Mechanical injury potentiates proteoglycan catabolism induced by interleukin‐6 with soluble interleukin‐6 receptor and tumor necrosis factor α in immature bovine and adult human articular cartilage

Abstract

Objective. Traumatic joint injury can damage cartilage and release inflammatory cytokines from adjacent joint tissue. The present study was undertaken to study the combined effects of compression injury, tumor necrosis factor ␣ (TNF␣), and interleukin-6 (IL-6) and its soluble receptor (sIL-6R) on immature bovine and adult human knee and ankle cartilage, using an in vitro model, and to test the hypothesis that endogenous IL-6 plays a role in proteoglycan loss caused by a combination of injury and TNF␣.Methods. Injured or uninjured cartilage disks were incubated with or without TNF␣ and/or IL-6/sIL-6R. Additional samples were preincubated with an IL-6-blocking antibody Fab fragment and subjected to injury and TNF␣ treatment. Treatment effects were assessed by histologic analysis, measurement of glycosaminoglycan (GAG) loss, Western blot to determine proteoglycan degradation, zymography, radiolabeling to determine chondrocyte biosynthesis, and Western blot and enzyme-linked immunosorbent assay to determine chondrocyte production of IL-6.Results. In bovine cartilage samples, injury combined with TNF␣ and IL-6/sIL-6R exposure caused the most severe GAG loss. Findings in human knee and ankle cartilage were strikingly similar to those in bovine samples, although in human ankle tissue, the GAG loss was less severe than that observed in human knee tissue. Without exogenous IL-6/sIL-6R, injury plus TNF␣ exposure up-regulated chondrocyte production of IL-6, but incubation with the IL-6-blocking Fab significantly reduced proteoglycan degradation.Conclusion. Our findings indicate that mechanical injury potentiates the catabolic effects of TNF␣ and IL-6/sIL-6R in causing proteoglycan degradation in human and bovine cartilage. The temporal and spatial evolution of degradation suggests the importance of transport of biomolecules, which may be altered by overload injury. The catabolic effects of injury plus TNF␣ appeared partly due to endogenous IL-6, since GAG loss was partially abrogated by an IL-6-blocking Fab.Osteoarthritis (OA) is a highly prevalent joint disease characterized by progressive degradation and loss of articular cartilage. Joint injury in young adults dramatically increases the risk for developing OA (1,2). Acute knee injury, such as anterior cruciate ligament tear, can subject cartilage to high mechanical stress and is accompanied by an increase in synovial fluid levels of matrix metalloproteinase 3 (MMP-3) (3) and multiple

Single impact trauma in human early-stage osteoarthritic cartilage: Implication of prostaglandin D2 but no additive effect of IL-1β on cell survival

“…The additive IL-6 induction by IL-1β in impacted explants in our study, however, caused no additional cell loss. Sui et al described an amplifying effect of IL-6 in a bovine cartilage injury model concerning proteoglycan catabolism (12). But IL-6 seems not to be responsible for cell death, which was also described for another cartilage injury model (22).…”

“…Interactions of traumagenic and inflammation-derived effects are described. Mechanical injury potentiates the catabolic effects of TNF-α and IL-1α causing an increased degradation of proteoglycans in cartilage (11,12).…”

Novel Cartilage Oligomeric Matrix Protein (COMP) Neoepitopes Identified in Synovial Fluids from Patients with Joint Diseases Using Affinity Chromatography and Mass Spectrometry

“…Disks were maintained in high glucose DMEM supplemented with 10 mM HEPES buffer, 1% insulin-transferrin-selenium (10 g/ml, 5.5 g/ml, and 5 ng/ml, respectively), 0.1 mM nonessential amino acids, 0.4 mM proline, 20 g/ml ascorbic acid, 100 units/ml penicillin G, 100 g/ml streptomycin, 0.25 g/ml amphotericin B in a 37°C, 5% CO 2 incubator prior to treatment. After 2 days of equilibration, groups of cartilage explants were cultured with an added cytokine mixture consisting of 100 ng/ml TNF-␣, 50 ng/ml IL-6, and 250 ng/ml sIL-6R as described previously (31). Control explants were maintained in culture medium as above with no cytokines added.…”

Development of a Cartilage Shear-Damage Model to Investigate the Impact of Surface Injury on Chondrocytes and Extracellular Matrix Wear

“…5 For acute events, most cartilage injury models apply a single supraphysiologic impact to create the initial insult. 8,9 For chronic stress, few in vitro models exist, usually through high loading cycles of dynamic compression. [10][11][12] Modeling shear damage to the surface, which could be classified as a form of chronic stress, has not been well evaluated in cartilage explant studies.…”