Hepatocyte growth factor: renotropic role and potential therapeutics for renal diseases

Hepatocyte growth factor and the kidney

Hepatocyte growth factor (HGF) and its specific c-met receptor constitute a paired signaling system that plays an important role in renal development and in the maintenance of normal adult kidney structure and functions. HGF elicits potent mitogenic, motogenic, morphogenic, and antiapoptotic activities in renal tubular epithelial cells. The nature of these pleiotropic actions renders it to be specifically suited to preserve and to reconstitute the structural and functional integrity of renal tubules after acute renal injury. Emerging evidence also indicates that both endogenous and exogenous HGF are beneficial by inhibiting the onset and progression of chronic renal diseases in various animal models. Administration of exogenous HGF protein, or its gene, effectively inhibits the activation of matrix-producing myofibroblasts, attenuates extracellular matrix deposition and interstitial fibrosis, and suppresses profibrogenic cytokine transforming growth factor-beta1 and its type I receptor expression in vivo. Hence, although more studies are warranted to further clarify its role in various chronic renal fibrosis models, delivery of either HGF or its gene may hold promise as a novel therapeutic strategy for promoting initial protection and subsequently regenerative repair after acute insult, and for ameliorating renal fibrosis and kidney dysfunction in chronically diseased conditions.

Targeting growth factors to the kidney: myth or reality?

Growth factors and cytokines play a crucial role in the progression of renal diseases. A growing body of evidence has been obtained from experimental studies, suggesting that manipulation of the activity of growth factors and cytokines is a potential form of therapy for renal diseases. To preserve the renal function structure in progressive renal diseases, this approach is achieved by inhibition of apoptosis of renal intrinsic cells and by decrease in the fibrotic signal. Inhibition of transforming growth factor beta, platelet-derived growth factor, interleukin-1 and tumor necrosis factor alpha, and supplementation of hepatocyte growth factor, vascular endothelial growth factor and bone morphogenic protein-7 may be beneficial. Recent progress in therapeutic implements including humanized antibodies, chimeric soluble receptors, aptamers, antisense oligonucleotides, and gene therapy allow us to target the causal molecules. Administration of a combination of growth factors and cytokines is a potential therapeutic approach. Targeting signal transduction molecules and their co-factors and regulators is another possibility because the signals from various growth factors use a common pathway. Thus, targeting growth factors and cytokines in renal diseases could be a promising therapeutic approach.

Systemic administration of naked plasmid encoding hepatocyte growth factor ameliorates chronic renal fibrosis in mice

The progression of chronic renal diseases is considered as an irreversible process that eventually leads to end-stage renal failure characterized by extensive tissue fibrosis. At present, chronic renal fibrosis is incurable and the incidence of affected patients is on the rise worldwide. In this study, we demonstrate that delivery of hepatocyte growth factor (HGF) gene via systemic administration of naked plasmid vector markedly ameliorated renal fibrosis in an animal model of chronic renal disease induced by unilateral ureteral obstruction. A high level of exogenous HGF protein was detected in the obstructed kidneys following intravenous injection of naked plasmid encoding human HGF. Delivery of human HGF gene induced a sustained activation of extracellular signal-regulated kinases-1 and -2 in the obstructed kidneys. Exogenous HGF expression dramatically inhibited alpha-smooth muscle actin expression, attenuated renal interstitial accumulation and deposition of collagen I and fibronectin. In addition, exogenous HGF suppressed renal expression of pro-fibrogenic cytokine TGF-beta1 and its type I receptor in vivo. These results suggest that systemic administration of naked plasmid vector introduces a high level of exogenous HGF to the diseased kidneys, and that HGF gene transfer may provide a novel therapeutic strategy for amelioration of chronic renal fibrosis in vivo.