Expression Profiling of Cultured Podocytes Exposed to Nephrotic Plasma Reveals Intrinsic Molecular Signatures of Nephrotic Syndrome

Abstract

Background: Nephrotic syndrome (NS) is a common renal disorder in children attributed to podocyte injury. However, children with the same diagnosis have markedly variable treatment responses, clinical courses, and outcomes, suggesting molecular heterogeneity. Purpose: This study aimed to explore the molecular responses of podocytes to nephrotic plasma to identify specific genes and signaling pathways differentiating various clinical NS groups as well as biological processes that drive injury in normal podocytes. Methods: Transcriptome profiles from immortalized human podocyte cell line exposed to the plasma of 8 subjects (steroid-sensitive nephrotic syndrome [SSNS], n = 4; steroid-resistant nephrotic syndrome [SRNS], n = 2; and healthy adult individuals [control], n = 2) were generated using microarray analysis. Results: Unsupervised hierarchical clustering of global gene expression data was broadly correlated with the clinical classification of NS. Differential gene expression (DGE) analysis of diseased groups (SSNS or SRNS) versus healthy controls identified 105 genes (58 upregulated, 47 downregulated) in SSNS and 139 genes (78 upregulated, 61 downregulated) in SRNS with 55 common to SSNS and SRNS, while the rest were unique (50 in SSNS, 84 genes in SRNS). Pathway analysis of the significant (p ≤ 0.05,-1 ≤ log 2 FC ≥ 1) differentially expressed genes identified the transforming growth factor-β and JAK-STAT pathways to be involved in both SSNS and SRNS. DGE analysis of SSNS versus SRNS identified 2350 genes with values of p ≤ 0.05, and a heatmap of corresponding expression values of these genes in each subject showed clear differences in SSNS and SRNS. Conclusion: Our study observations indicate that, although podocyte injury follows similar pathways in different clinical subgroups, the pathways are modulated differently as evidenced A c c e p t e d A r t i c l e 3 by the heatmap. Such transcriptome profiling with a larger cohort can stratify patients into intrinsic subtypes and provide insight into the molecular mechanisms of podocyte injury.

Nephrotic syndrome sera induce different transcriptomes in podocytes based on the steroid response

“…Later, Panigrahi et al. investigated the gene expression of human immortalized podocytes exposed to plasma from patients already treated with NS by using a microarray method (Panigrahi et al., 2021). There were four steroid‐sensitive NS serum‐induced profiles that clustered separately from the profiles induced by two steroid‐resistant NS samples (which clustered along with two healthy controls).…”

“…Although none of the differentially expressed genes were found to be differentially expressed in our study, the other two cellular processes are involved; that is, both blood mononuclear cells and podocytes increase their redox and proteosynthetic capacity. Later, Panigrahi et al investigated the gene expression of human immortalized podocytes exposed to plasma from patients already treated with NS by using a microarray method (Panigrahi et al, 2021). There were four steroidsensitive NS serum-induced profiles that clustered separately from the profiles induced by two steroid-resistant NS samples (which clustered along with two healthy controls).…”

Perturbations in podocyte transcriptome and biological pathways induced by FSGS associated circulating factors

“…Since then, further studies from several groups have shown that sera from FSGS patients causes loss of stress fibers and activation of β3 integrin and sites of focal adhesion ( 7 , 8 ). Microarray studies have also demonstrated that genes associated with cytokine signaling and apoptosis are activated in podocytes exposed to sera from FSGS patients ( 9 , 10 ).…”