The contribution of human c-fos DNA to cultured synovial cells: a transfection study.

To clarify the role of c-fos DNA in the activation of human synovial cells, the pH8 expression vector containing human c-fos DNA under the control of murine leukemia virus long terminal repeat was transfected into cultured synovial cells. After G418 selection, the control transfectant clones transfected with pH8 vector not containing c-fos DNA insertion changed their original fibroblastic shape into dendritic cells. They stopped growing at this stage. However, the c-fos DNA transfectant clones continued to grow actively beyond this stage, and regained the fibroblastic appearance. Furthermore, c-fos DNA transfectants adhered to and grew on hyaluronidase treated cartilage surfaces more extensively than control transfectants after 6 days in culture. These findings suggest that c-fos DNA supports active growth of human synovial cells by facilitating transition of synovial dendritic cells into fibroblastic cells.