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）中。这些垫由间充质细胞构成，是心脏瓣膜和膜隔的原基。在鉴定调节缓冲形成的初始步骤（阶段14 -22）的基因方面已经取得了很大进展（Gitleretal.，2003年; Moorman和Christoffels，2004年）。然而，很少有人知道这些垫如何分化成瓣叶（阶段35-45）。由于瓣膜缺损是所有心脏畸形中最常见和最有害的，因此也必须阐明晚期瓣膜发育的机制。研究早期瓣膜发育的研究人员受益于缓冲形成初始阶段的良好体外模型。直到最近，这种用于后期阀开发的模型还不存在。拟议的研究使用我们开发的体外模型来研究晚期瓣叶形成。这种新模型由胶原管支架组成，其中垫原基成熟为瓣膜组织（Goodwin等，2005）。该新模型通过提供三维（3-D）环境扩展了先前的心脏垫模型（Runyan和Markwald，1983），其中心脏垫组织在分子和形态学水平上再现了瓣膜发育的后期阶段。测试该模型的初始实验表明，瓣膜小叶形态发生和细胞外基质（ECM）蛋白表达/沉积取决于管模型中的流体流动。在该提议中测试的中心假设是，流体流动在瓣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在瓣膜形态发生中所起作用的独特能力。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的分化和形态发生的影响。目的2）确定fasciclin在流量调节瓣膜培养中的表达缺失。目的3）确定心前外膜（PE）细胞在房室垫成熟中的作用。该提案旨在提供描述维持瓣叶形成早期阶段的流动条件的具体数据。这些信息将是有价值的组织工程瓣膜的设计，以及提供新的策略，治疗出生缺陷。

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.