Effect of canonical WNT signaling on the mRNA expression of GREM1 , FRZB and DKK1 . (A) Primary human chondrocytes were exposed to 100 ng/ml WNT3A or three different concentrations of GIN. After 48 hours, AXIN2 mRNA expression was analyzed by quantitative PCR. (B) to (F) Chondrocytes were exposed to a single dose of 10 nM GIN or 100 ng/ml WNT3A. At indicated time points, mRNA expression was analyzed by quantitative PCR of AXIN2 (B), FRZB (C), DKK1 (D), GREM1 (E) and ID1 (F). Data expressed as fold-change relative to untreated time-point-matched control and represents the mean of three donors ± standard deviation. *P <0.05 compared with unstimulated cells (A) or 0 hours of stimulation (B) to (F). DKK1, dickkopf 1 homolog (Xenopus laevis); FRZB, frizzled-related protein; GADPH, glyceraldehyde 3-phosphate dehydrogenase; GREM1, Gremlin 1; WNT, wingless-type MMTV integration site.