Activin A and BMP4 Signaling Expands Potency of Mouse Embryonic Stem Cells in Serum Free Media

Inhibitors of Mek1/2 and Gsk3b, known as 2i, and together with leukemia inhibitory factor, enhance the derivation of embryonic stem cells (ESCs) and promote ground-state pluripotency (2i/L-ESCs). However, recent reports show prolonged Mek1/2 suppression impairs the developmental potential of ESCs, and is rescued by serum (S/L-ESCs). In spite of the unclear roles of growth factors in serum, the coculture system has remained the gold standard. Here we show that culturing ESCs in Activin A, BMP4 and in the absence of MEK1/2 inhibitor (ABC/L medium) establishes stable ESCs, named advanced pluripotent stem cells derived from ESCs (esASCs). We demonstrate that esASCs contributed to germline lineages, full term chimeras and generated esASCs-derived mice by tetraploid complementation. We show that in contrast to 2i/L-ESCs, these esASCs display distinct molecular signatures and stable hypermethylated epigenome which is reversible and similar to S/L-ESCs. Importantly, we also derived novel ASCs (blASCs) from blastocysts in ABC/L medium. These blASCs are persisting at an intermediate state between naïve and primed state of pluripotency and stable hypermethylated epigenome. Our results provide insights into the derivation of novel ESCs with DNA hypermethylation from blastocysts in a chemically defined medium.