Let-7a is differentially expressed in bronchial biopsies of patients with severe asthma

Asthma is a chronic inflammatory disease. Around 5 to 10% of patients classified as having severe asthma can-not be adequately controlled despite the use of all currently available therapeutic approaches. Previous studies have revealed the potential important role of miRNAs in the regulation of a variety of inflammatory processes, including asthma. Expression of selected miRNAs, specifically let-7a, miR-21 and miR-223, that were shown to have important roles in asthma pathogenesis, were analyzed in bronchial biopsies of 24 patients with asthma, 12 mild and 12 severe, and 10 controls with no chronic disease. We found significantly reduced expression of let-7a in bronchial biopsies from patients with severe asthma in comparison to patients with mild asthma as well as in comparison to the non-asthmatic controls. On the other hand, no significant differences in miR-21 and miR-223 expression were found between the different groups analyzed. Reduced let-7a levels in bronchial biopsies of patients with severe therapy-resistant asthma could not only be used as a potential biomarker to discriminate between different asthma phenotypes, but also might be a target for modulation of treatment at the inflammatory site for a group of patients that are most affected and still lack effective treatment.