Reproduction Abstracts

The implantation process requires well-coordinated interactions between the maternal uterus and the developing embryo. In pigs, embryo implantation begins around day (D) 12 of pregnancy. During this period, the conceptus undergoes a dramatic morphological change and the elongated filamentous conceptus secretes various biological products such as estrogens and cytokines, interleukin-1β (IL1B), interferon-γ (IFNG), and IFN-δ (IFND). In response to these conceptus signals as well as the ovarian hormone, progesterone, the uterine endometrium becomes receptive to the conceptus. Estrogen acts as the signal for maternal recognition of pregnancy, and increases expression of many uterine endometrial genes, including AKR1B1, FGF7, IL1RAP, LPAR3, SPP1, STAT1, and TRPV6. IL1B of conceptus origin also affects endometrial functions. Especially, IL1B affects synthesis and transport of endometrial prostaglandins (PGs) by increasing endometrial expression of PG-synthetic enzymes, PTGS1, PTGS2, and AKR1B1, and PG transporters, ABCC4 and SLCO2A1. IL1B induces endometrial expression of IL1B receptors. IL1B in concert with estrogen also increases endometrial production of salivary lipocalin 1, a lipid-binding protein, during early pregnancy. It is known that IFNG and IFND, which are produced by the conceptus with the highest levels on D14 – D16 of pregnancy, do not have an anti-luteolytic effect as IFN-τ in ruminants does, but the detailed function of IFNG and IFND in the uterus is not well understood in pigs. Recent data from ours and others indicate that IFNG induces endometrial expression of the IFN signaling molecules, STAT1, STAT2, IRF1, and IRF2, and CIITA, SLA-DQA, and SLA-DQB. Further analysis of the molecules derived from the conceptus and the endometrium will provide insights into the cellular and molecular basis of maternal–conceptus interactions during early pregnancy in the pig.