Synovial tissue macrophage populations and articular damage in rheumatoid arthritis

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Abstract
Objective. To examine the relative contribution of individual synovial cell populations to polyarticular destruction in rheumatoid arthritis (RA).Methods. Serial measurements of disease activity and articular destruction, obtained prospectively in 28 RA patients followed up for a mean of 5.8 years, were correlated with synovial cell populations quantified using immunohistochemical techniques.Results. The mean radiologic score worsened (from 37 to 86; P = 0.0001) despite significant improvement in disease activity. Synovial lining layer cell depth and sublining layer macrophage, but not lymphocyte, cell counts correlated significantly with radiologic course. Detailed analysis of 11 patients demonstrated reduced synovial lining expression of CD14 compared with CD68 (P = 0.003), whereas sublining expression of CD14 and CD68 was equivalent.Conclusion. Synovial macrophage numbers correlated with articular destruction in RA. In addition, the study results provided further evidence that lining layer macrophages may represent a distinct subpopulation that is of importance in this process. These findings have implications for the development of new therapies for RA.