In chronic kidney disease, functional impairment correlates with tubulointerstitial fibrosis characterised by inflammation, accumulation of extracellular matrix, tubular atrophy and rarefaction of peritubular capillaries. Loss of the microvasculature implies a hypoxic milieu and suggested an important role for hypoxia when the "chronic hypoxia hypothesis" was proposed a decade ago as an explanation for the progressive nature of fibrosis. Recent data in man provide evidence of decreased renal oxygenation in chronic kidney disease while more direct support for a causal role comes from data in rodent models showing that the decline in renal oxygenation precedes matrix accumulation, suggesting hypoxia may both initiate and promote the fibrotic response. Indeed, in vitro studies show that hypoxia can induce pro-fibrotic changes in tubulointerstitial cells. Additional postulated roles for hypoxia in chronic kidney disease are the sustaining of the inflammatory response, the recruitment, retention and differentiation towards a pro-fibrotic phenotype of circulating progenitor cells and the alteration of the function of intrinsic stem cell populations. Given that accumulating data suggests that chronic hypoxia is a final common pathway to end-stage renal disease, therapeutic strategies that target hypoxia may be of benefit in retarding progression. Normalisation of microvascular tone, administration of pro-angiogenic factors to restore microvasculature integrity, activation of hypoxia-inducible transcription factors and hypoxia-mediated targeting and mobilisation of progenitor cells are all potential targets for future therapy. The limited success of existing strategies in retarding chronic kidney disease mandates that these new avenues of treatment be explored.

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Is there a common mechanism for the progression of different degree of tubulointerstitial fibrosis was more closely cortypes of renal diseases other than proteinuria? Towards the related with the reduction in glomerular filtration rate unifying theme of chronic hypoxia. The question of why chronic (GFR) than was glomerular pathology, suggesting that renal diseases progress is a topic only recently investigated. glomerular injury was not the major determinant of dis-Putative causes such as proteinuria do not account for all asease progression [2, 3]. There followed a period where pects of progressive renal disease. An alternative mechanism, chronic hypoxia, is proposed that might better explain certain

Abstract. Several lines of evidence suggest that hepatocyte growth factor/scatter factor (HGF/SF), a soluble protein secreted by embryo fibroblasts and several fibroblast lines, may elicit morphogenesis in adjacent epithelial cells. We investigated the role of HGF/SF and its membrane receptor, the product of the c-met protooncogene, in the early development of the metanephric kidney. At the inception of the mouse metanephros at embryonic day 11, HGF/SF was expressed in the mesenchyme, while met was expressed in both the ureteric bud and the mesenchyme, as assessed by reverse transcription PCR, in situ hybridization, and immnuohistochemistry. To further investigate the expression of met in renal mesenchyme, we isolated 13 conditionally immortal clonal cell lines from transgenic mice expressing a temperature-sensitive mutant of the SV-40 large T antigen. Five had the HGF/ SF+/met + phenotype and eight had the HGF/SF-/met + phenotype. None had the HGF/SF+/met -nor the HGF/SF-/met-phenotypes. Thus the renal mesenchyme contains cells that express HGF/SF and met or met alone. When metanephric rudiments were grown in serum-free organ culture, anti-HGF/SF antibodies (a) inhibited the differentiation of metanephric mesenchymal cells into the epithelial precursors of the nephron; (b) increased cell death within the renal mesenchyme; and (c) perturbed branching morphogenesis of the ureteric bud. These data provide the first demonstration for coexpression of the HGF/SF and met genes in mesenchymal cells during embryonic development and also imply an autocrine and/or paracrine role for HGF/SF and met in the survival of the renal mesenchyme and in the mesenchymal-epithelial transition that occurs during nephrogenesis. They also confirm the postulated paracrine role of HGF/SF in the branching of the ureteric bud.