Transgene-free mouse embryo models from chemical reprogramming reach early organogenesis.

Embryo models derived from pluripotent stem cells (PSCs) have become powerful tools for dissecting mammalian embryonic development and advancing regenerative medicine. Two recent studies in Cell and Cell Stem Cell report major advances in generating mouse embryo models that replicate development up to early organogenesis (equivalent to embryonic day 8.5~8.75). Li et al. describe a purely chemical strategy to reprogram mouse embryonic stem cells (mESCs) into induced embryo founder cells (iEFCs) capable of forming complete embryo models (iEFC-EMs). In parallel, Yilmaz et al. demonstrate transgene-free generation of post-gastrulation models (TF-SEMs) from naive mESCs and induced pluripotent stem cells (iPSCs) using a similar chemical cocktail. Both models faithfully recapitulate key developmental events, including gastrulation, neural tube formation, cardiogenesis, and somitogenesis. These advances not only deepen understanding of early mammalian development but also pave the way for applications in regenerative medicine and disease modeling.