Periostin promotes cell cycle in lung fibroblasts. Periostin promotes cell cycle in lung fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a devastating disease with only three to five years of the median survival. Fibroblast proliferation is a hallmark of IPF as well as secretion of extracellular matrix proteins from fibroblasts. However, it is still uncertain how IPF fibroblasts acquire the ability to progressively proliferate. Periostin is a matricellular protein that is highly expressed in the lung tissues of IPF patients and plays a critical role in the pathogenesis of pulmonary fibrosis. However, it remains undetermined whether periostin affects proliferation of lung fibroblasts. In this study, we first comprehensively tried to identify periostin-dependently expressed genes in lung fibroblasts finding that many cell-cycle–related genes are involved in the gene profile. We confirmed that periostin silencing downregulates expression of several cell-cycle–related molecules including the cyclin family, the CDK family, the E2F family, and the transcriptional factors such as B-MYB and FOXM1 in lung fibroblasts. Accordingly, periostin silencing slowed proliferation of lung fibroblasts and affects the distribution of cell cycle particularly at the G1/S checkpoint and drives the cells into G1 arrest. Lung fibroblasts derived from IPF patients also required periostin for maximum proliferation. Moreover, CP4715, a potent inhibitor against integrin V3, a periostin receptor, downregulated proliferation along with expression of cell-cycle–related genes in IPF lung fibroblasts as well as normal lung fibroblasts. These results demonstrate that periostin plays a critical role in proliferation of lung fibroblasts and provide us a beneficial basis to apply the inhibitors against the periostin/integrin V3 interaction to IPF patients. Overall design: To comprehensively identify genes expressed dependently on periostin in lung fibroblasts, we compared the gene expression profiles with or without knockdown of periostin in lung fibroblasts (MRC-5 cells). MRC-5 cells were transfected with 10 nM periostin siRNA for 48 h.