Preclinical development of biological pacemakers

翻译后摘要：慢性右心室（RV）起搏可导致RV起搏诱导的心肌病（RPVIC）。 大约20%的右心室心尖部起搏患者发生右心室起搏后并发症， 功能症状性心力衰竭并不少见，长期预后不良。显然，替代品 RV起搏是理想的，但没有经过验证的RVPIC临床前模型来帮助理解机制 并指导治疗在此，我们试图在猪模型中验证RVPIC的非心动过速起搏模型， 完全心脏传导阻滞，并使用该模型测试生物起搏器（BioP）。基于基因的BioP首先 描述了十多年前;各种构建体的体细胞基因转移（显性负突变体的 内向整流通道[Kir2.1AAA]、野生型HCN通道和转录因子[Tbx18]）都具有 被证明能产生生物活性物质然而，直到最近，体内临床前应用主要是 仅限于高侵入性开胸模型。我们已经开发出一种临床上现实的微创输送 技术，并使用它来创建BioP在猪模型的完全心脏传导阻滞。在这里，我们建议使用这个 这是一种比较两种具有根本不同作用机制的"最终候选"治疗方法的方法。 第一个是野生型离子通道（HCN 2），人工诱导心室心肌细胞的自律性 通过功能重组。我们的目标不是创造一个起搏细胞的忠实复制品，而是 操纵膜通道库的单个组分，以便诱导细胞中的自发放电。 可兴奋但通常静止的细胞。第二种治疗候选物Tbx18的活性成分， 将心室心肌细胞重编程为窦房结（SAN）样起搏细胞（诱导SAN [iSAN]） 细胞）。没有一个决定兴奋性的因素是选择性过度表达的：整个基因表达程序是 改变，导致基本细胞生理学和形态学的变化。本提案利用了上述 上述经皮给药方法进行了简化和验证，在RVPIC的大动物模型中， 翻译到诊所所需的方法。我们将描述和比较起搏有效性， HCN 2和Tbx 18衍生的BioP的安全性，检验iSAN细胞将提供上级变时性的假设 与HCN2相比，一旦确定了最有希望的治疗候选药物，我们将测试 BioP在RVPIC中的应用。我们假设通过希氏束恢复顺行传导 使用BioP起搏可以减弱或逆转与右心室重构相关的不良心室重构。 起搏本研究提案旨在为优化的BioP在临床试验中的测试奠定临床前基础。 有RVPIC风险的患者。

Abstract: Chronic right ventricular (RV) pacing can cause RV pacing-induced cardiomyopathy (RPVIC). Approximately 20% of patients paced from the RV apex develop RVPIC, with a dramatic depression of systolic function. Symptomatic heart failure is not infrequent, and long-term outcomes are poor. Clearly, alternatives to RV pacing are desirable, but there are no validated preclinical models of RVPIC to help understand mechanisms and to guide therapy. Here we seek to validate a non-tachycardic pacing model of RVPIC in a porcine model of complete heart block, and to use this model to test biological pacemakers (BioP). Gene-based BioP were first described more than a decade ago; somatic gene transfer of various constructs (a dominant-negative mutant of the inward rectifier channel [Kir2.1AAA], wild-type HCN channels, and a transcription factor [Tbx18]) have all been shown to create BioP activity. However, until recently, in vivo preclinical applications have been mostly limited to highly-invasive open-chest models. We have developed a clinically-realistic minimally-invasive delivery technique and used it to create BioP in a porcine model of complete heart block. Here, we propose to use this approach to compare two “finalist” therapeutic candidates with fundamentally different mechanisms of action. The first one is a wild-type ion channel (HCN2) that artificially induces automaticity in ventricular cardiomyocytes by functional re-engineering. The goal is not to create a faithful replica of a pacemaker cell, but rather to manipulate a single component of the membrane channel repertoire so as to induce spontaneous firing in an excitable but normally-quiescent cell. The active principle of the second therapeutic candidate, Tbx18, reprograms ventricular cardiomyocytes into sinoatrial node (SAN)-like pacemaker cells (induced SAN [iSAN] cells). No one determinant of excitability is selectively over-expressed: the entire gene expression program is altered, with resultant changes in fundamental cell physiology and morphology. This proposal utilizes the above mentioned percutaneous delivery method to reduce to refine and validate, in a large-animal model of RVPIC, the approaches required for translation to the clinic. We will characterize and compare the pacing efficacy and safety of HCN2 and Tbx18-derived BioP, testing the hypothesis that iSAN cells will provide superior chronotropic support as compared to HCN2. Once designating the most promising therapeutic candidate, we will then test the utility of BioP in the setting of RVPIC. We hypothesize that restoring antegrade conduction by his-bundle pacing with a BioP can attenuate or reverse the adverse ventricular remodeling associated with right ventricular pacing. This research proposal is designed to lay the pre-clinical groundwork for testing of an optimized BioP in patients at risk for RVPIC.