Abstract Body: Introduction: Immune rejection remains a major hurdle in the clinical translation of hPSC-derived cardiomyocyte mediated regeneration.
Hypothesis: In this study, we hypothesized that cardiac organoids derived from hPSCs modified via deletion of the beta-2 microglobulin (B2M) gene as well as knock-in with HLA-E fusion molecule (termed B2M^-/- HLA-E⁺ ‘UDET hPSCs’) could evade the host immune response while maintaining functional potential as a cardiovascular cell therapy.
Methods and Results: In vitro cytotoxicity assays were performed following the co-culture of allogeneic human immune cells with target hPSC-derived cardiac cells, revealing that UDET hPSC-derived cells evaded both NK- and T cell-mediated cell lysis at significantly higher levels compared to wild type cells. Self-assembled, spontaneously contracting cardiac organoids were fabricated by seeding hPSC-derived cells in low-attachment agarose molds. We examined the in vivo immune response via injection of cardiac organoids in the kidney capsule of humanized mice. Quantification of engraftment after 14 days suggested immune evasion of UDET cardiac organoids due to their significantly larger presence compared to wild type organoids. Finally, cardiac organoids were injected into athymic rat models of ischemia/reperfusion (I/R) injury. Echocardiography as well as histology of explanted rat hearts suggested UDET cardiac organoids robustly engraft and significantly promote cardiac functional recovery, performing comparably to their wild-type counterparts.
Conclusions: In this study, we validated the ability of UDET-derived cells to evade immune cell-mediated lysis, showing that UDET-derived cells were significantly less vulnerable to immune cell killing. Furthermore, we demonstrated the similar capacity of wild type and UDET-derived cardiac organoids to improve I/R-injured rat heart function and structure compared to controls. Altogether, our findings underscore the potential of hypoimmunogenic hPSC-derived cardiac organoids as a clinically relevant approach for allogenic cardiac regenerative therapy, eliminating the need for immunosuppression while promoting effective cardiac recovery