Inhibiting FKBP5 might alleviate obstetric antiphospholipid syndrome by regulating macrophage polarization.

The disturbance of immune balance at the maternal-fetal interface is a significant contributor to obstetric antiphospholipid syndrome (OAPS); however, the precise mechanisms underlying this disturbance remain unclear. This study investigates the immune regulatory role of FK506-binding protein 5 (FKBP5) to elucidate its molecular mechanisms in pathological pregnancies associated with OAPS. We conducted RNA sequencing (RNA-seq) analysis and immune cell typing on decidual tissue from OAPS patients and healthy controls. The results indicated that the FKBP5 gene and inflammation-related pathways were significantly expressed in the maternal-fetal interface of OAPS patients, characterized by an increase in M1 (iNOS+/CD86+) macrophages and a decrease in M2 (Arg-1+/CD206+) macrophages. In vitro experiments demonstrated that FKBP5 promotes M1-like polarization of macrophages via the JAK1/STAT1 pathway while inhibiting M2-like polarization through the PPARγ/STAT6 pathway. Using a macrophage-trophoblast cell co-culture model, we found that FKBP5-induced abnormal macrophage polarization at the maternal-fetal interface negatively impacted the migration, invasion, and proliferation of trophoblast cells. In a mouse model of OAPS, the knockout of FKBP5 regulated the abnormal polarization of macrophages between M1 and M2 phenotypes, facilitated epithelial-to-mesenchymal transition (EMT), and mitigated antiphospholipid antibodies (aPLs)-mediated placental pathological damage. Notably, SAFit2, a small molecule inhibitor of FKBP5, effectively improved adverse pregnancy outcomes in OAPS mice. The immune microenvironment imbalance at the maternal-fetal interface, driven by FKBP5-regulated macrophage polarization, constitutes a critical immunological basis for aPLs-mediated placental damage. Therefore, FKBP5 presents a potential therapeutic target for OAPS.