Oviductal extracellular vesicles interact with bovine spermatozoa and enhance capacitation

ANAHÍ FRANCHI; ESTEBAN DOMINGUEZ; AMIRA J. ADRE; MARÍA PIOTTO; LAURA C. GIOJALAS

Buenos Aires

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

Sociedades de Biociencias

Secretions present in the uterus and oviductal fluids affect oocyte and sperm function, whereas the underlying cellular mechanisms are unknown. Extracellular vesicles EV are composed of a lipid bilayer containing transmembrane proteins and enclosing cytosolic proteins and nucleic acids. EV have been recently identified along the female reproductive tract, including the uterus and oviduct, where they were called uteromes and oviductosomes, respectively. In a previous publication we showed that EV secreted by endometrial cells stimulated the level of capacitated human spermatozoa up to 4-fold, which may enhance the in vitro fertilization rate. Since sperm capacitation is ultimately accomplished in the oviduct, we propose that oviductosomes also induce sperm capacitation thus favoring in vitro fertilization. In vitro fertilization procedures cannot be performed in humans for ethical reasons. Therefore, in order to test the hypothesis that oviductal EV induce sperm capacitation, we first established an animal model. EV obtained from bovine oviductal fluid were characterized, and their in vitro interaction with spermatozoa was analyzed. A heterogeneous, ~50-500 nm diameter EV population with the characteristic cup-shape morphology was observed. PKH26-labeled EV were incubated with bovine sperm, and after only 15 minutes the lipidic fluorescent membrane marker PKH26 was detected in spermatozoa, suggesting that fusion mechanism had occurred between EV and sperm membranes. Moreover, sperm capacitation triggered by EV collected from the ampula and istmus regions of the oviduct was determined by evaluating acrosome reaction and protein tyrosine phosphorylation. Similar to our observations with human uterosome-like vesicles, a rapid incorporation of oviductal EV to bovine spermatozoa was observed, which results in enhanced sperm fertilizing capacity. Thus, our preliminary results suggest a novel EV-mediated mechanism of intercellular communication between oviductal cells and spermatozoa.