Decreased glomerular expression of agrin in diabetic nephropathy and podocytes, cultured in high glucose medium

Aim: A decrease in glomerular heparan sulfate (MS) proteoglycan (PG), witho ut apparent decrease in HSPG core protein expression, has been reported to occur in diabetic nephropathy (DN). In most studies however, agrin, the maj or HSPG core protein in the glomerular basement membrane, has not been stud ied. This prompted us to study the glomerular expression of agrin in parall el to the expression of HS-glycosaminoglycans (GAG) in biopsies of patients with DN. Furthermore, the influence of glucose on agrin production in cult ured podocytes and the expression of agrin in fetal kidneys was investigate d. Methods: Cryostat sections of renal biopsies from patients with DN (n = 8) and healthy controls (HC, n = 8), were stained for agrin and MS-GAG. Sec tions of fetal kidneys were double stained for agrin and CD35 or CD31. Stai nings were performed by indirect immunofluorescence (IIF). The production o f agrin by cultured human podocytes was tested by ELISA and IIF. Results: T he expression of agrin, detected by AS46, was significantly reduced in biop sies from patients with DN compared to MC (p < 0.01). Similar findings were observed when monoclonal antibody JM72 was used (p < 0.05). In addition, a significant reduction in the glomerular expression of MS-GAG was detected with JM403 in these patients (p < 0.01). Agrin is expressed in cultured pod ocytes, the expression hereof was reduced when the cells were cultured in t he presence of 25 mM D-glucose (p < 0.01). In biopsies of human fetal kidne ys, glomerular expression of agrin coincided with the expression of CD31, I n early stages of glomerular differentiation there was a strong staining fo r agrin and CD31 while CD35 was only slightly positive. Conclusions: Our da ta argue against a selective dysregulation in HSPG sulfation in DN, but sug gest a pivotal role for hyperglycemia in the downregulation of agrin core p rotein production. Copyright (C) 2001 S Karger AG, Basel.