Extracellular Space as Modulator of Gap Junction-Conduction Velocity Relationship

描述（由申请人提供）：心力衰竭期间的心源性猝死是美国和其他西方国家的主要关注点。本研究的广泛长期目标是了解心力衰竭期间异质性间隙连接和细胞外间隙重构的时间进程和影响。最近的研究表明，缝隙连接功能重塑先于传导速度改变大约两周。1由于传导减慢被认为是心脏性猝死的一种机制，缝隙连接和传导速度之间的关系是一个有重大争议和争论的话题，因此必须了解改变这种关系的所有机制。更广泛地说，差距连接-传导速度（Gj-8）关系对于理解缺血、肥大和心力衰竭等疾病中的心脏性猝死很重要，因为这三种疾病都与间隙连接重塑和传导改变有关。 如果细胞外空间显著调节差距连接传导速度关系，如本申请中初步证明的，则调节心脏细胞外空间可能是心力衰竭的先前未开发的治疗靶点。 我们解决这一假设的方法将汇集三种最先进的方法和相关专家。1. Steven Poelzing博士（PI）是量化Cx43-传导速度关系的专家，他将负责证明在Cx43功能下调的药理学和遗传模型中，心室ECS调节Gj-8的关系。2. Mohamed Salama博士（合作者）是细胞结构和细胞外基质的形态学分析专家，他将负责确定Poelzing博士实施的离体干预如何改变细胞大小和ECS。3.最后，James Keener博士，心脏传导数学建模专家，将开发一个心脏传导模型，其中包括电场耦合以及间隙连接耦合。该模型将包括从Poelzing博士和Salama博士收集的所有数据。将针对动物实验中提出的所有干预措施对数学模型进行验证。 公共卫生相关性：在美国每年发生的超过45万例心脏性猝死病例中，室性心律失常占80%。虽然在异常传导和心律失常之间存在确定的关联，但是在诸如心力衰竭和缺血的疾病中传导衰竭的机制仍然未知。有趣的是，心力衰竭和缺血的两个常见发现是细胞外体积增加（即水肿）和细胞间偶联受损。细胞间偶联的作用已经得到了很好的研究，但有争议，细胞外容积的作用直到最近才被很大程度上忽视。本提案的目的是证明细胞外间隙是心源性猝死风险的重要决定因素，因为它调节细胞间耦合和心脏传导之间的关系。调节细胞外间隙代表了心力衰竭和心源性猝死的新治疗靶点。

DESCRIPTION (provided by applicant): Sudden cardiac death during heart failure is a major concern in the United States and other Western Nations. The broad long term objectives of this study are to understand the time course and impact of heterogeneous gap junction and extracellular space remodeling during heart failure. It has been recently demonstrated that gap junction functional remodeling precedes conduction velocity changes by approximately two weeks.1 Since conduction slowing is implicated as a mechanism of sudden cardiac death, and the relationship between gap junctions and conduction velocity is a topic of significant controversy and debate, it is imperative to understand all the mechanisms that modify this relationship. Even more broadly speaking, the gap junction-conduction velocity (Gj-8) relationship is important for understanding sudden cardiac death in diseases such as ischemia, hypertrophy, and heart failure, because all three are associated with gap junctional remodeling and altered conduction. If the extracellular space significantly modulates the gap junction conduction velocity relationship as preliminarily demonstrated in this application, then modulating the cardiac extracellular space may be a previously untapped therapeutic target for heart failure. Our approach to address this hypothesis will bring together three state of the art methodologies and associated experts. 1. Dr. Steven Poelzing (PI), an expert on quantifying the Cx43-conduction velocity relationship, will be responsible for demonstrating that pharmacologically modulating ventricular ECS modulates Gj-8 relationship in pharmacologic and genetic models of Cx43 functional down-regulation. 2. Dr. Mohamed Salama (collaborator), an expert on morphometric analysis of cell structure and the extracellular matrix, will be responsible for determining how the ex-vivo interventions implemented by Dr. Poelzing changes cell size and the ECS. 3. Finally, Dr. James Keener, an expert of mathematically modeling cardiac conduction will develop a model of cardiac conduction that includes electric-field coupling in addition to gap junctional coupling. This model will include all the data collected from Drs. Poelzing, and Salama. The mathematical model will be validated against all interventions proposed in the animal experiments. PUBLIC HEALTH RELEVANCE: Ventricular arrhythmias account for 80% of over 450,000 cases of sudden cardiac death that occur in the U.S. each year. While there is an established association between aberrant conduction and arrhythmias, the mechanisms of conduction failure in diseases such as heart failure and ischemia remain unknown. Interestingly, two common findings in heart failure and ischemia are an increased extracellular volume (i.e. edema) and impairment of intercellular coupling. The role of intercellular coupling is well researched, but controversial, and the role of the extracellular volume has been largely ignored until recently. The purpose of this proposal is to demonstrate that the extracellular space is an important determinant of risk for sudden cardiac death since it modulates the relationship between intercellular coupling and cardiac conduction. Modulating the extracellular space represents a novel therapeutic target for heart failure and sudden cardiac death.