Periostin is one of the matricellular proteins, a class of extracellular matrix (ECM)-related molecules defined by their ability to modulate cell–matrix interactions. We previously reported an elevated level of circulating periostin in patients with systemic sclerosis (SSc) and its association with severity of skin sclerosis. In this study, we examined the role of periostin on transforming growth factor-β (TGF-β) signaling mediating fibrosis. We first determined periostin levels in skin and lung fibroblasts obtained from SSc patients. Protein levels of ECM proteins and pro-fibrotic factors were further evaluated in periostin expressed-human skin fibroblasts in the presence or absence of TGF-β. Effects of periostin to Smad proteins following TGF-β stimulation were also evaluated by immunoblotting and immunofluorescence staining. Finally, protein levels of Smad 7 were assessed in fibroblasts with RNA interference of periostin. As results, periostin was strongly expressed in skin and lung primary SSc fibroblasts compared with healthy subjects. Recombinant periostin (rP) -treated fibroblasts and periostin overexpressed fibroblasts produced significant ECM proteins in the presence of TGF-β compared to respective control fibroblasts stimulated with TGF-β alone. Overexpression of periostin enhanced the induction of α-SMA and Egr-1 in the presence of TGF-β. In addition, R-Smad activity induced by TGF-β was not affected by periostin significantly, but a level of Smad 7 was reduced in periostin expressed-fibroblasts with TGF-β stimulation. On one hand, a level of Smad 7 was increased in fibroblasts with RNA interference of periostin in the presence of TGF-β. These results suggest that periostin may contribute to fibrosis by enhancing TGF-β signaling via Smad 7 inhibition, which leads to further ECM deposition and periostin generation. Periostin may be a therapeutical target molecule mediating fibrosis.

Pro-fibrotic Phenotype of Human Skin Fibroblasts Induced by Periostin via Modulating TGF-β Signaling