The potential role of seminal extracellular vesicles as biomarkers of male fertility and sperm cryotolerance in livestock species

Abstract

Abstract Seminal extracellular vesicles are lipid bilayer membrane-bound vesicles that contain the important biomolecules of semen and function in intercellular communication in the reproductive tract. They are secreted by the male reproductive tract epithelium and the accessory sex glands particularly seminal vesicle and prostate. The number of extracellular vesicles in seminal plasma is greater than that in other body fluids, but are the least studied, especially in livestock species. In vitro studies on the influence of seminal extracellular vesicles on spermatozoa functions have revealed their potential role in improving semen quality and preservation. Their role as cryoprotectants in semen cryopreservation is a less developed area and has a good scope for research. SEVs are isolated from seminal plasma by various methods based on the principle of size and density gradient separation. Ultracentrifugation combined with density gradient ultracentrifugation is the most commonly used isolation method. Characterization is done based on their morphology, specific membrane markers (CD9and CD63), particle size and concentration. Many proteomic and transcriptomic studies have revealed compositional differences between the seminal extracellular vesicles of fertile and sub-fertile populations. This provides the hope of utilizing these vesicles as noninvasive diagnostic biomarkers of fertility. The ability of these vesicles to protect their cargo from phagocytosis and degradation makes them more relevant and reliable diagnostic biomarkers. This review discusses and summarizes the information from the studies available on seminal extracellular vesicles and their potential applications in improving semen quality and preservation. Also micro RNAs and protein cargo of SEVs show altered expression in pathological and infertility conditions. Hence their expression level in SEVs could be used as potential biomarkers for male fertility in livestock species.

Keywords

• Seminal extracellular vesicles
• Exosomes
• Isolation
• Characterization
• Fertility
• Biomarkers