1. ¹Nephrology Research Laboratory, Department of Nephrology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
2. ²Department of Matrix Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
3. ³Department of Pediatric Nephrology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
4. ⁴Department of Medical Biochemistry and Microbiology, Biomedical Center Uppsala University, Uppsala, Sweden
5. ⁵Department of Oncology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
6. ⁶Department of Pathology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
7. ⁷Cancer and Vascular Biology Research Center, Rappaport Faculty of Medicine, Technion, Haifa, Israel

Correspondence: J van der Vlag, Nephrology Research Laboratory (279), Department of Nephrology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Geert Grooteplein 26-28, Nijmegen 6525 GA, The Netherlands. E-mail: J.vanderVlag@NIER.UMCN.NL

Received 18 April 2007; Revised 28 September 2007; Accepted 9 October 2007; Published online 28 November 2007.

Abstract

Heparan sulfate in the glomerular basement membrane has been considered crucial for charge-selective filtration. In many proteinuric diseases, increased glomerular expression of heparanase is associated with decreased heparan sulfate. Here, we used mice overexpressing heparanase and evaluated the expression of different heparan sulfate domains in the kidney and other tissues measured with anti-heparan sulfate antibodies. Glycosaminoglycan-associated anionic sites were visualized by the cationic dye cupromeronic blue. Transgenic mice showed a differential loss of heparan sulfate domains in several tissues. An unmodified and a sulfated heparan sulfate domain resisted heparanase action in vivo and in vitro. Glycosaminoglycan-associated anionic sites were reduced about fivefold in the glomerular basement membrane of transgenic mice, whereas glomerular ultrastructure and renal function remained normal. Heparanase-resistant heparan sulfate domains may represent remnant chains or chains not susceptible to cleavage. Importantly, the strong reduction of glycosaminoglycan-associated anionic sites in the glomerular basement membrane without development of a clear renal phenotype questions the primary role of heparan sulfate in charge-selective filtration. We cannot, however, exclude that overexpression of heparanase and heparan sulfate loss in the basement membrane in glomerular diseases contributes to proteinuria.