Exosomes from bovine endometrial epithelial cells ensure trophoblast cell development by miR‐218 targeting secreted frizzled related protein 2

Abstract Endometritis is a common disease affecting fertility in cows during the perinatal period, which disturbs the molecular milieu of the uterine environment and impairs embryo development and implantation. Exosomes are important extracellular components that transmit a variety of micro RNAs (miRNAs), which perform key regulatory functions. In this study, we investigated plasma exosomal miRNAs from cows with endometritis and from cultured endometrial epithelial cells (EECs) challenged with lipopolysaccharide (LPS) to explore the role of EEC‐derived exosomes and their miRNAs in bovine endometritis. Plasma exosomes were collected from nine healthy dairy cows and nine dairy cows with endometritis, and culture supernatant exosomes were isolated from EECs challenged with or without LPS. Exosomal RNA was extracted using commercial kits and miRNA profiles were generated using RNA‐seq. We found that miR‐218 was differentially expressed in EECs under conditions of endometrial inflammation. Inhibition studies suggested that reduced levels of miR‐218 in EEC‐derived exosomes when transferred into placental trophoblast cells impaired embryonic development and decreased placental trophoblast cell migration by targeting secreted frizzled related protein 2. We propose that exosomal miR‐218 secreted from EECs acts as a driver of embryonic development and differentiation. In addition, exosomal miR‐218 may provide a valuable diagnostic marker for bovine endometritis.