Sperm-mediated regulation of region-specific responses in the oviduct during establishment of pregnancy in mice

Abstract

The oviduct comprises 4 main regions: infundibulum (oocyte pick-up), ampulla (fertilization), isthmus (sperm capacitation and reservoir, preimplantation embryonic development), and uterotubal junction (UTJ; sperm and embryo transport). Mounting evidence in livestock and rodents suggest that gametes alter gene expression in secretory and ciliated epithelial cells of the oviduct. To elucidate whether adaptive interactions between the oviduct and gamete/embryo exist, we performed bulk RNA-sequencing on oviductal tissues collected from infundibulum+ampulla (IA) or isthmus+UTJ (IU) at various developmental stages (0.5, 1.5, 2.5-, and 3.5-days post coitus (dpc)) in mice. Samples were also collected during days 0.5, 1.5, 2.5, and 3.5 of pseudopregnancy (dpp). We found a strong region (IA vs. IU)-specific expression of large clusters of genes. The transition from 0.5 dpc to other pregnancy timepoints induces large sets of differentially expressed genes (DEGs) in pregnancy and pseudopregnancy in both IA and IU regions. Specifically, genes involved in pro-inflammatory responses were detected in both IU and IA regions. The presence of sperm at 0.5 dpc induces DEGs involved in pro-inflammatory responses in the IU region with an enrichment of biological processes for inflammatory cytokines, macrophage, and neutrophil recruitment. Additionally, DEGs are enriched in mitogen-activated protein kinase (MAPK) pathways along with genes in the Dusp family, Map3k8, Il1b, and Il1r2, among others. However, at 1.5 dpc we observed a strong shift to an anti-inflammatory condition in the IU region. These observations were absent in 0.5 and 1.5 dpp, suggesting that the DEGs observed for those inflammatory responses during pregnancy were likely induced by the presence of sperm. scRNA-seq analysis revealed that the inflammatory responsive genes were likely produced by secretory epithelial cells, compared to other cell types in the oviduct. In addition, multiple DEGs involved in pyruvate and glycolysis were enriched in the IU region, which could provide metabolic support for developing embryos. Lastly, we have also identified that there were cells that express immune markers in the oviduct, indicating that the oviduct is an immuno-dynamic tissue. In conclusion, our findings indicate that the oviduct is adaptive and responsive to the presence of sperm and embryos in a spatiotemporal manner. In this report, we intend to disseminate our findings on the transcriptional profiles during different stages of pregnancy. The complete study and validation at the protein level are currently underway and will be updated as soon as the data are available.