#3165 Molecular phenotype shifts in podocytes of primary FSGS: insights into WT-1, Podocin, and Mesenchymal Markers

Abstract Background and Aims Podocyte injury is a central feature of proteinuric glomerular diseases, including primary focal segmental glomerulosclerosis (pFSGS), leading to podocyte loss and progressive kidney dysfunction. We previously demonstrated that podocytes in pFSGS undergo significant molecular changes, including reduced expression of Wilms' tumor suppressor protein (WT-1), a key transcription factor for podocyte integrity. This study explores the molecular phenotype of podocytes in immune glomerulopathies, with a focus on WT-1 and markers of epithelial (podocin) and mesenchymal (desmin, vimentin, nestin) phenotypes in pFSGS. Method We conducted a quantitative immunomorphological analysis and confocal microscopy to assess glomerular expression of WT-1, podocin, desmin, vimentin, and nestin in kidney samples from patients with morphologically confirmed pFSGS (n = 14), IgA nephropathy (IgAN, n = 14) with CKD G1-3, and negative controls (NC, n = 12). NC samples were obtained from unaffected renal cortex during nephrectomy for malignant neoplasms (Fig. 1a). Results Patients with pFSGS exhibited nephrotic syndrome and typical glomerular alterations on light and electron microscopy (Fig. 1b, c), while IgAN showed milder proteinuria (Fig. 1d). Compared to controls, pFSGS demonstrated significantly lower glomerular expression of WT-1 and podocin, alongside elevated desmin and nestin levels (Fig. 2a). In the combined pFSGS and IgAN group, WT-1 and podocin expression correlated positively (r = 0.51, P < 0.013) and both markers inversely associated with proteinuria (WT-1: r = −0.49, P < 0.05; podocin: r = −0.52, P < 0.05). Notably, in pFSGS, WT-1 expression negatively correlated with desmin (r = −0.74, P < 0.05), and desmin localized predominantly in WT-1-negative podocytes (Fig. 2b). Conclusion Our findings reveal significant downregulation of WT-1 and podocin, alongside upregulation of desmin and nestin, in the early stages of primary FSGS. These findings are suggestive for the genomic reprogramming of podocytes as part of the epithelial-mesenchymal transition, determining the structural and functional disorders of these cells, more prominent in pFSGS.