Dysregulation of podocyte phenotype in idiopathic collapsing glomerulopathy and HIV-associated nephropathy.
BACKGROUND
Idiopathic collapsing glomerulopathy (ICG) and HIV-associated nephropathy (HIV-AN) are characterized by severe nephrotic syndrome, collapse and sclerosis of the glomerular tuft with prominent podocyte alterations and extensive tubulointerstitial lesions. We previously showed phenotypic changes in podocytes from patients with diffuse mesangial sclerosis, a severe glomerulopathy sharing several morphological features with collapsing glomerulopathy. The aim of this study was to analyze the podocyte phenotype in ICG and HIV-AN.


METHODS
Using immunohistochemical techniques, we studied the podocyte expression of the transcription factor WT1 and its target PAX2, GLEPP1, synaptopodin and vimentin as markers of podocyte maturity and of proliferating cell nuclear antigen (PCNA) as a marker of proliferation. Apoptosis was analyzed by the TUNEL method. Results from renal biopsies of ICG and HIV-AN were compared with those obtained from normal kidney, minimal change nephrotic syndrome (MCNS), focal and segmental glomerulosclerosis (FSGS) and membranous glomerulonephritis (MGN).


RESULTS
Abnormal distribution of WT1 and PAX2 and extensive loss of podocyte markers were observed in ICG and HIV-AN; this dysregulation was associated with podocyte proliferation without detectable apoptosis. In contrast, no podocyte changes were detected in MCNS or MGN. In FSGS, phenotypic changes, without proliferation, were restricted to podocytes surrounding focal and segmental glomerular lesions. Increased PCNA expression and apoptosis were observed in ICG and HIV-AN tubular cells.


CONCLUSIONS
Dysregulation of podocyte phenotype and proliferation are present in both ICG and HIV-AN. This suggests that, whatever their etiology, both types of collapsing glomerulopathy share a common pathogenic pathway. Upregulation of cell proliferation and apoptosis observed in tubular epithelial cells is probably involved in the occurrence of severe tubulointerstitial lesions in collapsing glomerulonephritis.
Yang
Youxin
Y
INSERM U 423, Tour Lavoisier, Hôpital Necker-Enfants Malades, Université René Descartes, 149 rue de Sèvres, F-75743 Paris Cedex 15, France.
Gubler
Marie-Claire
MC
Beaufils
Hélène
H
D016263:AIDS-Associated Nephropathy / Q000378:metabolism / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D017209:Apoptosis / Q000502:physiology; D015415:Biomarkers; D001706:Biopsy; D002455:Cell Division / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D004268:DNA-Binding Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005260:Female; D015433:Glomerulonephritis, Membranous / Q000378:metabolism / Q000473:pathology; D005923:Glomerulosclerosis, Focal Segmental / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D020287:In Situ Nick-End Labeling; D007678:Kidney Glomerulus / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D009402:Nephrosis, Lipoid / Q000378:metabolism / Q000473:pathology; D051762:PAX2 Transcription Factor; D010641:Phenotype; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3; D014157:Transcription Factors / Q000378:metabolism; D014746:Vimentin / Q000378:metabolism; D025721:WT1 Proteins / Q000378:metabolism
D015415:Biomarkers; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D051762:PAX2 Transcription Factor; C497318:PAX2 protein, human; D018809:Proliferating Cell Nuclear Antigen; C503967:SYNPO protein, human; D014157:Transcription Factors; D014746:Vimentin; D025721:WT1 Proteins; C516888:PTPRO protein, human; D017027:Protein Tyrosine Phosphatases; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3