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

描述（由申请人提供）：项目概述约1%的新生儿患有先天性心脏病（CHD），这是儿童死亡的主要原因。大多数CHD病例被认为没有遗传原因。其他因素，如胚胎和胎儿阶段的异常血流可导致心脏畸形，从而通过知之甚少的机制导致CHD。该项目将阐明早期心脏适应（细胞外基质蛋白沉积，细胞增殖和凋亡率的变化）， 改变的血流条件和这些适应在体内动物模型中发育后期的进展。该项目将使用鸡胚作为心脏发育的模型，重点是心脏流出道（OFT），它产生了室间隔和半月瓣。血流对心脏壁施加机械刺激（应力/应变），可以使用上一个奖项期间开发的技术进行量化。在第3天（HH 18），使用外科手术干预改变鸡胚中的正常血流，通过用外科缝线收缩或结扎血管来改变血压和剪切应力。目的1：确定血流动力学干预后机械刺激的早期变化。将使用光学相干断层扫描（OCT）成像和OFT的计算模型量化OFT必须适应的应力/应变的初始变化（干预后2小时内）。目的2：确定心脏对血流动力学干预引起的异常机械刺激的早期适应。将使用组织学和免疫组织化学技术确定干预后24小时心脏OFT中细胞外基质沉积和细胞增殖和凋亡的变化（相对于对照），并将其并入心脏适应图谱中。还将确定机械刺激分布在局部驱动适应模式的程度。目的3：阐明早期心脏适应改变血流动力学刺激的进展。介入24小时后，将通过移除手术缝线逆转手术介入。然后使用组织学、免疫组织化学和超声数据确定血流动力学“恢复”后1、3和6天（胚胎第5、7和10天）的早期适应进展。该研究将阐明早期心脏适应可逆的条件（心脏继续正常发育）和机械刺激阈值，超过该阈值，可逆性不再可能。

DESCRIPTION (provided by applicant): Project Summary About 1% newborn babies have congenital heart disease (CHD), the leading cause of death among children. The majority of CHD cases are believed not to have a genetic cause. Other factors, such as abnormal blood flow during embryonic and fetal stages can lead to heart malformations and thus CHD through poorly understood mechanisms. This project will elucidate early cardiac adaptations (changes in the rates of extracellular-matrix protein deposition, cell proliferation and apoptosis) in response to altered blood flow conditions and the progression of these adaptations at later stages of development in an in vivo animal model. The project will use chick embryos as models of cardiac development, focusing on the heart outflow tract (OFT), which gives rise to the intraventricular septum and semilunar valves. Blood flow exerts mechanical stimuli (stresses/strains) on the walls of the heart that can be quantified using techniques developed during the previous awarded period. Normal blood flow in chick embryos will be altered at day 3 (HH18) using surgical interventions that change blood pressure and shear stresses by constricting or ligating vessels with surgical sutures. Aims are: Aim 1: Determine early changes in mechanical stimuli in response to hemodynamic interventions. Initial changes (within 2 hrs of intervention) in stresses/strains to which the OFT has to adapt will be quantified using optical coherence tomography (OCT) imaging and computational models of the OFT. Aim 2: Determine early cardiac adaptations to abnormal mechanical stimuli induced by hemodynamic interventions. Changes (with respect to controls) in extracellular matrix deposition and cellular proliferation and apoptosis in the heart OFT 24hrs after intervention will be determined using histology and immunohistochemistry techniques, and incorporated into a cardiac adaptation atlas. The extent to which adaptation patterns are locally driven by distributions of mechanical stimuli will also be determined. Aim 3: Elucidate the progression of early cardiac adaptations to altered hemodynamic stimuli. After 24hrs of intervention, the surgical interventions will be reversed by removing surgical sutures. The progression of early adaptations 1, 3, and 6 days after hemodynamic 'restoration' (embryonic days 5, 7, and 10) will then be determined using histology, immunohistochemistry, and ultrasound data. The study will elucidate the conditions under which early cardiac adaptations are reversible (hearts continue to develop normally) and the thresholds of mechanical stimuli beyond which reversibility is no longer possible.