In brief: Insufficient trophoblast invasion at the maternal-fetal interface contributes to abortion-prone pregnancy. Our study shows that decreased levels of IGFBP7 in unexplained recurrent spontaneous abortion (URSA) trophoblast cells inhibit MMP2 and Slug expression as well as trophoblast invasion, suggesting that IGFBP7 should be considered a potential therapeutic protein target in URSA.
Abstract: Insufficient trophoblast invasion at the maternal-fetal interface contributes to abortion-prone pregnancy. Cyclosporine A (CsA) can exert therapeutic effects on URSA by promoting trophoblast invasion. A previous study showed decreased expression of insulin-like growth factor-binding protein 7 (IGFBP7) in the sera of recurrent spontaneous abortion patients. However, the role of IGFBP7 in URSA remains unknown. The aim of this study was to determine whether IGFBP7 modulates trophoblast invasion in URSA and the underlying molecular mechanisms. We found that IGFBP7 was expressed at lower levels in villous specimens from URSA patients. Manipulating IGFBP7 expression significantly affected the MMP2 and Slug expression in HTR-8/SVneo cells as well as trophoblast invasion in vitro. Inactivation of IGF-1R by IGFBP7 was observed, and IGF-1R inhibition increased the IGFBP7-induced MMP2 and Slug expression in HTR-8/SVneo cells. Moreover, the level of c-Jun was significantly upregulated in the URSA group. Silencing IGFBP7 increased the binding of downstream c-Jun to the MMP2 and Slug promoter regions in HTR-8/SVneo cells, thus suppressing transcription. In addition, increased expression of IGFBP7 in HTR-8/SVneo cells was observed upon CsA treatment. Knockdown of IGFBP7 inhibited the CsA-enhanced MMP2 and Slug expression in HTR-8/SVneo cells. Our results suggest that in normal pregnancy, IGFBP7 induces MMP2 and Slug expression via the IGF-1R-mediated c-Jun signaling pathway, thereby promoting trophoblast invasion. IGFBP7 depletion in URSA inhibits MMP2 and Slug expression as well as trophoblast invasion. Moreover, IGFBP7 participates in CsA-induced trophoblast invasion, suggesting that IGFBP7 is a potential therapeutic target for URSA.