Novel ion channel approaches to reentrant arrythymias

描述(申请人提供)：我们建议进行的研究的总体目标是利用我们对折返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，以成人间充质干细胞(HMSCs)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结构，以预防/抑制这种心律失常。我们提出的五年计划包括：(1)识别和测试特定基因在病毒载体和hMSC平台中过表达的效果，以改变细胞系中特定的离子通道表达；(2)使用数学模型、细胞系统和动物模型来测试我们设计的每个基因和细胞治疗方法的作用机制、有效性和诱发心律失常的潜力。我们特别假设基因和细胞疗法可以通过加速传导和/或延长不稳定(但不是复极)来抗心律失常，并在犬心脏原位研究了这些可能性。我们的前两个目标(作为假设)使用新的方法来加速传导。1：非心源性钠通道使去极化电位的失活转移到更多的去极化电位，将增加正常心肌细胞高频率放电的钠电流密度，并维持去极化心肌细胞的钠电流密度。这应该会增加动作电位(AP)的上搏速度和传导速度，从而使前向激活正常化，以防止折返性心律失常和/或激活波的“头”抓住“尾”以终止折返性心律失常。2.增加舒张期钾电导可使去极化的膜电位恢复正常，增强正常心肌细胞在高刺激频率下的兴奋性。第三种策略是延长AP持续时间的有效不应期(ERP)。3：在这里，我们假设过表达具有缓慢失活动力学的突变的HERG应该比apd更好地提高速率反应和延长ERP。这应该会加快高心率时的传导速度，同时阻止过早去极化的传播，降低再入的可能性。我们拟议的研究的意义在于识别新的离子通道结构，通过电子建模测试它们，然后在细胞实验中了解和微调作用机制；使用创新的方法在细胞系统中使用它们，最后在完整的动物身上治疗折返性心律-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.