Silencing TGF-β3 Alleviates Recurrent Spontaneous Abortion Inflammation in Mice: the Importance of Treg/Th17 Cell Balance

Recurrent spontaneous abortion (RSA), also known as repeated miscarriage, refers to the consecutive loss of pregnancy three times or more before the fetus reaches viability. In this study, we aimed to investigate the impact of transforming growth factor β3 (TGF-β3), which plays a crucial role in immune dysregulation, on the imbalance of regulatory T cell (Treg) and T helper 17 (Th17) cells. First, we isolated T cells from an RSA mouse model we established in-house. Tregs and Th17 cells were labeled by targeting forkhead box protein P3 (Foxp3) and retinoic-acid-receptor-γt (RORγt), respectively, and the levels of Tregs and Th17 were determined by flow cytometry. The expression levels of Foxp3, RORγt, TGF-β3, interleukin (IL)-10, and IL-17 in T cells were measured by means of reverse-transcription quantitative polymerase chain reaction (qRT-PCR) and Western blotting. The levels of interferon-γ (IFN-γ), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-4 in mouse serum were quantified using enzyme-linked immunosorbent assay (ELISA). si-TGF-β3 was transfected into RSA mice, and the expression levels of IL-17 and CD25 were determined by flow cytometry, during which T cells were labeled with antibodies against IL-17 and CD25, respectively. Additionally, si-TGF-β3 or TGF-β3 interference therapy was administered to RSA mice, and the expression levels of IL-1β, tumor necrosis factor-α (TNF-α), IL-6, IFN-γ, GM-CSF, and IL-4 in mouse serum were measured using ELISA. In the RSA model, there was a significant decrease in the percentage of Treg cells, alongside an elevation of TGF-β3 mRNA (p < 0.05). The percentage of Th17 cells in RSA mice significantly increased and correlated positively with TGF-β3 levels. In RSA, the levels of pro-inflammatory cytokines IL-1β, TNF-α, IL-6, IFN-γ, and GM-CSF increased, while those of anti-inflammatory cytokine IL-4 decreased (p < 0.05). Transfection of si-TGF-β3 into RSA mice reduced the percentage of Th17 cells and increased the percentage of Tregs and Treg/Th17 (p < 0.05). Increased levels of Th17-related markers and reduced levels of Tregs-related markers occurred following the administration of TGF-β3 to RSA mice (p < 0.05). Transfection of si-TGF-β3 into RSA mice also resulted in a decrease in pro-inflammatory cytokines and an increase in anti-inflammatory cytokines (p < 0.05), while TGF-β3 administration reversed these changes in RSA mice, indicating the role of TGF-β3 in modulating the inflammatory response during RSA. Knockdown of TGF-β3 enhanced Treg/Th17 balance in RSA, suggesting TGF-β3 as a potential therapeutic target for RSA.