Objective: To examine expression of CD40 on articular chondrocytes derived from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) and to investigate roles of CD40 on articular chondrocytes in production of inflammatory mediators associated with degradation of articular cartilage.
Methods: Articular cartilage samples were obtained from patients with RA and OA at total knee arthroplasty. Expression of CD40 on chondrocytes was examined using immunohistochemistry, reverse transcriptase-polymerase chain reaction (RT-PCR), and flow cytometry. Tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6), matrix metalloproteinase (MMP)-3, and tissue inhibitor of matrix metalloproteinase (TIMP)-1 in culture supernatants of chondrocytes were measured by ELISA.
Results: Immunohistochemical staining revealed that CD40 was expressed on RA chondrocytes in vivo, but not in OA chondrocytes. RT-PCR and flow cytometry showed that cultured articular chondrocytes from RA patients, but not from OA patients, constitutively expressed CD40, and that interferon-gamma (IFN-gamma) enhanced the expression of CD40 on chondrocytes from both RA and OA patients. Membrane fraction of mouse myeloma Ag8 cells that was transfected with human CD154 (Ag8-hCD154) induced production of TNF-alpha, IL-6, and MMP-3 in RA chondrocytes, and pretreatment of RA chondrocytes with IFN-gamma enhanced the response. OA chondrocytes did not respond to stimulation with the membrane fraction of Ag8-hCD154 cells alone, but the cells did produce TNF-alpha, IL-6, and MMP-3 after pretreatment with IFN-gamma.
Conclusion: CD40-CD154 interaction augments the expression of inflammatory cytokines and MMP in chondrocytes and contributes to an intrinsic process of cartilage degradation in RA.