Whole hearts were minced and placed in a digestion solution composed of HBSS (with Ca/Mg), 5% FBS, 2mM EDTA, Collagenase D (450 UI/mL), DNase I (60 UI/mL),and Hyaluronidase (60 UI/mL). The tissue was digested for 45 min at 37°C in a thermomixer. Thereafter, the digested hearts were filtered through a 70µm cell strainer and pelleted by centrifugation (400g, 5 min at 4°C) in HBSS supplemented with 2% FBS + 0.2% BSA. Red blood cell lysis was done using RBC Lysis buffer (Biolegend) and resuspended in PBS containing 2% FBS and 2mM EDTA. Afterwards, samples were labeled with fluorescently tagged CD45 antibodies and cell sorted on a Cell Sorter (Sony MA900). Cell counting, gel beads-in-emulsion (GEMs) generation, reverse transcritpion and library preparation was performed according to the 10X Genomics Single Cell 3' v3 protocol.