Intercellular Communication and Cardiac Arrhythmias

描述(申请人提供)：心脏病通常与恶性室性心律失常的发展有关，在美国仍然是死亡的主要原因。不幸的是，引发和维持心律失常的潜在机制仍然知之甚少。纤维化与多种形式的心血管疾病有关，并被认为是导致心律失常的主要原因。传统上认为，纤维化通过对电传导造成物理障碍而间接促进心脏电生理。然而，大量研究表明，心肌细胞和成纤维细胞之间的直接电耦合有助于正常和疾病心脏的电生理。尽管成纤维细胞和肌细胞表达缝隙连接蛋白，但这些细胞类型之间的功能性电耦合目前是一个重要的争论主题。该项目的长期目标是确定成纤维细胞连接蛋白的表达对正常和受损心脏的电生理的贡献。这一目标将利用新开发的在成纤维细胞中缺乏连接蛋白亚型的转基因小鼠和一种新的心脏损伤模型来实现。具体目标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。所提出的研究将检验这一假设，即成纤维细胞连接蛋白的表达有助于在正常生理条件下窦房结、心房和脑室的电生理特性。实验方法将包括电生理研究，以及对成纤维细胞中缺乏连接蛋白亚型的成年和衰老小鼠的窦房结、心房和脑室进行详细的组织学和形态分析。特异目的2将确定成纤维细胞连接蛋白表达对受损心脏组织传导特性的贡献。在这里，我们将检验成纤维细胞连接蛋白表达有助于心脏修复和受损心脏传导特性的假设。详细的组织学、高分辨率光学标测、微电极记录和心律失常分析将在损伤后选定的时间点对成纤维细胞中缺乏Cx43和Cx45的小鼠进行。特异目的3将确定连接蛋白在心脏损伤后常驻和骨髓来源的成纤维细胞中的表达。在这个特定的目标中，我们将检验一种假设，即连接蛋白在常驻和骨髓来源的成纤维细胞中的表达有助于损伤心脏的电生理特性和心律失常动力学。将使用放射嵌合体来确定常驻和骨髓来源的成纤维细胞中连接蛋白表达的贡献。骨髓移植后心脏会受到损伤，并在不同的时间点进行研究。将进行详细的组织学、高分辨率光学标测、微电极记录和心律失常分析。本申请中提出的研究对心律失常的治疗具有广泛的意义，并将极大地有助于我们理解支配健康和受伤心脏的电生理学的基本原理。

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.