ALTERATION OF GLYCOCALYX ON ENDOTHELIUM OF PERITUBULAR CAPILLARIES IN CKD

Abstract BACKGROUND AND AIMS The glycocalyx is a carbohydrate-rich gel-like mesh, which covers the luminal surface of cells, including the endothelium. The glycocalyx is involved in many regulatory functions of the endothelium, including vascular permeability. In chronic kidney disease (CKD), peritubular capillaries undergo anatomical, structural and functional alterations such as rarefaction, increased tortuosity and increased permeability. Here, we hypothesized that the glycocalyx of peritubular capillaries might be affected in CKD and investigated morphological and ultrastructural pathological alterations of the glycocalyx in different murine CKD models and human kidney tissue. METHOD We stained the glycocalyx of peritubular capillaries in kidney tissue of murine and human CKD specimen using different fluorescently labeled plant-derived lectins. Next, we established the Lanthanum Dysprosium Glycosamino Glycan adhesion (LaDy GAGa) staining technique to visualize the ultrastructure of the glycocalyx using transmission electron microscopy and to perform quantitative analyses. Finally, we analyzed the expression and regulation of glycocalyx components in primary murine endothelial cells. RESULTS Fluorescence stainings using different lectins with high affinity to components of the renal glycocalyx revealed a reduced binding to the endothelium in CKD. We found a similar change in a human kidney tissue. The LaDy GAGa staining technique visualized the ultrastructure of the glycocalyx and enabled quantitive analyses. We found a significant reduction of the glycocalyx thickness and density in two different models of renal fibrosis and CKD, i.e. unilateral ureteral obstruction and ischemia–reperfusion injury. Additionally, mRNA expression of proteins involved in glycocalyx biology, synthesis and turnover, i.e. syndecan 1 and glypican 1, which are main components of the glycocalyx, and exostosin 2, involved in the synthesis of the glycocalyx, were significantly upregulated in endothelial cells isolated from murine CKD models. CONCLUSION Visualization of glycocalyx using specific ultrastructural analyses allows qualitative and quantitative analyses, revealing significant pathological alterations in the glycocalyx of peritubular capillaries in CKD.