title: Chondrocyte hypertrophy and osteoarthritis: role in initiation and progression of cartilage degeneration?
abstract: OBJECTIVE
  To review the literature on the role and regulation of chondrocyte terminal differentiation (hypertrophy-like changes) in osteoarthritis (OA) and to integrate this in a conceptual model of primary OA development.
  
  
  METHODS
  Papers investigating chondrocyte terminal differentiation in human OA cartilage and experimental models of OA were recapitulated and discussed. Focus has been on the occurrence of hypertrophy-like changes in chondrocytes and the factors described to play a role in regulation of chondrocyte hypertrophy-like changes in OA.
  
  
  RESULTS
  Chondrocyte hypertrophy-like changes are reported in both human OA and experimental OA models by most investigators. These changes play a crucial part in the OA disease process by protease-mediated cartilage degradation. We propose that altered chondrocyte behavior and concomitant cartilage degradation result in a disease-amplifying loop, leading to a mixture of disease stages and cellular responses within an OA joint.
  
  
  CONCLUSIONS
  Chondrocyte hypertrophy-like changes play a role in early and late stage OA. Since not all cells in an OA joint are synchronized, inhibition of hypertrophy-like changes might be a therapeutic target to slow down further OA progression.
authors.affiliation: Department of Rheumatology, Radboud University, Medical Centre, Geert Grooteplein 28, 6525 Nijmegen, The Netherlands. P.vanderkraan@reuma.umcn.nl
authors.forename: P M
authors.initials: PM
authors.lastname: van der Kraan
authors.forename: W B
authors.initials: WB
authors.lastname: van den Berg
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D002114:Calcinosis / Q000150:complications; D002357:Cartilage Diseases / Q000150:complications; D002358:Cartilage, Articular / Q000473:pathology*; D002454:Cell Differentiation; D019902:Chondrocytes / Q000473:pathology*; D018450:Disease Progression; D006801:Humans; D006984:Hypertrophy / Q000150:complications; D010003:Osteoarthritis / Q000209:etiology*
chemical_list: D015415:Biomarkers