Mechanical Control of Coronary Angiogenesis in Myocardial Adaptation to Ischemia

毛细血管生长不充分;灌注不足和随之而来的缺血可引发 导致从初始代偿性左心室肥大（LVH）进展的事件（响应于 血液动力学挑战）至导致心力衰竭的适应不良。虽然促血管生成策略，如 虽然生长因子和基因治疗的递送是有希望的，但存在局限性和担忧，包括 递送方式、不受控制的血管生成、生长因子的有限半衰期以及对其他器官的影响。 我们的建议采取了另一种方法来检验这一假设，即肥大细胞中的机械力 心室在心力衰竭期间不利地影响冠状动脉血管生成。这项建议的中心目标是 以证明在局部缺血和肥大期间机械力阻碍冠状动脉血管生成。我们 目的是基于以下违反直觉的观察：a）内皮细胞（EC）对于 瞬时受体电位香草酸-4（TRPV 4）在机械敏感性离子通道中表现出增加， 与野生型EC相比的增殖、迁移、Rho活性和管形成（B），两者均离体（主动脉 在TRPV 4KO小鼠中，与对照小鼠相比， WT和c）全局（TRPV 4KO）或内皮特异性（TRPV 4 ECKO）TRPV 4敲除小鼠表现出改善的 心脏功能与心脏纤维化减少和冠状动脉血管生成增加相关， 心肌梗死（MI）或压力超负荷（横主动脉）引起的LVH的WT 缩窄（TAC）。这些发现表明，机械力对血管生成产生抑制作用， 解偶联这种机械作用（内皮TRPV 4机械转导）恢复血管生成， 心脏功能因此，我们的工作假设是TRPV 4通道通过以下途径调节血管生成： 通过雅普调节EC收缩和VEGFR 2运输的Rho活性的调节 TRPV 4的表达增加心肌血管生成，保护心脏免受缺血或压力超负荷的影响， 导致心脏损伤。我们将在以下具体目标中检验这一假设：1）确定结构 TRPV 4内的结构域，其是调节内皮机械敏感性、Rho激活 2）确定TRPV 4整合Rho/雅普和VEGF的分子机制 3）确定内皮TRPV 4的功能意义， 用小分子抑制剂靶向TRPV 4以诱导心肌中的血管生成。为了实现这一点， 我们建议使用先进的体外和体内技术如FRET的创新组合， 对比超声心动图，多光子显微镜，模拟心脏僵硬的工程ECM凝胶， 内皮特异性TRPV 4KO小鼠（常规和诱导型）与MI和TAC模型的联合。我们 拟议的研究将提供深入了解机械力调节冠状动脉的机制， 本发明的目的是提供一种新的血管生成的治疗方法，并且可以为血管生成的治疗方法的开发开辟全新的途径。

Inadequate capillary growth; inadequate perfusion and the consequential ischemia can initiate the sequelae of events causing the progression from an initial compensatory left ventricular hypertrophy (LVH) (in response to hemodynamic challenge) to maladaptation leading to heart failure. Although pro-angiogenic strategies such as delivery of growth factors and gene therapy are promising, there are limitations and concerns, including delivery modalities, uncontrolled angiogenesis, limited half-life of growth factors, and effects on other organs. Our proposal takes an alternative approach to test the hypothesis that mechanical forces in the hypertrophied ventricle adversely affect coronary angiogenesis during heart failure. The central objective of this proposal is to demonstrate that mechanical forces impede coronary angiogenesis during ischemia and hypertrophy. Our objective is based on the counterintuitive observations that a) endothelial cells (EC) null for a mechanosensitive ion channel, Transient Receptor Potential Vanilloid-4 (TRPV4) exhibited increased proliferation, migration, Rho activity, and tube formation compared to wild type EC b) both ex vivo (aortic sprouting) and in vivo (Matrigel, tumor and retinal) angiogenesis is enhanced in TRPV4KO mice compared WT and c) global (TRPV4KO) or endothelial specific (TRPV4ECKO) TRPV4 knockout mice exhibited improved cardiac function that correlated with reduced cardiac fibrosis and increased coronary angiogenesis compared to WTs subjected to LVH induced by either myocardial infarction (MI) or pressure-overload (transverse aortic constriction (TAC). These findings suggest that mechanical forces exert restraint on angiogenesis and uncoupling this mechanical effect (endothelial TRPV4 mechanotransduction) restores angiogenesis and cardiac function. Thus, our working hypothesis is that TRPV4 channels regulate angiogenesis via modulation of Rho activity that regulates EC contraction and VEGFR2 trafficking via YAP and that the absence of TRPV4 increases angiogenesis in myocardium and protects heart from ischemia- or pressure-overload- induced cardiac injury. We will test this hypothesis in the following specific aims 1) To identify the structural domains within TRPV4 that are required for the modulation of endothelial mechanosensitivity, Rho activation and angiogenesis 2) To define the molecular mechanism(s) by which TRPV4 integrates Rho/YAP and VEGF signaling in coronary angiogenesis and 3) To ascertain the functional significance of endothelial TRPV4 and to target TRPV4 with a small molecule inhibitor to induce angiogenesis in the myocardium. To accomplish this, we propose to use an innovative combination of advanced in vitro and in vivo techniques such as FRET, contrast echocardiography, multi-photon microscopy, engineered ECM gels that mimic stiffness of heart, endothelial-specific TRPV4KO mice (conventional and inducible) in conjunction with MI and TAC models. Our proposed studies will provide insights into the mechanism by which mechanical forces regulate coronary angiogenesis and may open entirely new avenues for development of therapeutics for angiogenesis.