an in vitro ischemic model of oxygen glucose deprivation. The luciferase expressing NPC/EPC will be transplanted into the contralateral striatum of the mice subjected to MCAO and migrating cells will be tracked using bioluminescence imaging (Aim 2). Importantly, DPPIV inhibitors are FDA approved anti-diabetic drugs that increase circulating EPCs in diabetic patients. Our studies if successful can be translated to pre-clinical and clinical studies for improved angiogenesis and neurogenesis. Results from these studies may provide strong foundation for better understanding of novel targets and mechanisms of brain injury repair and may also open up a new direction for stroke therapy.