Nephrin Loss Can Be Used to Predict Remission and Long-term Renal Outcome in Patients With Minimal Change Disease

Abstract

Introduction: Minimal change disease is a common cause of nephrotic syndrome. In general, patients with minimal change disease respond to corticosteroids and have excellent long-term renal survival. However, some patients have less favorable outcome. These patients are often thought to have progressed to focal segmental glomerulosclerosis. We previously reported that a segmental loss of podocyte markers is present before the development of focal segmental glomerulosclerosis in a rat model. Here, we investigated whether loss of podocyte marker nephrin can serve as a biomarker for predicting poor outcome in patients with minimal change disease.

Methods: We obtained 47 kidney biopsy samples from patients diagnosed with minimal change disease and stained sections with periodic acid-Schiff and for nephrin. Nephrin loss was scored by 2 independent researchers who were blinded to clinical outcome. Clinical data were collected retrospectively, and nephrin loss was correlated with clinical follow-up data.

Results: Nephrin loss was present in 34% of the biopsy samples. During follow-up, patients with nephrin loss achieved remission less frequently (61%) compared to patients without (96%) (P = 0.002). Moreover, 5-year eGFR was lower in the patients with renal nephrin loss. The risk of eGFR decreasing to < 60 ml/min per 1.73m² increased with each percentage of glomeruli with nephrin loss (hazard ratio = 1.044, 95% confidence interval = 1.02-1.07).

Conclusion: These results indicate that nephrin loss in patients with minimal change disease can help predict both remission and long-term renal outcome.

Keywords: biomarker; focal segmental glomerulosclerosis; minimal change disease; nephrin; nephrotic syndrome.

Figure 1

Normal nephrin staining pattern and nephrin loss in patients with minimal change disease. Nephrin-stained kidney sections from a healthy control (a), a patient with minimal change disease (MCD) without nephrin loss (b), and 2 patients with MCD with nephrin loss (c,d). Panels (a) and (b) show a normal linear pattern of nephrin staining along the glomerular basement membrane. In panels (c) and (d), nephrin loss was either (c; arrowhead) segmental or (d) global. (e) Quantification of nephrin loss (defined as nephrin loss in at least 1 glomerulus) in the biopsy samples obtained from patients with MCD. (f,i) To determine whether podocytes were still present at the site of nephrin loss, sections with nephrin loss were stained for the podocyte marker Wilms Tumor 1 (WT1). Example images of WT1 (f,i), nephrin (g,j), and periodic acid−Schiff (h,k) staining in a patient without nephrin loss (f−h) and a patient with nephrin loss (i−k). Podocytes in glomeruli without nephrin loss (f−h) were WT1 positive (f, arrows) and nephrin positive (g, arrows). The presence of WT1-positive cells (i, arrowhead) at the site of nephrin loss (j, arrowhead) indicates that podocytes were still present. Bar = 50 μm.

Figure 2

Proteinuria and estimated glomerular filtration rate (eGFR) during short-term follow-up. Proteinuria was measured over time in each patient with nephrin loss (a) and in each patient without nephrin loss (c). At 16 weeks, proteinuria was higher in the patients with nephrin loss (1.0 g/24 h) compared to the patients without nephrin loss (0.15 g/24 h, P = 0.02). Differences in proteinuria were associated with the time point (linear mixed model, P_interaction = 0.04). (b,d) eGFR levels were similar between the patients with nephrin loss (b) and the patients without nephrin loss (d; P = 0.69).

Figure 3

Renal insufficiency in minimal change disease patients with nephrin loss. Kaplan−Meier survival curve depicting renal insufficiency in patients with nephrin loss and patients without nephrin loss. Renal insufficiency developed earlier in the patients with nephrin loss compared to the patients without nephrin loss. Moreover, the likelihood of developing renal insufficiency increased with every percentage of glomeruli with nephrin loss, as shown by Cox regression analysis (hazard ratio = 1.04, 95% confidence interval 1.02−1.07).