title: Short-term exposure of cartilage to blood results in chondrocyte apoptosis.
abstract: Studies have shown that joint bleeding leads to cartilage degradation independent of concurrent synovitis. We hypothesized that the blood-induced cartilage damage is because of increased chondrocyte apoptosis after short-term exposure of whole blood or isolated mononuclear cells plus red blood cells to cartilage. Human cartilage tissue samples were co-cultured for 4 days with whole blood (50% v/v) or with mononuclear cells plus red blood cells (50% v/v equivalents). Cartilage matrix proteoglycan synthesis ((35)SO(4)(2-) incorporation) was determined after 4 days as well as at day 16 (after a 12-day recovery period in the absence of any additions). To test the involvement of apoptosis a specific caspase-3 inhibitor (acDEVDcho, 0 to 500 micro mol/L) as well as a pan-caspase inhibitor (zVADfmk, 0 to 500 micro mol/L) were added. Chondrocyte apoptosis was evaluated by immunohistochemical staining of single-strand DNA and by terminal dUTP nick-end labeling. Cartilage co-cultured with whole blood as well as mononuclear cells plus red blood cells induced a long-term inhibition of proteoglycan synthesis (74% and 78% inhibition on day 16, respectively). Immunohistochemistry showed a threefold increase in apoptotic chondrocytes in cultures with 50% whole blood as well as with mononuclear cells plus red blood cells. Both the specific caspase-3 inhibitor and the pan-caspase inhibitor partially restored proteoglycan synthesis in the cartilage after blood exposure. This effect was accompanied by a decrease in the number of apoptotic chondrocytes. These data suggest that a single joint hemorrhage (a 4-day exposure of cartilage to 50% v/v blood) results in induction of chondrocyte apoptosis, responsible for the observed inability of the chondrocytes to restore the proteoglycan synthesis during recovery from a short-term exposure to blood. This reduced restoration could eventually lead to cartilage degeneration and ultimately joint destruction.
authors.affiliation: Department of Rheumatology and Clinical Immunology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Michel
authors.initials: M
authors.lastname: Hooiveld
authors.forename: Goris
authors.initials: G
authors.lastname: Roosendaal
authors.forename: Marion
authors.initials: M
authors.lastname: Wenting
authors.forename: Marijke
authors.initials: M
authors.lastname: van den Berg
authors.forename: Johannes
authors.initials: J
authors.lastname: Bijlsma
authors.forename: Floris
authors.initials: F
authors.lastname: Lafeber
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001344:Autopsy; D001790:Blood Physiological Phenomena / Q000187:drug effects; D002358:Cartilage, Articular / Q000166:cytology* / Q000473:pathology / Q000502:physiology; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D018920:Coculture Techniques; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D006811:Humerus; D007375:Interleukin-1 / Q000494:pharmacology; D007700:Kinetics; D011509:Proteoglycans / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D015853:Cysteine Proteinase Inhibitors; D007375:Interleukin-1; D011509:Proteoglycans; D013431:Sulfates; D013462:Sulfur Radioisotopes; D014409:Tumor Necrosis Factor-alpha