Seminal plasma AnnexinA2 protein is a relevant biomarker for stallions which require removal of seminal plasma for sperm survival upon refrigeration†.

The research article discusses the identification of potential biomarkers in the seminal plasma (SP) of stallions, specifically the AnnexinA2 protein, required for maintaining sperm quality when the semen is cooled and stored. This biomarker helps identify the stallions which require removal of seminal plasma for sperm to survive during refrigeration.

Experiment Design and Methodology

• The study utilized high-performance liquid chromatography coupled with tandem mass spectrometry to define the proteome of the seminal plasma derived from 10 different stallions.
• Stallions were classified into three categories depending on their semen’s ability to maintain quality during refrigeration: good quality post direct extension in a commercial extender (good), stallions requiring seminal plasma removal (RSP) to maintain quality (good-RSP), and stallions unable to maintain quality post RSP (poor).
• A pathway enrichment analysis was carried out by g: profiler using the human orthologs of the proteins identified in equine seminal plasma, exposing enriched pathways related to hexose metabolism, vesicle mediated transport, post-translational protein modification, and immune response.

Key Findings

• Peroxiredoxin-6 like protein and transcobalamin-2, a primary vitamin B12-binding and transport protein, were found to be overrepresented in stallions that tolerate conservation by refrigeration.
• The protein ST3 beta-galactoside alpha-2,3-sialyltransferase 1, involved in protein glycosylation, was also prominent in these ‘good’ stallions, whereas it was almost absent in ‘poor’ stallions.
• Notably, the protein AnnexinA2 emerged as a strong discriminant variable for the identification of stallions needing RSP before refrigeration, showing a highly significant statisticical value (P = 0.002, q value = 0.005).

Significance and Impact

• This is the first detailed study of the protein structure of equine seminal plasma and demonstrates the potential value of particular proteins as discriminative biomarkers.
• These findings may significantly enhance the clinical classification of stallions for artificial insemination, improving the overall sperm conservation process and ensuring higher success rates in artificial insemination procedures.
• The research contributes to a better understanding of the sperm physiology of stallions and could also inform future therapeutic strategies to improve fertility in horses.