Osteoarthritis synovial fluid activates pro-inflammatory cytokines in primary human chondrocytes

Two of the most common joint diseases are rheumatoid arthritis (RA) and osteoarthritis (OA). Cartilage degradation and erosions are important pathogenetic mechanisms in both joint diseases and have presently gained increasing interest. The aim of the present study was to investigate the effects of the synovial fluid environment of OA patients in comparison with synovial fluids of RA patients on human chondrocytes in vitro.

Primary human chondrocytes were incubated in synovial fluids gained from patients with OA or RA. The detection of vital cell numbers was determined by histology and by using the Casy Cell Counter System. Cytokine and chemokine secretion was determined by a multiplex suspension array.

Microscopic analysis showed altered cell morphology and cell shrinkage following incubation with synovial fluid of RA patients. Detection of vital cells showed a highly significant decrease of vital chondrocyte when treated with RA synovial fluids in comparison with OA synovial fluids. An active secretion of cytokines such as vascular endothelial growth factor (VEGF) of chondrocytes treated with OA synovial fluids was observed.

Significantly increased levels of various cytokines in synovial fluids of RA, and surprisingly of OA, patients were shown. Activation of pro-inflammatory cytokines of human chondrocytes by synovial fluids of OA patient supports a pro-inflammatory process in the pathogenesis of OA.