Matrix metalloproteinases in inflammatory myopathies: enhanced immunoreactivity near atrophic myofibers

OBJECTIVES: To further examine the role of proteolytic enzyme expression of matrix metalloproteinases (MMP) and T-cell markers in inflammatory myopathies and controls. MATERIAL AND METHODS: We studied the expression of MMP-2, MMP-7, and MMP-9 in 19 cases of inflammatory myopathies and controls using immunocytochemistry. RESULTS: Inflammatory myopathies showed distinct patterns of up-regulation of MMP. MMP-9 was strongly expressed in atrophic myofibers in all inflammatory myopathies. MMP-2 immunoreactivity was similar in its distribution, however, to a weaker intensity. In dermatomyositis the perifascicular atrophy showed pronounced MMP-9 immunoreactivity, probably reflecting denervated patterns of myofibers. Moreover, MMP-7 strongly immunolabeled invaded myofibers in polymyositis cases only. CONCLUSION: These patterns confirm, that MMP-7 up-regulation is prominent in PM, while MMP-2 immunoreactivity is only slightly elevated in inflamed muscle. In general, MMP-9 up-regulation appears to be an important additional molecular event in the multistep process of all inflammatory myopathies.