Novel ion channel approaches to reentrant arrythymias

描述（由申请人提供）：我们提出的研究的总体目标是利用我们对心肌梗死相关室性心动过速再入和心肌梗死相关室性心动过速的病理生理学知识来假设创新的、基于机制的治疗方法。我们的一般假设是，使用成人间充质干细胞（hMSCs）作为平台和/或使用病毒载体的基因治疗可以传递过表达的离子通道基因构建物来预防/抑制这种心律失常。我们提出的5年计划包括：(1)鉴定和测试特定基因构建物在病毒载体和hMSC平台中的过表达对细胞系中特定离子通道表达的影响；(2)利用数学建模、细胞系统和动物模型来测试我们设计的每种基因和细胞治疗方法的作用机制、功效和促心律失常的潜力。我们特别假设基因和细胞疗法可以通过加速传导和/或延长难治性（但不是复极化）来抗心律失常，并在犬心脏原位研究这些可能性。我们的前两个目标（假设）采用新的方法来加速传导。1：非心脏钠通道将失活转移到更多的去极化电位，将提高正常肌细胞的高速率放电钠电流密度，并保持去极化肌细胞的钠电流密度。这将增加动作电位（AP）上冲程速度和传导速度，从而使顺行激活正常化以防止重入性心律失常和/或激活波的“头”抓住“尾”以终止重入性心律失常。2：舒张期K电导的增加应使去极化膜电位恢复正常，并在高刺激频率下增强正常肌细胞的兴奋性。第三种策略是延长相对于AP持续时间（APD）的有效不应期（ERP）。3：在这里，我们假设与APD相比，过表达具有减慢失活动力学的突变hERG应该提高率反应性并延长ERP。这将加速高心率下的传导，同时阻止过早去极化的传播，降低再入的可能性。我们提出的研究的意义在于鉴定新的离子通道结构，通过硅模型和细胞实验对它们进行测试，以了解和微调作用机制；使用创新的方法在细胞系统中施用这些药物，最后在完整的动物身上治疗再入性心律——室性心动过速——这是当今美国发病率和死亡率的主要原因。这些方法的选择性和特异性远远超过药物和消融术，为心律失常的治疗和预防开辟了新的前景。

DESCRIPTION (provided by applicant): The overall objective of our proposed research is to use our knowledge of the pathophysiology of reentry and of myocardial infarct-associated ventricular tachycardia to hypothesize innovative, mechanism-based approaches to therapy Our general hypothesis is that gene therapy using adult human mesenchymal stem cells (hMSCs) as platforms and/or using viral vectors can deliver overexpressed ion channel gene constructs to prevent/suppress this arrhythmia. Our proposed 5-year plan incorporates: (1) identification and testing the effect of overexpression of specific gene constructs in viral vectors and in hMSC platforms to modify specific ion channel expression in cell lines; (2) using mathematical modeling, cell systems, and animal models that previously have been validated by us and others to test the mechanism of action, efficacy and proarrhythmic potential of each gene and cell therapy approach we design. We specifically hypothesize that gene and cell therapies can be antiarrhythmic by speeding conduction and/or prolonging refractoriness (but not repolarization) and study these possibilities in the canine heart in situ. Our first two Aims (stated as hypotheses) employ novel approaches to speed conduction. 1: A non-cardiac Na channel that shifts inactivation to more depolarized potentials will enhance Na current density in normal myocytes firing at high rates and preserve Na current density in depolarized myocytes. This should increase action potential (AP) upstroke velocity and conduction velocity, such that antegrade activation is normalized to prevent reentrant arrhythmias and/or the "head" of the activating wave catches the "tail" to terminate reentrant arrhythmias. 2: Increasing diastolic K conductance should restore depolarized membrane potentials towards normal and enhance excitability for normal myocytes at high stimulation frequencies. The third strategy is to prolong the effective refractory period (ERP) with regard to AP duration (APD). 3: Here, we hypothesize that overexpression of a mutant hERG with slowed deactivation kinetics should improve rate responsiveness and prolong ERP compared to APD. This should speed conduction at high heart rates while blocking propagation of premature depolarizations, reducing the likelihood of reentry. The significance of our proposed research is seen in the identification of novel ion channel constructs, testing them via in silico modeling and then in cell experiments to understand and fine-tune mechanism of action; using innovative means to administer them in cell systems and finally in intact animals to treat a reentrant rhythm - ventricular tachycardia - that is a major cause of morbidity and mortality in the US today. The selectivity and specificity of these approaches far exceed those of drugs and of ablation and open promising new vistas for arrhythmia treatment and prevention.