99 EXTRACELLULAR VESICLES OF BOVINE OVIDUCTAL FLUID MODIFY THE GENE EXPRESSION ON BOVINE IN VITRO-DERIVED EMBRYOS

Abstract

Extracellular vesicles (EVs) act as intercellular communicators through their protein, lipid, and mRNA content. The interaction of EVs from oviducal environment and the first stages of embryo development is currently an enigma. The aim of the present study was to evaluate the developmental competence and the expression profile of bovine blastocysts cultured with previously purified EVs recovered from ampullary and isthmic oviducal fluid (OF) under different centrifugal forces. OF-EVs recovered from oviducts of slaughtered heifers in early luteal phase were quantified with a nanoparticle tracking analysis system, and their integrity and size were assessed by electron microscopy. In vitro-produced zygotes were cultured in SOF+3 mg mL^–1 BSA (C–), C– with 3 × 10⁵ OF-EVs/mL from the ampulla (A) and isthmus (I) isolated at 1 × 10³ (A10k and I10k, respectively) and 1 × 10⁵ (A100k and I100k, respectively) × g. A control culture group of SOF+5% FCS (C+) was included. Blastocyst development was recorded on Day 7, 8, and 9 (D0: day of fertilization). Blastocysts on Days 7/8 cultured in C–, C+, I10k, and I100k were used to measure the relative mRNA expression of genes related with membrane trafficking (AQP3, AQP11, and ATP1A1), metabolism (LDLR and LDHA), and epigenetics (DNMT3A, IGF2R, GRB10, and SNRPN) by RT-qPCR. One-way ANOVA was used for statistical analysis. The size of ampullary and isthmic OF-EVs was similar with a mean of 220 nm. The concentration of I10k was significantly lower compared with A100k (3.6 × 10⁸ v. 10.5 × 10⁸ EVs/mL, respectively; P < 0.05); however, no differences were found in the rest of the groups with a mean concentration of 7.6 × 10⁸ EVs/mL. EVs and C– groups showed a delayed embryo development at Day 7 compared with C+ (range: 12.0–13.8 v. 20.6%, respectively, P < 0.05); however, it was compensated at Days 8 and 9 (Day 9 range: 28.5–30.8%). The water channel related protein AQP3, associated with blastocoel formation, water, and cryoprotectant movement during cryopreservation, was up-regulated in I10k and I100k blastocysts compared with C+. The lipid receptor LDLR, proposed as a regulator of lipid uptake in blastocysts, was significantly down-regulated in C+ compared with the other groups, a possible consequence of a higher concentration of lipids in the C+ group. The de novo DNA methyltransferase DNMT3A and the imprinting gene SNRPN were down-regulated in the C+ compared with I100k, suggesting alterations in imprinting. In conclusion, bovine isthmic OF-EVs supplementation in in vitro embryo culture has a positive effect on gene expression patterns of developmental related genes compared with serum supplementation, suggesting an association between the oviducal environment and the developing embryo.

Funded by the Spanish Ministry of Science and Innovation (AGL2012–37510 and AGL2012–39652-C02–01).