Endometrial gland impacts on stromal cell decidualization

Uterine glands and, by inference, their secretions impact uterine receptivity, blastocyst implantation, stromal cell decidualization, and placental development. Changes in gland function across the menstrual cycle are impacted by steroid hormones, estrogen and progesterone, as well as stroma-derived factors. Using an endometrial epithelial organoid (EEO) system, transcriptome and proteome analyses identified distinct responses of the EEO to steroid hormones and prostaglandin E2 (PGE2). Notably, steroid hormones and PGE2 modulated the basolateral secretion of EEO proteins, where cystatin C (CST3) was significantly increased by progesterone and PGE2. CST3 treatment of decidualizing stromal cells significantly decreased the decidualization markers PRL and IGFBP1. The attenuation of stromal cell decidualization via CST3 suggests a role for uterine gland-derived proteins in controlling the extent of decidualization. These findings provide evidence that uterine gland-derived factors directly impact stromal cell decidualization, which has strong implications for better understanding pregnancy establishment and female fertility in humans.