Extracellular vesicles from oviductal and uterine fluids supplementation in sequential in vitro culture improves bovine embryo quality

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In vitro production of bovine embryos is a well-established technology, but the in vitro culture (IVC) system still warrants improvements, especially regarding embryo quality. This study aimed to evaluate the effect of extracellular vesicles (EVs) isolated from oviductal (OF) and uterine fluid (UF) in sequential IVC on the development and quality of bovine embryos. Zygotes were cultured in SOF supplemented with either BSA or EVs-depleted fetal calf serum (dFCS) in the presence (BSA-EV and dFCS-EV) or absence of EVs from OF (D1 to D4) and UF (D5 to D8), mimicking in vivo conditions. EVs from oviducts (early luteal phase) and uterine horns (mid-luteal phase) from slaughtered heifers were isolated by size exclusion chromatography. Blastocyst rate was recorded on days 7-8 and their quality was assessed based on lipid contents, mitochondrial activity and total cell numbers, as well as survival rate after vitrification. Relative mRNA abundance for lipid metabolism-related transcripts and levels of phosphorylated hormone-sensitive lipase (pHSL) proteins were also determined. Additionally, the expression levels of 383 miRNA in OF- and UF-EVs were assessed by qRT-PCR.

This work was supported by the Spanish Ministry of Science and Innovation (PID2019-111641RB-I00 to DR, and RTI2018-093548-B-I00 to AGA); São Paulo Research Foundation, Brazil (FAPESP; #2017/20339-3 and CNPq-Brazil 304276/2018-9 to CLVL; #2019/04981-2 to RM; 2014/22887-0 and 2015/21829-9 to JCDS); Minciencias-Colombia Postdoctoral Fellowship (848-2019) to KC-B; Secretaria de Educación Superior, Ciencia y Tecnología e Innovación (SENESCYT-Ecuador) to YNC.

Peer reviewed