RBPJ mediates uterine repair in the mouse and is reduced in women with recurrent pregnancy loss.

Unexplained recurrent pregnancy loss (uRPL) is associated with repeated embryo loss and endometrial repair with elevated endometrial expression of inflammatory cytokines, including IFN-γ. Notch signaling through its transcription factor recombination signal binding protein Jκ (RBPJ) regulates mechanisms including the immune response and repair after tissue injury. Initially, null mutation of RBPJ in the mouse uterus ( Pgr ^cre/+ Rbpj ^f/f ; Rbpj c-KO) results in subfertility, but we have found that these mice become infertile after pregnancy as a result of dysfunctional postpartum uterine repair, including delayed endometrial epithelial and myometrial regeneration. RNA sequencing of postpartum uterine repair sites revealed global up-regulation of inflammatory pathways, including IFN signaling. Consistent with elevated IFN-γ, macrophages were recruited and polarized toward an M1-cytotoxic phenotype, which is associated with preventing repair and promoting further tissue injury. Through embryo transfer experiments, we show that dysfunctional postpartum repair directly impairs future embryo implantation in Rbpj c-KO mice. Last, we clinically correlated our findings from the Rbpj c-KO mouse in women diagnosed with uRPL. Reduced RBPJ in women with uRPL was associated with increased levels of IFN-γ. The data, taken together, indicate that RBPJ regulates inflammation during endometrial repair, which is essential for future pregnancy potential, and its dysregulation may serve as an unidentified contributor to uRPL in women.-Strug, M. R., Su, R.-W., Kim, T. H., Mauriello, A., Ticconi, C., Lessey, B. A., Young, S. L., Lim, J. M., Jeong, J.-W., Fazleabas, A. T. RBPJ mediates uterine repair in the mouse and is reduced in women with recurrent pregnancy loss.