The influence of synovial fluids from patients with rheumatic diseases on chick embryo fibroblasts.

Primary chick-embryo fibroblasts (PCEF) were used as target cells to measure the influence of synovial fluids of patients suffering from osteoarthritis (OA; n = 5), rheumatoid arthritis (RA; n = 12) and psoriatic arthritis (PA; n = 2). The following metabolic cell products were measured: DNA, RNA, glycosaminoglycans (GAG), sulfated glycosaminoglycans, protein and collagen, with the same joint effusions being used in each test. Since it is not a single substance that provokes a stimulating or inhibiting effect in the joint, the crude synovial fluids were applied in these preliminary experiments. It was found that each type of synovial fluid showed an influence on the biological processes in the PCEF. The DNA, RNA and GAG syntheses were strongly influenced by the joint effusions, in contrast to the protein, collagen and sulfated glycosaminoglycan syntheses which were less affected. Generally, the nucleic acid synthesis differed significantly between the OA, RA and PA synovial fluids. The addition of heparin to the synovial fluids caused an additive inhibiting effect on the DNA synthesis but did not influence the other biochemical parameters. The synovial fluids of RA patients, and to a much greater extent those of PA patients, inhibited the thymidine incorporation whereas OA synovial fluids had a less pronounced effect. This result indicates a disease-dependent composition of the synovial fluids. RNA synthesis was diminished in all three groups, but again this effect was strongest in the case of the PA synovial fluids. GAG synthesis was markedly stimulated by the PA synovial fluids and somewhat, though to a lesser extent, by the OA and RA synovial fluids. The sulfated glycosaminoglycan synthesis in the PCEF, as revealed by 35S incorporation into the GAG, was less influenced and on the whole stimulated by the OA and RA synovial fluids. The same trend could be observed with regard to the collagen synthesis. The intracellular protein synthesis was less influenced by the OA (91.9%) and more strongly suppressed by the RA (78.7%) and the PA (76.7%) synovial fluids. PCEF therefore appear to be a convenient and sensitive target cell system to study alterations of biochemical processes caused by crude synovial fluids and also of different origin by individual factors isolated from synovial fluids.