title: Do the matrix degrading enzymes cathepsins B and D increase following a high intensity exercise regime?
abstract: OBJECTIVE
  It has been shown by others that levels of matrix degrading enzymes are increased in osteoarthritis (OA) and so are proposed to be involved in the aetiopathogenesis of the disease, including exercise-associated OA. Therefore we hypothesised that cathepsin B and cathepsin D were increased in cartilage samples previously shown to have early stage OA from 2-year-old Thoroughbred horses, euthanased for reasons other than this study, that had a history of 19-week high intensity exercise (n=6) compared to age and sex-matched horses with a history of low intensity exercise (n=6).
  
  
  METHODS
  Cartilage samples were used from four specific sites within the carpal joints. Standard immunolocalisation protocols and blind counting of positive and negative cells within the articular surface, mid-zone and deep zone (DZ) were used to test our hypothesis.
  
  
  RESULTS
  A high intensity exercise regime did not significantly alter the number of chondrocytes positive for cathepsin B, whereas a significant decrease was found for cathepsin D in the DZ, indicating that these enzymes are regulated differently by mechanical loading. Furthermore, cathepsin D varied according to the topographical location within the joint, reflecting biomechanical differences experienced during a high compared to a low intensity exercise regime.
  
  
  CONCLUSIONS
  This study disproves our hypothesis that cathepsins B and D are increased following a high intensity exercise regime unlike that reported for other matrix enzymes.
authors.affiliation: Department of Clinical Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.
authors.forename: E A
authors.initials: EA
authors.lastname: Bowe
authors.forename: R C
authors.initials: RC
authors.lastname: Murray
authors.forename: L B
authors.initials: LB
authors.lastname: Jeffcott
authors.forename: M E
authors.initials: ME
authors.lastname: Davies
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000201:enzymology*; D002401:Cathepsin B / Q000032:analysis*; D002402:Cathepsin D / Q000032:analysis*; D019902:Chondrocytes / Q000201:enzymology*; D006736:Horses; D007124:Immunoenzyme Techniques; D010003:Osteoarthritis / Q000201:enzymology*
chemical_list: D002401:Cathepsin B; D002402:Cathepsin D