Effect of normal synovial fluid on the metabolism of articular chondrocytes in vitro.

It is thought that articular cartilage gains most of its nutrition in vivo, via diffusion, from synovial fluid. There have been few studies investigating the effect of synovial fluid on chondrocyte metabolism in vitro. In the current study, bovine articular chondrocytes were isolated and cultured in agarose using normal allogenic synovial fluid as culture medium. Dulbecco's minimal essential medium + 20% fetal calf serum and Earle's balanced salt solution were used as control media. Cell viability at the end of the experiment showed that neither synovial fluid nor Earle's balanced salt solution had a significant effect on viability when compared with Dulbecco's minimal essential medium + 20% fetal calf serum during the period assessed. Results indicate that levels of glycosaminoglycan synthesis can be maintained when Dulbecco's minimal essential medium + 20% fetal calf serum is diluted with Earle's balanced salt solution to levels of 80% Earle's balanced salt solution. When Dulbecco's minimal essential medium + 20% fetal calf serum was diluted with synovial fluid, glycosaminoglycan synthesis was stimulated in a dose dependent manner to 80% synovial fluid. Even at 100% synovial fluid, synthesis levels were significantly higher than for Dulbecco's minimal essential medium + 20% fetal calf serum. Tritiated thymidine uptake decreased with increasing concentrations of either Earle's balanced salt solution or synovial fluid. The results suggest that culture in synovial fluid induces a state similar to that seen in vivo, with high levels of glycosaminoglycan synthesis and low levels of cell division.