Gao, X. et al. Nat. Cell Biol. 21, 687–699 (2019).

Expanded potential stem cells (EPSCs) can differentiate into extraembryonic and embryonic lineages. Culture conditions for establishing and maintaining murine EPSCs have been described, but the same conditions are not suitable for deriving human or porcine EPSCs. Gao et al. screened 400 combinations of small molecules and cytokines for their potential to inhibit differentiation in porcine induced pluripotent stem cells. A cocktail of GSK3, SRC and Tankyrase inhibitors along with vitamin C, activin A and LIF did the trick. This cocktail also allowed them to derive porcine EPSCs from pre-implantation embryos. After establishing these conditions, the researchers tested the cocktail on human embryonic stem cells and found that minor modifications were necessary in order for the cocktail to establish the expanded potential. The human EPSCs may be helpful in gaining a better understanding of embryonic development in humans.