Defined conditions control the morphological dualism of rat primitive extraembryonic endoderm stem cells

We report two chemically defined conditions that differ by the addition of the cytokine Lif and the β-catenin-stabilizing drug Chir99021 and enable permanent self-renewal as mesenchymal and epithelial morphotypes, respectively. The morphotypes are interconvertible and differentiate equipotently. Surprisingly, the proliferation of both morphotypes requires Lif/Gp130/Stat3 signaling (autocrine in the absence of added Lif) and non-canonical Wnt signaling (autocrine). Additionally, the epithelial version requires β-catenin for proliferation and morphology. Interestingly, the mesenchymal cells also express key epithelial markers, but those are improperly structured and/or not functional, indicating a primed state. The results provide an improved platform for studying the proliferation and plasticity of the early extraembryonic endoderm, which occurs in mesenchymal and epithelial forms in vivo. mRNA profiles of rat pXEN cells routinely cultured in T,LPE and CPE conditions were generated by deep sequencing, in triplicate, on an Illumina HiSeq 2500