Osteoarthritic Synovial Fluid And Tgf-Beta 1 Induce Interleukin-18 In Articular Chondrocytes

Objective Synovial fluid (SF) plays an important role in the maintenance of articular cartilage. SF is a dynamic reservoir of proteins derived from cartilage and synovial tissue; thus, its composition may serve as a biomarker that reflects the health and pathophysiological condition of the joint. The purpose of the current study was to evaluate the osteoarthritic synovial fluid (OASF) and transforming growth factor-beta 1 (TGF-beta 1) activity in articular chondrocytes catabolic and inflammatory responses. Design Chondrocytes were seeded at passage 2 and cultured for 72 hours under different conditions. Human chondrocytes were subjected to OASF while rat chondrocytes were subjected to either healthy synovial fluid (rSF) or TGF-beta 1 and then assigned for cell viability analysis. In addition, the effects of OASF and TGF-beta 1 on chondrocytes metalloprotease (MMP)-3 and MMP-13 and interleukin-18 (IL-18) expression were evaluated by immunocytochemistry, ELISA, and reverse transcriptase-polymerase chain reaction. Results SF from osteoarthritic patients significantly induced MMP-3, MMP-13, and IL-18 receptor expression in chondrocytes. To put in evidence the inflammatory activity of OASF, healthy chondrocytes from rat were cultured with TGF-beta 1. In the presence of TGF-beta 1 these cells started to expressMMP-3, MMP-13, andIL-18genes and attached to each other forming a chondrocyte aggregated structure. Healthy SF was able to maintain a typical monolayer of rounded chondrocytes with no inflammatory response. Conclusion In summary, these observations demonstrated that TGF-beta 1, one of the components of OASF, has a dual effect, acting in chondrocyte maintenance and also inducing inflammatory and catabolic properties of these cells.