title: Ochronosis in a murine model of alkaptonuria is synonymous to that in the human condition.
abstract: OBJECTIVE
  Alkaptonuria (AKU) is a rare genetic disease which results in severe early onset osteoarthropathy. It has recently been shown that the subchondral interface is of key significance in disease pathogenesis. Human surgical tissues are often beyond this initial stage and there is no published murine model of pathogenesis, to study the natural history of the disease. The murine genotype exists but it has been reported not to demonstrate ochronotic osteoarthropathy consistent with the human disease. Recent anecdotal evidence of macroscopic renal ochronosis in a mouse model of tyrosinaemia led us to perform histological analysis of tissues of these mice that are known to be affected in human AKU.
  
  
  METHODS
  The homogentisate 1,2-dioxygenase Hgd(+/)(-)Fah(-)(/)(-) mouse can model either hereditary tyrosinaemia type I (HT1) or AKU depending on selection conditions. Mice having undergone Hgd reversion were sacrificed at various time points, and their tissues taken for histological analysis. Sections were stained with haematoxylin eosin (H&E) and Schmorl's reagent.
  
  
  RESULTS
  Early time point observations at 8 months showed no sign of macroscopic ochronosis of tissues. Macroscopic examination at 13 months revealed ochronosis of the kidneys. Microscopic analysis of the kidneys revealed large pigmented nodules displaying distinct ochre colouration. Close microscopic examination of the distal femur and proximal fibula at the subchondral junctions revealed the presence of numerous pigmented chondrocytes.
  
  
  CONCLUSIONS
  Here we present the first data showing ochronosis of tissues in a murine model of AKU. These preliminary histological observations provide a stimulus for further studies into the natural history of the disease to provide a greater understanding of this class of arthropathy.
authors.affiliation: Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, UK. a.m.taylor@lancs.ac.uk
authors.forename: A M
authors.initials: AM
authors.lastname: Taylor
authors.forename: A J
authors.initials: AJ
authors.lastname: Preston
authors.forename: N K
authors.initials: NK
authors.lastname: Paulk
authors.forename: H
authors.initials: H
authors.lastname: Sutherland
authors.forename: C M
authors.initials: CM
authors.lastname: Keenan
authors.forename: P J M
authors.initials: PJ
authors.lastname: Wilson
authors.forename: B
authors.initials: B
authors.lastname: Wlodarski
authors.forename: M
authors.initials: M
authors.lastname: Grompe
authors.forename: L R
authors.initials: LR
authors.lastname: Ranganath
authors.forename: J A
authors.initials: JA
authors.lastname: Gallagher
authors.forename: J C
authors.initials: JC
authors.lastname: Jarvis
mesh_terms: D000474:Alkaptonuria / Q000150:complications*; D000818:Animals; D019902:Chondrocytes / Q000473:pathology*; D004195:Disease Models, Animal; D018450:Disease Progression; D005260:Female; D006614:Hindlimb / Q000473:pathology; D050560:Homogentisate 1,2-Dioxygenase / Q000235:genetics; D007592:Joint Diseases / Q000473:pathology*; D007674:Kidney Diseases / Q000473:pathology*; D008297:Male; D051379:Mice; D009794:Ochronosis / Q000150:complications / Q000473:pathology*
chemical_list: D050560:Homogentisate 1,2-Dioxygenase