Modeling human embryo implantation in vitro.

Summary

The authors created a 3D in vitro model of receptive human endometrium comprising luminal, glandular, and stromal compartments that supports implantation of human embryos and blastoids to day 14. Single-cell RNA sequencing identified conceptus–endometrium signaling at the interface, and disrupting extravillous trophoblast–stromal signaling impaired trophoblast outgrowth, revealing essential crosstalk for early placental development.

Key Findings

• Developed a 3D endometrial model recapitulating luminal, glandular, and stromal compartments that supports implantation of human embryos and blastoids.
• Achieved post-implantation hallmarks including advanced trophoblast structures and early placental development features up to day 14.
• Single-cell RNA-seq of the embryo–endometrium interface identified predicted ligand–receptor interactions; disrupting extravillous trophoblast–stromal signaling impaired trophoblast outgrowth.

Clinical Implications

While preclinical, this model can inform diagnostics (endometrial receptivity biomarkers), embryo selection strategies, and drug safety studies by identifying pathways critical for implantation and early trophoblast invasion.

Limitations

• In vitro model may not capture all systemic maternal factors; generalizability to in vivo conditions remains to be established.
• Developmental progression assessed only to day 14, limiting study of later placentation and fetal development.

Future Directions

External validation across diverse donor sources, integration with immune and vascular components, and application to model implantation failure, preeclampsia, and drug safety.