title: Obstructive uropathy in the mouse: role of osteopontin in interstitial fibrosis and apoptosis.
abstract: BACKGROUND
  Osteopontin is a macrophage adhesive protein that is expressed by renal tubules in tubulointerstitial disease.
  
  
  METHODS
  To investigate the function of OPN, we induced tubulointerstitial disease in OPN null mutant (OPN-/-) and wild-type (OPN+/+) mice by unilateral ureteral ligation. Tissue was analyzed for macrophages (ED-1), types I and IV collagen deposition, TGF-beta expression, and for tubular and interstitial cell apoptosis.
  
  
  RESULTS
  Obstructed kidneys from both OPN-/- and OPN+/+ mice developed hydronephrosis, tubular atrophy, interstitial inflammation and fibrosis. OPN was absent in OPN-/- kidneys but was increased in obstructed OPN+/+ kidneys. Macrophage influx, measured by computer-assisted quantitative immunostaining, was less in OPN-/- mice compared to OPN+/+ mice at day 4 (threefold, P < 0.02), day 7 (fivefold, P < 0.02), but not at day 14. Interstitial deposition of types I and IV collagen were also two- to fourfold less in obstructed OPN-/- kidneys (P < 0.02). There was also a reduction of TGF-beta mRNA expression in the interstitium at day 7 (by in situ hybridization) and a near significant 34% reduction in cortical TGF-beta activity (P = 0.06) compared to obstructed OPN+/+ kidneys at day 14. Obstructed kidneys from OPN-/- mice also had more interstitial and tubular apoptotic cells (TUNEL assay) compared to obstructed OPN+/+ mice at all time points. The ability of OPN to act as a cell survival factor was also documented by showing that the apoptosis of serum-starved NRK52E renal epithelial cells was markedly enhanced in the presence of neutralizing anti-OPN antibody.
  
  
  CONCLUSIONS
  OPN mediates early interstitial macrophage influx and interstitial fibrosis in unilateral ureteral obstruction. OPN may also function as a survival factor for renal tubulointerstitial cells.
authors.affiliation: Division of Nephrology, Department of Medicine, University of Washington, Seattle 98195, USA.
authors.forename: V
authors.initials: V
authors.lastname: Ophascharoensuk
authors.forename: C M
authors.initials: CM
authors.lastname: Giachelli
authors.forename: K
authors.initials: K
authors.lastname: Gordon
authors.forename: J
authors.initials: J
authors.lastname: Hughes
authors.forename: R
authors.initials: R
authors.lastname: Pichler
authors.forename: P
authors.initials: P
authors.lastname: Brown
authors.forename: L
authors.initials: L
authors.lastname: Liaw
authors.forename: R
authors.initials: R
authors.lastname: Schmidt
authors.forename: S J
authors.initials: SJ
authors.lastname: Shankland
authors.forename: C E
authors.initials: CE
authors.lastname: Alpers
authors.forename: W G
authors.initials: WG
authors.lastname: Couser
authors.forename: R J
authors.initials: RJ
authors.lastname: Johnson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D002470:Cell Survival / Q000502:physiology; D003094:Collagen / Q000032:analysis / Q000378:metabolism; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D005260:Female; D005355:Fibrosis; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D007684:Kidney Tubules / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D008264:Macrophages / Q000276:immunology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D053495:Osteopontin; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D012795:Sialoglycoproteins / Q000235:genetics* / Q000276:immunology; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D014517:Ureteral Obstruction / Q000235:genetics* / Q000276:immunology / Q000473:pathology*
chemical_list: D012333:RNA, Messenger; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D016212:Transforming Growth Factor beta; D053495:Osteopontin; D003094:Collagen