LSC Abstract – miR-17 and -21 in intercellular communication via exosomes in allergic airway inflammation

Abstract

Background: miRNAs are critical regulators of signalling pathways and have lately been shown to be secreted into exosomes as a way of inter-cell communication (Valadi et al ., Nat Cell Biol, 2007). Previously, we found an increase of miR-17, -144 and -21 in murine lung homogenate in Ovalbumin (OVA) induced allergic airway inflammation (AAI) and in nasal epithelial cells of children with allergic asthma. Objective: We now aimed to decipher the role of the bronchial epithelium in the production and secretion of miRNAs in asthma. Methods: Air-liquid interface cultures of primary normal human bronchial epithelial (NHBE) cells were treated with Interleukin (IL)13 to model early epithelial changes to a T-helper 2 environment. Exoquick-TC (System Biosciences) was used to isolate exosomes and they were quantified by flow cytometry or ELISA for CD63. miRNAs were analysed by qRT-PCR. Results: Initially, miR-17 and -21 levels were increased upon IL13 in the basal compartment of NHBE cells and later on the apical side. Both miRNAs were significantly up-regulated in murine bronchoalveolar lavage of OVA- and house dust mite induced AAI, although total exosome amounts were similar. We were able to detect all miRNAs in exosomes of human nasal washes. Conclusion: NHBE cells secrete exosomes upon IL13 to the apical and basal cell side, which show differential miR-17 and -21 levels. Both exosomal miRNAs were increased in murine BALF in AAI and detectable in human paediatric asthma. This is a first hint that exosomal miRNA patterns are changing during AAI development which could perpetuate an asthmatic response between epithelial cells and expand it to e.g. immune cells.