Expression of wnt signaling molecules in the synovial membranes of rabbit ankle joints injected with Enterococcus faecalis cell fractions

The cell adhesion molecule β-catenin mediates the transduction of wnt signals to various downstream events such as gene expression, cell proliferation, and cell adhesion. In this study, the results of reverse transcriptase polymerase chain reaction (RT–PCR) amplification showed that wnt1 and β-catenin expression increased in response to E. faecalis, and that the increases in wnt1 and β-catenin activated transcription of cyclin D1. Immunohistochemistry also showed that stimulating wnt1 with E. faecalis cell fractions leads to the stabilization and accumulation of β-catenin in the synovial membrane. On the other hand, the results of RT–PCR showed overexpression of various inflammatory cytokines, including IL-1-β, TGF-β, TNF-α, and IL-6, in the synovial membrane of joints injected with E. faecalis cell fractions. These findings suggest that expression of cyclin D1 is strongly dependent on β-catenin/Tcf and has a direct effect on the proliferation of synoviocytes, such as IL-1-β and TGF-β, that leads to inhibition of Fas-antigen-mediated apoptosis of synovial cells.