Engineering the Human Endometrial–Embryo Interface: Breakthroughs in 3D Uterine Models

Three-dimensional (3D) organoid and co-culture models have emerged as transformative tools for studying human endometrial function, implantation, and placental development, overcoming key limitations of animal and two-dimensional in vitro systems. This review synthesises available information of recent advances in endometrial epithelial organoids (EEOs), trophoblast organoids (TBOs), and increasingly complex co-culture platforms incorporating stromal, vascular, and trophoblast compartments to model epithelial-stromal crosstalk, decidualisation, angiogenesis, and embryo implantation. Emerging developments include assembloid systems, synthetic and semi-synthetic extracellular matrices, and microfluidic organ-on-a-chip technologies that enable long-term culture, hormonal responsiveness, and patient-specific modelling. These approaches have recapitulated key features of the mid-secretory endometrium, placental villous architecture, trophoblast differentiation, and early implantation events while revealing disease-associated dysfunctions in conditions such as endometriosis, adenomyosis, polycystic ovarian syndrome, and endometrial cancer. Despite significant progress, current models remain limited by incomplete cellular diversity, polarity constraints, and challenges in fully modelling immune and vascular interactions. Collectively, emerging 3D organoid and co-culture systems provide physiologically relevant platforms to interrogate human reproductive biology, elucidate mechanisms underlying implantation failure and placental disease, and support the development of personalised therapeutic strategies to improve reproductive outcomes.