Modeling Inherited Cardiac Pathologies with Organs-on-Chips

Abstract

The heart integrates chemical, electrical, and mechanical signals to form a coordinated, two-stage fluid pump. These systems operate across multiple structure-function levels, and their disruption underlies the leading cause of mortality in the United States. Understanding how these relationships govern normal and pathological cardiac function underlies all therapeutic interventions, yet their mechanistic dissection remains challenging. To address this, we developed vertically integrated cardiac models, or organs-on-chips, to replicate the cardiac microenvironment and inform concepts in heart disease, drug development, and regenerative medicine. Initially, these systems relied on primary rat cardiomyocytes, but to enhance translational relevance, we transitioned to human cell sources. We systematically compared human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) generated through two-dimensional monolayer and three-dimensional embryoid-body differentiation systems using identical Wnt-modulated protocols. Across micropatterned substrates, laminar tissue chips, and anisotropic muscular thin films, we found that 3D bioreactor-derived hiPSC-CMs achieved superior yield, organization, conduction velocity, and contractile performance, establishing them as a scalable, reproducible, and human-relevant replacement for the neonatal rat ventricular myocyte. Using this optimized human model, we next studied catecholaminergic polymorphic ventricular tachycardia (CPVT), the most difficult to treat of the inherited arrhythmia syndromes, to understand why some patients respond to flecainide while others do not. Pathogenic variants in genes governing cardiomyocyte Ca²⁺ handling are associated with CPVT, with as many as 60-80% of cases harboring mutations in the ryanodine receptor 2 (RYR2). In gene-edited and patient-derived hiPSC-CMs carrying the G3946S RYR2 variant, we observed slowed conduction, increased dispersion, and abnormal calcium release events (aCREs), recapitulating CPVT phenotypes. Flecainide suppressed aCREs and normalized calcium handling only in gene-edited cells, mirroring the differential clinical response and suggesting the influence of additional genetic modifiers. These results position hiPSC-CMs as predictive tools for individualized drug response in arrhythmia syndromes. Finally, we extended the application of bioreactor-derived hiPSC-CMs and organ-on-chip technologies to model rare cardiac diseases such as NAA10-related syndrome and Fabry disease and explored termination of CPVT rotors using membrane-targeted molecular photoswitches. We also employed single-cell platforms to study dyad assembly in cardiac hiPSCCMs and combined them with tissue-scale chips to map nanoscale calcium dynamics across RYR2 mutations. Collectively, these studies demonstrate how bioengineered cardiac systems integrating patient genetics, stem cell biology, and microphysiological modeling can elucidate mechanisms of inherited cardiac disorders while accelerating the discovery and testing of emerging therapeutics.