title: Albumin-induced epithelial mesenchymal transformation.
abstract: BACKGROUND
  Progressive chronic kidney disease is often associated with albuminuria and renal fibrosis linked to the accumulation of myofibroblasts producing extracellular matrix. Renal myofibroblasts are derived from a number of cells including tubular epithelial cells (TECs) through epithelial mesenchymal transformation (EMT). This study explores the hypothesis that exposure of TECs to albumin induces EMT.
  
  
  METHODS
  Normal rat TECs (NRK52E) were exposed in culture to de-lipidated bovine serum albumin (dBSA; 10 mg/ml) for 2, 4 and 6 days. Binding/uptake of fluoresceined albumin by PTCs was evaluated. Transformation into myofibroblasts was assessed by light and electron microscopy, immunofluorescence and Western blotting for α-smooth muscle actin (α-SMA), E-cadherin and transforming growth factor-β1 (TGF-β1). We also investigated the expression of fibroblast-specific protein-1 (FSP-1) and collagens I, III and IV. TGF-β1 biological activity, mRNA and protein were measured. A neutralising anti-TGF-β1 antibody was used to analyse the role of TGF-β1 in albumin-induced EMT.
  
  
  RESULTS
  Exposure of TECs to dBSA led to binding/uptake of albumin as well as fibroblastic morphological changes. Incubation of TECs with dBSA caused a reduction of TEC marker E-cadherin (ANOVA p = 0.0002) and de novo expression of fibroblast markers α-SMA and FSP-1 (ANOVA p = 0.0001) in a time-dependent manner. It also increased expression and activity of TGF-β1. Neutralisation of TGF-β1 significantly reduced EMT (p < 0.01).
  
  
  CONCLUSIONS
  This study demonstrates that in vitro, albumin induces the transformation of TECs into cells with myofibroblast characteristics; a process that may be TGF-β1 dependent.
authors.affiliation: Sheffield Kidney Institute and Academic Nephrology Unit, University of Sheffield, Sheffield, UK.
authors.forename: J
authors.initials: J
authors.lastname: Ibrini
authors.forename: S
authors.initials: S
authors.lastname: Fadel
authors.forename: R S
authors.initials: RS
authors.lastname: Chana
authors.forename: N
authors.initials: N
authors.lastname: Brunskill
authors.forename: B
authors.initials: B
authors.lastname: Wagner
authors.forename: T S
authors.initials: TS
authors.lastname: Johnson
authors.forename: A M
authors.initials: AM
authors.lastname: El Nahas
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D057134:Antibodies, Neutralizing / Q000494:pharmacology; D015152:Blotting, Northern; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D003094:Collagen / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism; D008055:Lipids / Q000737:chemistry; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009130:Muscle, Smooth / Q000737:chemistry; D058628:Myofibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D000199:Actins; D057134:Antibodies, Neutralizing; D015820:Cadherins; D008055:Lipids; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; C499412:S100a4 protein, rat; D053773:Transforming Growth Factor beta1; D012710:Serum Albumin, Bovine; D003094:Collagen