Pluripotent stem cells (ES cells or iPS cells) have almost infinite proliferation ability and ability to differentiate into many cells, and are expected to be applied to regenerative medicine.On the other hand, heart diseases such as myocardial infarction have a high morbidity and mortality rate, and development of a new treatment method is desired.

　In 2012, the research group reported research results that when cells (= cardiomyocytes) that make up the heart muscle were created from human ES cells and transplanted into a guinea pig myocardial infarction model, cardiac function was restored after myocardial infarction. (Published in the British scientific magazine "Nature").However, previous studies, including this one, have been studies by "xenotransplantation" in which cardiomyocytes produced from humans (derived from humans) are transplanted into another animal.In the study of xenotransplantation, it was not possible to evaluate post-transplant immune rejection because the cells to be transplanted and the host to be transplanted are different animal species.

　In this study, iPS cells were generated using cynomolgus monkeys, which are less likely to cause rejection.Next, myocardial infarction was caused in normal cynomolgus monkeys, and cardiomyocyte transplantation was performed between cynomolgus monkeys (allogeneic transplantation).As a result, the transplanted cardiomyocytes were engrafted with almost no influence of rejection, and recovery of cardiac function after myocardial infarction was confirmed.However, animals transplanted with cardiomyocytes showed a transient increase in arrhythmia as a side effect.Research is needed to reduce side effects in the future.