Spermatozoa induce transcriptomic alterations in bovine oviductal epithelial cells prior to initial contact

The capability of spermatozoa to directly influence maternal gene expression is already established. Indeed, some of the changes induced by spermatozoa may be of direct functional importance in the pre-conception period. Although the mechanisms underlying these sperm-maternal interactions are not well characterized, it is possible that they could involve ligands that are released from the sperm surface. This study therefore aimed to test whether physical contact between bovine spermatozoa and oviductal epithelial cells (BOECs) is a prerequisite for spermatozoa-induced gene expression changes.We used two co-culture models: a contact co-culture model in which spermatozoa interact directly with BOECs, and a non-contact co-culture model in which an insert of pore size 0.4um was placed between spermatozoa and BOECs.Messenger RNA sequencing of BOECs revealed ten differentially expressed genes in response to contact co-culture and 108 differentially expressed genes in response to the non-contact co-culture system after 10 hours. Retinol metabolism and ovarian steroidogenesis were examples of significantly enriched pathways in the non-contact co-culture system. Subsequently, q-PCR analysis revealed that transcriptional responses can be rapid, with increased expression of four genes (DHRS3, CYP1B1, PTGS2, and ATF3) detectable within just 90 minutes of co-incubation, but with expression levels highly dependent on the type of co-culture system.The findings from our study demonstrate for the first time that direct contact with spermatozoa is not necessary to induce changes in gene expression of oviductal epithelial cells, suggesting that spermatozoa may be able to signal to maternal tissues in advance of their arrival.