title: Blood-induced joint damage: a human in vitro study.
abstract: OBJECTIVE
  To investigate mechanisms underlying cartilage damage caused by brief exposure of cartilage to blood, such as that occurring during intraarticular bleeding.
  
  
  METHODS
  Human articular cartilage was cultured for 4 days in the presence of blood (components; 7.5-50% volume/volume). The synthesis of cartilage matrix, as determined by proteoglycan synthesis (incorporation of 35SO4(2-)), was measured directly after exposure and after a recovery period of 20 days, during which the cartilage was cultured in the absence of blood or blood components. The production of the cytokines interleukin-1 (IL-1) and tumor necrosis factor a (TNFalpha), which have a destructive effect on cartilage, was determined by enzyme-linked immunosorbent assay, and the viability of chondrocytes was determined by measuring lactate dehydrogenase release and with electron microscopy. The involvement of oxygen metabolites was evaluated by using N-acetylcysteine.
  
  
  RESULTS
  Brief exposure to blood resulted in dose-dependent inhibition of proteoglycan synthesis. The combination of mononuclear cells and red blood cells was responsible for this effect. The effect was irreversible, independent of IL-1 and TNFalpha production, and was accompanied by chondrocyte death. These effects were partially prevented by N-acetylcysteine.
  
  
  CONCLUSIONS
  Brief exposure of cartilage to blood, as occurs after a single episode or a limited number of bleeding episodes, results in lasting cartilage damage in vitro, in which cytotoxic oxygen metabolites play a role.
mesh_terms: D000368:Aged; D001769:Blood; D002358:Cartilage, Articular / Q000166:cytology / Q000473:pathology; D016923:Cell Death / Q000502:physiology; D016207:Cytokines / Q000502:physiology; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D006395:Hemarthrosis / Q000150:complications / Q000473:pathology; D006801:Humans; D007592:Joint Diseases / Q000209:etiology / Q000473:pathology; D007596:Joints / Q000473:pathology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism / Q000633:toxicity; D011509:Proteoglycans / Q000096:biosynthesis