Lung exosomal miRNAs discriminate between healthy ex-smokers and COPD

Exosomes are small extracellular vesicles released by all cell types in the lung. They contain miRNAs, small non-coding RNAs, able to regulate vast networks of genes relevant to pathologies such as COPD.  The aim of this work was to identify differentially expressed exosomal miRNA in the lungs of COPD that target genes important in the underlying pathogenesis. Exosomes were isolated from bronchoalveolar lavage fluid (BALF) by size exclusion chromatography from 14 healthy ex-smokers and 17 mild to moderate COPD patients, with a mean FEV1 of 78.9% predicted (SD±14.4%). Exosomal miRNA was sequenced using the Illumina NextSeq500, de-multiplexed, trimmed and aligned to hg19. Differentially expressed miRNA were identified and validated by RT-qPCR. A greater proportion of miRNA (p=0.02) and small RNA (p=0.01) were found in COPD exosomes. 54 miRNAs were significantly differentially expressed between COPD and healthy ex-smokers (FDR 2, with two upregulated and three downregulated in COPD. 3 of these miRNA had a good predictive ability of discriminating between COPD and healthy ex-smokers (area under receiver operating characteristic curve >0.8). Network-based analysis identified these miRNA targeted genes as central to pro-inflammatory pathways (e.g. Jak-STAT & MAPK signalling) important in COPD pathogenesis. These genes and pathways are being investigated using primary ex-vivo cell culture models. Importantly, we observed differential expression of exosomal microRNAs in these relatively mild COPD subjects, which target key proinflammatory genes. These data provide new insights into the persistent inflammation seen in COPD and could identify future targets for disease modifying therapies.