ABSTRACT. Evidence suggests that hepatocyte growth factor (HGF) ameliorates renal fibrosis in animal models of chronic renal disease by promoting extracellular matrix catabolism. This study examined the molecular mechanisms of HGF-induced alterations in matrix degradation both
in vitroand in vivo. In vitro, HGF increased the collagen catabolizing activity of human proximal tubular epithelial cells (HKC) that were treated with TGF-β1. Increased collagen catabolism was associated with enhanced activity of both matrix metalloproteinases (MMP) and plasminogen activators (PA)/plasmin proteolytic pathways. HGF abrogated TGF-β1–induced production of the profibrotic tissue inhibitor of metalloproteinase-2 (TIMP-2) and plasminogen activator inhibitor-1 (PAI-1). In addition, HGF induced the production of MMP-9. In vivo, continuous infusion of HGF in the rat remnant kidney model ameliorated renal fibrosis and tubulointerstitial collagen deposition. This was associated with increased tubular expression of MMP-9, enhanced in situgelatinolytic activity, partially restored plasmin activity and decreased expression of TIMP-2 and PAI-1 in tubular cells, and upregulation of renal TIMP-3 expression. Conversely, blocking of endogenous HGF by an anti-HGF neutralizing antibody increased renal fibrosis and interstitial collagen. This was accompanied by decreased tubular expression of MMP-9, less in situproteolytic activity, and elevated expression of TIMP-2 and PAI-1 in tubular cells. Collectively, these findings demonstrate that HGF ameliorates renal fibrosis by enhancing extracellular matrix catabolism via both MMP and the PA/plasmin proteolytic pathways.
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