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: The main of this study is to clarify whether hPSC-CVPCs can engraft for long time in the heart of primates after myocardial infarction (MI) and compare the effectiveness and safety of immunosuppression with cyclosporine alone or multiple-drug regimen (MDR) containing cyclosporine, methylprednisolone, and basiliximab in cynomolgus monkeys that had received intramyocardial injections of 1x10(7) EGFP (enhanced green fluorescent protein)-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 recovery of left ventricular function on 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, although both immunosuppression regimens were associated with transient hepatic dysfunction. Conclusions: This is the largest study of hPSCs in nonhuman primates in cardiovascular field to date (n=32). Compared with 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 recovery of left ventricular function at 28 days. However, even with MDR, transplanted hPSC-CVPCs do not engraft and do not survive at 140 days after transplantation, thereby excluding remuscularization as a mechanism for the functional effect.