Improving the Contractile Performance of Human Pluripotent Stem Cell-Derived Cardiomyocytes for Cardiac Cell Therapy

Abstract

Heart disease is the leading cause of death worldwide, and each year over 1 million Americans suffer from a myocardial infarction, with many subsequently developing heart failure. Our labs have worked extensively to develop next-generation therapies for heart failure based upon remuscularizing the scar with stem cell-derived cardiomyocytes. While promising, these immature cells fail to recapitulate the adult cardiomyocyte phenotype and lack the ability to generate meaningful force, which may explain the relatively modest gains in cardiac function seen in most studies to date. Motivated by this challenge, I hypothesized that developing novel strategies to improve the contractile performance of human pluripotent stem cell-derived cardiomyocytes will improve the efficacy of cardiac cell therapy. My thesis work has focused on developing two independent strategies to improve the contractile capabilities of these cells. First, I developed a novel maturation process whereby immature cardiomyocytes begin to recapitulate key structural and functional characteristics of mature adult cardiomyocytes. These cells become larger and more directional, exhibit highly organized intracellular contractile machinery, and demonstrate improved contractility, Ca2+-handling, and action potential characteristics. I then worked to develop a second approach based on the small molecule dATP, which our lab has shown dramatically increases cardiac function by substituting for ATP as the energy substrate for cardiac myosin. Based upon preliminary studies, I hypothesized that like other small metabolites, dATP is capable of crossing gap junctions and diffusing between neighboring cells. Using several independent techniques, I confirmed this phenomenon and subsequently showed that transplanting stem cell-derived cardiomyocytes overexpressing ribonucleotide reductase, the enzyme that synthesizes dATP, dramatically improves global heart function via gap junction-mediated dATP transfer. Based upon these studies, our lab is currently testing both approaches in models of myocardial infarction, with hopes of one day translating these approaches to a future clinical therapy for heart failure.