Human Cardiac Microtissues Display Improved Engraftment and Survival in a Porcine Model of Myocardial Infarction

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) constitute a promising therapy for myocardial infarction (MI). The lack of an effective immunosuppressive regimen, combined with single-cell transplantations, results in suboptimal outcomes, such as poor engraftment and compromised therapeutic efficacy. This study aimed to confirm the increased retention of hiPSC-CMs microtissues (CMTs) over single-cell grafts. To ensure the long-term survival of CMTs for potential cardiac applications, CMTs were transplanted in a porcine model of MI using a triple immunosuppression protocol designed to limit immune cell infiltration. Acute evaluation of spherical hiPSC-CMs aggregates and dissociated aggregates followed by the development of a triple immunosuppression protocol were performed in healthy animals. Long-term survival of CMTs was later examined in pigs that underwent a transient coronary occlusion. Two weeks post-MI, the immunosuppression treatment was initiated and on day 28 the animals were transplanted with CMTs and followed for four more weeks. Acutely, CMTs showed superior retention compared to their dissociated counterparts. The immunosuppression regimen led to no organ damage and stable levels of circulating drugs once optimal dose was achieved. Two weeks post-xenotransplantation in healthy pigs, histology revealed that immunosuppressed animals displayed a significant decrease in total cellular infiltrates, particularly in CD3⁺ T cells. Pigs that underwent coronary occlusion, which later were immunosuppressed and treated with CMTs (5 × 10⁷ cells), showed cell engraftment onto the native myocardium four weeks post-transplantation. This study supports the use of a triple immunosuppression cocktail to ensure long-term survival of CMTs for the treatment of MI.