Mechanisms of Coronary Ostium Formation and Coronary Artery Patterning

描述（由申请人提供）：该项目的广泛和长期目标是了解冠状动脉的模式及其潜在机制。当氧气和营养物质的被动扩散不再足以满足心脏的生长和功能时，冠状动脉循环开始。冠状动脉必须通过冠状动脉口（主动脉窦的开口）连接到主动脉，以接收来自体循环的含氧血液和营养物质。我们已经产生了新的遗传小鼠模型，以研究冠状动脉-主动脉连接和冠状动脉模式的发育和分子机制。初步结果表明，心肌血管内皮生长因子-a（Vegfa）是连接形成所必需的。我们还发现，Vegfa的主要受体Vegfr 2以及转录因子Nfatc 1在主动脉窦内皮中共表达。此外，主动脉窦周围是产生高水平Vegfa的缺氧心肌细胞。基于这些发现，该项目将在小鼠中研究何时何地需要心肌Vegfa进行冠状动脉-主动脉连接，以及其功能是否具有缺氧依赖性。我们还将讨论Vegfr 2和Nfatc 1是否共同调节连接过程。具体来说，我们将在冠状动脉发育后期以时空方式遗传性破坏Vegfa、Vegfr 2或Nfatc 1。消融缺氧心肌细胞或其Vegfa表达将确立缺氧在冠状动脉图案形成和开口形成中的作用。在主动脉窦内皮细胞中缺失Vegfr 2和Nfatc 1将确定它们在这些过程中的作用和潜在的相互作用。对这些小鼠突变体中正在发育的冠状动脉和口进行形态学、细胞学和分子学分析，将确定以前未知的发育机制和参与晚期冠状动脉发育的分子相互作用。这些信息将有助于了解先天性冠状动脉异常的病因。

DESCRIPTION (provided by applicant): The broad and long-term goal of this project is to understand the patterning of coronary arteries and their underlying mechanisms. The coronary circulation starts when the passive diffusion of oxygen and nutrients is no longer sufficient for the heart growth and function. The coronary arteries must connect to the aorta through the coronary ostia, the openings at the aortic sinus, to receive the oxygenated blood and nutrients from systemic circulation. We have generated new genetic mouse models to study the developmental and molecular mechanisms of the coronary-aorta connection and coronary patterning. Preliminary results have shown that the myocardial vascular endothelial growth factor-a (Vegfa) is necessary for the connection to form. We have also found that the main receptor for Vegfa, Vegfr2, as well as transcription factor Nfatc1 are co- expressed in the aortic sinus endothelium. Additionally, the aortic sinus is surrounding by hypoxic cardiomyocytes that produce a high level of Vegfa. Building upon these findings, this project is to study in mice when and where the myocardial Vegfa is required for the coronary-aorta connection and whether its function is hypoxia-dependent. We will also address whether Vegfr2 and Nfatc1 function together to regulate the connection process. Specifically, we will genetically disrupt Vegfa, Vegfr2, or Nfatc1 in a spatiotemporal manner during late coronary artery development. Ablation of the hypoxic cardiomyocytes or their expression of Vegfa will establish the role of hypoxia in coronary artery patterning and ostium formation. Deletion of Vegfr2 and Nfatc1 in the endocardium of the aortic sinus will ascertain their roles and potential interactions in these processes. Morphologic, cellular, and molecular analysis of the developing coronary arteries and ostia in these mouse mutants will identify previously unknown developmental mechanisms and molecular interactions involved in late coronary artery development. The information will help understand the etiology of congenital coronary anomalies.