Abstract 14682: Blunting of Electrophysiological Effects of Isoproterenol in a Tissue Model of Arrhythmogenic Cardiomyopathy

IntroductionArrhythmogenic cardiomyopathy (ACM) is a genetic disorder, which results in non-ischemic cardiomyopathy and an increased risk of sudden cardiac death. Mutations in Desmoglein-2 (DSG2) have been implicated in ACM, and defects in DSG2 localization have been shown to alter the localization and function of several ion channels and cause arrhythmia susceptibility. Isoproterenol is known to induce arrhythmia in ACM patients and accelerate disease progression in animals, but a recent report suggests that adrenergic stimulation also increases DSG2 trafficking to the cell membrane in cardiomyocytes. We used human induced pluripotent stem cells (hiPSC) from an ACM patient to investigate DSG2 as a mechanistic link between adrenergic signaling and ACM pathophysiology.MethodsWe generated a novel hiPSC line from a patient carrying a frameshift mutation in DSG2, along with a CRISPR-Cas9-corrected isogenic control line. hiPSCs were differentiated into cardiomyocytes (hiPSC-CMs) using established protocols, and plated to form syncytial, beating monolayers. We used immunostaining, time-lapse microscopy and optical voltage mapping to analyze the morphology and electrophysiological behavior of the cell lines, at baseline and in response to several hour-long isoproterenol treatment.ResultsWestern blot and immunostaining showed that mutant hiPSC-CMs contained more DSG2 immunoreactive protein compared to the control line, but expressed less full-length DSG2 with less cell membrane localization. Cultured in monolayers, mutant hiPSC-CMs displayed higher spontaneous beat rates, shortened action potentials and faster upstrokes as compared to isogenic control. Interestingly, the increase in conduction velocity and upstroke velocity elicited by isoproterenol in the isogenic control line was not apparent in the disease cells. And while isoproterenol caused beat rate acceleration in both lines, the effect was much less pronounced in the mutant hiPSC-CMs.ConclusionsThese results suggest that an ACM-associated DSG2 mutation prevents isoproterenol-induced increase in cellular excitability and supports the hypothesis that altered DSG2 localization could play a role in the arrhythmia risk of adrenergic stimulation in ACM patients.