Dynamic changes in the chick developing heart in response to altered hemodynamics

描述（由申请人提供）：在美国，大约1%的新生儿患有先天性心脏病（CHD），这是婴儿死亡的主要原因。血液动力学力是由血液流动产生的壁剪切应力和压力，是调节心脏发育的关键因素，如果异常，可能导致CHD。即使CHD有遗传原因，由心脏缺陷产生的血流条件改变也可能导致其他异常。然而，血流动力学的改变影响心脏细胞并最终影响心脏形成的程度尚不清楚。详细研究血液动力学对心脏发育的影响需要在完整的体内动物模型中定量血液动力学力和心脏生长、形态和基因表达的变化。该项目的目的是阐明早期发育阶段血液动力学、心脏生长、心脏形态和选定基因表达之间的关系;最终目标是了解血液动力学影响心脏发育的生物学机制。该项目将使用2个早期发育阶段的鸡胚（21天孵化期的3天和3.5天-HH 18和HH 21），并将重点关注心脏流出道（OFT），其作用类似原始瓣膜。正常的血流动力学将通过流出道结扎术改变，在流出道结扎术中，在OFT周围放置缝线，限制OFT壁的运动;以及通过卵黄静脉结扎术，在卵黄静脉结扎术中，夹住卵黄静脉以阻塞血流。该假设是，由于流出道束带和卵黄静脉结扎在HH 18的血流动力学力的改变导致可测量的，相关的变化在HH 21的OFT壁形态，生长和基因表达。该项目的目的是：目的1：确定OFT壁的运动、形态和生长对血流动力学改变的响应的体内变化。为了测量鸡胚OFT中的壁运动和几何变化，将使用光学相干断层扫描对OFT进行成像。目标二：确定在正常和改变的血流动力学条件下心动周期内OFT中血流动力学力的动态变化和选定基因的相关表达。将使用伺服零位系统测量血压。将通过OFT有限元模型的模拟来量化壁面剪切应力。整联蛋白和胶原VI的基因表达水平（OTB后上调）将通过真实的时间聚合酶链反应定量，并通过原位杂交和免疫组织化学确定定位。公共卫生相关性：虽然血液动力学力长期以来被认为是心脏发育的关键因素，但这些力影响心脏发育并导致先天性心脏病（CHD）的机制尚未完全了解。该项目旨在更好地了解血液动力学条件的改变与心脏发育变化之间的关系-这些变化可能导致CHD，甚至使心脏在以后的生活中容易衰竭。更好地了解血流和心脏形成之间的关系最终可以用于预防和治疗冠心病和其他心脏相关疾病。

DESCRIPTION (provided by applicant): About 1% of newborn babies in the US have congenital heart disease (CHD), the leading cause of death among infants. Hemodynamic forces, which are wall shear stresses and pressures generated by the flow of blood, are key factors that regulate heart development and, if abnormal, can lead to CHD. Even when CHD has a genetic cause, altered blood-flow conditions produced by heart defects may lead to additional abnormalities. However, the extent to which alterations in hemodynamics affect cardiac cells and ultimately heart formation is not yet clear. A detailed study of the effects of hemodynamics on heart development requires quantification of hemodynamic forces and of changes in heart growth, morphology and gene expression in an intact, in vivo animal model. The objective of this project is to elucidate the relationship among hemodynamic forces, cardiac growth, heart morphology and expression of selected genes during early developmental stages; with the ultimate goal of understanding the biological mechanisms by which hemodynamics affect heart development. This project will use chick embryos at 2 early stages of development (3 and 3.5 days of a 21-day incubation period - HH18 and HH21), and will focus on the heart outflow tract (OFT), which acts like a primitive valve. Normal blood-flow dynamics will be altered by outflow tract banding, a procedure in which a suture is placed around the OFT, constraining the motion of the OFT wall; and by vitelline-vein ligation, in which a vitelline vein is clipped to obstruct blood flow. The hypothesis is that alterations of hemodynamic forces due to outflow tract banding and vitelline-vein ligation at HH18 lead to measurable, correlated changes in OFT wall morphology, growth and gene expression at HH21. The aims of the project are: Aim 1: Determine in vivo changes in the motion, morphology, and growth of the OFT wall in response to altered hemodynamics. To measure wall motion and geometrical changes in the OFT of chick embryos, the OFT will be imaged using optical coherence tomography. Aim 2: Determine dynamic variations of hemodynamic forces in the OFT and associated expression of selected genes under normal and altered hemodynamic conditions over the cardiac cycle. Blood pressure will be measured using a servo null system. Wall shear stress will be quantified from simulations of finite element models of the OFT. Gene expression levels of integrins and collagen VI (up-regulated after OTB) will be quantified by real time polymerase chain reaction, and localization determined from in situ hybridization and immunohistochemistry. PUBLIC HEALTH RELEVANCE: Although hemodynamic forces have long been recognized as key factors in heart development, the mechanisms by which these forces affect heart development and lead to congenital heart disease (CHD) are not well understood. This project seeks to better understand the relationship between alterations in hemodynamic conditions and changes in heart development - changes that could lead to CHD or even predispose the heart for failure later in life. A better understanding of the relationship between blood flow and heart formation could eventually be used in the prevention and treatment of CHD and other heart-related diseases.