Green tea catechin, (–)-epigallocatechin-3-gallate
[(–)-EGCG], was found to increase osteogenic functioning in mesenchymal stem
cells. This study qualified EGCG, the strongest inhibitory efficiency for
receptor activator of nuclear factor-κB
(NF-κB) ligand (RANKL)-activated
osteoclastogenesis among other green tea catechins for RAW264, a murine
preosteoclast cell line. Moreover, EGCG inhibited tartrate-resistant acid
phosphatase (TRAP)-positive multinucleated cell formation dose dependently in
both single culture and co-culture systems, the expression of transcription
factor, nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) and some osteoclastic
genes. Especially, EGCG exhibited a strong inhibitory effect on the expression
levels of RANK, the receptor of RANKL, and OSCAR, a key co-stimulator of the
RANKL/RANK signal. Simultaneously, apoptotic genes expression and Hoechst
staining revealed that EGCG induced apoptosis in RAW264. Taken together, these
data suggest that the inhibitory effect of EGCG to osteoclastogenesis is
associated with a down regulation of RANKL/RANK signal, and increased apoptosis
of preosteoclasts.