Role of microRNAs and exosomes in asthma

Purpose of review Numerous signaling pathways and inflammatory responses in cells and tissues are under microRNA (miRNA) control. In the present review, the role of miRNAs and exosomes in the pathogenesis of asthma will be discussed. Recent findings MiRNAs differentially expressed with asthma, for example, miRNA-34/449, let-7, miRNA-19, miRNA-21, and miRNA-455, were identified in various cell types and tissues including epithelial cells, T cells, type 2 innate lymphoid cells, lung tissues, and smooth muscles. Current data suggest the involvement of these miRNAs in epithelial differentiation, mucus production, airway remodeling, inflammation, etc. However, it is often difficult to predict which genes are targeted by a specific miRNA. We recently combined genome-wide miRNA analyses together with transcriptome in bronchial biopsies, in relation to chronic mucus hypersecretion, then performed a genome-wide miRNA-mRNA network analysis and identified the key miRNA regulators for chronic mucus hypersecretion. Summary There is now growing evidence suggesting that miRNAs play critically important roles in asthma. Several asthma-associated miRNAs have already been identified. Although miRNAs are attractive targets for therapeutic intervention, a safe and effective delivery to target tissues and cells in humans remains a challenge.