Mechanisms of vaginal bacteria-induced fetal membrane damage and tocilizumab's therapeutic potential in PPROM

This study investigates the deleterious effects of vaginal opportunistic pathogens on fetal membranes and evaluates the therapeutic potential of tocilizumab (TCZ), an interleukin-6 (IL-6) receptor antagonist, in attenuating these effects, aiming to improve strategies for the prevention and treatment of preterm prelabor rupture of membranes (PPROM).

Bioinformatics analyses were conducted to identify inflammatory pathways associated with PPROM. Clinical specimens, including placental tissue and peripheral blood samples, were collected postpartum. Placental pathology was performed to assess the incidence of histological chorioamnionitis. Peripheral blood levels of IL-6 were quantified using enzyme-linked immunosorbent assay (ELISA). The expression of phosphorylated JAK2 and STAT3, key components of the JAK-STAT signaling pathway, in fetal membrane tissues was examined by Western blotting. Immunohistochemistry (IHC) was employed to detect the expression and localization of matrix metalloproteinase-9 (MMP-9) and its tissue inhibitor-1 (TIMP-1) in placental tissues. For in vitro experiments, a co-culture model incorporating bacteria and fetal membrane-derived WISH cells was established to evaluate the effects of bacterial infection on cell viability and apoptosis. Subsequently, IL-6 levels in the cell supernatants were measured. Western blotting was used to detect the activation of the JAK-STAT pathway in bacterially infected WISH cells, and immunocytochemistry (ICC) was performed to assess the expression and localization of MMP-9 and TIMP-1. Finally, the modulatory effects of TCZ on bacterially infected WISH cells were analyzed.

Bioinformatics analysis identified inflammatory pathways, particularly the JAK-STAT pathway, as being associated with PPROM. Clinical samples revealed a higher incidence of clinic chorioamnionitis(CCA) in PPROM cases. Elevated peripheral plasma IL-6 levels were detected in individuals with PPROM, accompanied by increased phosphorylation of JAK2 and STAT3 in fetal membrane tissues, along with upregulated MMP-9 and downregulated TIMP-1 expression. In vitro, infection with Streptococcus agalactiae(S.agalactiae), Enterococcus faecalis(E. faecalis), or Escherichia coli (E.coli) significantly reduced WISH cell viability and induced apoptosis. Bacterial infection also led to markedly increased IL-6 levels in culture supernatants. In infected WISH cells, enhanced p-JAK2 and p-STAT3 were observed, together with elevated MMP-9 and reduced TIMP-1 expression. TCZ treatment reduced IL-6 levels. It inhibited JAK2 and STAT3 phosphorylation in fetal membrane tissues. MMP-9 expression was downregulated, and TIMP-1 expression was restored.

Vaginal opportunistic pathogens contribute to PPROM by compromising fetal membrane integrity through activation of inflammatory pathways such as JAK-STAT, disruption of the MMP-9/TIMP-1 balance, reduction of cell viability, and induction of apoptosis. TCZ, by targeting the IL-6 signaling axis, demonstrates potential to intervene in this pathological process, offering a promising therapeutic strategy for the prevention and treatment of PPROM.