Regulation of vascular maturation/regression in diabetes

描述（由申请人提供）：心肌血管生成和冠状动脉侧支生长受损可能导致糖尿病心肌梗死的高死亡率。我们的长期目标是确定糖尿病心脏血管成熟异常和血管生成受损的分子机制。这项修订后的提案将研究异常糖尿病相关血管成熟和毛细血管退行中血管生成素（Ang）/Tie-2和爱帕琳途径可能受到的破坏。我们的实验室已经显示了糖尿病小鼠中血管生成素-2（Ang-2）和脯氨酰羟化酶-2（PHD 2）表达的持续增加，以及Ang-1/Tie-2和HIF- 11/apelin表达的减少。我们先前在糖尿病小鼠中证实了心肌血管成熟受损;暗示有利于Ang-2的血管生成素/Tie-2系统的破坏，其导致未成熟血管形成和毛细血管消退，可能是糖尿病心脏中血管生成受损的新机制。我们的总体假设是，糖尿病通过涉及Ang-2和PHD 2激活的机制破坏Ang-1/Tie-2和apelin通路;并且这些异常导致糖尿病心脏中的异常血管成熟和毛细血管消退。具体目标1将定义高血糖症干扰血管成熟和毛细血管消退的机制，重点关注Ang-2在破坏Ang-1/Tie-2和apelin通路中的作用。使用心脏微血管内皮细胞（EC）、共培养的EC-SMC球状体和从野生型（WT）或糖尿病db/db小鼠分离的小鼠主动脉外植体，我们将确定：（i）高糖诱导的过量Ang-2是否破坏Ang-1/Tie-2信号传导并减弱Ang-1诱导的apelin表达;和（ii）Ang-2和爱帕琳之间的相互作用对于高葡萄糖条件下血管生成和血管退化的调节是关键的。在具体目标2中，我们将确定Ang-2和PHD 2激活在体内心肌缺血模型中糖尿病相关的血管成熟和血管生成破坏以及血管消退促进中的作用。使用Ang-2缺陷和PHD 2条件性敲除糖尿病小鼠模型，我们将确定Ang-2缺陷或PHD 2的内皮细胞缺失是否挽救受损的爱帕琳蛋白表达，使未成熟的新血管正常化，并改善心肌血管生成。在具体目标3中，我们将进一步确定全身施用爱帕琳是否挽救受损的血管生成信号传导，使未成熟的新血管正常化，并增加糖尿病心脏中的心肌血管生成。我们的研究将为开发降低Ang-2和PHD 2活化的靶向治疗提供框架，以改善或逆转糖尿病血管成熟和血管生成的异常，这些异常是糖尿病状态的特征。 公共卫生相关性：心肌血管生成和冠状动脉侧支生长受损导致糖尿病患者死亡率高。本提案的长期目标是探索高血糖诱导的血管生成素/Tie-2和apelin/APJ相互作用破坏的分子机制和新途径，这些相互作用有助于糖尿病患者异常心肌血管成熟和血管生成。我们提出的研究应提供一个框架，为发展新的治疗策略，治疗糖尿病受损的侧支和血管生成。

DESCRIPTION (provided by applicant): Impairment of myocardial angiogenesis and coronary collateral growth may contribute to high mortality in diabetic myocardial infarction. Our long-term goal is to define the molecular mechanism(s) responsible for abnormal vascular maturation and impairment of angiogenesis in the diabetic hearts. This revised proposal will investigate a possible disruption in the angiopoietins (Ang)/Tie-2 and apelin pathway in abnormal diabetes- associated vascular maturation and capillary regression. Our laboratory has shown a sustained increase in angiopoietin-2 (Ang-2) and prolyl hydroxylase-2 (PHD2) expression, and reduced Ang-1/Tie-2 and HIF- 11/apelin expression in diabetic mice. Our previous demonstration of impaired myocardial vessel maturation in diabetic mice; implicate that disruption of angiopoietins/Tie-2 system in favor of Ang-2, which leading to immature vessel formation and capillary regression, might be a novel mechanism responsible for impaired angiogenesis in diabetic hearts. Our overall hypothesis is that diabetes disrupts Ang-1/Tie-2 and apelin pathway by a mechanism involving Ang-2 and PHD2 activation; and these abnormalities lead to abnormal vascular maturation and capillary regression in diabetic hearts. Specific Aim 1 will define the mechanism(s) by which hyperglycemia interferes with vascular maturation and capillary regression with a focus on the role of Ang-2 in the disruption of Ang-1/Tie-2 and apelin pathway. Using heart microvascular endothelial cells (EC), co-cultured EC-SMC spheroids and mouse aortic explants isolated from wild type (WT) or diabetic db/db mice, we will determine whether: (i) high glucose-induced excess of Ang-2 disrupts Ang-1/Tie-2 signaling and attenuates Ang-1-induced apelin expression; and (ii) interactions between Ang-2 and apelin are critical for the regulation of angiogenesis and vascular regression under high glucose conditions. In specific aim 2, we will determine the role of Ang-2 and PHD2 activation in diabetes-associated disruption of vascular maturation and angiogenesis and promotion of vessel regression in an in vivo model of myocardial ischemia. Using Ang-2 deficient and PHD2 conditional knockout diabetic mice models, we will determine whether deficiency of Ang-2 or endothelial cell deletion of PHD2 rescues impaired apelin expression, normalizes immature neovessels, and improves myocardial angiogenesis. In specific aim 3, we will further determine whether systemic administration of apelin rescues impaired angiogenic signaling, normalizes immature neovessels, and increases myocardial angiogenesis in diabetic hearts. Our studies will provide a framework for the development of a targeted therapeutic reduction in Ang-2 and PHD2 activation to ameliorate or reverse the abnormalities in diabetic vessel maturation and angiogenesis that characterizes the diabetic state. PUBLIC HEALTH RELEVANCE: Impairment of myocardial angiogenesis and coronary collateral growth has contributed to high mortality in diabetic patients. The long-term objectives of this proposal are to explore the molecular mechanisms and novel pathways of hyperglycemia-induced disruption of the angiopoietins/Tie-2 and apelin/APJ interaction that contributes to the abnormal myocardial vasculature maturation and angiogenesis in diabetes. Our proposed studies should provide a framework for developing new therapeutic strategies for the treatment of diabetic impaired collateralization and angiogenesis.