Heparan Sulfate 3-O-sulfation in renal fibrosis

Abstract

Chronic kidney disease globally affects 10% of the population with fibrosis being one of the hallmarks of disease progression. Renal fibrosis is characterised by a change in the extracellular matrix (ECM) that can lead to tissue remodelling and organ loss. Throughout this process the kidney is exposed to damaging cytokines and growth factors. Heparan Sulfate (HS) proteoglycans present on the ECM and cell membranes play a crucial role in protecting, storing and presenting these cytokines and growth factors to the surrounding cells. This study focuses on HS sulfation and the enzymes modulating it, particularly HS 3-O-sulfotransferases (HS3ST), in the context of renal fibrosis. Initially, this work used an in vivo murine model of renal fibrosis to assess changes in HS sulfation during disease progression. The amount of HS total O-sulfation and particularly 2-O-sulfation were increased. HS 3-O-sulfation was localised on the basal membrane of tubules and more intensively on blood vessels and the glomerulus. In this model, the level of mRNA encoding HS3ST1, Sulfatase 1 and HS2ST1 was increased, whilst HS3ST3A was decreased. Amongst all enzymes studied, HS3ST1 displayed the strongest correlation with collagen deposition during fibrosis. The generation of renal epithelial cells overexpressing HS3ST1 enabled the identification of a differential signalling pattern of Heparin Binding Epidermal Growth Factor like growth factor (HBEGF) in cells with higher HS 3-O-sulfation. Additionally, this project found that pro-fibrotic factors downregulated HS3ST1 expression in human renal epithelial cells and rat renal fibroblasts. Finally, this project attempted to generate competing peptides and peptoids for Fibroblast Growth Factor 2 (FGF2) binding to renal epithelial cells. Although peptides and peptoids were found to bind to heparin by isothermal titration calorimetry, no binding competition was observed in vitro. However, the peptides and peptoids studied did emphasise the importance of secondary structure in the binding of HS to protein. Overall this highlights the complexity of HS modification during fibrosis. This work emphasises the need to study HS3ST in inflammation as it seems to be a potential marker of fibrosis.