nephrin and Hyperplasia

Collapsing focal segmental glomerulosclerosis (cFSGS) is a progressive kidney disease characterized by glomerular collapse with epithelial hyperplasia. Here we used a transgenic mouse model of cFSGS with immunotoxin-induced podocyte-specific injury to determine the role for Notch signaling in its pathogenesis. The mice exhibited progressive loss of podocytes and severe proteinuria concomitant with histological features of cFSGS. Hyperplastic epithelium was negative for genetic podocyte tags, but positive for the parietal epithelial cell marker claudin-1, and expressed Notch1, Jagged1, and Hes1 mRNA and protein. Enhanced Notch mRNA expression induced by transforming growth factor-β1 in cultured parietal epithelial cells was associated with mesenchymal markers (α-smooth muscle actin, vimentin, and Snail1). Notch inhibition in vitro suppressed these phenotypic transcripts and Notch-dependent cell migration. Moreover, Notch inhibition in vivo significantly decreased parietal epithelial cell lesions but worsened proteinuria and histopathology in our cFSGS model. Thus, aberrant Notch1-mediated parietal epithelial cell migration with phenotypic changes appears to underlie the pathogenesis of cFSGS. Parietal epithelial cell hyperplasia may also represent an adaptive response to compensate for a disrupted filtration barrier with progressive podocyte loss.

Topics: Amyloid Precursor Protein Secretases; Animals; Antibodies, Monoclonal; Apoptosis; Basic Helix-Loop-Helix Transcription Factors; Biomarkers; Calcium-Binding Proteins; Cell Line; Cell Movement; Cell Proliferation; Claudin-1; Dibenzazepines; Disease Models, Animal; Enzyme Inhibitors; Epithelial Cells; Exotoxins; Glomerulosclerosis, Focal Segmental; Homeodomain Proteins; Humans; Hyperplasia; Integrases; Intercellular Signaling Peptides and Proteins; Interleukin-2 Receptor alpha Subunit; Jagged-1 Protein; Kidney Glomerulus; Membrane Proteins; Mice; Mice, Transgenic; Podocytes; Proteinuria; Receptor, Notch1; RNA, Untranslated; Serrate-Jagged Proteins; Time Factors; Transcription Factor HES-1; Transforming Growth Factor beta1

Congenital nephrotic syndrome of the Finnish type (NPHS1, CNF) is an autosomal recessive disease caused by mutations in a major podocyte protein, nephrin. NPHS1 is associated with heavy proteinuria and the development of glomerular scarring. We studied the cellular and molecular changes affecting the glomerular mesangium in NPHS1 kidneys. Marked hyperplasia of mesangial cells (MC) was mainly responsible for the early mesangial expansion in NPHS1 glomeruli. The levels of the proliferation marker, mindbomb homolog 1 and the major MC mitogen, platelet-derived growth factor, and its receptors, however, were quite normal. Only a small number of cells were positive for CD68 (marker for phagocytic cells) and CD34 (marker for mesenchymal precursor cells) in the NPHS1 mesangium. MCs strongly expressed alpha-smooth muscle actin, indicating myofibloblast transformation. The expression levels of the profibrotic mediators osteopontin and transforming growth factor beta were up-regulated in NPHS1 glomeruli by 3.2 and 1.6-fold, respectively, compared to the controls. The synthesis by MCs of the typical fibroblast products collagen I, fibronectin, and tenascin, however, was low, and the extracellular matrix increase was caused by the accumulation of a normal MC product, collagen IV. The results indicate that severe glomerular sclerosis can develop without major qualitative cellular or molecular changes in the mesangium.

Topics: Actins; Adolescent; Antigens, CD; Antigens, CD34; Antigens, Differentiation, Myelomonocytic; Biopsy; Case-Control Studies; Cell Proliferation; Child; Child, Preschool; Disease Progression; Extracellular Matrix Proteins; Genotype; Glomerular Mesangium; Humans; Hyperplasia; Immunohistochemistry; Infant; Membrane Proteins; Mesangial Cells; Middle Aged; Mutation; Nephrectomy; Nephrotic Syndrome; Osteopontin; Phenotype; Platelet-Derived Growth Factor; Receptors, Platelet-Derived Growth Factor; Sclerosis; Ubiquitin-Protein Ligases

Focal segmental glomerulosclerosis (FSGS) is a progressive renal disease, and the glomerular visceral cell hyperplasia typically observed in cellular/collapsing FSGS is an important pathological factor in disease progression. However, the cellular features that promote FSGS currently remain obscure. To determine both the origin and phenotypic alterations in hyperplastic cells in cellular/collapsing FSGS, the present study used a previously described FSGS model in p21-deficient mice with visceral cell hyperplasia and identified the podocyte lineage by genetic tagging. The p21-deficient mice with nephropathy showed significantly higher urinary protein levels, extracapillary hyperplastic indices on day 5, and glomerular sclerosis indices on day 14 than wild-type controls. X-gal staining and immunohistochemistry for podocyte and parietal epithelial cell (PEC) markers revealed progressive podocytopenia with capillary collapse accompanied by PEC hyperplasia leading to FSGS. In our investigation, non-tagged cells expressed neither WT1 nor nestin. Ki-67, a proliferation marker, was rarely associated with podocytes but was expressed at high levels in PECs. Both terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and electron microscopy failed to show evidence of significant podocyte apoptosis on days 5 and 14. These findings suggest that extensive podocyte loss and simultaneous PEC hyperplasia is an actual pathology that may contribute to the progression of cellular/collapsing FSGS in this mouse model. Additionally, this is the first study to demonstrate the regulatory role of p21 in the PEC cell cycle.

Topics: Animals; Apoptosis; Cell Lineage; Cyclin-Dependent Kinase Inhibitor p21; Disease Models, Animal; Glomerular Filtration Rate; Glomerulosclerosis, Focal Segmental; Hyperplasia; In Situ Nick-End Labeling; Integrases; Ki-67 Antigen; Kidney Glomerulus; Male; Membrane Proteins; Mice; Mice, Knockout; Podocytes; Proteinuria; WT1 Proteins