Increased stromelysin-1 (MMP-3), proteoglycan degradation (3B3- and 7D4) and collagen damage in cyclically load-injured articular cartilage.
OBJECTIVE
To determine whether load-induced injury causes alterations in proteoglycan (PG), stromelysin-1 (MMP-3) and collagen in articular cartilage.


METHODS
Mature bovine cartilage was cyclically loaded at 0.5 Hz with 1 and 5 MPa for 1, 6 and 24h. Immediately after loading explants were evaluated for cell viability. Alterations in matrix integrity were determined by measuring PG content, PG degradation using 7D4 and 3B3(-) antibodies, broken collagen using COL2-3/4m antibody, and stromelysin-1 content using a MMP-3 antibody.


RESULTS
Mechanical load caused cell death and PG loss starting from the articular surface and increasing in depth with loading time. There was a decrease in the 7D4 epitope (native chondroitin sulfate) in the superficial zone of cartilage loaded for longer than 1h, but an increase around chondrocytes in the deep zone. The 3B3(-) staining for degraded/abnormal chondroitin-4-sulfate neoepitope appeared only in cartilage loaded under the most severe condition (5 MPa, 24 h). The elevation of stromelysin-1 was co-localized with broken collagen (COL2-3/4m) at the articular surface in explants loaded with 1 and 5 MPa for 24 h.


CONCLUSIONS
Cell death and PG loss occurred within 6h of cyclic loading. The elevation of MMP-3 following cell death was consistently found in the superficial zone of loaded cartilage. Since MMP-3 can degrade PG and super-activate procollagenase, the increase of MMP-3 can therefore induce matrix degradation and PG depletion in mechanically injured articular cartilage, both of which are important to the development of osteoarthritis.
Lin
Peggy M
PM
Laboratory for Soft Tissue Research, Hospital for Special Surgery, New York 10021, USA.
Chen
Chih-Tung Christopher
CT
Torzilli
Peter A
PA
D000818:Animals; D002358:Cartilage, Articular / Q000293:injuries* / Q000378:metabolism* / Q000473:pathology; D002417:Cattle; D016923:Cell Death; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology; D002809:Chondroitin Sulfates / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism; D013314:Stress, Mechanical
D011509:Proteoglycans; D002809:Chondroitin Sulfates; D003094:Collagen; D019278:Matrix Metalloproteinase 3