Serum Exosomal Expression of miR-155 and miR-221 in Moderate-to-severe Asthmatic Patients

The cardinal features of asthma include airway inflammation, airway hyper responsiveness (AHR) and airway remodeling. Exosomes help orchestrate the immune response and contain microRNAs (miRNAs) such as miRNA-155 and miRNA-221 which play significant roles in the pathogenesis and exacerbations of severe asthma. In this study, we aimed to investigate the exosomal expression of miRNAs (155, 221) in the serum of severe asthma patients. Eighteen moderate-to-severe asthma patients and eighteen healthy subjects were recruited for this study. Serum exosomes were isolated and characterized according to their shape, size, and exosomal markers by transmission electron microscopy, dynamic light scattering (DLS) and flow cytometry, respectively. Exosomal miRNA extraction and quantitative real-time PCR (qRT-PCR) were used to measure miR-155 and miR-221. Besides the forced expiratory volume in 1 second and forced vital capacity (FVC) were evaluated in the patient groups. Round exosomes with a mean size of 25.8 nm were isolated from serum of asthmatic patients. Flow cytometry shows high expression of CD63 and CD81 on isolated exosomes. Serum exosomes from severe asthma patients and healthy donors contained miR-155 and miR-221 but miR-155 and miR-221 expression levels were significantly increased in severe asthma patients. There was a positive correlation between miR-221 expression and FVC). Receiver operating characteristic (ROC) analysis indicated that miR-155 and miR-221 had an excellent diagnostic efficiency in predicting asthma (AUC=0.91 and AUC=0.76, respectively). Serum exosomal miR-155 and miR-221 may be a potential biomarker for severe asthma. However, the results need to be validated in another cohort, and further studies with larger samples size should be conducted on the effects of these miRNAs on effector cells.