Expression of glomerular extracellular matrix components in human diabetic nephropathy: decrease of heparan sulphate in the glomerular basement membrane

Abstract

Diabetic nephropathy is characterized by albuminuria which proceeds to overt proteinuria. The highly negatively stained HS side chain of heparan sulphate proteoglycan (HSPG) is a major determinant of the charge-dependent permeability of the GBM. We set out to study the presence of HS and HSPG in the GBM of patients with diabetic nephropathy using newly developed monoclonal antibodies, and to compare HSPG expression to the expression of other previously investigated glomerular extracellular matrix compounds. Immunohistochemically, glomerular extracellular matrix components were analysed in 14 renal biopsies of patients with diabetic nephropathy and compared with those of normal control subjects. Monoclonal antibodies used were: JM403 against the HS side chain of GBM HSPG and JM72 against the HSPG-core protein. Also, a polyclonal antiserum (B31) against human GBM-HSPG-core protein was used. Additionally, antibodies were used against collagen types I, III, IV and against alpha 1 (IV)NC, alpha 3(IV)NC and fibronectin. Staining was scored for intensity and for staining pattern by four independent observers who had no previous knowledge of the sample origin. No glomerular staining was seen for collagen type I. Collagen type III was present in some diabetic nodules. Anti-collagen type IV showed a decreased GBM staining in patients with diabetic nephropathy (p = 0.04). With anti-alpha 1 (IV)NC no changes in GBM staining intensity were observed; with anti-alpha 3 (IV)NC brilliant GBM staining was seen in both groups. Increased mesangial staining (p = 0.003) was seen with anti-collagen type IV in biopsies with nodular lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Heparanase induces a differential loss of heparan sulphate domains in overt diabetic nephropathy

“…Degradation of heparan sulphate by the bacterial heparan sulphate-cleaving enzyme heparinase III resulted in an increased permeability of the GBM to ferritin and albumin [2][3][4]. In addition, a loss of heparan sulphate in the GBM has been observed in many glomerular diseases, including diabetic nephropathy, and correlated with the degree of proteinuria [10][11][12][13][14]. However, several recent studies suggest that heparan sulphate in the GBM may not play a primary decisive role in the chargeselective permeability properties and development of proteinuria.…”

“…In addition, changes in GBM heparan sulphate content have been associated with the pathogenesis of diabetic nephropathy. Studies in patients with overt diabetic nephropathy revealed a decreased heparan sulphate content within the GBM [10][11][12][13][14], which inversely correlated with the degree of albuminuria [11]. Production of the core protein of agrin, the major heparan sulphate proteoglycan in the GBM, was not aberrant [11,13].…”

“…Studies in patients with overt diabetic nephropathy revealed a decreased heparan sulphate content within the GBM [10][11][12][13][14], which inversely correlated with the degree of albuminuria [11]. Production of the core protein of agrin, the major heparan sulphate proteoglycan in the GBM, was not aberrant [11,13]. However, these heparan sulphate changes occur at the macroalbuminuric stage of diabetic nephropathy, since no glomerular heparan sulphate alterations were found at the microalbuminuric stage [15].…”

“…Although previous studies using JM403, a monoclonal antibody (mAb) that is specific for N-unsubstituted glucosamine residues of heparan sulphate domain, suggest that the GBM of kidneys in patients with diabetic nephropathy has a reduced heparan sulphate content [10][11][12][13][14], it remains to be determined whether loss of heparan sulphate, as detected by JM403, is due to a change of the heparan sulphate structure that favours the binding by this antibody. Alternatively, loss of heparan sulphate in the GBM could be due to the reduced biosynthesis of the nascent heparan sulphate backbone structure.…”

Functional and molecular alterations of the glomerular barrier in long-term diabetes in mice

“…In diabetic nephropathy, studies have suggested that decreased synthesis of heparan sulphate proteoglycans [27][28][29][30] such as perlecan [31] is the reason for altered barrier function. Perlecan and agrin are the major proteoglycans in the GBM, both carrying heparan sulphate.…”