Alterations in miRNA expression may play a role in the pathogenesis of asthma. Our aim was to identify miRNAs that are differentially expressed in bronchial biopsies of asthmatics compared to healthy controls and to explore their association with clinical asthma parameters. Small RNA sequencing data from bronchial biopsies of 79 asthmatics and 82 healthy controls was used to determine differential miRNA expression. The analysis was repeated in 30 non-smoking, ICS negative asthmatics and 42 non-smoking healthy controls. The differentially expressed miRNAs were associated with clinical parameters, including FEV1% predicted, neutrophil and eosinophil counts in blood, sputum and bronchial biopsies. In total 78 miRNAs were differentially expressed in bronchial biopsies from asthmatics compared to healthy controls. Of those 78 miRNAs, 62 were also differentially expressed in non-smoking, ICS negative asthmatics compared to non-smoking healthy controls. The most significant miRNAs were miR-16-5p, miR-451a, miR-125a/b and the let-7 family. Of the 62 asthma-associated miRNAs, 25 miRNAs correlated with one or more clinical asthma parameters. Lower levels of let-7a and let-7c were significantly associated with higher levels of blood and tissue eosinophils within asthma, while lower levels of miR-125a/b were associated with lower FEV1% predicted and higher blood eosinophils and neutrophils within asthma. In conclusion, various miRNAs including miR-125a/b and the let-7 family are differentially expressed in bronchial biopsies from asthmatics compared to healthy controls and are associate with multiple clinical asthma features. Based on the literature and our data, we suggest that those miRNAs might serve as potential asthma biomarker.
