Correlation between Podocyte Foot Process Effacement and Proteinuria in Human Glomerular Diseases

The podocyte is a specialized epithelial cell with numerous interdigitating foot processes which play an important role in the regulation of the glomerular basement membrane (GBM) permeability. The nephrotic syndrome results from increased glomerular permeability to proteins and is structurally belived to be associated with podocyte foot process effacement. Despite increasing knowledge of the molecular composition of the glomerular filtration barrier, the relationship between proteinuria and foot process effacement remains unclear. The aim of this study is to analyze the relationship between podocyte foot process effacement and the level of proteinuria. Morphometric analysis was performed on electron microscopy images taken randomly from 37 patients diagnosed with various glomerular diseases. 17 of the patients had nephrotic syndrome and 20 had subnephrotic proteinuria. The mean foot process width (FPW) was quantitated for each patient and for each group and correlated with the level of proteinuria. In the non nephrotic group segmental effacement of the foot processes was present and the mean FPW was 422 ± 90 nm. In the nephrotic group the foot processes were diffusely effaced, reflected by a FPW of 1196 ± 517 nm, significantly larger than in the subnephrotic group. The level of proteinuria correlated with the FPW only when all 37 patients were analyzed together. There was no correlation when the groups were studied separately. The mean FPW was significantly larger in the nephrotic group compared to the non nephrotic group. Podocyte foot process effacement correlated with proteinuria.