Cheong Hoon Seo, Hui Song Cui, June-Bum Kim
Abstract: Hyperproliferation of fibroblasts and excessive extracellular matrix (ECM) deposition are pathological hallmarks of hypertrophic scars, the most common complication of burn injury. Calpains are Ca2+-dependent proteases and associated with fibroblast proliferation and ECM synthesis, resulting in the development of several fibrotic diseases. However, the role of calpain in the formation of postburn hypertrophic skin scars remains unknown. In the present study, we assessed the expression and activity of calpain in skin fibroblasts obtained directly from patients with third-degree burns who consequently developed postburn hypertrophic scars. The differential activity profiles of calpains were evaluated using short-interfering RNAs (siRNAs). We also evaluated the antifibrotic effect of calpain inhibition by calpeptin in human fibroblasts and animal burn models. Calpain activity and the mRNA and protein levels of calpain-1 and calpain-2 were significantly higher in burn-wound fibroblasts than in normal fibroblasts. Calpain-1 knockdown with siRNA significantly reduced the mRNA and protein expression of transforming growth factor-beta 1, α-smooth muscle actin, type I and type III collagens, fibronectin, and vimentin in burn-wound fibroblasts; however, calpain-2 knockdown with siRNA did not reduce their expression. Selective calpain inhibition by calpeptin significantly reduced the proliferation of burn-wound fibroblasts. Calpain inhibition by calpeptin also significantly reduced the mRNA and protein expression of hypertrophic markers in burn-wound fibroblasts. The molecular, histological, and visual anti-scarring effects of calpeptin were confirmed in murine burn models. The present study delineated a differential mechanism between calpain-1 and calpain-2 in postburn hypertrophic scar formation. Our results indicated that calpain inhibition by calpeptin could constitute a novel treatment strategy for the prevention of hypertrophic scar formation following burn injury.