Extracellular vesicle-encapsulated miR-21-5p in seminal plasma prevents sperm capacitation via Vinculin inhibition

Abstract

To penetrate the zona pellucida before sperm-egg binding, sperm must undergo highly time-controlled capacitation and acrosome reaction in the female reproductive tract. Our previous study demonstrated that miR-21-5p is the most abundant miRNA in boar seminal plasma (SP)-derived extracellular vesicles (EVs) and can target Vinculin (VCL) gene, which may participate in boar sperm capacitation. Thus, this study aims to explore the potential role of miR-21-5p from SP-derived EVs in preventing sperm capacitation and its underlying mechanism. We observed that sperm could incorporate miR-21-5p from SP-derived EVs. The roles of SP-derived EVs miR-21-5p in sperm capacitation were then determined using gain- and loss-of-function analyses. In addition, the expression levels of miR-21-5p, VCL, and VCL protein in liquid-preserved boar sperm following transfection were determined using RT-qPCR and Western blotting. Our results revealed that miR-21-5p overexpression inhibited sperm capacitation and acrosome reaction. Similarly, miR-21-5p expression was significantly lower (P < 0.05) in capacitated sperm than un-capacitated sperm. However, the protein level of VCL was also significantly lower (P < 0.05) in capacitated sperm than un-capacitated sperm. Furthermore, immunofluorescence analysis showed that VCL protein mainly located in sperm head and sperm capacitation was inhibited after treating with VCL protein inhibitor (Chrysin). In conclusion, our study provides reasonable evidence that miR-21-5p expression in SP-derived EVs could prevent sperm capacitation via VCL inhibition.

Keywords: Boar; Extracellular vesicles; Sperm; Sperm capacitation; Vinculin; miR-21-5p.