A 3-D model system to study cardiac valve formation

描述(申请人提供)：早期的心脏垫位于胚胎心脏的房室管(AV)。这些垫层由间充质细胞填充，是未来心脏瓣膜和膜性隔膜的原基。瓣膜缺陷是所有心脏畸形中最常见和危害最大的一种。重要的是，随着大量基因的识别，在描述调节缓冲形成的早期步骤的分子机制方面已经取得了重大进展。然而，人们对这些气垫如何分化为瓣叶知之甚少。这在一定程度上是因为没有一个足够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一点，在这种支架系统中，软垫胶原成熟为瓣膜组织。这一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。在自发性收缩管培养物的管腔内生长的小鸡阶段22室壁垫被发现经历了模拟瓣膜发育后期阶段的形态变化。一致的和有希望的初步结果表明，管状模型中瓣叶的形成依赖于心肌细胞的存在。这项建议旨在研究管状模型重述活体小叶形成的保真度和实用性。拟议的实验旨在测试在管状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，管状培养系统可用于研究心肌组织和流体力在心脏瓣膜叶发育中所起的作用。由于瓣膜形成具有重要的生物医学意义，模拟体内瓣膜形成后期阶段的模型系统将是确定单个和集体生化和物理因素在瓣膜形成中所起作用的关键。为了解决这一应用的假说，已经制定了两个具体的目标：目的1：测试管状模型系统在瓣膜形成的后期阶段准确再现心肌作用的能力：目标2：测试流体可以驱动房室瓣膜成熟的假说。

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.