Ex utero monkey embryogenesis from blastocyst to early organogenesis

The third and fourth weeks of gestation in primates are marked by several developmental milestones, including gastrulation and the formation of organ primordia. However, our understanding of this period is limited due to restricted access to in vivo embryos. To address this gap, we developed an embedded 3D culture system that allows for the extended ex utero culture of cynomolgus monkey embryos for up to 25 days post-fertilization. Morphological, histological, and single-cell RNA-sequencing analyses demonstrate that ex utero cultured monkey embryos largely recapitulated key events of in vivo development. With this platform, we were able to delineate lineage trajectories and genetic programs involved in neural induction, lateral plate mesoderm differentiation, yolk sac hematopoiesis, primitive gut, and primordial germ-cell-like cell development in monkeys. Our embedded 3D culture system provides a robust and reproducible platform for growing monkey embryos from blastocysts to early organogenesis and studying primate embryogenesis ex utero. [Display omitted] •A 3D culture system supports cynomolgus monkey embryo development until 25 d.p.f.•Cultured monkey embryos initiate early organogenesis and recapitulate key events•Neural induction, yolk sac hematopoiesis, and early germ cell development are seen•scRNA-seq shows the developmental trajectory of early monkey organogenesis An embedded 3D culture system for monkey embryos is developed that allows for in vitro culturing up to 25 days post-fertilization. Previous ex utero culture methods arrested during the initial stages of gastrulation, and this extended window of culture allows for development into early organogenesis.