Association of CD90 Expression by CD14(+) Dendritic‐Shaped Cells in Rheumatoid Arthritis Synovial Tissue With Chronic Inflammation

OBJECTIVE: CD14(+) dendritic‐shaped cells show a dendritic morphology under the electron microscopy and engage in a pseudoemperipolesis phenomenon with lymphocytes. CD90 has been used as a marker of a major subset of fibroblast‐like synoviocytes in rheumatoid arthritis (RA). In this study, we investigated the significance of CD90 expression in CD14(+) dendritic‐shaped cells and its correlation with RA chronic inflammation. METHODS: Double immunofluorescence staining for CD14 and CD90 was performed in the collected tissues, including 12 active RA synovial tissues. The localization of CD14(+)CD90(+) cells, the percentages of CD14(+)CD90(+) cells and vascular areas, the degree of synovitis, and clinical data were investigated. Furthermore, CD14(+)CD90(+) cells analyzed by flow cytometry (CD14(high)CD90(intermediate (int)) cells) were sorted from RA synovial cells, and we examined their potential to differentiate into dendritic cells. RESULTS: Double immunofluorescence staining showed that CD14(+)CD90(+) cells were abundant in RA synovial tissues. The percentages of CD14(+)CD90(+) cells and vascular areas correlated with some of the Krenn synovitis scores, but neither showed a strong correlation with RA disease activity parameters. Flow cytometry analysis indicated that CD14(high)CD90(int) cells were more abundant in both peripheral blood samples and synovial tissues in patients with active RA. CD14(high)CD90(int) cells were more likely to differentiate into dendritic cells in vitro. CONCLUSION: CD14(+) dendritic‐shaped cells expressed CD90 in the perivascular areas of RA synovial tissues. These findings suggest that CD14(+)CD90(+) dendritic‐shaped cells migrate from the peripheral blood to the synovial tissue, the site of inflammation, and may contribute to the chronic inflammation of RA as dendritic progenitor cells.