Sperm-oviduct interaction and the binding test: insights into bull fertility and endocrine modulation
Carvalho, José de OliveiraCortat, Paula RenataDode, Margo Alves NunesSartori, Roberto
The interaction between spermatozoa and bovine oviductal epithelial cells (BOEC) plays a crucial role in fertilization, particularly in the formation of the sperm reservoir in the isthmus. This adhesion not only prolongs sperm viability and functionality but also regulates the timed release of spermatozoa towards the fertilization site. The process is mediated by specific molecular mechanisms, including sperm surface proteins (such as BSPs), annexins, and glycoproteins from the oviductal extracellular matrix. Moreover, the hormonal environment, especially circulating estradiol and progesterone concentrations, modulates the epithelial receptivity and the dynamics of sperm binding. Historically, the sperm-BOEC binding assay has been used to assess sperm viability and function. However, emerging studies have demonstrated its potential as a predictive biomarker of bull fertility. Notably, experiments using long-term co-incubation with oviductal explants have revealed significant correlations between sustained sperm binding capacity and field fertility outcomes. Bulls with higher pregnancy per artificial insemination tend to maintain sperm binding for longer periods, suggesting a link between binding longevity and reproductive competence. Additionally, despite widespread use, conventional semen analysis often fails to detect subfertile bulls, as many sperm traits do not consistently correlate with field fertility. The sperm-BOEC binding assay offers a more integrative approach by evaluating the ability of sperm to interact with the female reproductive tract under conditions that closely mimic the in vivo environment. This review highlights the physiological and molecular mechanisms involved in sperm-oviduct interaction and supports the binding assay as a potential tool for improving fertility assessment in bulls, with implications for AI programs and reproductive efficiency in cattle.(AU)
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