MTSC-Protocol v1

Successful derivation of mouse trophoblast stem cells (TSCs) and trophectoderm stem cells (TESCs) greatly facilitates understanding of trophoblast differentiation. However, understanding of early trophectoderm differentiation remains incomplete. Here, we report establishment of a morula-derived trophectoderm stem cell line (MTSCs) from 32-cell embryos that show enhanced and uniformed trophoblast core gene expression. Importantly, distinct from TSCs or TESCs, MTSCs represent a much earlier trophectoderm state (E3.5) than those of TSCs(E5.5-6.5) and TESCs(E4.5-5.5). MTSCs can robustly integrate into all cell lineages of the placenta. Moreover, MTSCs can self-organize to form placenta organoids. When partially differentiated MTSCs aggregated with embryonic stem cells (ESCs), they form blastoids that efficiently implant uteruses. Finally, MSTC medium can efficiently convert ESCs into MTSC-like cells. Thus, MTSCs capture an early blastocyst trophectoderm state and provide a research model for studying trophoblast development.