Seminal plasma has conventionally been viewed as a transport and survival medium for mammalian sperm; however, its role now extends beyond this process to actively targeting female tissues. Studies in rodents, swine, and humans demonstrate that seminal plasma induces molecular and cellular changes within the endometrium or cervix following insemination. Seminal-plasmainduced alterations to the maternal environment have been theorized to facilitate embryo development, modulate maternal immunity toward the conceptus, and potentially improve pregnancy success. It is unknown if bovine seminal plasma modulates the uterine environment following insemination in the cow, where routine use of artificial insemination reduces maternal exposure to seminal plasma. We hypothesize that seminal plasma modulates the expression of inflammatory mediators in the endometrium, altering the maternal environment of early pregnancy. In vitro, seminal plasma altered intact endometrial explant expression of CSF2, IL1B, IL6, IL17A, TGFB1, IFNE, PTGS2, and AKR1C4. Furthermore, endometrial epithelial cell CSF2, CXCL8, TGFB1, PTGS2, and AKR1C4 expression were increased after seminal plasma exposure, while endometrial stromal cell CSF2, IL1B, IL6, CXCL8, IL17A, TGFB1, PTGS2, and AKR1C4 expression were increased following seminal plasma exposure. Endometrial expression of IL1B was increased in the cow 24 h after uterine infusion of seminal plasma, while other evaluated inflammatory mediators remained unchanged. These data indicate that seminal plasma may induce changes in the bovine endometrium in a temporal manner. Understanding the role of seminal plasma in modulating the maternal environment may aid in improving pregnancy success in cattle. Summary SentenceExposure of endometrial cells to seminal plasma alters gene expression of inflammatory mediators, reminiscent of the postcoital inflammatory response in other species.

The microenvironment of the ovarian follicle is key to the developmental success of the oocyte. Minor changes within the follicular microenvironment can significantly disrupt oocyte development, compromising the formation of competent embryos and reducing fertility. Previously described as a sterile environment, the ovarian follicle of women has been shown to contain colonizing bacterial strains, whereas in domestic species, pathogen-associated molecules are concentrated in the follicular fluid of animals with uterine infection. The aim of this study is to determine whether human granulosa-luteal cells mount an innate immune response to pathogenassociated molecules, potentially disrupting the microenvironment of the ovarian follicle. Human granulosa-luteal cells were collected from patients undergoing assisted reproduction. Cells were cultured in the presence of pathogen-associated molecules (LPS, FSL-1 and Pam3CSK4) for 24 h. Supernatants and total RNA were collected for assessment by PCR and ELISA. Granulosa-luteal cells were shown to express the molecular machinery required to respond to a range of pathogen-associated molecules. Expression of TLR4 varied up to 15-fold between individual patients. Granulosa-luteal cells increased the expression of the inflammatory mediators IL1B, IL6 and CXCL8 in the presence of the TLR4 agonist E. coli LPS. Similarly, the TLR2/6 ligand, FSL-1, increased the expression of IL6 and CXCL8. Although no detectable changes in CYP19A1 or STAR expression were observed in granulosa-luteal cells following challenge, a significant reduction in progesterone secretion was measured after treatment with FSL-1. These findings demonstrate the ability of human granulosa-luteal cells to respond to pathogen-associated molecules and generate an innate immune response.Reproduction (2016) 152 261-270

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Semen induces post-coital inflammation of the endometrium in several species. Post-coital inflammation is proposed to alter the endometrial environment of early pregnancy, mediate embryonic development and modulate the maternal immune response to pregnancy. In cattle, it is common for pregnancies to occur in the absence of whole semen due to the high utilization of artificial insemination. Here, we have utilized a cell culture system to characterize semen-induced expression of inflammatory mediators in bovine endometrial cells and test the efficacy of transforming growth factor beta as the active agent in mediating any such change. We hypothesize that seminal plasma-derived transforming growth factor beta increases the expression of inflammatory mediators in bovine endometrial cells. Initially, we describe a heat-labile cytotoxic effect of seminal plasma on BEND cells, and a moderate increase in IL1B and IL6 expression. In addition, we show that transforming growth factor beta is present in bovine semen and can increase the expression of endometrial IL6, whereas blocking transforming growth factor beta in semen ameliorates this effect. However, intra-uterine infusion of seminal plasma, sperm or transforming growth factor beta did not alter the endometrial expression of inflammatory mediators. We conclude that bovine semen can modulate endometrial gene expression in vitro, which is partially due to the presence of transforming growth factor beta. It is likely that additional, unidentified, bioactive molecules in semen can alter the endometrial environment. Characterizing bioactive molecules in bovine semen may lead to the development of additives to improve artificial insemination in domestic species.

The question of ‘how does the allogeneic fetus survive gestation in the face of the maternal immune system?’ has yet to be definitively answered. Several acceptable mechanisms exist to facilitate survival of the semi-allogeneic fetus in various species; paramount is the immunological separation of maternal and fetal tissues during gestation. However, keen observation of the maternal immune system during pregnancy has noted maternal immune tolerance to paternal-specific antigens. A mechanism by which the maternal immune system tolerates specific paternal antigens expressed on the fetus would be far more beneficial than the previously proposed immune indolence that would leave the mother susceptible to infection. In species like human or rodent, implantation occurs days after fertilisation and, as such, the mechanisms to establish antigen-specific tolerance must be initiated very early during pregnancy. We and others propose that these mechanisms are initiated at the time of insemination when paternal antigens are first introduced to the maternal immune system. Indeed, a new paradigm demonstrating the importance of paternal–maternal communication at the time of insemination is becoming evident as it relates to maternal tolerance to fetal antigen and ultimately pregnancy success.