Sperm-female interactions in the pig oviduct, a key for insemination success?

Fertilization in mammals depends on a finely tuned dialogue between spermatozoa and the female reproductive tract, particularly within the utero-tubal junction and oviduct. These regions serve as sites for sperm storage, selection, and final preparation for fertilization, and as such, are crucial for insemination success and fertility outcomes. This review summarizes current knowledge on sperm-oviduct interactions, focusing on four key aspects. First, recent advances in in vitro models used to investigate sperm-oviduct dynamics are provided, from traditional cell monolayers to advanced three-dimensional models that more closely reproduce the oviduct lumen. Second, molecular insights into the oviductal sperm reservoir are presented, emphasizing adhesion molecules involved in sperm binding and lifespan. Third, evidence indicating that oviduct epithelial cells and ligands could select high-quality sperm based on morphology, viability, capacitation level and fertilizing capacity, thereby contributing to reproductive efficiency is provided. Finally, this review examines the influence of insemination timing on the functional role of the sperm reservoir, along with the potential use of sperm binding assays to predict boar fertility under field conditions. Overall, the oviduct emerges as a dynamic and selective environment that plays multiple roles in fertilization. Despite major progress in identifying molecular players and developing relevant in vitro models, the mechanisms by which sperm-interactions shape reproductive success in pigs remains an exciting partly unknown topic for future research.