FRESH™ 3D Bioprinted Cardiac Tissue, a Bioengineered Platform for in vitro Toxicology and Pharmacology

There is critical need for a predictive model of human cardiac physiology in the drug development process for assessment of compound toxicology and pharmacology. In vitro two-dimensional monolayer culture of cardiomyocytes provides biochemical and cellular readouts, and in vivo small and large animal models provide information on systemic cardiovascular response. However, there remains a significant gap in these models due to an incomplete recapitulation of adult human cardiovascular physiology, which results in more difficult safety interpretations. Recent efforts in developing in vitro models from engineered heart tissues have demonstrated potential for bridging this gap using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) in a three-dimensional tissue structure. Here we advance this paradigm by implementing FRESH™ 3D bioprinting to build human cardiac tissues in a medium throughput, well-plate format with controlled tissue architecture, tailored cellular composition, and native-like physiological function, specifically in its adrenergic agonist drug response. To do this, we combined hiPSC-CMs, endothelial cells and fibroblasts in a cellular bioink and FRESH™ 3D bioprinted this mixture in the format of a thin tissue strip stabilized on a tissue fixture. Our results confirmed that FRESH™ 3D bioprinted cardiac tissues could be fabricated directly in a 24-well plate format, were composed of dense and highly aligned hiPSC-CMs at >600 million cells/mL, and within 14 days demonstrated reproducible calcium transients and fast conduction velocity of ∼25 cm/s. Interrogation of these cardiac tissues with the ß-adrenergic receptor agonist isoproterenol showed native-like positive chronotropic and inotropic responses, a combination of responses that is not typically observed in 2D monolayer models or standard 3D engineered heart tissue approaches. These results confirm that FRESH™ 3D bioprinted cardiac tissues represents a novel in vitro platform that enables early in vitro pharmacology and toxicology screening. ### Competing Interest Statement The authors have declared no competing interest.