Fig. 2

The role of periostin inthe pathogenic process of subepithelial fibrosis. Briefly, Th2-polarized inflammation leads to the recruitment of various immune cells and these secrete IL-4 and IL-13 in combination with TGF-β to stimulate fibroblasts and epithelial cells to produce periostin. Periostin, in turn through an autocrine pathway (indicated with green colored receptors), acts on fibroblasts and epithelial cells, thereby leading to a vicious cycle. Additional functions of periostin include: the promotion of fibroblast differentiation into myofibroblasts, the induction of fibroblast migration, and as a co-factor of TGF-β, periostin promotes ECM production and the differentiation of myofibroblasts. Periostin further enhances fibrosis by binding to other ECM proteins (e.g., collagen I, fibronectin, and tenascin-C) and by inducing collagen fibrillogenesis. Adapted from [27]