Expression and production of CCN2 induced in osteoclast-like cells by GST-RANKL. (A) The expressions of osteoclast marker genes in RAW264.7 cells on days 1, 6, and 7 after treatment with GST-RANKL were determined by real-time RT-PCR. The expression of the NFATc1 gene was upregulated on day 1 after the addition of GST-RANKL and the expressions of Tracp, Ccn2, Dc-stamp, and cathepsin K genes were upregulated on days 6 and 7. Data are presented as mean and SD of two sets of independent cultures. (B) CCN2 protein production in RAW264.7 cells stimulated with GST-RANKL was determined by Western blot analysis. The band density of CCN2 for the extract of the GST-RANKL–treated cells was increased time dependently (upper panel). Signals for β-actin were used to normalize the band densities (bottom panel). The lower graph represents the relative value of CCN2 normalized to the amount of β-actin using densitometric analysis. Each column is standardized against the value of day 1 sample and all columns are presented as mean and SD of two individual experiments.