Matrix metalloproteinases and their role in the renal epithelial mesenchymal transition.

Tubular cell epithelial-mesenchymal transition (EMT) is a fundamental contributor to renal fibrosis. The aim of this study was to investigate the activity of different matrix metalloproteinases by immunohistochemistry and gel-zymography in a model of chronic canine kidney disease. Immunohistochemistry for antibodies against MMP-9, MMP-2, MMP-13, MMP-14 and TIMP-2 was performed on 28 renal biopsy specimens. Selected cases were chosen for gelatin zymography. In moderate and severe tubulo-interstitial damage, increased expression of MMP-2 was noted. A peculiar staining pattern for MMP-2 in variable-sized vesicles, corresponding to the area of basement membrane splitting, was observed. The immunoexpression of MMP-9 and TIMP-2 was reduced in the same cases, compared to control dogs. The splitting of the membrane suggests an active role of this gelatinase in the disruption of type-IV collagen, the main basement membrane component, confirmed by MMP2 gelatinolytic activity by gel-zymography. These data could provide the basis for clinical trials examining the potential benefits of selective MMP-2 inhibitors in dogs with chronic kidney disease.