P-517 Downregulated INHBB in endometrial tissue of recurrent implantation failure patients impeded decidualization through the ADCY1/cAMP signalling pathway

Abstract

Abstract Study question To identify the mechanism of Inhibin Subunit Beta B (INHBB) in the regulation of human endometrial stromal cells (HESCs) decidualization in recurrent implantation failure (RIF). Summary answer INHBB was decreased in endometrial stromal cells of women with RIF, which attenuated decidualization in vitro by suppressing ADCY1-induced cAMP production and cAMP-mediated signalling. What is known already INHBB encodes a preprotein subunit of inhibin/ activin, functional cytokines belonging to the transforming growth factor-β (TGF-β) family. INHBB mRNAs were expressed in human decidualized endometrium from the first trimester of pregnancy and increased as the gestation progressed. Furthermore, INHBB expression increases in the mouse uterus in areas undergoing decidualization. These studies indicated that INHBB might play an essential role in endometrial decidualization. Study design, size, duration The Medical Ethics Committee of Nanjing Drum Tower Hospital approved this study (No. 2013-081-01). Written informed consent was obtained from each participant. Between January 2020 and November 2021, 28 infertile and 18 fertile control women aged 20-40 years with normal and regular menstrual cycles (25-35 days) and no history of steroid hormone medication in the last 3 months were included in the study. Participants/materials, setting, methods RNA-seq was conducted to identify the differentially expressed genes in the endometria from control and RIF patients. RT-qPCR, WB, and immunohistochemistry were performed to analyse the expression levels of INHBB in decidualised HESCs. RT-qPCR and immunofluorescence were used to detect changes in decidualization after knockdown INHBB. Then, RNA-seq was used to dig out the mechanism of INHBB regulating decidualisation. Main results and the role of chance Our results showed significantly reduced expression of INHBB in endometrial stromal cells of women with RIF. In addition, INHBB was increased in the endometrium of the secretory phase and significantly induced in in-vitro decidualization of HESCs. Notably, with RNA-seq and siRNA-mediated knockdown approaches, we demonstrated that the INHBB-ADCY1-mediated cAMP signalling pathway regulates the reduction of decidualization. We found a positive association between the expression of INHBB and ADCY1 in endometria with RIF (R2= 0.3785, P = 0.0005). Limitations, reasons for caution Our results indicated that INHBB regulates cAMP level by inducing the expression of ADCY1, while the regulation mechanism between INHBB and ADCY1 in endometrial decidualization requires further exploration. Wider implications of the findings The decline of INHBB in HESCs suppressed ADCY1-induced cAMP production and cAMP-mediated signalling, which attenuated decidualization in RIF patients, indicating that INHBB is an essential component in the decidualization process. Trial registration number not applicable