A 3-D model system to study cardiac valve formation

描述（由申请人提供）：早期心脏垫位于胚胎心脏的房室管（AV）。这些缓冲层充满间充质细胞，是未来心脏瓣膜和膜间隔的原基。瓣膜缺损是所有心脏畸形中最常见和最有害的。重要的是，在描述调节缓冲层形成早期步骤的分子机制方面取得了重大进展，因为已经确定了许多基因。然而，很少有人知道这些缓冲是如何分化成气门小叶的。这部分是由于没有一个适当的模型系统来研究阀门发展的后期阶段。目前的研究建议通过开发一种新的胶原管支架系统来改变这种情况，在这种支架系统中，缓冲胶原蛋白成熟为瓣膜组织。这个新模型扩展了我们最近开发的培养胚胎心肌细胞的组织工程系统。在自然收缩管培养的管腔内生长的鸡22期AV垫发现发生了模拟瓣膜发育后期的形态学变化。一致和有希望的初步结果表明，在管模型中瓣膜小叶的形成依赖于心肌细胞的存在。本研究旨在研究试管模型的保真度和效用，以概括体内小叶的形成。本实验旨在测试在试管模型中调节房室瓣膜形态发生的分子、细胞和组织机制。中心假设是管培养系统可用于研究心肌组织和流体力在心脏瓣膜小叶发育中的作用。由于瓣膜形成具有重要的生物医学意义，因此模拟体内瓣膜形成后期的模型系统对于确定个体和集体生化和物理因素在瓣膜形成中的作用至关重要。为了解决这一应用的假设，已经制定了两个具体目标：目的1：测试管模型系统准确再现心肌在瓣膜形成后期的作用的能力；目的2：测试流体流动可以驱动房室瓣膜成熟的假设。

DESCRIPTION (provided by applicant): The early cardiac cushions are located in the atrioventricular canal (AV) of the embryonic heart. These cushions are populated with mesenchymal cells and are the primordia of future cardiac valves and membranous septa. Valvular defects are among the most common and deleterious of all cardiac malformations. Importantly, significant progress has been made in delineating the molecular mechanisms that regulate the early steps of cushion formation, as numerous genes have been identified. However, little is known about how these cushions differentiate into valve leaflets. This is due, in part, to the fact that there is not an adequate model system to study later stages of valve development. The present research proposes to change this with the development of a new collagen tube scaffold system in which cushion anlagen matures into valve tissue. This new model expands upon our recently developed tissue engineering system of culturing embryonic cardiac myocytes. Chick stage 22 AV cushions grown within the lumen of spontaneously-contracting tube cultures were found to undergo morphological changes that model the later stages of valve development. Consistent and promising initial results indicate that valve leaflet formation in the tube model is dependent on the presence of cardiac myocytes. This proposal seeks to investigate the fidelity and utility of the tube model to recapitulate in vivo leaflet formation. The proposed experiments are designed to test the molecular, cellular, and tissue mechanisms that regulate the morphogenesis of AV valves in the tube model. The central hypothesis is that the tube culturing system can be used to investigate the roles that myocardial tissues and fluid forces play in the development of cardiac valve leaflets. Since valve formation is of significant biomedical interest, a model system that mimics late stages of in vivo valve formation will be essential in determining the roles that individual and collective biochemical and physical factors play in valve formation. Two specific aims have been developed to address the hypothesis of this application: Aim1: Test the ability of the tube model system to accurately reproduce the role of the myocardium in the later stages of valvulogenesis: Aim 2: Test the hypothesis that fluid flow can drive the maturation of AV valves.