Ka Wai Wong

Understanding early primate embryogenesis remains limited by ethical and technical constraints. To address this, we established a stem cell-based embryo model from the North Bornean orangutan ( Pongo pygmaeus pygmaeus ). Using integration-free induced pluripotent stem cells (iPSCs), we generated blastoids that self-organized into structures resembling human blastocysts in morphology, lineage composition, and transcriptomic identity. Initial aggregation of primed iPSCs produced blastoids with organized lineage segregation. We enhanced this approach by combining isogenic iPSCs maintained under different culture conditions at optimized ratios, generating "bi-blastoids" with high formation efficiency, balanced lineage specification, and dimensions matching human blastocysts. Single-cell RNA sequencing revealed epiblast-, trophectoderm-, and hypoblast-like populations with transcriptomic profiles closely resembling human E6-7 blastocysts. Comparative analysis demonstrated that orangutan blastoids exhibited stronger transcriptional fidelity to human embryos than existing macaque models, establishing their unique value for developmental studies. Functional validation confirmed that orangutan blastoids could generate embryonic stem cell-like and trophectoderm stem cell-like lines, recapitulate trophoblast differentiation and secrete chorionic gonadotropin. However, primitive endoderm/hypoblast-like cells failed to form a distinct compartment, mirroring limitations observed across other primate models. This orangutan blastoid system provides a less ethically restrictive platform for studying human-relevant embryogenesis while maintaining high developmental fidelity. Beyond developmental insights into primate development, this model may inform future reproductive interventions for critically endangered great apes as conservation technologies advance.

Embryonic stem cells possess the remarkable ability to self-organize into blastocyst-like structures upon induction. These stem cell-based embryo models serve as invaluable platforms for studying embryogenesis and therapeutic developments. Nevertheless, the specific intrinsic regulators that govern this potential for blastoid formation remain unknown. Here we demonstrate an intrinsic program that plays a crucial role in both blastoids and blastocysts across multiple species. We first establish metrics for grading the resemblance of blastoids to mouse blastocysts, and identify the differential activation of gene regulons involved in lineage specification among various blastoid grades. Notably, abrogation of nuclear receptor subfamily 1, group H, member 2 (Nr1h2) drastically reduces blastoid formation. Nr1h2 activation alone is sufficient to rewire conventional ESC into a distinct pluripotency state, enabling them to form blastoids with enhanced implantation capacity in the uterus and contribute to both embryonic and extraembryonic lineages in vivo. Through integrative multi-omics analyses, we uncover the broad regulatory role of Nr1h2 in the transcriptome, chromatin accessibility and epigenome, targeting genes associated with embryonic lineage and the transposable element SINE-B1. The Nr1h2-centred intrinsic program governs and drives the development of both blastoids and early embryos.