Epithelial cells lining the uterine lumen are the first line of defense against pathogenic microbes. The objective of this study was to examine the expression of Toll-like receptors (TLRs), defensins and secretory leukocyte protease inhibitor (SLPI) in the mouse uterus and vagina and in primary uterine epithelial cells and to determine whether TLR agonists induce TLR and defensin expression.
Method of study
The mRNA expression of α- and β-defensins (AD1, 2 and 5 and BD1, 2 and 4) and SLPI was examined by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) along with the secretion of macrophage chemotactic protein-1 (MCP-1), measured by enzyme-linked immunosorbent assay.
Expression of TLR1–9 as well as β-defensins 1, 2 and 4 and SLPI by uterine and vaginal tissues was demonstrated by RT-PCR. β-Defensins and SLPI expression was greater in the vagina than in the uterus. Comparison of fresh and polarized uterine epithelial cells indicated that TLR2–6 expression was unaffected by culture. Incubation of polarized epithelial cells with TLR agonists [lipopolysaccharide (LPS), Pam3Cys, Poly (I:C) or PGN] induced TLR5 and TLR9 expression but had no effect on TLR4, defensins or SLPI. Furthermore, exposure to LPS, Pam3Cys, Poly (I:C) or PGN, induced MCP-1 secretion by polarized epithelial cells in culture.
These results indicate that the uterus and vagina as well as uterine epithelial cells are responsive to bacterial and viral pathogens. Not only do epithelial cells respond to TLR agonists by releasing MCP-1, which mediates inflammatory responses, but they also influence the expression of selected TLR genes to further enhance innate immune protection.