Assessing myofilament phenotype and contractile response to pharmacotherapies in a human induced pluripotent stem cell cardiomyocyte (hiPSC-CM) model of hypoplastic left heart syndrome (HLHS)

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Project Summary Despite tremendous advances in surgical technique and post-operative care, children with hypoplastic left heart syndrome (HLHS) remain at lifelong risk for systolic failure of the systemic right ventricle (RV). In HLHS patients, traditional adult heart failure medications have been overall ineffective in preventing pathologic cardiac remodeling or preserving contractile function. Thus, once children with HLHS develop heart failure symptomatology secondary to decreased cardiac function, heart transplantation is often the only long-term therapeutic option. The central hypothesis of this proposal is that HLHS cardiomyocytes have inherent alterations at the level of the myofilament that may confer a heart failure predisposition and alter the contractile response to medical heart failure therapies. Preliminary data demonstrates abnormalities in calcium sensitivity and decreased cardiac troponin I phosphorylation in cardiomyocytes from HLHS subjects with end-stage heart failure. Nevertheless, there is a need to expand upon these studies utilizing a HLHS model system to further evaluate the impact of these myofilament changes. Therefore, the goal of this proposal is to develop a human induced pluripotent stem cell cardiomyocytes (hiPSC-CM) model derived from HLHS subjects to define the myofilament contribution to the contractile abnormalities present in HLHS and assess the impact of myofilament differences on the contractile response to HF therapies. Patient-specific HLHS hiPSC-CM will be generated from 3 HLHS subjects with end-stage heart failure, and the myofilament contractile phenotype will be defined through mechanical studies of skinned hiPSC-CM, quantification of myofilament protein isoforms, and assessment of myofilament post-translational modifications. These findings will be paired with the myofilament phenotype demonstrated in the explanted, HLHS heart tissue from the same subject. Additionally, myofilament assessments will be performed following treatment of HLHS hiPSC-CM with current and emerging HF pharmacotherapies in order to directly measure the consequences of drug therapy on the HLHS myofilament. Ultimately, augmenting mechanistic understanding of the contractile dysfunction present in HLHS cardiomyocytes has the potential to improve outcomes for HLHS patients by informing an accurate HF risk- stratification paradigm. Furthermore, prioritizing an HLHS-specific appraisal of the contractile response to pharmacotherapies may result in personalized pharmacologic strategies to preserve systemic RV function.