Attributes of a large cohort of human seminal extracellular vesicles with varied sperm features.

RESEARCH QUESTION: Do human seminal plasma extracellular vesicles (SPEV) vary with distinct sperm features and possess clinical relevance for male infertility?

DESIGN

Semen samples were provided for analysis: normozoospermic (n = 64); oligozoospermic (n = 35); asthenozoospermic (n = 51); teratozoospermic (n = 16); and azoospermic cases (n = 134). Size-exclusion chromatography was used to isolate SPEV, and concentration and size distribution were assessed via nanoparticle tracking analysis. Protein concentrations were measured using BCA Protein Assay Kits. Continuous variables were analysed as mean with a 95% CI.

RESULTS

Highest mean SPEV concentration was observed in the normozoospermic group (4.9 × 1010/ml; 95% CI 3.5 -6.3 × 1010/ml); lowest mean concentration was found in azoospermic group (0.6 × 1010/ml; 95% CI 0.5 -0.8 × 1010/ml). Pearson coefficients of SPEV concentration with sperm count, progressive motility and total motile sperm count were 0.250, 0.344 and 0.433, respectively. Mean SPEV size from infertile men with non-obstructive azoospermia (NOA) is significantly smaller than that from men who have undergone a vasectomy or with obstructive azoospermia (151.3 nm, 95% CI 147.6 to 155.0 nm versus 159.4 nm, 95% CI 154.0 to 164.8 nm, P = 0.049). Mean protein content per SPEV particle is significantly higher in the NOA group than the vasectomy or obstructive azoospermia group (93.41 ag, 95% CI 50.67 to 132.6 ag versus 44.24 ag, 95% CI 24.74 to 63.74 ag, P < 0.001). The AUC curve is 0.702 (P < 0.001).

CONCLUSION

Concentration of SPEV significantly correlates with total motile spermatozoa. Protein content per SPEV particle may be a potential marker to distinguish obstructive azoospermia from NOA.