Deconstructing human peri-implantation embryogenesis based on embryos and embryoids†.

ABSTRACT

The peri-implantation period from blastula to gastrula is one of the crucial stages of human embryo and stem cell development. During development, human embryos undergo many crucial events, such as embryonic lineage differentiation and development, structural self-assembly, pluripotency state transition, cell communication between lineages, and crosstalk between the embryo and uterus. Abnormalities in these developmental events will result in implantation failure or pregnancy loss. However, because of ethical and technical limits, the developmental dynamics of human peri-implantation embryos and the underlying mechanisms of abnormal development remain in a "black box." In this review, we summarize recent progress made toward our understanding of human peri-implantation embryogenesis based on extended in vitro cultured embryos and stem cell-based embryoids. These findings lay an important foundation for understanding early life, promoting research into human stem cells and their application, and preventing and treating infertility. We also propose key scientific issues regarding peri-implantation embryogenesis and provide an outlook on future study directions. Finally, we sum up China's contribution to the field and future opportunities.