Abstract
The human endometrium is a dynamic tissue that lines the uterus and undergoes constant remodeling, making it especially susceptible to gynecological diseases like endometriosis and endometrial cancer. The molecular mechanisms of these conditions are not well understood, partly due to the lack of in vitro models that mimic endometrial physiology, which limits options for targeted intervention and treatment of these diseases. Mouse models are also inadequate, as common laboratory strains do not naturally undergo a menstrual cycle comparable to that of humans. This study addresses this need by developing a 3D multi-compartment assembloid that mimics the architecture of endometrial tissue and recapitulates all three phases of the menstrual cycle (proliferative, secretory, and menstrual regression) within a single platform. The cellular and extracellular matrix (ECM) components in each compartment are carefully tuned based on a 3D spatial cellular map of endometrial tissue. The model contains endometrial epithelial cells enveloped in a basement membrane and endometrial stromal cells in a surrounding collagen-rich layer; this architecture allows realistic interactions between these cells and their respective ECMs. This assembloid successfully supports the controlled growth and organization of these cells, revealing reciprocal regulation of cell behavior and exhibiting compartment-specific hormonal responses, i.e., stromal decidualization. This platform enables the study of dynamic, phase-resolved, and compartment-specific paracrine signaling in human endometrial biology. By combining tissue-informed design, modular fabrication, and full-cycle hormonal responsiveness, this model sets a new benchmark for blastocyst implantation studies, organ modeling, and precision diagnostics in human reproductive health.