Periostin: contributor to abnormal airway epithelial function in asthma?

Periostin may serve as a biomarker for type-2-mediated eosinophilic airway inflammation in asthma. We hypothesised that type-2 cytokine IL-13 induces airway epithelial expression of periostin, which in turn contributes to epithelial changes observed in asthma. We studied the effect of IL-13 on periostin expression in BEAS-2B and air-liquid interface (ALI)-differentiated primary bronchial epithelial cells (PBECs). Additionally, effects of recombinant human periostin on epithelial-to-mesenchymal transition (EMT) markers and mucin genes were assessed. In bronchial biopsies and induced sputum from asthma patients and healthy controls, we analysed periostin single cell gene expression and protein levels. IL-13 increased POSTN expression in both cell types, which was accompanied by EMT-related features in BEAS-2B. In ALI-differentiated PBECs, IL-13 increased periostin basolateral and apical release. Apical administration of periostin increased the expression of MMP9, MUC5B and MUC5AC. In bronchial biopsies, POSTN expression was mainly confined to basal epithelial cells, ionocytes, endothelial cells and fibroblasts, showing higher expression in basal epithelial cells from asthma patients versus controls. Higher protein levels of periostin, expressed in epithelial and subepithelial layers, was confirmed in bronchial biopsies from asthma patients compared to healthy controls. Although sputum periostin levels were not higher in asthma, levels correlated with eosinophil numbers and coughing up mucus. Periostin expression is increased by IL-13 in bronchial epithelial cells and higher in bronchial biopsies from asthma patients. This may have important consequences, as administration of periostin increased epithelial expression of mucin genes, supporting the relationship of periostin with type-2 mediated asthma and mucus secretion.