Proof-of-Concept for Long-Term Human Endometrial Epithelial Organoids in Modeling Menstrual Cycle Responses

Endometrial disorders, such as infertility and endometriosis, significantly impact reproductive health, thus necessitating better models to study endometrial function. Current in vitro models fail to replicate the complexity of the human endometrium throughout the entire menstrual cycle. This study aimed to assess the physiological response of human endometrial organoids (hEOs) to in vitro hormonal treatments designed to mimic the hormonal fluctuations of the menstrual cycle. Endometrial biopsies from three healthy women were used to develop hEOs, which were treated over 28 days with three hormonal stimulation strategies: (1) estrogen only (E) to mimic the proliferative phase, (2) the addition of progesterone (EP) to simulate the secretory phase, and (3) the further addition of cAMP (EPC) to enhance the secretory functions of hEOs. Gene and protein expression were analyzed using qPCR, IHC, and ELISA. The hEOs exhibited proliferation, gland formation, and appropriate expression of markers such as E-cadherin and Ki67. The hormonal treatments induced significant changes in PR, HSD17B1, PAEP, SPP1, and other genes relevant to endometrial function, closely mirroring in vivo physiological responses. The prominent changes were observed in EPC-treated hEOs (week 4) with significantly high expression of uterine milk components such as glycodelin (PAEP) and osteopontin (SPP1), reflecting mid- to late-secretory phase physiology. This model successfully recapitulates human menstrual cycle dynamics and offers a promising platform for studying endometrial disorders and advancing personalized treatments in gynecology.