Generation of Blastoids from Human Naïve Pluripotent Stem Cells.

Human embryo research is essential for understanding the development of human embryos and their unique features that cannot be investigated in mouse embryos. Natural development of human embryos remains challenging to study both in vivo and in vitro owing to ethical concerns, technical difficulties, and limited availability of embryos for research purposes. Until recently, access to human embryo research, especially the implantation period, was limited. However, optimization of a stem cell-based model known as a blastoid has opened a new era for human embryo research. In contrast with mouse embryonic stem cells, human naïve pluripotent stem cells retain extended cell lineage plasticity. They can differentiate into hypoblast and trophectoderm while retaining characteristic resembling the naïve epiblast in the inner cell mass region. Taking this unique differentiation potential and inherent propagation capacity as pluripotent stem cells, human blastoids are generated by the self-organization of naïve pluripotent stem cells. They resemble human blastocyst structures, consisting of the three founder cell lineages that closely resemble the gene expression profile of human blastocysts. This protocol for generating blastoids solely from naïve human pluripotent stem cells utilizing simple, efficient, and scalable procedures is a robust tool for advancing aspects of human embryo research.