Engineered Heart Tissues for Advanced Disease Modeling

Abstract

Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) are a powerful, in vitro tool for investigating cardiac pathologies. Although hiPSC-CMs have a relatively immature phenotype compared to primary adult cardiomyocytes, their physiological relevance can be improved by incorporating them into a biomimetic three-dimensional environment to generate engineered heart tissues (EHTs). The EHT platform matures hiPSC-CMs by providing the environmental cues present in the in vivo myocardium while allowing for assessments of cardiac function. Although heart failure is the leading cause of death in patients with Duchenne muscular dystrophy (DMD), a severe, X-linked, neuromuscular disease, the mechanisms underlying the associated dilated cardiomyopathy (DCM) are not completely understood. This is due in part to the lack of suitable animal models of DMD-associated DCM which can accurately reproduce the disease’s progression in human patients. We addressed this deficiency by developing a novel in vitro model of DMD using EHTs generated with hiPSC-CMs which had been edited with CRISPR to lack dystrophin. These dystrophic EHTs recapitulated key aspects of the DMD-associated DCM including impaired contractile function and slower kinetics. Dystrophic EHTs also showed elevated beat rate variability, reduced Ca2+ transients and delayed kinetics, and smaller cardiomyocyte size and sarcomere length. Additionally, we improved our EHT platform by addressing its throughput and lack of regional heterogeneity, two limitations of the system that exist in its current form. To increase the throughput, we designed a miniaturized EHT (mEHT) platform that is compatible with a standard 96-well culture plate. The mEHTs generated on this platform produce measurable, uniaxial, synchronous contractions and have the potential to be used for high throughput screening of cardiomyopathy phenotypes and candidate therapies. We also developed a method for multi-region suspended tissue patterning with collaborators. Using this method, we generated EHTs with localized fibrosis that showed alterations in contraction kinetics and spontaneous beat rates compared to tissues lacking a fibrotic region. Future studies may be able to use spatial heterogenous EHTs for more complex investigations of myocardial development or pathologies.