title: Variations in chondrocyte apoptosis may explain the increased prevalence of osteoarthritis in some joints.
abstract: OBJECTIVE
  To investigate whether there are any variations in chondrocyte susceptibility to an apoptotic stimulus between cells of articular cartilage (AC) from equine joints that differ in prevalence of osteoarthritis (OA).
  
  
  METHODS
  Cartilage from macroscopically normal equine metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints was used. Prior to culture, chondrocyte viability was assessed using the fluorescein diacetate (FDA) and propidium iodide paravital staining method. AC explants were subsequently treated with tumour necrosis factor-α (TNF-α) in combination with Actinomycin D to induce apoptosis. Apoptosis of chondrocytes in cartilage sections was assessed by expression of active caspase-3 using indirect immunohistochemistry and sections also histologically graded using a 'modified' Mankin scoring system.
  
  
  RESULTS
  Prior to culture (mean ± standard deviation) chondrocyte viability was 80.7% (3.5). The extent of chondrocyte apoptosis induced by TNF-α/Actinomycin D varied markedly according to the joint type that the cartilage was sampled from. For MCP joints, the extent of overall chondrocyte apoptosis was significantly higher (P < 0.001) in stimulated explants (26.7%, 10.3) than that observed in unstimulated control samples (9.6%, 7.5). Conversely, chondrocytes from PIP and DIP joint cartilage did not respond significantly to apoptotic stimulation (P > 0.05). Significant variations in cellularity and thickness were also evident between cartilages of different joint types.
  
  
  CONCLUSIONS
  Data in this study demonstrate that chondrocytes from three equine joint types with varying prevalences of OA differ significantly in terms of susceptibility to apoptosis induction. This may provide a possible explanation for the joint-specific nature of the disease.
authors.affiliation: Department of Anatomy, University of Bristol, Southwell Street, Bristol, BS2 8EJ, UK.
authors.forename: C M
authors.initials: CM
authors.lastname: Thomas
authors.forename: C E
authors.initials: CE
authors.lastname: Whittles
authors.forename: C J
authors.initials: CJ
authors.lastname: Fuller
authors.forename: M
authors.initials: M
authors.lastname: Sharif
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002358:Cartilage, Articular / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000473:pathology*; D004195:Disease Models, Animal; D005260:Female; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses; D008297:Male; D008662:Metacarpophalangeal Joint / Q000473:pathology; D009928:Organ Specificity; D010003:Osteoarthritis / Q000453:epidemiology* / Q000473:pathology*; D015995:Prevalence; D014033:Toe Joint / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology
chemical_list: D014409:Tumor Necrosis Factor-alpha
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