Phosphatidic acid induces cytoskeletal rearrangements through the Src‐ <scp>FAK</scp> ‐ <scp>R</scp> ho <scp>A</scp> / <scp>ROCK</scp> signaling pathway during decidualization

Decidualization, the transformation of human endometrial stromal cells from a fibroblast-like to a rounded morphology, is crucial for creating a receptive intrauterine environment that supports successful embryo implantation. While decidual markers such as insulin-like growth factor-binding protein 1 and prolactin are well studied, the specific signaling mechanisms underlying morphological changes during decidualization remain unclear. In this study, we identified the phosphatidic acid (PA)-Src-focal adhesion kinase (FAK)-RhoA/Rho-associated protein kinase (ROCK) signaling pathway as a critical regulator of cytoskeletal rearrangement during PA-induced decidualization in human endometrial stromal cells. PA, a product of phospholipase D1, activates FAK, initiating a cascade of events involving Src-family kinases and RhoA signaling, ultimately leading to the cytoskeletal changes necessary for decidualization. Our in vitro experiments showed that PA-induced decidualization involved the formation of stress fibers mediated by ROCK activation. The traditional decidual markers, insulin-like growth factor-binding protein 1 and prolactin, did not significantly influence these morphological changes, suggesting that the PA-induced pathway operates independently of these markers. In vivo studies in ovariectomized mice demonstrated that PA injection into the uterine horn increased the uterine cavity weight and wall thickness, reinforcing the role of PA in promoting decidualization. These findings highlight the importance of the PA-Src-FAK-RhoA-ROCK pathway in regulating cytoskeletal dynamics during decidualization and suggest potential therapeutic targets for addressing implantation-associated infertility.