Tea extract increases cell fusion via regulation of cell surface DC-STAMP

Mononuclear osteoclast precursor cells fuse with each other to become mature multinucleated osteoclasts, which is regulated by dendritic cell-specific transmembrane protein (DC-STAMP). We evaluated the effects of tea extract and catechins on cell-cell fusion and DC-STAMP expression to elucidate their relationship with osteoclast development. When tea extract or epigallocatechin gallate (EGCg) was applied to RAW264.7 cells, multinucleated cells were increased significantly, while tartrate-resistant acid phosphatase (TRAP) activity was hardly upregulated. Flow cytometric analysis revealed that EGCg suppressed DC-STAMP expression on the cell surface, which is similar to osteoclast development. These observations suggest that TRAP activity is not activated even when suppression of both surface DC-STAMP expression and multinucleation occurs, which might be mediated by another pathway.