Endothelial Cell Growth and Differentiation in Semilunar Heart Valves

描述（由申请人提供）：正确形成的心脏瓣膜小叶对于实现单向血液流动至关重要，因此对生命至关重要。每次心脏跳动时，这些精致的小叶都会打开和关闭，通过防止反流来促进最佳的心脏功能，从而将氧气输送到全身各组织。先天性心脏缺陷的发生率约为百分之一，其中许多会影响心脏瓣膜。有些先天性瓣膜缺陷从出生的那一刻起就危及生命；其他的问题较少，但最终在成人生活中必须更换瓣膜。尽管瓣膜在心脏功能中起着至关重要的作用，但人们对瓣膜的发育知之甚少，对成年后维持瓣膜功能的细胞和分子过程的了解就更少了。我们已经证明，来自成人肺动脉瓣和主动脉瓣小叶的内皮细胞表现出瓣膜特异性，这让人想起瓣膜形成的关键步骤，表明来自成人小叶的内皮细胞保留了再现胚胎发育过程的能力。我们已经证明，在人瓣膜内皮细胞中，转录因子NFATc1的激活和核易位是vegf诱导的增殖和迁移所必需的，我们还表明，成人瓣膜内皮细胞克隆群体可以被诱导经历内皮到间充质转分化（EMT），这是心内膜垫形成瓣膜小叶的关键事件。我们建立的瓣膜内皮细胞培养模型为鉴定控制内皮细胞增殖和分化的基因以及了解心脏瓣膜增殖和分化之间的相互作用提供了强有力的工具。将实现三个具体目标。首先是鉴定和功能表征瓣膜内皮中VEGF/NFATc1信号通路的靶点。第二个将是鉴定和功能表征参与tgf - β介导的EMT的基因。第三个目标将是检查心脏瓣膜内皮细胞增殖和分化之间的交叉调节。基于新的初步数据，我们假设骨形态发生蛋白-2 （BMP-2）连接这两种途径。Aim 3在修订后的应用中得到扩展，专门测试BMP-2在心脏瓣膜内皮细胞增殖、迁移和EMT中的作用。本文提出的研究将提供以下方面的见解：1)瓣膜内皮的正常功能和能力；2)心脏瓣膜疾病和潜在的修复机制；3)为患有瓣膜特异性缺陷的患者创造改进的瓣膜替代物的策略。

DESCRIPTION (provided by applicant): Properly formed heart valve leaflets are essential to achieve unidirectional blood flow and thus, are critical for life. The delicate leaflets open and close with each heart beat, promoting optimal heart function by preventing regurgitation and thus, oxygen delivery to tissues throughout the body. Congenital heart defects, many of which affect the heart valves, occur in about 1 in 100 infants. Some congenital valve defects are life threatening from the moment of birth; others are less problematic, but eventually valve replacement becomes necessary in adult life. Despite the critical role of the valves in heart function, relatively little is known about the development of the valves and even less about the cellular and molecular processes that sustain valve function through adult life. We have shown that endothelial cells from adult pulmonary and aortic valve leaflets exhibit valve specific properties that are reminiscent of critical steps in valvulogenesis, indicating that endothelial cells from adult leaflets retain the ability to recapitulate embryonic developmental processes. We have shown that in human valvular endothelial cells, activation and nuclear translocation of the transcription factor NFATc1 is required for VEGF-induced proliferation and migration, we have also shown that clonal populations of adult valvular endothelial cells can be induced to undergo an endothelial to mesenchymal transdifferentiation (EMT), a critical event in formation of valve leaflets from the endocardial cushions. The valvular endothelial cell culture models we have established provide powerful tools for identifying genes that control endothelial proliferation and differentiation and for understanding the interplay between proliferation and differentiation in cardiac valves. Three specific aims will be pursued. The first will be to identify and functionally characterize targets of the VEGF/NFATc1 signaling pathway in valve endothelium. The second will be to identify and functionally characterize genes involved in TGF-beta mediated EMT. The third aim will be to examine the cross-regulation between proliferation and differentiation in cardiac valve endothelial cells. Based on new preliminary data, we hypothesize the bone morphogenetic protein-2 (BMP-2) links these two pathways. Aim 3 has been expanded in this revised application to specifically test the role of BMP-2 in proliferation, migration and EMT in cardiac valve endothelium. The studies proposed here will provide insights on 1) normal functions and capabilities of valvular endothelium, 2) heart valve diseases and potential mechanisms for repair, and 3) strategies to create improved valve replacements for patients suffering from valve-specific defects.