PROBLEM: The objective of this study was to examine the susceptibility of rat uterine epithelial cells (UEC) to infection with Chlamydia trachomatis and to study the epithelial–stromal interactions following infection.
METHOD OF STUDY: UEC were isolated from adult rats and grown in culture. Polarized, confluent monolayers of UEC were infected with 106 IFU/well C. trachomatis (MoPn). In order to confirm infection, MoPn was labeled with a fluorescent tracking dye, PKH-26, and then used in epithelial cell infections. Transepithelial resistances were measured prior to and following infection to test the effect of Chlamydia on the integrity of the epithelial monolayers. In other experiments, polarized epithelial cultures were infected in the presence and absence of stromal cells. Media was collected from the apical and basolateral compartments of the cultures before and after infection and analyzed for cytokines IL-1α and TNF-α.
RESULTS: Epithelial cell cultures infected with PKH-26 labeled MoPn were examined 4–5 days later. Bacterial inclusions were detected inside epithelial cells indicating infection had occurred. Co-localization of PKH-26 labeled bacteria with FITC-labelled anti-Chlamydia antibody on the epithelial cells confirmed infection. No changes were found in resistance across the monolayers of epithelial cells in the presence or absence of infection. ELISA results indicate that UEC secrete IL-1α constitutively in vitro. Stromal cells secrete very little IL-1α. When stromal cells were co-incubated with epithelial cells there was a decrease in the amount of IL-1α secreted by epithelial cells 48 hr post-infection. On the other hand, maximum TNF-α was found in stromal cells, both with and without infection. Epithelial cells, in these studies made very little TNF-α.
CONCLUSIONS: These results show that primary rat epithelial cells can be infected with Chlamydia in vitro. Epithelial and stromal cells from uteri of adult rats make IL-1α and TNF-αin vitro both prior to and following infection with Chlamydia. This system can be used to analyze the role played by epithelial–stromal interactions in providing protection on this mucosal surface.