Proteomic profiling of porcine seminal extracellular vesicles reveals potential in vivo fertility biomarkers.

Background: Predicting male fertility in farm animals remains a challenge. Seminal plasma (SP) contains a high amount of heterogeneous seminal extracellular vesicles (sEVs), believed involved in reproductive processes and maybe key to understanding male fertility.

Aims: To identify the sEV proteins that are differentially expressed between more and less fertile boars and that could be candidates for fertility biomarkers in boars used in artificial insemination (AI) programs.

Materials and methods: Small (S) and large (L) sEV subsets from SP samples of AI boars with differences in fertility: high (H) or low (L) farrowing rate (FR) and large (L) or small (S) litter size (LS). The S- and L-sEV subsets were isolated by size exclusion chromatography and characterized according to the Minimal Information for Studies of Extracellular Vesicles (MISEV2023) guidelines. Proteomic analyses (three biological replicates per fertility group and sEV subset) were performed using a Bruker timsTOF fleX™ instrument with data-independent acquisition parallel accumulation-serial fragmentation (diaPASEF) technology.

Results: A total of 470 and 726 proteins were quantified in S-sEVs and 1801 and 1834 proteins in L-sEVs from FR and LS boars, respectively. Differentially expressed sEV proteins (log₂fold change ≥±1, p ≤ 0.05 and effect size d of Cohen >2.0) were found between the fertility groups: seven in S-sEVs and 52 in L-sEVs between H-FR and L-FR boars, and 47 in S-sEVs and 52 in L-sEVs between L-LS and S-LS boars. Many of these differentially expressed sEV proteins are involved in reproductive processes, particularly in sperm function and sperm-zona pellucida binding, but also in embryo development and implantation.

Conclusions: The sEV proteome differs between more and less fertile boars, with many of the differentially expressed proteins known as involved in reproductive processes. This would suggest that sEVs may be involved in male fertility and that some of the differentially expressed sEV proteins could be potential fertility markers for AI boars.