Elevated plasma levels of tissue inhibitors of metalloproteinase-1 and their overexpression in muscle in human and mouse muscular dystrophy

Abstract

To investigate the role of tissue inhibitors of metalloproteinases (TIMPs) in muscular dystrophy, we examined the expression of TIMP-1 using plasma and biopsied muscle from patients with various muscular dystrophies by ELISA, immunohistochemistry, and Western blot analysis. TIMP-1 immunolocalization was also studied in mouse models of muscular dystrophy. Plasma TIMP-1 was elevated and correlated with TGF-β1 in Duchenne muscular dystrophy (DMD) and congenital muscular dystrophy (CMD), but not in Becker muscular dystrophy. In dystrophic human muscles, TIMP-1 was immunopositive in the regenerating and non-regenerating muscle fibers, and interstitial cells that consist of activated fibroblasts and macrophages. TIMP-1 immunoreactivity was also closely associated with TGF-β1. Western blot analysis showed elevated TIMP-1 protein in muscles in DMD. The semiquantitative analysis of TIMP-1 staining intensity and tissue fibrosis showed that TIMP-1 immunoreactivity is closely associated with the extent of tissue fibrosis in human and mouse dystrophic muscles. In conclusion, the present study implied that the TGF-β1–TIMP-1 pathway is activated in dystrophic muscles and the overexpression of TIMP-1 may result in increased deposition of extracellular matrix leading to tissue fibrosis.