Periostin Facilitates Skin Sclerosis via PI3K/Akt Dependent Mechanism in a Mouse Model of Scleroderma

Objective: Periostin, a novel matricellular protein, is recently reported to play a crucial role in tissue remodeling and is highly expressed under fibrotic conditions. This study was undertaken to assess the role of periostin in scleroderma. Methods: Using skin from patients and healthy donors, the expression of periostin was assessed by immunohistochemistry and immunoblotting analyses. Furthermore, we investigated periostin (-/-) (PN-/-) and wild-type (WT) mice to elucidate the role of periostin in scleroderma. To induce murine cutaneous sclerosis, mice were subcutaneously injected with bleomycin, while untreated control groups were injected with phosphate-buffered saline. Bleomycin-induced fibrotic changes were compared in PN-/- and WT mice by histological analysis as well as by measurements of profibrotic cytokine and extracellular matrix protein expression levels in vivo and in vitro. To determine the downstream pathway involved in periostin signaling, receptor neutralizing antibody and signal transduction inhibitors were used in vitro. Results: Elevated expression of periostin was observed in the lesional skin of patients with scleroderma compared with healthy donors. Although WT mice showed marked cutaneous sclerosis with increased expression of periostin and increased numbers of myofibroblasts after bleomycin treatment, PN-/- mice showed resistance to these changes. In vitro, dermal fibroblasts from PN-/- mice showed reduced transcript expression of alpha smooth actin and procollagen type-I alpha 1 (Col1 alpha 1) induced by transforming growth factor beta 1 (TGF beta 1). Furthermore, recombinant mouse periostin directly induced Col1 alpha 1 expression in vitro, and this effect was inhibited by blocking the alpha v integrin-mediated PI3K/Akt signaling either with anti-alpha v functional blocking antibody or with the PI3K/Akt kinase inhibitor LY294002. Conclusion: Periostin plays an essential role in the pathogenesis of Bleomycin-induced scleroderma in mice. Periostin may represent a potential therapeutic target for human scleroderma.