Abstract
Oviductal extracellular vesicles (oEVs) have been proposed as key modulators of gamete/embryo maternal interactions. The aim of this study was to examine the metabolite content of oEVs and its regulation across the estrous cycle in cattle. Oviductal EVs were isolated from bovine oviducts ipsilateral and contralateral to ovulation at four stages of the estrous cycle (post-ovulatory stage, early and late luteal phases, and pre-ovulatory stage). The metabolomic profiling of EVs was performed by proton nuclear magnetic resonance spectroscopy (NMR). NMR identified 22 metabolites in oEVs, among which 15 were quantified. Lactate, myoinositol, and glycine were the most abundant metabolites throughout the estrous cycle. The side relative to ovulation had no effect on the oEVs’ metabolite concentrations. However, levels of glucose-1-phosphate and maltose were greatly affected by the cycle stage, showing up to 100-fold higher levels at the luteal phase than at the peri-ovulatory phases. In contrast, levels of methionine were significantly higher at peri-ovulatory phases than at the late-luteal phase. Quantitative enrichment analyses of oEV-metabolites across the cycle evidenced several significantly regulated metabolic pathways related to sucrose, glucose, and lactose metabolism. This study provides the first metabolomic characterization of oEVs, increasing our understanding of the potential role of oEVs in promoting fertilization and early embryo development.
Highlights
Exosomes and microvesicles, collectively known as extracellular vesicles (EVs), are membrane-enclosed particles able to transfer a complex selection of molecular compounds from one cell to another, and in this way play key roles in cell-to-cell communications [1]
Oviductal EVs samples contained a majority of vesicles resembling exosomes and a small population of vesicles resembling microvesicles (>100 up to 500 nm: 23.7 ± 0.8%), with similar proportions among stages, as we previously showed in cattle [9]
There is an increasing number of studies analyzing the metabolomics of EVs in different biological fluids, since both metabolites and EVs are being considered as valuable biomarkers of health conditions and play a crucial part in cell-to-cell communications
Summary
Collectively known as extracellular vesicles (EVs), are membrane-enclosed particles able to transfer a complex selection of molecular compounds from one cell to another, and in this way play key roles in cell-to-cell communications [1]. Previous studies in mice showed that incubation of spermatozoa with oEVs activates a Ca2+ efflux pomp, PMCA4, which is important for the acquisition of sperm hyperactivated motility and fertilizing competence [6]. OEVs from donor oviduct fluid in the transfer medium were shown to improve birth rates after the transfer of in vitro produced embryos to recipient mothers [11]. All together, these data support the idea that oEVs play important roles in sperm capacitation, fertilization, and early embryo development
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