Sulforaphane inhibits osteoclast differentiation by suppressing the cell-cell fusion molecules DC-STAMP and OC-STAMP.

Sulforaphane (SFN), a kind of isothiocyanate, is derived from broccoli sprouts. It has anti-tumor, anti-inflammatory, and anti-oxidation activity. The molecular function of SFN in the inhibition of osteoclast differentiation is not well-documented. In this study, we assessed the effect of SFN on osteoclast differentiation in vitro. SFN inhibited osteoclast differentiation in both bone marrow cells and RAW264.7 cells. Key molecules involved in the inhibitory effects of SFN on osteoclast differentiation were determined using a microarray analysis, which showed that SFN inhibits osteoclast-associated genes, such as osteoclast-associated receptor (OSCAR), nuclear factor of activated T cells cytoplasmic-1, tartrate-resistant acid phosphatase, and cathepsin K. Moreover, the mRNA expression levels of the cell-cell fusion molecules dendritic cell specific transmembrane protein (DC-STAMP) and osteoclast stimulatory transmembrane protein (OC-STAMP) were strongly suppressed in cells treated with SFN. Furthermore, SFN increased the phosphorylation of signal transducer and activator of transcription 1 (STAT1), a regulator of macrophage and osteoclast cell fusion. Thus, our data suggested that SFN significantly inhibits the cell-cell fusion molecules DC-STAMP and OC-STAMP by inducing the phosphorylation of STAT1 (Tyr701), which might be regulated by interactions with OSCAR.