[IL-25 derived from epithelial cells has the potential to promote airway remodeling in asthma]

To explore the role of interleukin-25(IL-25) in the pathogenesis of eosinophilic asthma (EA) and non-eosinophilic asthma (NEA) through detecting its expression in serum, induced sputum and bronchial epithelial mucosa of asthmatic patients.

Serum and induced sputum were collected from 55 untreated asthmatic patients and 27 healthy control subjects. The asthmatic patients were divided into EA and NEA groups according to sputum eosinophils(EOS) percentage (3% as a dividing point). The level of IL-25 in serum and induced spntum was determined by ELISA; the expression of IL-25 in bronchial epithelium was quantified by immunohistochemistry in biopsied specimens from 10 cases of EA, 10 NEA and 10 controls. Basement membrane thickness as an important index of airway remodeling was detected by HE staining.

Compared with healthy control subjects, the lung function was impaired in patients with EA and NEA. ELISA results showed that the levels of IL-25 in the serum and induced sputum of asthmatic patients were significantly higher than those in healthy subjects (P<0.05). But there were no statistic differences between EA and NEA patients (P>0.05). The immunohistochemical results indicated that the expression of IL-25 was higher in asthmatic bronchial epithelium than in control ones. HE staining showed that the basement membrane thickness increased in EA and NEA patients(P<0.05). Correlation analysis showed that the levels of IL-25 in serum and induced sputum were positively correlated with the average thickness of basement membrane in asthmatic patients.

IL-25 secreted from epithelial cells has the potential to promote airway remodeling in asthma. EOS has nothing to do with the thickness of basement membrane, and it may not be necessary for airway remodeling in asthma.