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 non-vesicular
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 three 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 (ROS) through Glutathione
S-transferase Mu 2 (GSTM2).This study provides novel insights into
important aspects of seminal EVs constituents and sounder footing to
explore their functional properties in male fertility.