ABSTRACT: BMI1, a polycomb transcriptional repressor, regulates the cell cycle, stem cells, proliferation, invasion, and apoptosis. However, the specific role of BMI1 in spontaneous abortion (SA) remains unclear. BMI1 expression levels were detected in control and SA tissues by qRT-PCR and immunofluorescence. HTR-8/SVneo cells were subjected to interference, PTC-209 treatment, or overexpression experiments to evaluate the impact of BMI1 on the biology of trophoblasts and reactive oxygen species (ROS) production in vitro. RNA-seq, ChIP-seq, ChIP-qPCR, and cell salvage assays, identified CSTA and TGFB2 as target molecules associated with the epigenetic regulation of BMI1. Individuals with SA exhibited a reduced levels of BMI1 in villous tissues, as confirmed by qRT-PCR and immunofluorescence. In vitro interference with BMI1, or the application of PTC-209, a BMI1-specific inhibitor, inhibited the proliferation, clonogenicity, and migration of trophoblast cells but enhanced apoptosis. BMI1 overexpression induced the opposite effects. Moreover, we observed enhanced proliferation, migration, and colony formation in cells that had been treated with PTC-209 and a diverse range of NAC concentrations when compared to cells treated with PTC-209. Despite the reduction of ROS, full restoration was not achieved. CSTA and TGFB2 were identified as novel target molecules that participate in the epigenetic regulation of BMI1. Specifically, the overexpression of CSTA did not exert influence on total AKT protein expression but significantly reduced the levels of phosphorylated AKT. The overexpression of TGFB2 did not influence the levels of SMAD2/3 but induced a notable increase in phosphorylated SMAD2/3 proteins. Finally, the suppression of CSTA and TGFB2 counteracted the effects of BMI1 deficiency in trophoblasts. The regulation of trophoblast function by BMI1, including the production of ROS in the cytoplasm and the epigenetic modifications of CSTA and TGFB2 in nuclei, could facilitate the identification of mechanisms underlying SA.
