Chlamydia trachomatis (Ct), the most common sexually transmitted bacterium, has been associated with adverse pregnancy outcomes including controversial data on miscarriage, intrauterine growth restriction and low birth weight, however the causative mechanisms are unknown. A successful pregnancy requires normal endometrial stromal cell (ESC) decidualisation and trophoblast invasion, processes that involve chemokine action and lead to successful implantation. My objectives were to determine whether Ct infection impacts upon ESC decidualisation and chemokine secretion on human primary ESC invitro, to investigate the role of Ct infection in pregnancy in-vivo using a murine model of pregnancy and to investigate the role of Ct in miscarriage in a statistically powered case control study. A novel finding is that Ct can infect and proliferate in ESC, resulting in suboptimal decidualisation as measured by decidualisation marker prolactin’s reduced mRNA and protein levels in infected ESC. Furthermore, the altered secreted chemokine profile of decidualised ESC suggests an attenuated innate immune response from infected ESC. Focusing on chemokines C-X-C motif chemokine 12 (CXCL12) and CXCL16, important for trophoblast invasion, decreased mRNA and protein concentrations were detected in infected decidualised cells. From the in-vivo mouse model of past Ct infection in pregnancy, it was demonstrated that Ct infection did neither affect the fertility of the mice, pregnancy or resorption numbers in C3H mice nor alter embryonic and placental weight on e12 embryos. However, Ct infection caused reduction of embryo and placenta weight on e14 embryos. Finally, preliminary data from the case control study indicate that past Ct infection is not associated with miscarriage. Our in house PGP3 ELISA that detects past Ct infection was more sensitive than a commercially available MOMP ELISA. My data suggests that Ct infection affects pregnancy during the implantation stage by impairing decidualisation and altering chemokine secretion predisposing for adverse pregnancy outcomes that include growth restriction during later gestation.

Studies indicate that estrogen enhances Chlamydia trachomatis serovar E infection in genital epithelial cells. Hormones have direct and indirect effects on endometrial epithelial cells. Estrogen and progesterone exposure induces endometrial stromal cells to release effectors that subsequently regulate growth and maturation of uterine epithelial cells. Estrogen enhances C. trachomatis infection by aiding entry and intracellular development in endometrial epithelial cell (Ishikawa, IK)/SHT-290 stromal cell co-culture. Enhanced chlamydial infection was mediated by direct estrogen-stimulated signaling events in epithelial cells and indirectly via estrogen-induced stromal cell effectors. The current study investigates the effects of hormones on chlamydial development using culture conditions representative of the menstrual cycle. Chlamydia trachomatis-infected IK or IK/SHT-290 cultures were exposed to 10(-8) M estrogen (E2), 10(-7) M progesterone (P4) or a combination of both hormones (10(-8) M E2 followed by 10(-9) M E2/10(-7) M P4). Chlamydial infectivity and progeny production were significantly decreased (30-66%) in cultures exposed to progesterone or estrogen/progesterone combination compared to estrogen alone. Thus, progesterone antagonized the positive effects of estrogen on chlamydial infection. These data indicate the susceptibility of endometrial epithelial cells to C. trachomatis infection during the menstrual cycle is altered by phase specific actions of sex hormones in the genital tract.