hiPSC Modeling of Restrictive Cardiomyopathy for Drug Testing

限制性心肌病(RCM)是一种常染色体显性遗传性心肌病，其特点是 舒张期功能障碍但正常或接近正常的心室内径、室壁厚度和收缩功能。 RCM患者的治疗选择更少，结果明显比其他形式的RCM患者差 心肌病。这在儿科RCM中尤其如此，对于RCM来说，唯一确定的治疗方法是心脏 移植，通常在儿童时期。 引起RCM的突变主要存在于肌节，肌节是心肌细胞的收缩单位。 由于这种功能障碍是心肌细胞固有的，人类在体外诱导的多能干细胞(HiPSC)来源 心肌细胞非常适合于RCM的建模和治疗策略的评估。然而，到目前为止， 目前尚无HiPSC来源的RCM心肌细胞模型的研究报道。因此，这项提议， 寻求使用基于HiPSC的家族性、儿科RCM模型来阐明病理特征，确定 某些突变是否会导致不同的致病机制，并评估 两种新批准的药物在治疗其他形式的心脏舒张性功能障碍方面显示出希望 疾病。 初步研究产生了一个患者衍生的、基于HiPSC的RCM模型，该模型由心脏基因突变引起 肌钙蛋白T(TnNT2)。我们发现，力量产生的钙敏感性增加和纤维化的增加可能 疾病发病机制的基础。除了TNNT2，其他肌节突变的突变也会导致严重的 儿科RCM，其中一些被认为是通过不同的病理生理机制诱发疾病。 因此，本方案的目的1是建立由不同基因变异引起的RCM的HiPSC模型。 确定不同的和共同的收缩功能障碍的机制。我们的假设是RCM是一种 异质性疾病和不同的基因变异特异性机制汇聚在一起，引发了显著的临床特征 RCM的特点。 AIM 2独立评估马卡班、美卡比利和钠-葡萄糖共转运体-2抑制剂 (SGLT2i)用于使用HiPSC模型治疗RCM收缩功能障碍的疗效。Mavacamten和 SGLT2i最近被批准用于其他形式的心脏病。Mavacamten，通过减少肌动蛋白-肌球蛋白交叉- 桥接，可能对RCM的治疗有效，不受遗传病因的影响。相比之下，SGLT2 抑制物(SGLT2i)，通过抑制多种蛋白质和降低细胞内[Ca~(2+)]来发挥作用 心肌细胞对基因突变可能表现出选择性，这取决于致病机制。刻画 RCM的基本发病机制和候选治疗方法的疗效评估是关键的一步 以改善对这一具有挑战性的疾病的管理。

Restrictive Cardiomyopathy (RCM) is an autosomal dominant form of cardiomyopathy characterized by profound diastolic dysfunction yet normal or near-normal ventricular dimensions, wall thickness, and systolic function. RCM patients have fewer treatment options and notably poorer outcomes than those with other forms of cardiomyopathy. This is especially true in pediatric-onset RCM, for which the only definitive therapy is heart transplantation, often in childhood. Mutations that cause RCM predominate in the sarcomere, which is the contractile unit of cardiac muscle cells. Since the dysfunction is intrinsic to cardiomyocytes, human in vitro induced pluripotent stem cell (hiPSC)-derived cardiomyocytes are well-suited to modeling the RCM and evaluating therapeutics strategies. To date, however, there are no reported investigation of hiPSC-derived cardiomyocyte models of RCM. This proposal, therefore, seeks to use hiPSC-based models of familial, pediatric RCM to elucidate pathological features, determine whether certain mutations cause distinct pathogenetic mechanisms, and evaluate the therapeutic potential of two newly approved drugs that have shown promise for treating diastolic dysfunction in other forms of heart disease. Preliminary studies generated a patient-derived, hiPSC-based model of RCM caused by mutations in cardiac Troponin-T (TNNT2). We found that heightened Ca2+ sensitivity of force generation and increased fibrosis might underlie disease pathogenesis. Besides TNNT2, mutations in other sarcomeric mutations also cause severe pediatric RCM, and some are hypothesized to induce disease by distinct pathophysiological mechanisms. Therefore, AIM 1 of this proposal is to develop hiPSC models of RCM caused by diverse gene variants, and identify distinct and common mechanisms of contractile dysfunction. Our hypothesis is that RCM is a heterogeneous disease and distinct gene variant-specific mechanisms converge to elicit hallmark clinical features of RCM. Independently, AIM 2 is to evaluate mavacamten mecarbil and sodium-glucose cotransporter-2 inhibitors (SGLT2i) for efficacy in treating contractile dysfunction in RCM using the hiPSC models. Mavacamten and SGLT2i are newly approved for other forms of heart disease. Mavacamten, by decreasing actin-myosin cross- bridging, might be therapeutically effective for RCM independently of genetic etiology. In contrast, SGLT2 inhibitors (SGLT2i), which operate by inhibiting multiple proteins and decrease intracellular [Ca2+] in cardiomyocytes, might show selectivity for gene mutation depending on pathogenic mechanism. Characterizing the basic disease mechanisms of RCM and evaluating the efficacy of candidate therapeutics is a critical step towards improving management of this challenging disease.