Increased expression of toll-like receptors 2 and 9 is associated with reduced DNA methylation in spontaneous preterm labor

Highlights • DNA methylation was significantly reduced for TLR-2 and TLR-9 genes in decidual tissue of women with spontaneous preterm labor not associated with clinical symptoms of infection as compared to women with normal term labor. • Reduced DNA methylation was associated with increased expression of TLR-2 and TLR-9, which was associated with a marked infiltration of macrophages and neutrophils into decidual tissue. • Gene expression of inflammatory cytokines and chemokines was remarkably increased in women with spontaneous preterm labor. • These data are consistent with epigenetic mechanisms playing a role in increasing the sensitivity of decidual tissue via increased leukocyte infiltration and expression of TLRs that might trigger labor prematurely in the absence of clinical infection.