Fibroblast-like synovial cells derived from synovial fluid.

Objective. To obtain fibroblast-like synovial cells (FLS) from synovial fluid (SF). Methods. SF aspirated from joints of patients with rheumatoid arthritis (RA), other types of inflammatory arthritis, and osteoarthritis (OA) was centrifuged and the resulting cell pellet resuspended in growth medium. After 2 days, nonadherent cells were removed. FLS were also cultured from surgical specimens of synovial tissue (td-FLS). Phenotype characterization of fluid derived FLS (fd-FLS) was accomplished by flow cytometry and immunohistochemistry staining. Tumor necrosis factor-cc (TNF-alpha) induced interleukin 6 (IL-6), IL-8, and cyclooxygenase 2 (COX-2) mRNA levels were assessed. Results. Second and later passage fd-FLS exhibited uniform fibroblast-like morphology. Fd-FLS and td-FLS expressed a similar profile of cell surface antigens including the fibroblast marker Thy-L Less than 2% of either cell type expressed surface markers characteristic of dendritic cells, phagocytic cells, T cells, or leukocytes. Immunohistochemistry staining revealed the presence of fibroblast products prolyl-4 hydroxylase, procollagen I, and procollagen III in both culture types. TNF-alpha induced increases in IL-6, IL-8, and COX-2 mRNA were suppressed by dexamethasone in both fd-FLS and td-FLS. Conclusion. FLS can be cultured from SF. The fibroblast phenotype was confirmed by analysis of surface antigens and intracellular proteins. Inflammatory mediators produced after stimulation of both fd-FLS and td-FLS were suppressed by dexamethasone. In addition to providing a more accessible source of FLS, fd-FLS may also facilitate study of synovial cells in early RA when tissue specimens are not readily available.