FABP3 Mediates Lipid Droplet Accumulation and Adhesive Capacity in Bovine Endometrial Epithelial Cells via PGE2/PTGER4/PPAR Axis

Prostaglandin E₂ (PGE₂) has been implicated in multiple biological processes during pregnancy in ruminants. However, the regulatory effects of PGE₂ on endometrial function during the diestrus period and its underlying molecular mechanisms remain poorly understood. Herein, PGE₂ treatment promoted the accumulation of lipid droplets and induced cytoskeletal reorganization in bEECs. As a well-established inducer of lipid droplet formation, oleic acid (OA) treatment significantly increased the number of lipid droplets in bEECs, altered the distribution of F-actin and disrupted the expression patterns of key adhesion-related proteins. Transcriptomic analysis revealed that the PPAR signaling pathway was the key pathway that responded to PGE₂ treatment in bEECs, and its downstream target gene FABP3 was markedly up-regulated. Knockdown of FABP3 led to a reduced number of BTC spheroids and down-regulation of adhesion-related proteins in bEECs while increasing the density of microvilli and up-regulating the expression of epithelial markers. Prostaglandin E receptor 4 (PTGER4) was the primary receptor that responded to PGE₂ treatment, and PTGER4 knockdown or pharmacological inhibition with GW-627368 suppressed FABP3 expression in bEECs. Moreover, uterine samples from dairy cows at different stages of the estrous cycle showed that FABP3 expression was significantly elevated in the endometrium tissue during mid-diestrus compared to metestrus, with predominant localization in the luminal and superficial glandular epithelium. Collectively, these findings indicate that FABP3 regulates lipid droplet accumulation and adhesion ability in bEECs via the PGE₂/PTGER4/PPAR signaling axis, providing new insights into the metabolic regulation of endometrial receptivity in ruminants.