YKL-40 and cytokines - a New Diagnostic Constellation in Rheumatoid Arthritis?

Background: Rheumatoid arthritis (RA) causes chronic inflammation and alteration of articular tissue and joints. The pathogenesis of the disease remains unclear although it is known that proinflammatory cytokines play a major role in its induction. YKL-40 is a chitinase-like glycoprotein produced by activated macrophages, neutrophils, arthritic chondrocytes and cancer cells. It has been shown that YKL-40 is implicated in tissue remodeling, angiogenesis and inflammation.

Aim: to investigate serum and synovial YKL-40 levels in relation to IL-1β, TNF-α, and IL-6 in RA patients.

Materials And Methods: Serum and synovial concentrations of YKL-40, TNF-α, IL- 6, and IL-1β were determined by ELISA in 39 patients (mean age 53.18 ± 16.54 yrs) with active RA.

Results: Serum YKL-40 levels were increased in all patients. The highest levels were found in synovial fluid (P<0.01). Our study showed a strong association between serum and synovial levels of YKL-40 and serum TNF-α and IL-1 β (P<0.05).

Conclusion: This is the first study finding a significant correlation between serum TNF-α and IL-1β and YKL-40 in active RA. We suggest that these molecules together might play a dominant role in the pathogenesis and disease activity and could possibly serve as a new diagnostic constellation in rheumatoid arthritis.