RhoB Promotes Endometrial Stromal Cells Decidualization Via Semaphorin3A/plexinA4 Signaling in Early Pregnancy

Endometrial decidualization refers to a series of morphological changes and functional remodeling of the uterine endometrium to accept the embryo under the effect of estrogen and progesterone secreted by ovaries after ovulation. During decidualization, endometrial stromal cells (ESCs) proliferate and differentiate into decidual stromal cells (DSCs), undergoing cytoskeletal rearrangement-mediated morphological changes and expressing decidualization markers, such as insulin-like growth factor-binding protein-1 (IGFBP1) and Prolactin (PRL). Ras homology (Rho) proteins, a family of small G proteins, are well-known as regulators of cellular morphology and involved in multiple other cellular processes. In this study, we found Ras homolog family member B (RHOB) was the most significantly upregulated gene in Rho protein family after the in vitro decidualization of human primary ESCs. RhoB expression was induced mainly by cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA)/cAMP-response element binding protein (CREB) signaling and partly by progesterone signaling. Knockdown of RhoB in ESCs greatly inhibited actin cytoskeletal rearrangement, cell morphological transformation and upregulation of IGFBP1, suggesting an indispensable role of RhoB in decidualization. Mechanistically, the downstream target of RhoB was Semaphorin3A (Sema3A) which mediated its signaling via interacting with the receptor, plexinA4. More importantly, decreased expression of RhoB, Sema3A and plexinA4 were detected in deciduas from patients with unexplained spontaneous miscarriage. Collectively, our results indicate that RhoB/Sema3A/plexinA4 signaling plays a positive role in endometrial decidualization and relates to unexplained spontaneous miscarriage, which is worthy of further exploration so as to provide new insights into therapeutic strategies for pregnancy diseases associated with poor decidualization.