Podocin and uPAR are good biomarkers in cases of Focal and segmental glomerulosclerosis in pediatric renal biopsies

Abstract

There are controversies whether Minimal Change Disease (MCD) and Focal and Segmental Glomerulosclerosis (FSGS) are distinct glomerular lesions or different manifestations within the same spectrum of diseases. The uPAR (urokinase-type plasminogen activator receptor) and some slit diaphragm proteins may be altered in FSGS glomeruli and may function as biomarkers of the disease in renal biopsies. Thus, this study aims to evaluate the diagnostic potential of uPAR and glomerular proteins for differentiation between MCD and FSGS in renal pediatric biopsy. Renal biopsies from 50 children between 2 and 18 years old were selected, with diagnosis of MCD (n = 29) and FSGS (n = 21). Control group consisted of pediatric autopsies (n = 15) from patients younger than 18 years old, with no evidences of renal dysfunction. In situ expressions of WT1, nephrin, podocin and uPAR were evaluated by immunoperoxidase technique. Renal biopsy of patients with MCD and FSGS expressed fewer WT1 (p≤0.0001, F = 19.35) and nephrin (p<0.0001; H = 21.54) than patients in the control group. FSGS patients expressed fewer podocin than control (p<0.0359, H = 6.655). FSGS cases expressed more uPAR than each of control and MCD (p = 0.0019; H = 12.57) and there was a positive and significant correlation between nephrin and podocin (p = 0.0026, rS = 0.6502) in these cases. Podocin had sensitivity of 73.3% and specificity of 86.7% (p = 0.0068) and uPAR had sensitivity of 78.9% and specificity of 73.3% (p = 0.0040) for diagnosis of FSGS patients. The main limitation of the study is the limited number of cases due to the difficulty in performing biopsy in pediatric patients. Podocin and uPAR are good markers for FSGS and differentiate these cases from MCD, reinforcing the theory of distinct glomerular diseases. These findings suggest that podocin and uPAR can be used as biomarkers in the routine analysis of renal biopsies in cases of podocytopathies when the lesion (sclerosis) is not sampled.

In situ evaluation of podocytes in patients with focal segmental glomerulosclerosis and minimal change disease

“…Previous results from our group have shown that podocytes have increased expression of urokinase plasminogen activator receptor (uPAR) in situ in biopsies from adult [ 8 ] and pediatric [ 9 ] patients with morphological lesions compatible with FSGS. From these findings, we evaluated the possible causes of cellular injury in podocytopathies.…”

“…Animal model studies have demonstrated the relationship between reduction in WT1-labeled podocytes and glomerulosclerosis [ 15 ]. However, we have previously shown that there is no difference in the density of WT1-labeled podocytes in biopsies of pediatric patients with FSGS and MCD [ 9 ]. Unlike other studies, we excluded glomeruli that presented sclerosis.…”

“…It has been reported that the expression of dystroglycan, an adhesion molecule between the podocyte and GBM, is significantly lower in biopsies of patients with MCD than in those of patients with FSGS [ 22 ]. Another protein, uPAR, is upregulated in podocytes from cases as compared to those from MCD cases [ 8 , 9 ] and is related to the activation of β3 integrin, leading to the foot process effacement in FSGS [ 23 ]. In this study, the mean FPW showed a positive and significant correlation with the levels of proteinuria in FSGS cases.…”

“…For TEM, the sample was fixed with Karnovsky 2.5% + ruthenium red 0.2% and post-fixed in osmium tetroxide 2%, then dehydrated in graded alcohols and acetone solutions and embedded in Epon 812 resin. Ultrathin 60-nm-thick sections were cut and placed onto nickel grids and were subsequently contrasted with lead citrate 1% and uranyl acetate 3% and examined under an EM-900 transmission electron microscope (Zeiss, Germany) [ 8 , 9 ].…”

Challenges in primary focal segmental glomerulosclerosis diagnosis: from the diagnostic algorithm to novel biomarkers

“…Moreover, plasma suPAR levels have also been found to be elevated in several extrarenal pathologies that can potentially be concomitant to FSGS, such as cancer or inflammatory disorders, among others [ 91–95 ]. Recent studies suggest that both urinary levels of suPAR [ 96 , 97 ] and uPAR detection in kidney biopsies [ 98 ] may be useful in the diagnosis of primary FSGS, but further investigation is needed. Anti-CD40 blood levels have also been associated with FSGS, with 78% accuracy to predict post-transplant FSGS recurrence [ 99 ]; however, further studies are required to confirm these results.…”