title: Matrix metalloproteinases and inhibitor in knee synovial fluid as cartilage biomarkers in rabbits: the effect of high-intensity jumping exercise.
abstract: OBJECTIVE
  To study the cartilage injury of knee joint in a rabbit model under high-intensity jumping training and to investigate if levels of matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-3 (MMP-3), and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in synovial fluid (SF) can be used to predict early sports injury of articular cartilage effectively.
  
  
  METHODS
  Forty New Zealand white rabbits were divided into two groups randomly: untreated control group (CTRL, n = 8) and jumping training group (TG, n = 32). Concentrations of MMP-1, MMP-3, and TIMP-1 in SF were measured by ELISA assays at 4 and 8 weeks, respectively. Rabbits were euthanized at 4 and 8 weeks, and knee joints were taken out to be examined histologically. Sulfated glycosaminoglycan (GAG) content, thickness of cartilage and subchondral bone, dead cell ratio, and Mankin grades were measured.
  
  
  RESULTS
  At 4 weeks, sulfated GAG content, thickness of subchondral bone, and Mankin grades in TG were significantly higher than control. After 8 weeks, the TG cohort had a further increase in the articular cartilage injury. SF levels of MMP-3, TIMP-1, and MMP-3/TIMP-1 in TG were significantly higher than control, and the level of these biomarkers was significantly associated with the severity of the articular cartilage pathology.
  
  
  CONCLUSIONS
  Repetitive and high-intensity jumping movement may induce sports injury in the knee joint cartilage. MMP-1, MMP-3, TIMP-1, and MMP-3/TIMP-1 in the SF may accurately predict the severity and pathological characteristic of the joint cartilage injury.
authors.affiliation: Military Training Medicine Institute in the 150th Hospital of PLA, Luoyang, Henan Province, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Qi
authors.forename: Huang
authors.initials: H
authors.lastname: Changlin
authors.forename: Huang
authors.initials: H
authors.lastname: Zefeng
mesh_terms: D000818:Animals; D015415:Biomarkers; D002358:Cartilage, Articular / Q000201:enzymology / Q000293:injuries; D007718:Knee Injuries / Q000378:metabolism* / Q000473:pathology; D007719:Knee Joint / Q000201:enzymology / Q000473:pathology; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism*; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism*; D009043:Motor Activity / Q000502:physiology; D011817:Rabbits; D013582:Synovial Fluid / Q000201:enzymology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D019715:Tissue Inhibitor of Metalloproteinase-1; D019278:Matrix Metalloproteinase 3; D020781:Matrix Metalloproteinase 1