Amniotic Fluid Soluble Myeloid Differentiation‐2 ( sMD ‐2) as Regulator of Intra‐amniotic Inflammation in Infection‐induced Preterm Birth

Problem TLR 4 mediates host responses to pathogens through a mechanism that involves protein myeloid differentiation‐2 ( MD ‐2) and its soluble form sMD ‐2. The role of sMD 2 in intra‐amniotic inflammation‐induced preterm birth has not been previously explored. Method of study Human amniotic fluid ( AF ) sMD ‐2 was studied by Western blotting in 152 AF samples of patients who had an amniocentesis to rule‐out infection (yes infection, n  = 50; no infection, n  = 50) or women with normal pregnancy outcome (second trimester genetic karyotyping, n  = 26; third trimester lung maturity testing, n  = 26). Histological localization and mRNA expression of MD 2 in fetal membranes were studied by immunohistochemistry and RT ‐ PCR . The ability of fetal membrane to release sMD ‐2 and inflammatory cytokines was studied in vitro . Results Human AF contains three sMD ‐2 proteoforms whose levels of expression were lower at term. Intra‐amniotic infection upregulated sMD ‐2. MD ‐2 mRNA and immunohistochemistry findings concurred. In vitro , LPS and monensin increased, while cycloheximide decreased sMD ‐2 production. Recombinant sMD ‐2 modulated TNF ‐α and IL ‐6 levels in a dose‐ and time‐dependent fashion. Conclusion sMD 2 proteoforms are constitutively present in human AF . The intensity of the intra‐amniotic inflammatory response to bacteria or perhaps to other TLR 4 ligands may be facilitated through synthesis and release of sMD 2 by the amniochorion.