Extracellular vesicles from human Fallopian tubal fluid benefit embryo development in vitro
STUDY QUESTION:  Do extracellular vesicles (EVs) from human Fallopian tubes exert an influence on early embryo development in vitro?  SUMMARY ANSWER: Human Fallopian tube EVs carrying miRNAs increase murine embryo viability in vitro. WHAT IS KNOWN ALREADY: Oviductal EVs (oEVs) are recently identified key players in embryo-oviduct interactions that contribute to successful pregnancy in vivo. Their absence in current in vitro systems may partly explain the suboptimal embryo development observed, therefore further knowledge is needed about their impact on early embryos. STUDY DESIGN, SIZE, DURATION: The oEVs were isolated from the luminal fluid of human Fallopian tubes using ultracentrifugation. We cocultured oEVs with murine two-cell embryos until the blastocyst stage. The study was conducted between August 2021 and July 2022. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 23 premenopausal women were recruited for Fallopian-tubes collection, and the oEVs were isolated. The micro RNA (miRNA) contents were detected using high-throughput sequencing and their target genes and effects were analyzed. After in vitro culture with or without oEVs, the blastocyst and hatching rates were recorded. Furthermore, for the blastocysts formed, we assessed the total cell number, inner cell mass proportion, reactive oxygen species (ROS) level, number of apoptotic cells and mRNA expression levels of genes involved in development. MAIN RESULTS AND THE ROLE OF CHANCE: EVs were successfully isolated from the human Fallopian tubal fluid and the concentrations were evaluated. A total of 79 known miRNAs were identified from eight samples that had been sequenced, all involved in various biological processes. The blastocyst rate, hatching rate, as well as total cell number of blastocysts were significantly increased in the oEVs-treated groups (p < 0.05 versus untreated), while the proportion of inner cell mass showed no significant difference between groups. ROS levels and apoptotic cell proportions were decreased in the oEVs-treated groups (p < 0.05 versus untreated). The genes, Actin-Related Protein 3 (Actr3), Eomesodermin (Eomes), and Wnt Family Member 3A (Wnt3a)  were upregulated in blastocysts in the oEVs-treated group. Overall design: Extracellular vesicles were isolated from eight Fallopian tube samples