Evaluation of podocyte lesion in patients with diabetic nephropathy: Wilms' tumor-1 protein used as a podocyte marker.

INTRODUCTION: The reduction of podocyte number and density per glomerulus has been linked to the development of proteinuria and the progression of disease in patients with diabetic nephropathy (DN). However, it has been recognized that measurement of podocyte number by light microscope is quite difficult because of the complexity of both podocyte and glomerular structure, which is not suitable for clinical research. In our research institute, we used WT1 as podocyte marker to evaluate the podocyte lesion.

METHODS: In our experiment, we selected the C-terminal antibody of WT1 to stain the nuclei and the N-terminal antibody of WT1 to stain the cytoplasma of podocytes. Forty patients were enrolled with type 2 diabetes and proven to have DN by renal biopsy analysis. DN patients were classified into three groups based on the degree of proteinuria: microalbuminuria (n=10, 30-300mg/24h), overt proteinuria (n=15, 0.5-3.5g/24h), and heavy proteinuria (n=15, >3.5g/24h).

RESULTS: The results demonstrated that the podocyte number was markedly decreased in patients with DN (30-51% reduction). There was a significant negative correlation between the proteinuria and both podocyte density and number. The cover area density of podocyte cytoplasma in glomerulus was also significantly decreased in all DN patients (39-80% reduction). A significant inverse correlation was observed between the cover area density and the degree of proteinuria. The correlation coefficient (r=-0.85) was much higher than that between proteinuria and podocyte density (r=-0.56) or podocyte number (r=-0.36).

CONCLUSION: In conclusion, podocyte damage occurred in patients with DN, even in the early stage and became more dramatic during the course of proteinuria progression. WT1 staining, using the polyclonal antibody to stain the nuclei and monoclonal antibody to stain the cytoplasma of podocytes together, is a valuable alternative technique in the study of podocyte injury.