Scalable differentiation of human cardiac organoids from iPSCs generates cardiac tissues for cardiac cell therapy.

Rationale: Cardiac organoids have the potential to overcome the limitations of cell-based therapies for myocardial infarction, particularly by improving cell engraftment. Methods: Differentiation of iPSCs into COs with matured-like action potentials and sarcomere lengths was achieved within 20 days. COs comprised cardiomyocytes, cardiac fibroblasts and endothelial cells. Transmission electron microscopy and light microscopy revealed organized sarcomeres and the presence of potential gap junctions. Furthermore, we validate a bioreactor-assisted upscaling strategy to produce the high cell densities necessary for cardiac regenerative medicine. The transplantation of COs into acutely infarcted pig hearts was successfully achieved, serving as a preclinical model for cardiac cell therapy. Results: A modest quantity of 3,500 organoids was used, and notable levels of engraftment into the infarcted area of the pig's heart were observed. In the 8- to 30-day follow-up period, the administration of CO did not result in the occurrence of arrhythmic events. Furthermore, CO-treated pigs exhibited an enhancement in cardiac function and a reduction in scar size when compared to the control group. Spatial transcriptomics demonstrates the downregulation of pro-fibrotic signalling in day 30 implanted COs. Conclusions: In summary, this study presents a novel technology for generating cardiac organoids composed of the primary cell types of functional myocardium, offering a platform for developing cell-based heart therapies.