title: Tissue transglutaminase: a mediator and predictor of chronic allograft nephropathy?
abstract: BACKGROUND
  The precise mechanisms underlying the development of chronic allograft nephropathy (CAN) and the associated renal fibrosis remain uncertain. The protein-crosslinking enzyme, tissue transglutaminase (tTg), has recently been implicated in renal fibrosis. METHODS.: We investigated the involvement of tTg and its crosslink product, epsilon-(gamma-glutamyl) lysine, in 23 human kidney allografts during the early posttransplantation period and related these to changes of CAN that developed in 8 of them. Sequential biopsies were investigated using immunohistochemical, immunofluorescence, and in situ enzyme activity techniques.
  
  
  RESULTS
  From implantation, tTg (+266%) and epsilon-(gamma-glutamyl) lysine crosslink (+256.3%) staining increased significantly (P <0.001) in a first renal biopsy performed within 3 months from transplantation. This was paralleled by elevated tTg in situ activity. The eight patients who developed CAN had further increases in immunostainable tTg (+197.2%, P <0.001) and epsilon-(gamma-glutamyl) lysine bonds (+465%, P <0.01) that correlated with interstitial fibrosis (r=0.843, P =0.009 and r=0.622, P =0.05, respectively). The staining for both was predominantly located within the mesangium and the renal interstitium. Both implantation and first biopsies showed tTg and epsilon-(gamma-glutamyl) lysine crosslinking levels in patients who developed CAN to be twice the levels of those with stable renal function. Cox regression analysis suggested the intensity of the early tTg staining was a better predictor of inferior allograft survival that other histologic markers (hazard ratio=4.48, P =0.04).
  
  
  CONCLUSIONS
  tTg and epsilon-(gamma-glutamyl) lysine crosslink correlated with the initiation and progression of scarring on sequential biopsies from renal-allograft recipients who experienced CAN. Elevated tTg may offer an early predictor of the development of CAN, whereas tTg manipulation may be an attractive therapeutic target.
authors.affiliation: Sheffield Kidney Institute, Sheffield, UK. t.johnson@sheffield.ac.uk
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Johnson
authors.forename: Hamdy
authors.initials: H
authors.lastname: Abo-Zenah
authors.forename: James N
authors.initials: JN
authors.lastname: Skill
authors.forename: Samantha
authors.initials: S
authors.lastname: Bex
authors.forename: Graham
authors.initials: G
authors.lastname: Wild
authors.forename: Colin B
authors.initials: CB
authors.lastname: Brown
authors.forename: Martin
authors.initials: M
authors.lastname: Griffin
authors.forename: A Meguid
authors.initials: AM
authors.lastname: El Nahas
mesh_terms: D000328:Adult; D002908:Chronic Disease; D004151:Dipeptides / Q000378:metabolism; D045604:Extracellular Fluid / Q000378:metabolism; D005260:Female; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007158:Immunologic Techniques; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D007674:Kidney Diseases / Q000209:etiology*; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011379:Prognosis; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012995:Solubility; D013194:Staining and Labeling; D014018:Tissue Distribution; D011503:Transglutaminases / Q000737:chemistry / Q000378:metabolism*; D014184:Transplantation, Homologous; D016896:Treatment Outcome
chemical_list: D004151:Dipeptides; C001299:epsilon-(gamma-glutamyl)-lysine; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins