Expression and regulation of interleukin 6 and its receptor at the maternal-conceptus interface during pregnancy in pigs.

It has been well established that interleukin 6 (IL6), a pleiotropic cytokine with multiple functional roles, is widely expressed in the female reproductive tract and mediates blastocyst implantation and placental development in many species. Uterine expression of IL6 during early pregnancy has been studied in pigs, but expression and function of IL6 at the maternal-placental interface throughout pregnancy have not been determined. Thus, we examined expression of IL6 and its receptors, IL6 receptor (IL6R) and GP130, in the uterine endometrium on Days 12 and 15 of the estrous cycle, and Days 12, 15, 30, 60, 90, and 114 of pregnancy, conceptus on Days 12 and 15, and chorioallantoic tissues on Days 30, 60, 90, and 114 of pregnancy in pigs. The expression of IL6, IL6R, and GP130 mRNA in the endometrial tissues increased dramatically during mid-to late-pregnancy and decreased at term. IL6, IL6R, and GP130 mRNAs were also expressed in conceptus and chorioallantoic tissues. Expression of IL6 mRNA was mainly localized to endometrial epithelial and stromal cells and chorioallantoic tissues, while IL6R and GP130 mRNAs were localized to glandular epithelial cells during pregnancy. The expression of IL6 mRNA was decreased by estrogen and progesterone treatment, whereas increasing doses of IL1β induced the expression of IL6 mRNA, but not IL6R and GP130 mRNAs, in endometrial tissue explants. These results indicate that expression of IL6 and its receptors at the feto-maternal interface is regulated in a stage- and cell-type-specific manner during pregnancy, suggesting that IL6 and its receptor signaling system may play an important role in the maintenance of pregnancy in pigs.