S100As are calcium-binding proteins with two EF-hand calcium-binding motifs. In several studies, S100A proteins are described to play important roles in pro-inflammatory responses including damage-associated molecular pattern (DAMP) signaling and in the establishment of pregnancy. However, the role of S100As have not been determined in the uterine endometrium during the estrous cycle in pigs. Thus, this study was performed to investigate expression and regulation of S100A8, S100A9, and S100A12 in the uterine endometrial tissues during the estrous cycle in pigs. Real-time RT-PCR analysis showed that S100A8, S100A9, and S100A12 mRNAs were expressed in the uterine endometrium during the estrous cycle with higher levels on days 15 and 18 of the estrous cycle than other days of cycle. To investigate the effects of steroid hormones, estradiol (E2) and progesterone (P4), on expression of S100A8, S100A9, and S100A12 mRNAs, endometrial tissue explants from immature pigs were treated with steroid hormones. Levels of S100A8, S100A9, and S100A12 were increased by the treatment of P4, and the increased levels of S100A8, S100A9, and S100A12 by P4 were not inhibited by the treatment of progesterone receptor antagonist, RU486. However, levels of S100A8, S100A9, and S100A12 were decreased by treatment of MEK inhibitor, U0126. These results exhibited that S100As were expressed in the uterine endometrium during the estrous cycle in a cyclic stage-specific manner, and their expression was affected by P4. These suggest that S100As may play an important role in endometrial function during the proestrous period of the estrous cycle in pigs. [Supported by the Next Generation Biogreen 21 program (#PJ01119103), Rural Development Administration, and by Korea Research Foundation (#2015R1D1A1A01058356)]

For the establishment and maintenance of successful pregnancy the maternal immune system must tolerate semi-allogenic fetus during pregnancy. Several mechanisms explaining immune tolerance have been proposed. Among those, it has been suggested that the CD40/CD40L system is involved in immune tolerance in several tissues. However, expression and function of CD40/CD40L in the maternal-fetal interface during pregnancy have not been studied in pigs. Thus, this study determined expression and localization of CD40 and CD40L in the uterine endometrium during pregnancy in pigs. We obtained uterine endometrial tissue samples from day (D) 12 and D15 of the estrous cycle and from D12, D15, D30, D60, D90 and D114 of pregnancy. Quantitative real-time PCR analysis showed that levels of CD40L mRNA expression during pregnancy increased on D15 of pregnancy and decreased thereafter whereas levels of CD40 mRNA was highest on D30 of pregnancy. Localization of CD40 and CD40L proteins by immunohistochemistry showed that CD40 was localized to vascular endothelial cells with strongest signal intensity on D15 of pregnancy, and CD40L was localized to luminal epithelial cells on D15 of pregnancy and amniotic membrane during mid- to late pregnancy. To determine the effect of IFNG on CD40 and CD40L expression, we took advantage of endometrial explant culture using tissues from D12 of the estrous cycle, and found that CD40 was up-regulated by IFNG in a dose-dependent manner. These results showed that CD40 and CD40L were expressed in the uterine endometrium in a cell-type and stage-specific fashion during pregnancy, and IFNG induced CD40, indicating that the CD40/CD40L system may be important for establishment and maintenance of pregnancy in pigs. [Supported by the Next Generation BioGreen21 Program (#PJ01110301), Rural Development Administration]