Antifibrotic action of Cu/Zn SOD is mediated by TGF-β1 repression and phenotypic reversion of myofibroblasts

Skin fibrosis is characterized by the proliferation and accumulation of activated fibroblasts called myofibroblasts. They exhibit specific cytoskeletal differentiation, overexpress the fibrogenic cytokine TGF-β1, synthesize excess extracellular matrix compounds and exhibit a depleted antioxidant metabolism. Recently, SOD was successfully used as an antifibrotic agent in vivo, thus challenging the postulate of established fibrosis irreversibility. We postulated that myofibroblasts could be a direct target for this therapeutic effect. To test this hypothesis, we used three-dimensional co-culture models of skin, in which specific phenotypes of normal fibroblasts versus myofibroblasts are retained. These 3-D models were treated with liposomal and carrier-free Cu/Zn SOD, and examined for their effects on cell number, cell death, and phenotypic differentiation. The results show that SOD did not induce myofibroblast cell death, whereas it significantly reduced TGF-β1 expression, thus demonstrating that SOD might be proposed as a potent antagonist of this major fibrogenic growth factor. We also found that SOD significantly lowered the levels of the myofibroblast marker α-sm actin, of β-actin, and of the extracellular matrix components α1(I) collagen and tenascin-C. In conclusion, our results suggest that SOD antifibrotic action occurred in vitro through the reversion of myofibroblasts into normal fibroblasts.