Abstract
OBJECTIVE: Imbalance of inflammatory and antiinflammatory cytokines plays a critical role in the pathogenesis of rheumatoid arthritis (RA). Precise determination of these cytokines would lead to better understanding of the progression of RA. METHODS: We developed an in vivo microdialysis technique to directly monitor cytokine profiles in knee joints of rats with adjuvant-induced arthritis (AIA). Microdialysates drained from knee joints of rats with AIA and controls were collected and cytokine concentrations were measured by ELISA. Pathological changes of the knee joints and the source of monocyte chemoattractant factor-1 (MCP-1) secretion were also determined by histology and immunohistochemistry. RESULTS: MCP-1 expression in knee joints was significantly higher in AIA rats with erosive changes in their ankles than in normal rats, while interleukin 6 (IL-6) levels were similar in both cases. IL-1beta and interferon-gamma were not detectable in the microdialysates. Increased synovial proliferation and mononuclear inflammatory infiltrates were observed. Synovial cells and mononuclear inflammatory cells expressed both MCP-1 and its receptor, CCR2. CONCLUSION: Our results indicate that the in vivo microdialysis technique is capable of detecting cytokines in the knee joints of rats. Increased expression of MCP-1 and CCR2 in knee joints of AIA rats suggests a role for this cytokine in triggering the mechanisms involved in the pathogenesis of knee joint after ankle erosion.
