Teratoma development in adult mice from extending pluripotency

Embryonic stem cells (ESCs) have practically unlimited proliferation capacity and unrivalled differentiation potential, thus providing an attractive source of cells for regenerative medicine. Numerous ESC culture systems have been established to achieve extended pluripotency. However, long-term safety evaluation on these extended pluripotent state cells (EPS) were largely overlooked. Here, we generate full ESC-mice through tetraploid embryo complementation assay from the prevailing extended pluripotent stem cells. Two years of safety evaluation show that all the EPS mice developed late onset retroperitoneal teratomas whereas no abnormality was observed in the conventional ESC mice. Whole exome sequencing and chromatin accessibility analysis on the EPS and the corresponding tumor tissues identify the global chromatin reconfiguration but only minor genetic variation in EPS. Correspondingly, the teratomas could be attributed to a proportion of undifferentiated cells from extended pluripotency. Our study uncovers the prevailing late onset tumorigenesis in EPS-mouse, highlighting the impact of early epigenetic variations on tumorigenicity in the adult. bisulfite sequencing of teratomas obtained after tetraploid embryo injection of ESCs cultured in different culture conditions