Reprogramming the epigenetic profile improves the B regulatory cell function of patients with recurrent pregnancy loss.

Nearly half of patients with recurrent pregnancy loss (RPL) link to disrupted maternal immune tolerance. IL-10-production regulatory B cells (Bregs) are functionally impaired in RPL, but the underlying mechanisms remain unclear. This study aimed to identify these mechanisms and test suberoylanilide hydroxamic acid (SAHA) as a potential therapy. Peripheral Bregs were isolated from 30 RPL patients and 30 healthy controls (HCs). Epigenetic assays (chromatin immunoprecipitation for DNMT1 occupancy, methylation profiling of the IL10 promoter), ubiquitination analyses (focusing on K48-linked polyubiquitin chains), and functional co-cultures with CD3/CD28-activated effector T cells (Teffs) were performed. SAHA (0.5-5 μM) was tested after validating non-toxicity via cell viability assays. Compared to HCs, RPL Bregs showed significantly elevated IL10 promoter methylation (HC: 22 ± 5% vs. RPL: 48 ± 8%; p < 0.0001) and overexpression of DNA methyltransferase 1 (DNMT1), which correlated with reduced IL-10 secretion (HC: 325 ± 45 pg/mL vs. RPL: 180 ± 30 pg/mL; p < 0.001) and impaired Teff suppression (suppressive index: HC: 0.52 ± 0.08 vs. RPL: 0.21 ± 0.06; p < 0.001). DNMT1 accumulation in RPL Bregs was driven by reduced binding to the E3 ubiquitin ligase TRIM28, leading to diminished K48-linked polyubiquitination (a signal for proteasomal degradation). Treatment with SAHA restored TRIM28 expression, enhanced DNMT1 ubiquitination and degradation, reversed IL10 promoter hypermethylation, and rescued IL-10 secretion and Breg-mediated Teff suppression. These effects were abolished by TRIM28 siRNA, confirming TRIM28 dependence. TRIM28 deficiency disrupts DNMT1 degradation, leading to DNMT1-mediated IL10 silencing and Breg dysfunction in RPL. SAHA targets the TRIM28-DNMT1-IL10 axis to restore immune tolerance, representing a precision therapy for immune-mediated RPL.