To determine whether the previously observed enhanced susceptibility of osteoarthritic (OA) cartilage to tumor necrosis factor-alpha (TNF-alpha) induced degradation could be due to differences in receptor expression.
Using specific monoclonal antibodies flow cytometry was used to identify and quantify 2 TNF-alpha receptors on the surface of chondrocytes isolated from human articular cartilage.
The proportion of chondrocytes expressing p55 TNF-alpha receptor was significantly higher in populations from OA cartilage (p < 0.01) when compared with similar populations from non-arthritic cartilage. The number of p55 receptors/chondrocyte was also significantly higher (p < 0.01) in OA. A significant correlation (r = 0.72, p < 0.18) was found in OA between the numbers of chondrocytes expressing p75 receptor and the number of receptors/chondrocyte.
p55 TNF-alpha receptor expression is significantly increased on OA chondrocytes ex vivo. Enhanced expression of p55, purported to be the biologically active receptor, could contribute to OA cartilage degradation.