New insights about myofibrillar myopathies: the role of metalloproteinases 2 and 9 in the pathogenesis

Abstract Background There are few reports suggesting that gene expression and activation of various matrix metalloproteinases (MMPs) are deregulated. MMP-2 and MMP-9 represent the two MMPs, which degrade type IV collagen, the component of basement membrane. Methods We analyzed the involvement of gelatinases, MMP-2 and MMP-9, in the pathogenesis of myofibrillar myopathy (MFM). Muscle specimens from 23 patients well diagnosed with MFM, were immunostained by MMP-2 and MMP-9. We analyzed qualitatively the immunoexpression in three compartments: subsarcolemmal (SSC), intracytoplasmic (ICC) and perinuclear (PNC). Results 95,7% and 100% samples showed MMP-2 and MMP-9 upregulation ICC, respectively. PNC showed MMP-2 (82,6%) and MMP-9 (8,7%) regulation (p<0.001). SSC and ICC did not present statistical significance. There was no correlation between mutated gene and immunohistochemical pattern distribution. Conclusion Our results suggest that MMP-2 and/or MMP-9 could participate in the pathomechanism of MFM, causing damage of sarcomere and deposition of protein aggregates.