Molecular Mechanisms of Stretch-Induced Electrical Remodeling in the Heart

项目摘要 室性快速性心律失常是心源性猝死的主要原因。虽然机械负荷的改变导致肥大和失代偿性心力衰竭是致死性室性心律失常的最强大的危险因素之一，但心脏中机械和电功能障碍的机制仍然知之甚少。因此，SCD仍然是一个尚未解决的重大公共卫生问题。申请者S导师最近报道，心室电重构(VER)是由局部机械拉伸通过机械-电反馈机制触发的，是一种响应激活序列变化的心室肌电生理特性的持续变化。来自他的实验室的初步数据显示，在起搏犬心脏的高应变心肌中，GQ/11蛋白偶联机械受体途径的表达发生了显著变化。考虑到该通路在心脏机械转导和压力超负荷性肥厚中的突出作用，它是解释VER的理想候选。申请者假设心肌拉伸通过增强GQ/11激活而导致VER和心律失常。在凯斯西储大学目前的职位上，他设计了一种斑马鱼全心拉伸系统，该系统将高精度拉伸和高分辨率电生理学与高通量基因操作结合在一起，在完整的脊椎动物心脏中进行。野生型和转基因斑马鱼胚胎心脏的心室在野外起搏过程中通过附加的10微米直径的细碳纤维拉伸几个小时，以诱导持续的VER。拉伸后，使用高分辨率荧光成像来确定VER。申请人S的初步数据显示，他的斑马鱼模型再现了他的导师S犬模型的关键电生理表型。申请者将使用他的斑马鱼模型来确定 (1)诱发VER的关键生物力学和生物电学条件， (2)牵张诱导的VER如何增加心脏对心律失常的易感性 (3)牵张诱导VER的分子信号机制。 这些研究将有助于确定预防和治疗心脏病患者的VER和相关心律失常的新治疗目标。通过K99/R00奖项对该项目的支持将在候选人S的职业发展中发挥关键和必要的作用。他的近期目标是： (1)通过额外的强化指导、技术培训和广泛的智力发展，巩固他的研究经验，这将直接源于这项提议。申请者在生物物理学和实验模型开发方面有相当丰富的经验，但需要在分子和综合生物学方面进行额外的培训，以发展心血管生物学的独立学术生涯。 (2)在5年奖励期结束前成功获得R01资金。 高度结构化的职业发展计划是这项建议的内在组成部分，旨在极大地促进候选人S长期职业目标的实现：建立一个充满活力的、独立资助的跨学科研究计划，将生物医学工程、高通量遗传学和高分辨率电生理学相结合，研究心律失常的分子机制。

Project Summary Ventricular tachyarrhythmias are a principal cause of sudden cardiac death (SCD). While altered mechanical loading leading to hypertrophy and decompensated heart failure is one of the most powerful risk factors for fatal ventricular arrhythmias, the mechanisms that link mechanical to electrical dysfunction in the heart remain poorly understood. Consequently, SCD remains a major unresolved public health problem. The applicant¿s mentor recently reported that ventricular electrical remodeling (VER), a persistent change in the electrophysiological properties of ventricular myocardium in response a change in activation sequence, is triggered by local mechanical stretch via a mechano-electrical feedback mechanism. Preliminary data from his laboratory revealed significant expression changes in the Gq/11-protein coupled mechanoreceptor pathway in high-strain myocardium from paced canine hearts. Considering the prominent roles of this pathway in cardiac mechanotransduction and pressure-overload hypertrophy, it is an ideal candidate to explain VER. The applicant hypothesizes that myocardial stretch causes VER and arrhythmias via enhanced Gq/11 activation. In his current position at Case Western Reserve University, he engineered a zebrafish whole-heart stretch system that combines high-precision stretch and high-resolution electrophysiology with high-throughput gene manipulation in an intact vertebrate heart. Ventricles from wild-type and genetically modified zebrafish embryo hearts are stretched during field-pacing for several hours via attached 10-micrometer-diameter thin carbon fibers to induce persistent VER. Following stretch, VER is determined using high-resolution fluorescence imaging. The applicant¿s preliminary data show that his zebrafish model reproduces the key electrophysiological phenotypes of his mentor¿s canine model of VER. The applicant will use his zebrafish VER model to determine (1) the key biomechanical and bioelectrical conditions that induce VER, (2) how stretch-induced VER enhances the susceptibility of the heart to arrhythmias and (3) the molecular signaling mechanisms that cause stretch-induced VER. These studies will help identify new therapeutic targets for preventing and treating VER and associated arrhythmias in patients with heart disease. Support for this project via a K99/R00 award would play a pivotal and requisite role in the candidate¿s career development. His immediate goals are: (1) to solidify his research experience through additional intensive mentorship, technical training and broad intellectual development that will result directly from this proposal. The applicant has considerable experience in biophysics and experimental model development, but requires additional training in molecular and integrative biology to develop an independent academic career in cardiovascular biology. (2) to successfully obtain R01 funding by the end of the 5-year award period. A highly structured career development plan is an intrinsic component of this proposal and is designed to greatly enhance the accomplishment of the candidate¿s long-term career goal: to establish a vibrant, independently funded, interdisciplinary research program that combines biomedical engineering, high-throughput genetics and high-resolution electrophysiology to study the molecular mechanisms of cardiac arrhythmias.