Ming Cheng

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.

Estrogen is a steroid hormone that plays a key role in regulating many physiological processes, such as follicle activation and development and oocyte maturation in mammals. Ca²⁺ is crucial in oogenesis, oocyte maturation, ovulation, and fertilization. However, the mechanism by which estrogen regulates Ca²⁺ during oocyte maturation in mice has not been reported. This study revealed that Ca²⁺ levels in oocytes significantly increase during the 4–12 h period in vitro. Oocytes treated with 0.1 µM estrogen and 1 µM G1, a G-protein-coupled estrogen receptor (GPER) agonist, showed significantly increased Ca²⁺ levels, while treatment with 1 µM G15, an antagonist of GPER, significantly decreased Ca²⁺ levels. Notably, estrogen regulates Ca²⁺ in oocytes through the GPER pathway and promotes the expression of the Ca²⁺-producing protein EPAC1. In addition, estrogen alleviates the inhibitory effect of the Ca²⁺ chelator BAPTA-AM during oocyte maturation by promoting Ca²⁺ production. Furthermore, estrogen can promote the expression of the mitochondrial generation-associated protein SIRT1 through the GPER pathway, alleviate mitochondrial oxidative damage caused by BAPTA-AM, and restore the mitochondrial membrane potential level. Collectively, this study demonstrates that estrogen can regulate Ca²⁺ through the GPER-EPAC1 pathway and promote the expression of SIRT1, which promotes oocyte mitochondrial function during oocyte maturation.