A transgene-free, human peri-gastrulation embryo model presents trilaminar embryonic disc-, amnion- and yolk sac-like...

Human peri-gastrulation is a critical developmental stage, yet challenging to study directly. Stem cell-based embryo models have emerged as promising tools for probing early human embryogenesis. Here we report a transgene-free human embryo model, namely peri-gastrulation trilaminar embryonic disc (PTED) embryoid, derived exclusively from primed human pluripotent stem cells, recapitulating certain features of peri-gastrulation human development, which include the formation of trilaminar embryonic layers positioned between the dorsal amnion and ventral definitive yolk sac, as well as primitive haematopoiesis. Our lineage tracing showed that, in PTED embryoids, embryonic and extraembryonic mesoderm as well as embryonic and extraembryonic endoderm arise from gastrulating epiblast-like cells, which provides support for extraembryonic lineage potential of peri-gastrulation human epiblast. Notably, active haematopoiesis and blood-cell generation occurred within the definitive yolk sac-like structure of PTED embryoids. Together, PTED embryoids offer a tractable and ethically less complex model for investigating the self-organizing properties of human peri-gastrulation development.