An inflammatory response is induced in the reproductive tract by deposition of semen during natural mating. This response might facilitate establishment and maintenance of pregnancy and alter the phenotype of the offspring by modifying the microenvironment of the reproductive tract. Here, we hypothesized that intrauterine infusion of 0.5 mL of seminal plasma at the time of artificial insemination (AI) in first-service lactating Holstein cows will improve pregnancy success after insemination. Cows were inseminated (511 primiparous cows inseminated with X-sorted semen, 554 multiparous cows inseminated with X-sorted semen, and 627 multiparous cows inseminated with conventional semen) using the Double-Ovsynch protocol. Cows were randomly assigned to receive intrauterine infusion of either 0.5 mL of seminal plasma or saline immediately after AI. There was no overall effect of seminal plasma infusion on the percentage of inseminated cows diagnosed pregnant at d 32 or 60 after AI, pregnancy loss, or percent of inseminated cows calving. If cows were inseminated with conventional semen, seminal plasma reduced pregnancies at d 32 and tended to reduce calvings. There was no effect of seminal plasma if cows were inseminated with X-sorted semen. Seminal plasma infusion increased the birth weight of heifer calves born using X-sorted semen but not conventional semen. These results do not support a beneficial effect of seminal plasma on pregnancy success after AI, but exposure to seminal plasma may program fetal development to affect phenotype at birth.

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.

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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.