Mechanisms of Coronary Ostium Formation and Coronary Artery Patterning

描述（由申请人提供）：本项目的长期目标是了解冠状动脉的形态及其潜在机制。当氧气和营养物质的被动扩散不再足以维持心脏的生长和功能时，冠状动脉循环就开始了。冠状动脉必须通过冠状动脉口（主动脉窦处的开口）与主动脉相连，以接收体循环中的含氧血液和营养物质。我们已经建立了新的遗传小鼠模型来研究冠状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vegf的主要受体Vegfr2和转录因子Nfatc1在主动脉窦内皮中共同表达。此外，主动脉窦被缺氧心肌细胞包围，产生高水平的vegf。在这些发现的基础上，本项目将在小鼠身上研究冠状动脉连接何时何地需要心肌Vegfa，以及其功能是否依赖于缺氧。我们还将探讨Vegfr2和Nfatc1是否共同调节连接过程。具体来说，我们将在冠状动脉发育晚期以时空方式从基因上破坏Vegfa、Vegfr2或Nfatc1。缺氧心肌细胞或其Vegfa表达的消融将确定缺氧在冠状动脉模式和口形成中的作用。主动脉窦心内膜中Vegfr2和Nfatc1的缺失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发育中的冠状动脉和口进行形态学、细胞和分子分析，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.