A Review of the Therapeutic Efficacy and Safety of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes in Preclinical Models of Subacute and Chronic Myocardial Infarction

For the past decade, cell-based therapies have been the focus of research to investigate their potential to treat ischemic heart disease. The translation to human clinical studies depends on the demonstration of therapeutic efficacy and safety, particularly when transplanted in the subacute and chronic post-MI phase. A number of studies were identified that reported the effect of hiPSC-CMs on cardiac outcomes when transplanted at least 7 days post-myocardial infarction. The mean sample size of the published studies was 30 (±17) animals with a mean follow-up duration of 51 (±37) days. hiPSC-CM transplantation enhanced systolic function through augmented myocardial contractility, decreased infarct size, attenuated ventricular remodeling, and enhanced angiogenesis in the infarct and border zones in both small and large animal models. This effect was enhanced by co-transplantation with cells of vascular or adipose origin and is associated with high expression of VEGF in most studies. Despite this effect, transplanted hiPSC-CMs were structurally immature with limited survival at the endpoint. Epicardial delivery was associated with better efficacy outcomes and lower rates of arrhythmia. No study reported teratoma formation or immune rejection. From the current literature, there appears to be no consensus on the extent to which hiPSC-CMs improved systolic function, nor the degree to which this arises directly from integration of the new myocardium or from a paracrine-mediated mechanism. The nature of this paracrine mechanism and ways to improve the maturity and survival of implanted cardiomyocytes are issues that have yet to be resolved. In summary, while therapeutic benefit from cell therapy is clear, further research is required to establish whether the key mechanisms require a cellular component.