Reciprocal Embryo-Endometrial adaptation at Implantation Onset Revealed by 3D Human Blastoid/Blastocyst-Endometrial Assembloid Co-Culture

Importantly, we identify co-culture-induced trophoblast subsets marked by SDC1⁺MMP7⁺ and enriched for transcriptional features associated with extracellular matrix remodeling and cell migration.

These subsets are reproducibly detected across independent implantation-like systems, emerge specifically within a decidualized stromal co-culture context, and are further linked to stromal-derived CSF3 signaling by intercellular communication analysis and targeted perturbation. In parallel, the endometrium displays transcriptional changes associated with enhanced decidualization and a glandular hypersecretory transition.