Transforming growth factor-β1 in polymyositis and dermatomyositis correlates with fibrosis but not with mononuclear cell infiltrate

Abstract

The idiopathic inflammatory myopathies are diseases of unknown etiology characterized by T cell-mediated myocytotoxicity in polymyositis and complement-mediated angiopathy of muscle fibers in dermatomyositis. A variable degree of fibrosis is present in muscles in these conditions both perimysially and endomysially. We evaluated the expression of TGF-β1, a pleiotropic cytokine with fibrogenic and immunomodulating activity, by means of quantitative-polymerase chain reaction and immunocytochemistry in DM and PM muscle biopsies. TGF-β1 mRNA was significantly higher in DM compared with controls, whereas in PM the values were not significantly different when compared with controls and DM. TGF-β1 was localized in connective tissue but did not correspond with mononuclear cell infiltrates. These findings suggest a correlation between TGF-β1 and connective tissue proliferation in inflammatory myopathy, while its immunomodulatory role remains to be elucidated.