The successful establishment and maintenance of pregnancy is achieved by well-coordinated interactions between the maternal uterus and the implanting conceptus. In pigs, the conceptus undergoes dramatic morphological and functional changes, and secretes various biological products such as estrogens and cytokines, interleukin-1beta (IL1B), interferon-gamma (IFNG), and IFN-delta (IFND) during the implantation period. The uterine endometrium in response to the conceptus-derived molecules and ovarian progesterone becomes receptive to the conceptus by changing cell adhesion molecule expression, epithelial cell depolarization and secretory activity. Conceptus-derived estrogen acts as the maternal pregnancy recognition signal which changes the direction of endometrial prostaglandin (PG) F2 secretion from the uterine vasculature into the uterine lumen. Estrogen also induces the expression of a variety of endometrial genes, including AKR1B1, FGF7, LPAR3, and SPP1. The function of cytokines, IL1B, IFNG, and IFND, in the endometrium is not fully understood, but some recent work shows that IL1B is involved in the synthesis and transport of endometrial PGs by regulating endometrial expression of PG-synthetic enzymes, PTGS1, PTGS2, and AKR1B1, and PG transporters, ABCC4 and SLCO2A1. Estrogen and IL1B also stimulate endometrial expression of IFN signaling molecules, suggesting that estrogen and IL1B act cooperatively on priming the endometrial function of conceptus IFNG and IFND. In turn, IFNG derived from the elongating conceptuses, induces many endometrial genes, including CXCL9, CXCL10, CXCL12, and SLA-DQ. The role of IFND at the maternal-conceptus interface is not well understood yet. Further analysis of the molecules derived from the endometrium and conceptus will provide insights into the cellular and molecular basis of maternal-conceptus interactions for the establishment of successful pregnancy in pigs.

• Hakhyun Ka(Division of Biological Science & Technology, Yonsei University)