Abstract
During early development, embryos secrete extracellular vesicles (EVs) that participate in embryo–maternal communication. Among other molecules, EVs carry microRNAs (miRNAs) that interfere with gene expression in target cells; miRNAs participate in embryo–maternal communication. Embryo selection based on secreted miRNAs may have an impact on bovine breeding programs. This research aimed to evaluate the size, concentration, and miRNA content of EVs secreted by bovine embryos with different developmental potential, during the compaction period (days 3.5–5). Individual culture media from in vitro–produced embryos were collected at day 5, while embryos were further cultured and classified at day 7, as G1 (conditioned-culture media by embryos arrested in the 8–16-cells stage) and G2 (conditioned-culture media by embryos that reached blastocyst stages at day 7). Collected nanoparticles from embryo conditioned culture media were cataloged as EVs by their morphology and the presence of classical molecular markers. Size and concentration of EVs from G1 were higher than EVs secreted by G2. We identified 95 miRNAs; bta-miR-103, bta-miR-502a, bta-miR-100, and bta-miR-1 were upregulated in G1, whereas bta-miR-92a, bta-miR-140, bta-miR-2285a, and bta-miR-222 were downregulated. The most significant upregulated pathways were fatty acid biosynthesis and metabolism, lysine degradation, gap junction, and signaling pathways regulating pluripotency of stem cells. The characteristics of EVs secreted by bovine embryos during the compaction period vary according to embryo competence. Embryos that reach the blastocyst stage secrete fewer and smaller vesicles. Furthermore, the loading of specific miRNAs into the EVs depends on embryo developmental competence.
Highlights
During the last years, molecular transfer within extracellular vesicles (EVs) has been described as a new mechanism for cellular communication [1,2]
Embryo developmental potential was considered to organize two groups of EVs: Non-competent embryos were those blocked during compaction (G1), while competent embryos were those that developed to blastocyst stage (G2)
The nanoparticles collected from each experimental group were characterized as EVs, using the criteria suggested by Théry et al [21]
Summary
Molecular transfer within extracellular vesicles (EVs) has been described as a new mechanism for cellular communication [1,2]. These are released to the extracellular environment by different cell types and are heterogeneous in origin, size, and content [3]. Due to their content (mRNAs, small RNAs, proteins, lipids, and DNA) and their ability to transfer signaling molecules to receptor cells, EVs have been proposed as disease biomarkers and potential therapeutic agents [4,5]. The most competent bovine embryos secrete fewer but larger EVs during blastulation [12,13]
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