In vitro 3D cell culture systems, termed organoids, are currently extensively used model systems that compared with 2D monolayer cell cultures, more closely resemble architectural and functional characteristics of tissues in vivo [1]. Human endometrium, the inner lining of the uterus, has long been a subject of cell biology research to study pregnancy-related physiology and gynecological problems. Despite that, studies regarding topics such as trophoblast implantation and invasion have been limited due to the absence of appropriate research models [2]. Human endometrial organoids have been reported fairly recently and this field of study still requires more work to improve current models since they have the potential to be used in patient-specific pregnancy and gynecological disease studies [3].
In this work, we aimed to construct patient-derived endometrial organoids that model endometrium in vitro and characterize their structural as well as functional properties. For organoid construction, endometrial epithelial cell clusters were cultured in a commercial extracellular matrix solution, which serves as a scaffold for 3D structure formation, in addition to an organoid culturing medium containing specific signaling factors. Self-assembling organoids were cultured and passaged after 5-7 days, and the formed organoids were assessed by microscopy along with immunofluorescence of marker proteins. Our results demonstrate that when cultured in extracellular matrix mimicking conditions, endometrial epithelial cells from ex vivo samples self-assemble into 3D spherical structures. They can be passaged while maintaining their morphology and structural properties. We observed that organoids express glandular epithelium-specific structural proteins (EpCAM, Cytokeratin, etc.) as well as functional proteins, such as MUC1, at different levels. Overall, our study presents the construction of patient-specific endometrial organoids that reproduce tissue-defining characteristics and function and can thus be applied to various physiological and pathological research experiments in vitro.