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Renal fibrosis is a common finding in progressive renal diseases. Matrix metalloproteinases (MMPs) are involved in epithelial-to-mesenchymal transition (EMT). We investigated the role of MMP-2 and the effect of inhibition of MMPs on the development of renal fibrosis. Renal fibrosis was induced in MMP-2 wild-type (MMP-2⁺/⁺) mice by unilateral ureteral obstruction (UUO). Renal histopathology, EMT-associated molecules, and activity of MMP-2 and MMP-9 were examined during the development of interstitial fibrosis. UUO-renal fibrosis was also induced in MMP-2 deficient (MMP-2⁻/⁻) and MMP-2⁺/⁺ mice treated with minocycline (inhibitor of MMPs). In MMP-2⁺/⁺ mice, MMP-2 and MMP-9 were expressed in damaged tubules, and their activities increased in a time-dependent manner after UUO. Interstitial fibrosis was noted at day 14, with deposition of types III and I collagens and expression of markers of mesenchymal cells (S100A4, vimentin, α-smooth muscle actin, and heat shock protein-47) in damaged tubular epithelial cells, together with F4/80+ macrophage infiltration. Fibrotic kidneys expressed EMT-associated molecules (ILK, TGF-β1, Smad, Wnt, β-catenin, and Snail). In contrast, the kidneys of MMP-2⁻/⁻ mice and minocycline-treated MMP-2⁺/⁺ mice showed amelioration of renal fibrosis with reduced expression of markers of mesenchymal cells in tubular epithelial cells, inhibition of upregulated EMT-associated molecules, and suppression of macrophage infiltration. The results suggested that MMP-2 have a pathogenic role in renal interstitial fibrosis, possibly through the induction of EMT and macrophage infiltration. Inhibition of MMPs may be beneficial therapeutically in renal fibrosis.

Matrix metalloproteinases (MMPs) are endopeptidases that degrade extracellular matrix and involved in ischemic organ injuries. The present study was designed to determine the role of MMP-2 in the development of ischemic acute kidney injury (AKI). AKI was induced in MMP-2 wild-type (MMP-2(+/+)) mice by 30, 60, 90, and 120 min renal ischemia and reperfusion. Renal histology, expression and activity of MMP-2 and MMP-9, and renal function were examined during the development of AKI. AKI was also induced in MMP-2-deficient (MMP-2(-/-)) mice and MMP-2(+/+) mice treated with inhibitor of MMPs (minocycline and synthetic peptide MMP inhibitor). In MMP-2(+/+) mice, MMP-2 and MMP-9 activities increased significantly at 2 to 24 h, peaked at 6 h, after reperfusion. Immunohistochemical analysis identified MMP-2 in the interstitium around tubules and peritubular capillaries in the outer medulla. Acute tubular injury (ATI), including apoptosis and necrosis, was evident in the outer medulla at 24 h, along with renal dysfunction. As ischemia period increases, MMP-2 and MMP-9 activities at 6 h and severity of AKI at 24 h increased depending on the duration of ischemia between 30 and 120 min. However, the kidneys of MMP-2(-/-) mice showed minimal ATI; serum creatinine 24 h after reperfusion was significantly low in these mice. Inhibitors of MMPs reduced ATI and improved renal dysfunction at 24 h. We conclude that MMPs, especially MMP-2 have a pathogenic role in ischemia-reperfusion AKI, and that inhibitors of MMPs can protect against ischemic AKI.