Periostin is induced by IL-4/IL-13 in dermal fibroblasts and promotes RhoA/ROCK pathway-mediated TGF-β1 secretion in abnormal scar formation

Excess scar formation can occur after skin injury and lead to abnormal scar formation, such as keloids and hypertrophic scars, which are characterised by substantial deposition of extracellular matrix in the dermis. Periostin, an extracellular matrix protein that plays a crucial role in skin development and maintaining homeostasis, is also involved in skin disorders such as systemic/limited scleroderma, wound closure, and abnormal scar formation. However, the mechanism of periostin involvement in abnormal scar formation is not yet fully understood. In this study, we investigated the mechanism by which periostin is involved in abnormal scar formation. Treatment of human dermal fibroblasts (HDFs) with IL-4 and IL-13, which are cytokines of Th2 type immune responses that are up-regulated in abnormal scars, dramatically elevated the levels of periostin mRNA and protein, and also promoted the secretion of periostin by HDFs. Transforming growth factor-beta 1 (TGF-beta 1) had the same effect on HDFs as IL-4 and IL-13. Stimulation of HDFs with periostin promoted RhoA/ROCK pathway-mediated TGF-beta 1 secretion from HDFs. Our results suggest that IL-4 and IL-13 induce periostin expression and secretion, and in turn, secreted periostin induces RhoA/ROCK pathway-mediated TGF-beta 1 secretion. Secreted TGF-beta 1 then induces further periostin production and secretion, thereby promoting abnormal scar formation.