Abstract 12201: Dissecting the Protective Effect of Phosphodiesterase 3A Hyperactivity on the Heart Using Single Nuclei Sequencing and Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Abstract

Mutations causing hyperactivity of phosphodiesterase 3A (PDE3A) lead to autosomal dominant hypertension with brachydactyly type E. Affected patients suffer from profoundly increased blood pressure and, if untreated, die from stroke at the age of 50 years. Surprisingly, the hearts of affected individuals show little signs of hypertrophic responses to these conditions, indicating a beneficial effect of PDE3A hyperactivity on the damaging mechanisms of the heart. PDE3A inhibition was previously tested as a treatment for heart failure. While PDE3A inhibitors lead to short term positive inotropy, treatment with these drugs decreases overall survival of heart failure patients, underlining the importance of PDE3A in the heart. As arterial hypertension is a major risk factor for cardiovascular disease and proves to be a major burden on the healthcare system, dissecting the mechanisms underlying the protective effect of PDE3A can open new paths to preventing and treating heart failure. We hypothesize that PDE3A activation protects the heart from the detrimental effects of high blood pressure via spatially distinct regulation of cAMP levels through its different isoforms, leading to an altered calcium handling of cardiomyocytes. We are focusing on two mutations causing PDE3A hyperactivity, one in a regulatory hotspot the other in the catalytic domain. Using single nuclei sequencing of left ventricles of rats, genetically engineered to recapitulate the human mutations, we are dissecting the differences in the cell type-specific gene regulatory response to high blood pressure compared to the wildtype. To follow up in a human model system, we used genome editing to introduce the mutations of interest into human induced pluripotent stem cells (hiPSC). hiPSC lines containing PDE3A mutations as well as isogenic matched control hiPSCs were differentiated to generate hiPSC-derived cardiomyocytes (hiPSC-CMs). Preliminary data from a well-established 2D system show significantly altered calcium handling of PDE3A-mutant hiPSC-CMs. Performing RNA-sequencing, calcium imaging and cAMP measurements in isogenic hiPSC-CMs, we are functionally characterizing the effect of PDE3A activity on cardiomyocyte profile and physiology to a high resolution.