Lack of Remuscularization Following Transplantation of Human Embryonic Stem Cell-Derived Cardiovascular Progenitor Cells in Infarcted Nonhuman Primates

Rationale: Human pluripotent stem cell-derived cardiovascular progenitor cells (hPSC-CVPCs) should be thoroughly investigated in large animal studies before testing in clinical trials. Objective: To clarify if hPSC-CVPCs can engraft for long time in the heart of primates after myo-cardial infarction (MI) and compare the effectiveness and safety of immunosuppression with cy-closporine alone or multiple-drug regimen (MDR) containing cyclosporine, methylprednisolone, and Simulect in cynomolgous monkeys that had received intramyocardial injections of 1×10 7 EGFP-expressing hPSC-CVPCs after MI. A third group of animals received the immunosuppression MDR but without cell therapy after MI (MI+MDR group). Methods and Results: Measurements of EGFP gene levels and EGFP immunofluorescence staining indicated that the hPSC-CVPC engraftment rate was greater in the MI+MDR+CVPC group than that in the MI+Cyclosporine+CVPC group. However, even in the MI+MDR+CVPC group, no transplanted cells could be detected at 140 days after transplantation. Concomitantly, immunofluorescent analysis of CD3, CD4, and CD8 expression indicated that T lymphocyte infiltration in the CVPC-transplanted hearts was less in the MDR-treated animals than in the cyclosporine alone-treated animals. The re-covery of left-ventricular (LV) function at day 28 post-MI in the MI+MDR+CVPC group was better than that in the MI+MDR group. Apoptotic cardiac cells were also less common in the MI+MDR+CVPC group than in the MI+MDR group, while both immunosuppression regimens were associated with transient hepatic dysfunction. Conclusions: This is the largest study of hPSCs in non-human primates in cardiovascular field so far (n=32). Compared to cyclosporine alone, MDR attenuates immune rejection and improves survival of hPSC-CVPCs in primates; this is associated with less apoptosis of native cardiac cells and better re-covery of LV function at 28 days. However, even with MDR, transplanted hPSC-CVPCs do not en-graft and do not survive at 140 days after transplantation, thereby excluding remuscularization as a mechanism for the functional effect.