Immunoexpression of podocyte-associated proteins in acquired human glomerulopathies with nephrotic syndrome

CD2AP, alpha-actinin-4 and podocalyxin are thought to play an important role in the structure and function of glomerular podocytes, therefore we intended to evaluate quantitatively, using computer image analysis system, the immunoexpression of these proteins in renal biopsy specimens in glomerulopathies presented with nephrotic syndrome: minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS) and nephropathy IgA (IgAN). As a control 10 biopsy specimens of the kidneys removed because of trauma were used. In normal kidneys CD2AP, alpha-actinin-4, and podocalyxin showed intense staining in podocytes along the capillary walls of the glomeruli. The intensity of immunoexpression of CD2AP and alpha-actinin-4 in renal tissue in patients with MCD, FSGS, and IgAN was similar to normal controls, but the distribution of these proteins was more granular in glomeruli of diseased kidney. The immunostaining of podocalyxin was weaker in podocytes in patients with FSGS as compared with normal glomeruli. The immunostaining of podocalyxin was not significantly altered in MCD and IgAN. The immunostaining of CD2AP and alpha-actinin-4 did not correlate with the intensity of proteinuria in patients with MCD, FSGS and IgAN, whilst in FSGS patients the significant correlation was found between the glomerular immunostaining of podocalyxin and proteinuria. In conclusion, revealed in our study diminished immunoexpression of podocalyxin and significant correlation with the level of proteinuria in FSGS patients suggests a possible role of this sialoprotein in the alteration of the glomerular filtration barrier in this disease.