Prepartum E2-driven tissue-specific transcriptomic changes in the ewe reproductive tract.

Estrogens regulate key processes in parturition, yet the specific effects of estradiol (E2) on maternal reproductive tissues in sheep remain unclear. This study investigated the impact of exogenous E2, mimicking physiological prepartum levels, on gene expression in the myometrium, endometrium, cervix, and placental membranes, as well as sex steroid receptor protein expression in uterine compartments of late pregnant ewes. Pregnant ewes (139-142 d gestation) received Silastic implants containing either E2 (200 µg/ewe, n = 6) or control (n = 6), and tissues were collected 26 h post-treatment. Bulk RNA sequencing assessed differential gene expression, while fluorescence immunohistochemistry evaluated nuclear receptor localization and intensity. Transcriptomic analysis (FDR < 0.05) revealed a tissue-specific response, with the cervix showing the most robust transcriptional changes. Gene ontology enrichment indicated downregulation of extracellular matrix organization pathways associated with cervical dilation at parturition. Targeted analyses revealed regulation of genes related to prostaglandin synthesis, steroid metabolism, immune signaling, and ECM remodeling. The endometrium displayed a moderate response, whereas the myometrium and placental tissues exhibited minimal changes. At the protein level, myometrial progesterone receptor (PR) expression was significantly reduced (p < 0.05), while ERα and ERβ were unaffected. These findings demonstrate that the prepartum rise in E2 is associated with tissue-specific gene expression changes in the ewe uterine tract. In the cervix, the most affected tissue, transcriptomic changes are consistent with cervical ripening. Reduced myometrial PR expression suggests decreased progesterone responsiveness.