Influence of Extracellular Vesicles of the Follicular Fluid on Morphofunctional Characteristics of Human Sperm

Abstract

We studied the effect of extracellular vesicles of the follicular fluid on morphofunctional characteristics of human spermatozoa using CASA (computer-assisted sperm analysis) analytical system. The vesicles were obtained by sequential centrifugation at different rotational speeds and frozen at -80°C in the Sydney IVF Gamete Buffer medium. The sperm fraction was isolated from the seminal fluid of 21 patients aged 27-36 years by differential centrifugation in a density gradient. The precipitate was suspended in Sydney IVF Gamete Buffer to a concentration of 10⁶/ml and incubated with vesicles (1:2) at 37°C in a CO₂ incubator for 30 min and 1 h. Sperm fraction incubated without vesicles served as the control. After incubation, some sperm samples were centrifuged at 700g for 5 min and fixed in 2.5% glutaraldehyde in 0.1 M buffer for transmission electron microscopy. After 30-min and 1-h incubation, the progressive and total sperm motility improved, the curvilinear and linear velocity of spermatozoa did not change significantly. Incubation with vesicles significantly changed the trajectory of sperm movement, which can attest to an increase in their hyperactivation and, probably, fertilizing capacity. Analysis of the effect of extracellular vesicles of follicular fluid on sperm motility will help to improve the effectiveness of assisted reproductive technology programs with male infertility factor by improving sperm characteristics in patients with asthenozoospermia and increasing the fertilizing ability of the sperm.

Keywords: assisted reproductive technology; exosomes; extracellular vesicles; follicular fluid; spermatozoa.