Mechanisms driving cardiac dysfunction in Autosomal Dominant Polycystic Kidney Disease

Cardiovascular disease is a major cause of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Characterized by progressive renal dysfunction, ADPKD imposes very significant healthcare and economic burdens. It has commonly been assumed that progressive renal impairment promotes cardiac disease; however, our preliminary data suggest that cardiac dysfunction originates in cardiomyocytes and manifests prior to renal failure in ADPKD. Recent clinical evidence supports our findings by showing that ADPKD patients exhibit ventricular dysfunction before the onset of renal failure, even in non-hypertensive individuals. Mutations in the gene encoding Polycystin-1 (PC1) occur in 85% of patients and are responsible for the most severe cases. Importantly, PC1 is expressed in cardiomyocytes, yet its role(s) there is(are) poorly understood. We propose that the mutant PC1 – in a cardiomyocyte-autonomous fashion – initiates and drives heart disease in ADPKD, independent of renal failure. Our data show that PC1 cardiomyocyte-specific deletion promotes systolic and diastolic dysfunction in mice. Furthermore, using a mouse model harboring a clinically established ADPKD-causing PC1 mutation (RC allele), we provide evidence of impaired calcium-cycling and contractility at the cardiomyocyte level, which occur before the onset of renal failure. Heterozygous RC/+ young mice manifest alterations in calcium handling/contractility in isolated cardiomyocytes, which correlate with reduced left ventricular global longitudinal strain and diastolic dysfunction. We discovered that PC1 regulates action potential duration via Kv channel current regulation. PC1 ablation shortens action potential duration and impairs both calcium transients and contractility in cardiomyocytes. Additionally, PC1 deletion impairs sarcoplasmic reticulum (SR) calcium loading through reduced SR calcium-ATPase (SERCA) activity. These data have led us to hypothesize that ADPKD-causing PC1 mutations disrupt PC1 actions in cardiomyocytes, impair cardiac function and predispose the heart to hypertension-induced heart failure, independent of renal dysfunction. To test this hypothesis, we propose three aims: 1) determine how PC1 mutations affect action potentials and Kv channel activity and impinge on calcium handling and contractility. 2) elucidate mechanisms whereby PC1 regulates SR calcium loading and SERCA to maintain cardiomyocyte function and test the impact of ADPKD mutations in PC1 on these events. 3) determine in vivo whether alterations in PC1 signaling in cardiomyocytes drive cardiac dysfunction and predispose the heart to hypertension-induced heart failure. Completion of our studies will provide paradigm-shifting information regarding the role of cardiomyocyte-autonomous events driving heart disease in ADPKD, the leading cause of death in these patients.