Differential expression patterns of secreted frizzled related protein genes in synovial cells from patients with arthritis

OBJECTIVE: To detect expression of the secreted frizzled related protein (sFRP) gene in synovial cells from patients with arthritis. METHODS: Expression of sFRP-1, 2, 3, 4, and 5 genes was detected in synovial cells from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. To identify synovial cell populations expressing sFRP-1, 3, and 4 genes, expression was compared in macrophage-rich populations and fibroblast-like cell-rich populations by RT-PCR. Levels of expression of these genes were also studied in activated peripheral blood mononuclear cells (PBMC) and activated skin fibroblasts. RESULTS: Expression of the sFRP-1, 3, and 4 genes was observed in both RA and OA synovial cells. sFRP-1 and 4 genes were expressed predominantly in fibroblast-like cell-rich populations, and the sFRP-3 gene was expressed predominantly in macrophage-rich populations. Levels of expression of sFRP-3 and 4 genes were elevated in activated PBMC and activated skin fibroblasts. CONCLUSION: Our findings suggest that sFRP-1, 3, and 4 may play different roles in the pathogenesis of synovitis.