Prevalence of the NPHS2 variants p.R229Q, p.A242V, and p.R138Q in patients with focal segmental glomerulosclerosis.

BACKGROUND: NPHS2 gene variants are associated with focal segmental glomerulosclerosis (FSGS) and steroid-resistant nephrotic syndrome (SRNS). In this study, the prevalence of NPHS2 variants p.R229Q, p.A242V, and p.R138Q was investigated in patients with familial or sporadic FSGS. MATERIALS AND METHODS: The sample consisted of 40 children and 70 adults diagnosed with FSGS confirmed by renal biopsy. Clinical and laboratory parameters were evaluated. Genotyping for the three single nucleotide polymorphisms (SNPs) was performed by real-time polymerase chain reaction: two variants in exon 5 (p.R229Q and p.A242V) and one in exon 3 (p.R138Q). Variants were correlated with ethnicity, clinical presentation, treatment response, and renal outcomes. RESULTS: Among the 40 children analyzed, 20% had familial and 80% sporadic FSGS and among adults, 4.3% had familial and 95.7% sporadic FSGS, respectively. Overall, SRNS was found in 70% of adults and 90% in children. Among children, variants were detected in 2 (5%) with sporadic FSGS, p.R229Q and p.A242V in 1 each. Among adults, variants were present in 9 (12.9%) patients, all with sporadic FSGS, p.R229Q in 4 and p.A242V in 5. No patient had the p.R138Q variant. Among adults, a trend of higher proteinuria at the end of follow-up (p = 0.06) was found in patients carrying a variant. There was no significant association between NPHS2 variants with the clinical presentation, dependence on immunosuppressive treatment, or renal outcomes. Regarding ethnicity, all patients carrying the p.R229Q variant were White, while 67% of carriers of the p.A242V variant were Black. CONCLUSION: In these patients with familial or sporadic FSGS, the prevalence of p.R229Q and p.A242V variants in children was 5% and in adults 12.9%. More studies of patients with FSGS could better define a strategy for genetic analysis and therapeutic management.

Markers of renal fibrosis: How do they correlate with podocyte damage in glomerular diseases?

BACKGROUND: Renal fibrosis is the result of the interaction of cellular and molecular pathways, which is induced by sustained glomerular injury and involves the podocytes and multiple profibrotic factors. In this study, we investigated the correlation of the mRNA expression of podocyte proteins and profibrotic factors with renal fibrosis measured in renal biopsies of patients with primary and secondary glomerulopathies. METHODS: Eighty-four adult patients with primary or secondary glomerular diseases and 12 controls were included. Demographic and clinical data were collected. Seventy-two percent of the renal biopsies were done less than one year from clinical disease manifestation. The quantification of the podocyte-associated mRNAs of alpha-actinin-4, podocin, and podocalyxin, as well as of the profibrotic factors TGF-ß1, CTGF, and VEGF-A were quantified by real-time polymerase chain reaction. The percent positive area of renal fibrosis was measured by immunohistochemistry staining, using anti-CTGF and anti-HHF35 antibodies and unpolarized Sirius Red. Correlations between the expression of tissue mRNAs and the positive area of fibrosis for the measured markers were made by Spearman's rank correlation coefficient. RESULTS: In relation to control biopsies, podocyte-specific proteins were downregulated in podocytopathies, in proliferative nephritis, in diabetic kidney disease (DRD), and in IgA nephropathy (IgAN). Messenger RNA of TGF-ß1, CTGF, and VEGF-A was upregulated in patients with podocytopathies and in DRD but not in proliferative nephritis and IgAN. Tissue mRNA expression of TGF-ß1, CTGF, and VEGF-A were strongly correlated with renal fibrosis, as measured by HHF35; however, the correlation, albeit significant, was moderate for Sirius Red and weak for CTGF. The percent positive area of renal fibrosis measured by Sirius Red was similar between podocytopathies and DRD and significantly higher in podocytopathies compared to IgAN or proliferative nephritis. CONCLUSIONS: In patients with glomerular diseases, the mRNA of TGF-ß1, CTGF, and VEGF-A correlated positively with the extent of renal fibrosis, and the positive area of fibrosis was larger in the podocytopathies and in DRD as measured by Sirius Red. The pathways connecting podocyte damage and activation of profibrotic factors to kidney tissue fibrosis need to be better investigated.