INTRODUCTION

The podocyte is thought to be the mainly affected cell type in focal segmental glomerulosclerosis (FSGS). However, recent studies have also indicated a role for glomerular endothelial cells and podocyte-endothelial crosstalk in FSGS development. An experimental model for podocyte injury showed that increased endothelin-1 (ET-1) signaling between podocytes and endothelial cells induces endothelial oxidative stress and subsequent podocyte loss. In the current study, we investigated endothelial endothelin receptor A (ETR) expression in patients with FSGS and its association with podocyte injury and glomerular oxidative stress.

METHODS

We selected 39 biopsy samples of patients with FSGS and 8 healthy control subjects, and stained them for ETR, nephrin and 8-oxo-guanine, a DNA lesion caused by oxidative damage. Glomeruli with ETR-positive endothelium and with nephrin loss were scored, and the 8-oxo-guanine-positive glomerular area was measured.

RESULTS

The mean percentage of glomeruli with ETR-positive endothelial cells in patients with FSGS was higher compared to that in healthy control subjects (52% vs. 7%;  < 0.001). The presence of glomerular ETR-positive endothelium was strongly associated with nephrin loss both on the biopsy level (rho = 0.47;  < 0.01), as on the level of individual glomeruli (odds ratio = 2.0;  < 0.001). Moreover, glomeruli with ETR-positive endothelium showed more 8-oxo-guanine-positive staining (1.9% vs. 2.4%;  = 0.037). Finally, 8-oxo-guanine positivity in glomeruli was associated with increased levels of proteinuria.

CONCLUSION

Taking together our findings, we show that ETR is increased in glomerular endothelial cells of patients with FSGS and associated with podocyte damage and glomerular oxidative stress. These findings support the hypothesis that ET-1 signaling in glomerular endothelial cells contributes to disease development in patients with FSGS.