Shahbazi, M.N. et al. Nat. Cell Biol. 18, 700–708 (2016).

Blastocyst implantation in the uterus is a critical event in human development that initiates germ layer establishment as well as the generation of extra-embryonic yolk sac and placenta. It is also difficult to model in vitro. Shahbazi et al. have now adapted their protocol for modeling implantation in the mouse for use with human embryos. They plated human blastocysts in two successive media and used microscopy to identify embryos that adhered at day 7 and underwent changes associated with implantation. Normoxic culture and KnockOut Serum supplementation were important for robust implantation and epiblast survival up to day 13. Cultured embryos segregated lineages, formed bilaminar discs and developed extraembryonic tissues. Using the protocol on both human embryos and matrigel-grown pluripotent stem cells, the researchers discovered that lumen formation in pro-amniotic cavity development is preceded by cell polarization.