Molecules regulating sperm adhesion to and release from the oviduct across species: A systematic review.

Despite advances in assisted reproductive technologies (ARTs) such as in vitro fertilization (IVF), fertilization failure remains a major bottleneck in both clinical and animal reproduction, often due to suboptimal sperm selection and premature capacitation processes. One critical but underutilized biological system in sperm selection is the functional sperm reservoir formed in the oviduct after insemination. In this context, spermatozoa bind to epithelial cells in the isthmic region of the oviduct to maintain viability while acquiring fertilization competence until ovulation signals trigger their release from the functional reservoir. While the role of steroid hormones in the sperm-oviductal epithelial cell interaction has been well elaborated, evidence gathered over the years shows that biomolecular factors play a complementary but equally important role in sperm binding to and release from oviductal cells. This review systematically synthesizes evidence from studies investigating interactive biomolecules influencing sperm binding to and release from oviductal epithelial cells (OEC) using in vitro models. Overall, studies reviewed indicate that sperm binding to and release from the OEC, as well as the fertilizing competency of the released spermatozoa, are influenced by specific carbohydrates, glycoproteins, glycosaminoglycans, seminal plasma proteins, and endocannabinoids. Tyrosine phosphorylation states of sperm and the effects of cryopreservation and sex-sorting, also play a role in sperm fertilization competence. Since the interaction between sperm and OEC is crucial for successful fertilization in vivo, these biomolecules, and sperm physiological states also represent a promising target for improving IVF outcomes using cryopreserved or fresh and sex-sorted or non-sorted semen in mammalian species.