Diabetic Nephropathy and Extracellular Matrix

Abstract

A key element in diabetic nephropathy (DN) is changes in the extracellular matrix (ECM) of several of the components in the kidney. From a clinical perspective, the changes seen in the ECM are important both in diagnostics and for prognostic and therapeutic purposes. In the current review, we present some of the central clinical issues related to DN, as well as the most relevant changes to the ECM from a diagnostic point of view, and also discuss some of the changes observed in one of the important ECM components, the proteoglycans (PGs). Our aim is not to cover all relevant research in this rather wide field, ranging from clinical trials to studies on microRNA and other important regulators of kidney function, but to focus particularly on some key issues related to PG changes in DN. Clinical Perspectives on DNAccording to estimates from the International Diabetes Federation, the worldwide prevalence of diabetes is estimated to increase from 285 million persons in 2010 to 439 millions in 2030, a relative increase of 50% (Shaw et al. 2010). Among patients with type 1 diabetes, the incidence of DN has apparently decreased from 30-35% in the cohorts who developed diabetes 40 to 50 years ago to 10-15% in recent cohorts (Bojestig et al. 1994;Hovind et al. 2003). However, due to the increase in type 2 diabetes, the absolute prevalence of DN has increased over the past two decades. In 2009, DN was reported to be the cause of 44% of all cases of end-stage renal disease (ESRD) in the United States (www.usrds.org), with an incidence of 155 diabetic patients developing ESRD per million each year. This fact was earlier announced as a "medical catastrophe of world-wide dimensions" (Ritz et al. 465073J HCXXX10.1369/0022155412465073Kolset et al.Extracellular Matrix and Diabetic Nephropathy 2012© The Author(s) 2010 Reprints and permission: sagepub.com/journalsPermissions. SummaryDiabetic nephropathy (DN) is a serious complication in diabetes. Major typical morphological changes are the result of changes in the extracellular matrix (ECM). Thus, basement membranes are thickened and the glomerular mesangial matrix and the tubulointerstitial space are expanded, due to increased amounts of ECM. One important ECM component, the proteoglycans (PGs), shows a more complex pattern of changes in DN. PGs in basement membranes are decreased but increased in the mesangium and the tubulointerstitial space. The amounts and structures of heparan sulfate chains are changed, and such changes affect levels of growth factors regulating cell proliferation and ECM synthesis, with cell attachment affecting endothelial cells and podocytes. Enzymes modulating heparan sulfate structures, such as heparanase and sulfatases, are implicated in DN. Other enzyme classes also modulate ECM proteins and PGs, such as matrix metalloproteinases (MMPs) and serine proteases, such as plasminogen activator, as well as their corresponding inhibitors. The levels of these enzymes and inhibitors are changed in plasma and in the kidneys in DN. Several growth factors, signali...

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