Baicalein prevents pregnancy loss by maintaining regulatory T cell activation through inhibition of the TLR4/NF-κB signaling pathway

Introduction Unexplained recurrent spontaneous abortion (URSA) involves multifactorial etiologies, with regulatory T cells (Tregs) playing a pivotal role in maintaining immune tolerance during pregnancy. Baicalein, a flavonoid from Scutellaria baicalensis, exhibits anti-inflammatory and immunomodulatory properties. This study evaluates baicalein's therapeutic potential in mitigating URSA via the TLR4/NF-κB signaling pathway. Methods A URSA mouse model was used, and baicalein was administered intraperitoneally. Pregnancy outcomes, abortion rates, and placental morphology were assessed on gestational day 14 (G14). Treg cells were quantified via flow cytometry, and gene/protein expression levels were analyzed by immunohistochemistry, Western blotting, and real-time PCR. In vitro experiments on ihESCs further investigated the role of the TLR4/NF-κB pathway. Results Baicalein reduced abortion rates from 33.3 % in URSA mice to 21.6 % (low dose) and 14.8 % (high dose), improved embryonic development by altering placental structure and decidual morphology, and reduced inflammation at the maternal-fetal interface. It expanded Treg cells and enhanced the expression of IGFBP-1 and PRL, markers of endometrial decidualization, and decreased TLR4, p-P65, and P65 expression. In vitro, baicalein's effects were abrogated by TLR4 inhibition, confirming pathway specificity. Discussion Baicalein improved pregnancy outcomes by enhancing Treg function and promoting decidualization via TLR4/NF-κB pathway inhibition. These findings highlight baicalein's potential as a therapeutic agent for URSA.