Intercellular Communication and Cardiac Arrhythmias

描述（由申请人提供）：心脏病通常与恶性室性心律失常的发展相关，并且在美国仍然是死亡的主要原因。不幸的是，导致心律失常发生和维持的潜在机制仍然知之甚少。纤维化与许多形式的心血管疾病有关，被认为是心律失常的主要原因。纤维化通常被认为通过制造电传导的物理障碍间接促进心脏电生理。然而，大量研究表明，肌细胞和成纤维细胞之间的直接电偶联有助于正常和患病心脏的电生理。虽然成纤维细胞和肌细胞表达间隙连接蛋白，但这些细胞类型之间的功能电偶联目前是一个有实质性争论的主题。该项目的长期目标是确定成纤维细胞连接蛋白表达对正常和受伤心脏电生理的贡献。这一目标将通过在成纤维细胞中缺乏连接蛋白异构体的新开发的转基因小鼠和一种新的心脏损伤模型来实现。特异性目的1将确定成纤维细胞连接蛋白表达对正常窦房结、心房和心室电生理特性的贡献。提出的研究将验证成纤维细胞连接蛋白表达有助于正常生理条件下窦房结、心房和心室电生理特性的假设。实验方法将包括对成纤维细胞中缺乏连接蛋白同种异构体的成年和老年小鼠的窦结、心房和心室进行电生理研究和详细的组织学和形态学分析。特异性目的2将确定成纤维细胞连接蛋白表达对损伤心脏组织传导特性的贡献。在这里，我们将验证成纤维细胞连接蛋白表达有助于心脏修复和损伤心脏的传导特性的假设。在损伤后的选定时间点，对成纤维细胞中缺乏Cx43和Cx45的小鼠进行详细的组织学、高分辨率光学制图、微电极记录和心律失常分析。特异性Aim 3将确定心脏损伤后居民和骨髓源性成纤维细胞中连接蛋白表达的贡献。在这篇文章中，我们将验证一种假设，即在常驻和骨髓来源的成纤维细胞中连接蛋白的表达有助于损伤心脏的电生理特性和心律失常动力学。连接蛋白在居民和骨髓来源成纤维细胞中的表达将通过辐射嵌合体来确定。骨髓移植后心脏会受到损伤，并在不同的时间点进行研究。详细的组织学、高分辨率光学成像、微电极记录和心律失常分析将被执行。本应用程序中提出的研究对心律失常的治疗具有广泛的意义，并将显著有助于我们理解健康和受伤心脏的电生理基本原理。

DESCRIPTION (provided by applicant): Heart disease is often associated with the development of malignant ventricular arrhythmias and remains a major cause of mortality in the United States. Unfortunately, the underlying mechanisms responsible for initiation and maintenance of cardiac arrhythmias remains poorly understood. Fibrosis is associated with many forms of cardiovascular disease and is recognized as a major contributing cause of arrhythmias. Fibrosis is classically thought to indirectly contribute to cardiac electrophysiology by creating physical barriers to electrical conduction. However, numerous studies have suggested direct electrical coupling between myocytes and fibroblasts contributes to the electrophysiology of the normal and diseased heart. Although fibroblasts and myocytes express gap junction proteins, functional electrical coupling between these cell types is currently a subject of substantial debate. The long term objectives of this project are determine the contribution of fibroblast connexin expression to the electrophysiology of the normal and injured heart. This objective will be achieved using newly developed transgenic mice that lack connexin isoforms in fibroblasts and a novel cardiac injury model. Specific Aim 1 will determine the contribution of fibroblast connexin expression to the electrophysiological properties of the normal sinus node, atria and ventricles. The studies proposed will test the hypothesis that fibroblast connexin expression contributes to the electrophysiological properties of the sinus node, atria, and ventricles under normal physiological conditions. The experimental approach will include electrophysiological studies and detailed histological and morphological analysis of the sinus node, atria and ventricles of adult and senescent mice that lack connexin isoforms in fibroblasts. Specific Aim 2 will determine the contribution of fibroblast connexin expression to the conduction properties of injured cardiac tissue. Here, we will test the hypothesis that fibroblast connexin expression contributes to cardiac repair and the conduction properties of injured hearts. Detailed histology, high resolution optical mapping, microelectrode recordings, and arrhythmia analysis will be performed in mice that lack Cx43 and Cx45 in fibroblasts at selected time points after injury. Specific Aim 3 will determine the contribution of connexin expression in resident and bone marrow derived fibroblasts following cardiac injury. In this Specific Aim, we will test the hypothesis that connexin expression in resident and bone marrow derived fibroblasts contributes to the electrophysiological properties and arrhythmia dynamics of injured hearts. The contribution of connexin expression in resident and bone marrow derived fibroblasts will be determined using radiation chimeras. Hearts will be injured after bone marrow transplantation and studied at different time points. Detailed histology, high resolution optical mapping, microelectrode recordings, and arrhythmia analysis will be performed. The studies proposed in this application have wide ranging implications for the treatment of cardiac arrhythmias and will significantly contribute to our understanding of the basic principles that govern electrophysiology in healthy and injured hearts.