EXPRESSION OF GLOMERULAR EXTRACELLULAR-MATRIX COMPONENTS IN HUMAN DIABETIC NEPHROPATHY - DECREASE OF HEPARAN-SULFATE IN THE GLOMERULAR-BASEMENT-MEMBRANE

Diabetic nephropathy is characterized by albuminuria which proceeds to overt proteinuria. The highly negatively stained HS side chain of hep aran sulphate proteoglycan (HSPG) is a major determinant of the charge -dependent permeability of the GBM. We set out to study the presence o f HS and HSPG in the GBM of patients with diabetic nephropathy using n ewly developed monoclonal antibodies, and to compare HSPG expression t o the expression of other previously investigated glomerular extracell ular 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 subjec ts. Monoclonal antibodies used were: JM403 against the HS side chain o f GBM HSPG and JM72 against the HSPG-core protein. Also, a polyclonal antiserum (B31) against human GBM-HSPG-core protein was used. Addition ally, antibodies were used against collagen types I, III, IV and again st alpha 1(IV)NC, alpha 3(IV)NC and fibronectin. Staining was scored f or intensity and for staining pattern by four independent observers wh o had no previous knowledge of the sample origin. No glomerular staini ng was seen for collagen type I, Collagen type III was present in some diabetic nodules. Anti-collagen type IV showed a decreased GBM staini ng in patients with diabetic nephropathy (p = 0.04). With anti-alpha 1 (IV)NC no changes in GBM staining intensity were observed; with anti-a lpha 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. No differences were observed for fibro nectin although it was abundantly present in the mesangial area of bio psies from patients with diabetic nephropathy. In biopsies with mesang ial expansion and in biopsies with diabetic nodules, we observed a dec reased GBM(p = 0.001) HS side chain staining (JM403) without changes i n HSPG-core protein staining (JM72,B31). The HS staining pattern regul arly changed from a linear to a more granular and irregular pattern. I n patients with a creatinine clearance of more than 15 ml/min, the int ensity of GBM HS staining showed an inverse correlation with the rate of proteinuria (r = -0.85, p = 0.004), suggesting a functional relatio nship. The decreased HS staining in the GBM may reflect the potentiall y disrupted charge barrier in diabetic nephropathy.