Egm 3 medium

hPSC-CMs (iCell Cardiomyocytes, Cellular Dynamics) were cultured according to the manufacturer’s protocol. iCell Cardiomyocytes (donor 01434) were used for all experiments. Briefly, hPSC-derived CMs were plated on a 0.1% gelatin coated 6 well plates in iCell Cardiomyocyte Plating Medium (CDI) at a density of 3–4 × 10⁵ cells per well and incubated at 37 °C in 5% CO₂ for 4 days. 2 days after plating, the plating medium was replaced with iCell Cardiomyocyte maintenance medium (CDI). After 4 days of monolayer preculture, cardiomyocytes were lifted using trypLE Express (Gibco Life Technologies) and prepared for organoid fabrication. Human cardiac ventricular fibroblasts (CC-2904, 0000401462, Lonza) were cultured in FGM-2 medium (Lonza), at passages 3–4 for organoid fabrication. Human umbilical vein endothelial cells (HUVECS; C2519A) were cultured in EGM-3 medium (Lonza) and were used passages 2–3 for organoids fabrication. Human adipose-derived stem cells (hADSCs; PT-5006, 0000410257, Lonza) were cultured in low-glucose Dulbecco’s modified Eagle’s medium supplemented with 10% FBS and 1% Penicillin-streptomycin, 1% glutamine and 1% antimycin (Gibco Life Technologies). hADSCs were used at passages 3–5 for organoid fabrication.