The Role of Fluid Flow in Valvulogenesis

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，是心脏瓣膜和膜间隔的原基。在确定调节垫层形成初始步骤的基因方面已经取得了很大进展（阶段14-22）。, 2003;Moorman and Christoffels, 2004)。然而，对于这些缓冲如何分化成瓣膜小叶（35-45期）知之甚少。由于瓣膜缺损是所有心脏畸形中最常见和最有害的，因此对晚期瓣膜发育的机制进行描述是至关重要的。研究早期瓣膜发育的研究人员受益于一个优秀的体外缓冲形成初期模型。直到最近，这种后期阀门开发模型还不存在。提出的研究使用我们开发的体外模型来研究晚期瓣膜小叶的形成。这种新模型由胶原管支架组成，其中缓冲基质成熟为瓣膜组织（Goodwin et al, 2005）。这个新模型扩展了之前的心脏缓冲模型（Runyan和Markwald， 1983），提供了一个三维（3-D）环境，在这个环境中，心脏缓冲组织在分子和形态水平上概括了瓣膜发育的后期阶段。该模型的初步实验表明，在试管模型中，瓣膜小叶的形态发生和细胞外基质（ECM）蛋白的表达/沉积依赖于流体的流动。本研究的中心假设是流体流动在阀门小叶形态发生中起关键作用。管状模型系统具有测试流体流动对阀门形态发生作用的独特能力。为了解决这一应用的假设，我们将追求三个具体目标：目标1)确定流体流动对瓣膜小叶分化和形态发生的影响。目的2)确定在流量调节阀培养中fasiclin错误表达的影响。目的3)确定心外膜前细胞（PE）在AV缓冲层成熟中的作用。该方案旨在提供描述维持阀门小叶形成早期阶段的流动条件的具体数据。这些信息将为组织工程瓣膜的设计提供有价值的信息，并为先天性缺陷的治疗提供新的策略。

DESCRIPTION (provided by applicant): 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 for the cardiac valves and membranous septa. A great deal of progress has been made in identification of genes that regulate the initial steps of cushion brmation (stage14-22) (Gitleretal., 2003; Moorman and Christoffels, 2004). However, little is known about how these cushions differentiate into valve leaflets (stage 35-45). As valvular defects are among the most common and deleterious of all cardiac malformations, it is critical that the mechanisms of late valve development be delineated as well. Researchers studying early valve development have benefited from an excellent in vitro model of the initial stages of cushion formation. Until recently, such a model for late stage valve development has not existed. The proposed research uses an in vitro model we have developed to study late valve leaflet formation. This new model is composed of a collagen tube scaffold in which cushion anlage matures into valve tissue (Goodwin et al, 2005). This new model expands upon the previous cardiac cushion model (Runyan and Markwald, 1983) by providing a three-dimensional (3-D) environment in which cardiac cushion tissues recapitulate the later stages of valve development, both at the molecular and morphological levels. Initial experiments testing this model indicate that valve leaflet morphogenesis and extracellular matrix (ECM) protein expression/deposition is dependent on fluid flow in the tube model. The central hypothesis being tested in this proposal is that fluid flow plays a key role in valve leaflet morphogenesis. The tubular model system has the unique ability to test the role that fluid flow plays in valve morphogenesis. To address the hypothesis of this application, we will pursue three specific aims:Aim 1) Determine the effect of fluid flow on the differentiation and morphogenesis of valve leaflets. Aim 2) Determine the effect of fasciclin missexpression in flow-regulated valve cultures. Aim 3) Determine the role that proepicardial (PE) cells have on AV cushion maturation. This proposal is designed to provide specific data that describe the flow conditions that sustain the early stages of valve leaflet formation. This information would be valuable for the design of tissue-engineered valves as well as to provide new strategies for the treatment of birth defects.