Morphologic analysis of urinary podocytes in focal segmental glomerulosclerosis

Abstract

Background: The development of glomerulosclerosis in focal segmental glomerulosclerosis is associated with a reduction in podocyte number in the glomerular capillary tufts. Although it has been reported that the number of urinary podocytes in focal segmental glomerulosclerosis exceeds that of minimal change nephrotic syndrome, the nature of events that promote podocyte detachment in focal segmental glomerulosclerosis remains elusive. Methods: In this present study, we provide detailed morphologic analysis of urinary podocytes obtained from focal segmental glomerulosclerosis patients by examining the size of the urinary podocytes from focal segmental glomerulosclerosis, minimal change nephrotic syndrome and glomerulonephritis patients. In addition, in urinary podocytes from focal segmental glomerulosclerosis and minimal change nephrotic syndrome patients, we analyzed podocyte hypertrophy and mitotic catastrophe using immunostaining of p21 and phospho-ribosomal protein S6. Results: The size of the urinary podocytes was strikingly larger in samples obtained from focal segmental glomerulosclerosis compared to minimal change nephrotic syndrome and glomerulonephritis patients (P <0.01). Urinary podocytes from focal segmental glomerulosclerosis patients had higher frequency of p21 (P <0.01) and phospho-ribosomal protein S6 (P =0.02) positivity than those in minimal change nephrotic syndrome. Characteristic features of mitotic catastrophe were more commonly observed in focal segmental glomerulosclerosis than minimal change nephrotic syndrome urinary samples (P <0.01). Conclusion: We posit that the significant increase in size of the focal segmental glomerulosclerosis urinary podocytes in comparison to those observed in minimal change nephrotic syndrome may potentially be explained by hypertrophy and mitotic catastrophe.