Extracellular vesicles regulate survival, Ca2+, and tyrosine phosphorylation in bovine spermatozoa

MORENO, A; ADRE, AA; FRANCHI, NA; GIOJALAS, LC

Parana

Congreso; 54th Annual Meeting Argetine Society for Biochemistry and Molecular Biology; 2018

SAIB

It is known that secretions present in the oviductal fluids affect sperm function, although the underlying mechanisms are unknown. Extracellular vesicles (EV) have been recently identified along the female reproductive tract, including the uterus and the oviduct. We have previously shown that endometrial EV stimulate human spermatozoa capacitation. Thus, since both capacitation and acrosome reaction (AR) depend on an increase in intracellular calcium concentration (Ca2+i), we hypothesized that the regulation of Ca2+i could be mediated by EV. Bovine oviductal EV isolated from isthmus and ampullary regions were composed of exosome and microvesicle populations of different size, determined by dynamic light scattering, and presented the EV protein markers CD81 and HSP70. Highly motile sperm cells from cryopreserved bovine semen samples were selected, and incubated either in medium containing EV or in control medium. Cell survival at different time points, the level of protein tyrosine phosphorylation (p-Tyr), Ca2+i, and AR were evaluated. We found that incubation with EV increased cell survival versus control conditions. Flow cytometry analysis of Ca2+i using the calcium indicator Fura-4 AM showed that oviductal EV induce an immediate increase in Ca2+i, and also showed that after a prolonged incubation time, a higher Ca2+i was found only in the presence of EV. Moreover, EV induced sperm capacitation, determined by an increase in both protein p-Tyr and AR. Thus, our results contribute to elucidate the role of EV in the regulatory mechanism of the oviductal environment on different processes associated with sperm fertilizing capacity.