The miRNA-24, miRNA-21 expressions and matrix metalloproteinase-7 level in exhaled breath condensate of children with primary spontaneous pneumothorax

Bullous lung diseases may cause primary spontaneous pneumothorax (PSP) in children. The microRNAs (miRNAs) are non-coding RNAs that participate in regulation of inflammation and cancer. We hypothesized that children with bullous lung disease and PSP may have altered miRNA expressions in their exhaled breath condensates (EBCs). Therefore, a prospective study was performed to evaluate the miRNA-24 and 21 expression, and the matrix metalloproteinase-7 (MMP-7) levels in EBC of children with PSP. Children with PSP were evaluated for age, gender, clinical features and results of surgical treatment. EBC samples (500–1000 ml) were collected to evaluate the miRNA-21, 24 expressions, and MMP-7, and tissue-inhibitor-MMP-1 (TIMP-1) levels. miRNA expressions and MMP levels of patients were compared with healthy controls (control group (CG), n = 12). Subjects (n = 16) with a mean age of 15 years (10–19 years), and a male-to-female ratio of 14:2 were enrolled in this study. The most common presenting symptom was sudden chest pain (n = 14). In 62.5% of the cases an underlying bullous lung disease were detected. During an average of 16.6 months (1–60 months) follow up period, four subjects relapsed. The mean MMP-7 (1.74–1.57 ng ml−1), and TIMP-1 (1.92–1.84 ng ml−1) levels were similar between both groups (p > 0.05). miRNA-24 expression was significantly decreased in the PSP group, when compared to the CG (0.16–1 2−ΔΔCT, p < 0.05). In addition, the miRNA-21 expression was not different between the two groups (p > 0.05). In conclusion, the miRNA-24 levels were significantly decreased in children with PSP. Taken together, children with PSP, especially those with bullous disease, should be closely monitored in the long-term period.