Daphnetin Modulates Immune Balance and Enhances Pregnancy Viability in a Mouse Model of Unexplained Recurrent Abortion.

Background: Our previous research revealed that daphnetin (7,8-dihydroxycou-marin) positively influences the balance between forked transcription factor P3 (Foxp3+) regulatory T cells (Treg) and T helper 17 (Th17) cells in the peripheral blood mononuclear cells of individuals with unexplained recurrent pregnancy loss. However, the specific mechanism remains unclear. This research aims to further examine how daphnetin regulates the Th17 cell/Foxp3+ Treg cell imbalance in a mouse model with unexplained recurrent spontaneous abortion (URSA).

Methods: Mice (n = 40) were allocated into the following groups: daphnetin high dose (4 mg/kg·day), daphnetin low dose (1 mg/kg·day), URSA model, and normal pregnancy (control). We used flow cytometry for assessing the Th17/Treg cell ratio in peripheral blood mononuclear cells, quantitative real-time polymerase chain reaction for measuring cytokine expression levels, and transmission electron microscopy for observing ultrastructural changes in decidual tissues and calculating the embryo absorption rate.

Results: Compared to the URSA model group, daphnetin significantly reduced the T17cell/Foxp3+ Treg cell ratio in peripheral blood mononuclear cells. Daphnetin also decreased the expression of Th17 cell-related cytokines, including orphan nuclear receptor γt (RORγt) and signal transduction and transcriptional activator 3 (STAT3), as well as increase the expression of Foxp3+ Treg cells-related cytokines, including STAT5 and Foxp3+. Furthermore, daphnetin reduced the embryo absorption rate and improved the decidual tissue ultrastructure of URSA model mice.

Conclusion: Daphnetin improves the Th17 cell/Foxp3+ Treg cell imbalance in URSA model mice, thereby contributing to the repair of decidual tissue damage and reducing the embryo absorption rate. These findings suggest that daphnetin may offer a new method for treating URSA.