Proteoglycan degradation after injurious compression of bovine and human articular cartilage in vitro: interaction with exogenous cytokines.
OBJECTIVE
Traumatic joint injury leads to an increased risk of osteoarthritis (OA), but the progression to OA is not well understood. We undertook this study to measure aspects of proteoglycan (PG) degradation after in vitro injurious mechanical compression, including up-regulation of enzymatic degradative expression and cytokine-stimulated degradation.


METHODS
Articular cartilage tissue explants were obtained from newborn bovine femoropatellar groove and from adult normal human donor knee and ankle tissue. Following injurious compression of the cartilage, matrix metalloproteinase 3 (MMP-3) and MMP-13 messenger RNA (mRNA) expression levels were measured by Northern analysis, and PG loss to the medium after cartilage injury was measured in the presence and absence of added exogenous cytokine (interleukin-1alpha [IL-1alpha] or tumor necrosis factor alpha [TNFalpha]).


RESULTS
During the first 24 hours after injury in bovine cartilage, MMP-3 mRNA levels increased 10-fold over the levels in control cartilage (n = 3 experiments), whereas MMP-13 mRNA levels were unchanged. PG loss was significantly increased after injury, but only by 2% of the total PG content and only for the first 3 days following injury. However, compared with injury alone or cytokine treatment alone, treatment of injured tissue with either 1 ng/ml IL-1alpha or 100 ng/ml TNFalpha caused marked increases in PG loss (35% and 54%, respectively, of the total cartilage PG content). These interactions between cytokine treatment and injury were statistically significant. In human knee cartilage, the interaction was also significant for both IL-1alpha and TNFalpha, although the magnitude of increase in PG loss was lower than that in bovine cartilage. In contrast, in human ankle cartilage, there was no significant interaction between injury and IL-1alpha.


CONCLUSIONS
The cytokines IL-1alpha and TNFalpha can cause a synergistic loss of PG from mechanically injured bovine and human cartilage. By attempting to incorporate interactions with other joint tissues that may be sources of cytokines, in vitro models of mechanical cartilage injury may explain aspects of the interactions between mechanical forces and degradative pathways which lead to OA progression.
Patwari
Parth
P
Center for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. pkp@mit.edu
Cook
Michael N
MN
DiMicco
Michael A
MA
Blake
Simon M
SM
James
Ian E
IE
Kumar
Sanjay
S
Cole
Ada A
AA
Lark
Michael W
MW
Grodzinsky
Alan J
AJ
D000328:Adult; D000818:Animals; D000831:Animals, Newborn; D000843:Ankle Joint; D002358:Cartilage, Articular / Q000187:drug effects / Q000293:injuries / Q000378:metabolism*; D002417:Cattle; D017364:Collagenases / Q000235:genetics / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000737:chemistry; D003513:Cycloheximide / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology*; D007719:Knee Joint; D053509:Matrix Metalloproteinase 13; D019278:Matrix Metalloproteinase 3 / Q000235:genetics / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011509:Proteoglycans / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013314:Stress, Mechanical; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D015854:Up-Regulation
D017077:Culture Media, Conditioned; D007375:Interleukin-1; D011500:Protein Synthesis Inhibitors; D011509:Proteoglycans; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide; D017364:Collagenases; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; D019278:Matrix Metalloproteinase 3