Expression of Toll-like receptors in murine vaginal epithelium is affected by the estrous cycle and stromal cells

Vaginal epithelium is regulated by female sex hormones and serves as the first line of innate immune defense against sexually transmitted infections (STIs). This occurs in part through recognition of pathogens via Toll-like receptors (TLRs); however, the expression and role of TLRs in reproductive tract immunity are poorly understood. Here, we have compared the effect of the estrous cycle and treatment with DepoProvera (Depo) on TLR mRNA expression in whole mouse vaginal tissue, vaginal epithelium isolated using laser capture microdissection (LCM) and in primary vaginal epithelial cells (ECs) grown in vitro. Distinct patterns of TLR expression were observed in LCM-isolated vaginal epithelium versus whole vaginal tissue. Absolute quantitative RT-PCR of LCM vaginal epithelium showed that expression of all TLRs, except TLR11, was significantly increased during the diestrus phase or following Depo-treatment. TLR2 mRNA showed an extraordinary increase in expression in both diestrus and following Depo-treatment (23-fold) over that in the estrus phase. Although TLR2 protein was expressed at similar levels over the estrous cycle in whole vaginal tissue, full-length TLR2 protein was only detected during diestrus or after Depo-treatment in LCM-isolated vaginal epithelium. Distinct TLR mRNA expression profiles were seen also in primary vaginal ECs in vitro and only expression of TLR2 was significantly decreased in ECs cultured in the presence of stromal cells. Thus, TLR expression in vaginal ECs is regulated by sex hormones and can be affected by stromal cells. These findings contribute to our understanding of innate immune defense against STIs and enhance the quality of woman's reproductive health.