Synthetic Embryos Can Complete Gastrulation and Initiate Organogenesis Ex Utero .

Developmental biology has been revolutionized by two recent articles showing that synthetic mouse embryos derived from embryonic stem cells (ESCs) can be grown ex vivo and complete gastrulation up to the organogenesis stage. This is a remarkable achievement that had never been attained using stem cells before. Both studies used transcription factors to reprogram extraembryonic cells, which they combined with naive ESCs. Further culture of these aggregates using gas-exchange bioreactors allowed these aggregates to proceed through gastrulation and organogenesis, resembling E8.5 stage mouse embryos. These advanced synthetic embryos will allow the modeling of challenging stages of mammalian development. Translation of these findings to human pluripotent systems may allow the production of rare cell types for engineering and therapy.