hiPSC Modeling of Restrictive Cardiomyopathy for Drug Testing

限制性心肌病（RCM）是一种常染色体显性形式的心肌病，其特征是严重的心肌梗死。 舒张功能障碍，但心室尺寸、室壁厚度和收缩功能正常或接近正常。 RCM患者的治疗选择较少，并且与其他形式的 心肌病这在儿科发作的RCM中尤其如此，其唯一确定的治疗是心脏 移植，通常在儿童时期。 导致RCM的突变在肌节中占主导地位，肌节是心肌细胞的收缩单位。 由于功能障碍是心肌细胞固有的，因此人体外诱导的多能干细胞（hiPSC）衍生的 心肌细胞非常适合于建模RCM和评估治疗策略。然而，迄今为止， 没有报道对RCM的hiPSC衍生的心肌细胞模型的研究。因此，这项建议， 旨在使用基于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发病机制，并评估 两种新批准的药物显示出治疗其他形式心脏舒张功能障碍的前景， 疾病 初步研究产生了一种源自患者的基于hiPSC的由心脏基因突变引起的RCM模型。 肌钙蛋白-T（TNNT 2）。我们发现力产生的Ca 2+敏感性增加和纤维化增加可能 构成疾病发病机制的基础。除了TNNT 2，其他肌节突变中的突变也引起严重的 儿童RCM，和一些被假设为通过不同的病理生理机制诱导疾病。 因此，本提案的目的1是开发由不同基因变体引起的RCM的hiPSC模型， 识别收缩功能障碍的不同和共同机制。我们的假设是，RCM是一个 异质性疾病和不同基因变体特异性机制汇聚在一起， RCM的特点。 AIM 2旨在独立评价mavacamten mecarbil和钠-葡萄糖协同转运蛋白-2抑制剂 （SGLT 2 i）使用hiPSC模型治疗RCM收缩功能障碍的疗效。Mavacamten和 SGLT 2 i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，可能是治疗有效的RCM独立的遗传病因。相比之下，SGLT 2 抑制剂（SGLT 2 i），通过抑制多种蛋白质并降低细胞内[Ca 2 +] 心肌细胞，可能显示出基因突变的选择性，这取决于致病机制。表征 RCM的基本发病机制和评价候选治疗药物的疗效是关键步骤 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.