Ectopic expression of DKK1 diminished Wnt3a induced OPG mRNA and protein in osteoblast cells. The expression of DKK family members in C2C12 (A) and human osteoblast cell lines (B) as determined by RT-PCR analysis are presented. Concentration of DKK1 protein in culture supernatant of indicated cell lines by ELISA analysis (C). C2C12 cells were stable transfected with an empty vector or DKK1-expressing vector. DKK1 protein expression was detected by the anti-V5 antibody (D). DKK1 protein in the supernatant of the clones was determined by ELISA (E). The cells were treated with recombinant 100 ng/mL of rWnt3a. Relative OPG mRNA (F) and OPG protein concentration (G) was measured by qPCR or ELISA analysis as described in Figure 1. Data represent the means plus or minus SD (n = 3) of representative experiments (*P < .05, ***P < .001, and vs control).