Reassessment of the Proteomic Composition and Function of Extracellular Vesicles in the Seminal Plasma

Seminal plasma contains a high concentration of extracellular vesicles (EVs). The heterogeneity of small EVs or the presence of nonvesicular extracellular matter (NV) pose major obstacles in understanding the composition and function of seminal EVs. In this study, we employed high-resolution density gradient fractionation to accurately characterize the composition and function of seminal EVs and NV. We found that the seminal EVs could be divided into 3 different subtypes-namely, high-density EV (EV-H), medium-density EV (EV-M), and low-density EV (EV-L)-after purification using iodixanol, while NV was successfully isolated. EVs and NV display different features in size, shape, and expression of some classic exosome markers. Both EV-H and NV could markedly promote sperm motility and capacitation compared with EV-M and EV-L, whereas only the NV fraction induced sperm acrosome reaction. Proteomic analysis results showed that EV-H, EV-M, EV-L, and NV had different protein components and were involved in different physiological functions. Further study showed that EV-M might reduce the production of sperm intrinsic reactive oxygen species through glutathione S-transferase mu 2. This study provides novel insights into important aspects of seminal EVs constituents and sounder footing to explore their functional properties in male fertility.