Role of 6-O-Sulphated Heparan sulphate in chronic renal fibrosis [Immunology]

May 30th, 2014 by Alhasan, A. A., Spielhofer, J., Kusche-Gullberg, M., Kirby, J. A., Ali, S.

Heparan sulphate (HS) plays a crucial role in the fibrosis associated with chronic allograft dysfunction by binding and presenting cytokines and growth factors to their receptors. These interactions critically depend on the distribution of 6-O-sulphated glucosamine residues which is generated by glucosaminyl-6-O-sulphotransferases (HS6STs) and selectively removed by cell surface HS-6-O-endosulphatases (Sulfs). Using human renal allografts we found increased expression of 6-O-sulphated HS domains in tubular epithelial cells during chronic rejection as compared to the controls. Stimulation of renal epithelial cells with TGF-β induced Sulf-2 expression. To examine the role of 6-O-sulphated HS in the development of fibrosis we generated stably HS6ST1 and SULF2 overexpressing renal epithelial cells. Compared to mock transfectants, the HS6ST1 transfectants showed significantly increased binding of FGF2 (p=0.0086) and pERK activation. HS6ST1 transfectants displayed a relative increase in mono-6-O-sulphated disaccharides accompanied by a decrease in iduronic acid 2-O-sulfated disaccharide structures. In contrast, Sulf-2 transfectants showed significantly reduced FGF2 binding and phosphorylation of ERK. Structural analysis of HS showed about 40% down-regulation in 6-O-sulphation with a parallel increase in iduronic acid mono-2-O-sulfated disaccharides. In order to assess the relevance of these data in vivo we established a murine model of fibrosis (Unilateral Uretric Obstruction (UUO)). HS specific phage display antibodies (HS3A8 and RB4EA12) showed significant increase in 6-O sulphation in fibrotic kidney compared to the control. These results suggest an important role of 6-O-sulphation in the pathogenesis of fibrosis associated with chronic rejection.