Clinical relevance of plasma miR-106b levels in patients with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is characterized by both chronic inflammation in the airway and systemic inflammation; however, the molecular mechanism of COPD has not been fully elucidated. By measuring microRNA (miRNA) expression in the plasma of COPD subjects, we aimed to identify the clinical relevance of plasma miRNA levels in these patients. Blood samples were obtained from COPD patients and age-matched normal controls. We initially produced plasma miRNA expression profiles using TaqMan low-density array screening. For further validation, individual qRT-PCRs were performed in 40 COPD patients and 20 healthy subjects. TaqMan low-density array screening showed that 9 miRNAs (miR-29b, miR-483-5p, miR-152, miR-629, miR-26b, miR-101, miR-106b, miR-532-5p and miR-133b) were significantly downregulated in the plasma from COPD patients when compared with normal smokers. Among these miRNAs, we focused on miR-106b. A reduction in the plasma miR-106b levels was evident in COPD ex-smokers and COPD current smokers compared with levels in smokers. There was a negative correlation between the plasma miR-106b level and the duration of disease since diagnosis in COPD ex-smokers and the duration of smoking in COPD current smokers. These findings support the concept that progressive reduction in the plasma miR-106b level may reflect persistent and systemic changes even after the discontinuation of smoking in COPD patients. miR-106b may therefore play an important role in the pathogenesis of COPD.