Specification of HiPS to in vivo placental cell types

Here we identify conditions that efficiently drive specification of primed induced pluripotent stem cells to trophectoderm, named Trophoblast Stem Cell (TS). iPS-derived-TS cells share transcriptional, morphological and functional characteristics with human ex vivo cytotrophoblasts including transcriptional activation of human endogenous retroviruses, expression of COVID-19 associated host factors and the ability to generate multinucleated syncytiotrophoblasts with a large fusion index. At high densities in 5% O2, iPS-derived-TS cells form villi-like structures and express extravillous and syncytiotrophoblast proteins HCG-ß, HLA-G. To define the molecular changes associated with specification, we compare temporal single cell RNAseq analysis under three separate conditions: 1) BMP4, 2) BMP4 and inhibition of Wnt, 3) Trophoblast Stem cell condition (TS) activation of EGF and Wnt, inhibition of TGFbeta, HDAC and ROCK signaling.