Increased periostin expression affects the proliferation, collagen synthesis, migration and invasion of keloid fibroblasts under hypoxic conditions

Periostin, a secreted extracellular matrix protein, is involved in the wound healing and pathological process of various human cancers. Keloid scars are fibroproliferative tumor-like lesions and develop under local hypoxia. Using suppression subtractive hybridization, in a previous study, we found that periostin is overexpressed in keloids compared with hypertrophic scars. However, little is known about the regulation and function of periostin in keloids. In this study, we examined the effects of periostin on the bioactivity of keloid fibroblasts (KFs) in order to determine whether periostin is involved in hypoxia-stimulated keloid pathogenesis by measuring the expression levels of periostin in KFs cultured under hypoxic conditions. We also investigated the association between periostin and hypoxia-inducible factor-1α (HIF-1α). The mRNA, intracellular protein and secreted protein level of periostin was examined by RT-PCR (and quantitative PCR), western blot analysis and enzyme-linked immunosorbent assay (ELISA), respectively. We also used shRNA targeting periostin to knockdown its expression in the KFs. We report that hypoxia (2% O(2)) upregulates both HIF-1α and periostin expression in KFs. In addition, hypoxia-upregulated periostin expression was regulated by HIF-1α. The inhibition of periostin by short hairpin RNA decreased the hypoxia-stimulated proliferation, collagen synthesis, migration and invasion of KFs and altered the cell cycle, but did not affect apoptosis; treatment with recombinant human periostin protein reversed these effects. Periostin also activated the αvβ3 integrin-PI3K/Akt pathway in the KFs. These findings suggest that hypoxia initiates hyperplasia of KFs and increases periostin expression under hypoxic conditions; periostin is involved in the pathogenesis of keloids, which indicates that periostin may be a novel therapeutic target for keloids and other fibroproliferative disorders.