Functional attributes of seminal proteins in bull fertility: a systematic review

Abstract

Proteomic approaches have been widely used in reproductive studies to uncover protein biomarkers of bull fertility. Seminal plasma is one of the most relevant sources of these proteins that may influence sperm physiology. Nonetheless, there are still gaps in existing knowledge in the functional attributes of seminal proteins. Thus, we reviewed the relationships between seminal plasma proteins and bull fertility by conducting a systematic review with data obtained from 71 studies. This review showed that the associations between fertility improvement with the use of total seminal plasma proteins are still controversial. None of the studies explored the sperm fertilizing ability following these interactions. By contrast, the exposure to a single protein, such as osteopontin, binder of sperm proteins, and heparin binding proteins, can increment sperm motility, capacitation, and fertilizing ability by modulating intracellular calcium concentrations, removing lipids from sperm membranes, and regulating the acrosome reaction. Variations in protein analyses and the protein contents and their abundances between animals contributed to the difficulty of establishing protein biomarkers of fertilizing potential of the bull sperm. Indeed, the heterogenicity of methodologies was a limitation of this review. Standardized methods of seminal protein analyses, as well as sperm endpoints, may minimize such discrepancies. In conclusion, potential biomarkers of sperm parameters are still to be established. Future studies should evaluate protein isoforms and how they interact with sperm to ascertain their biological functions.

Seminal Plasma: Relevant for Fertility?

“…Comprehensive sperm protein databases have been established for a plethora of species, including insects, avian, ruminants, porcine, equine, or human [ 11 , 32 , 34 , 62 , 63 , 64 , 65 ]. The sperm proteome covers the expected spectrum of function (from energy production to cell recognition), but few proteins are accurately linked to (in)fertility [ 66 ]. The seminal fluid proteome, even in species lacking all accessory sexual glands as in avian species [ 64 , 65 ], depicts clear phylogenetic relevance for fertility for its direct relation to sperm function, mechanisms of energy production/consumption, proteolysis and oxidoreduction.…”

“…However, differences in type and source of proteins are present among species, owing to the already named differences in glands and/or the sequence they are emptied, or the type of ejaculate they have. Comparative studies [ 63 ] have shown particular roles played by SP proteins in ruminants amply used for AI, holding single ejaculates [ 66 , 69 , 72 , 73 ], but also in species—including humans—with fractionated ejaculates, where the proteome type, concentration and temporal exposition are relevant [ 11 ].…”

Contributions of seminal plasma proteins to fertilizing ability of bull sperm: A meta‐analytical review

“…The fertilizing capacity of a male is influenced by sexual behaviour, endocrinology, genetics, and sperm intrinsic and extrinsic factors (Butler et al, 2019; Kastelic & Thundathil, 2008; Rodriguez‐Martinez et al, 2021). While intrinsic factors include sperm features, such as morphology, motility, concentration, and membrane integrity, extrinsic factors are related to non‐cellular components of semen capable of modulating sperm functional attributes (Evans et al, 2020; Özbek et al, 2020; Viana et al, 2021). Seminal plasma is one of these extrinsic factors.…”

“…Significant variations in fertility scores, sperm parameters, and sperm freezability of bulls relate to dissimilarities in the proteome of seminal fluid (Fouchécourt et al, 2002; Gomes et al, 2020; Jobim et al, 2004; Kasimanickam et al, 2019; Killian et al, 1993; Moura et al, 2006, 2007; Rego et al, 2016; Viana et al, 2018; Willforss et al, 2021). However, our recent systematic review found substantial asymmetry among the results published in those studies due to variations in methods of protein analysis, bovine breeds, semen collection, sperm endpoints, and sample storage conditions (Viana et al, 2021). Moreover, proteins associated with fertility parameters were tested in cause‐and‐effect experiments, which helped to confirm (or not) the empirical link detected between seminal protein and bull fertility (Viana et al, 2021).…”

“…Moreover, proteins associated with fertility parameters were tested in cause-and-effect experiments, which helped to confirm (or not) the empirical link detected between seminal protein and bull fertility (Viana et al, 2021).…”