Effect of sox9 knockdown on type II collagen gene (col2α1) A: and type I collagen α1 gene (col1α1) B: expression. Chondrocytes were transfected by sox9 siRNA (+) or by non-targeting siRNA (−) were treated with no growth factor (None), FGF-2 or the combination of IGF-I, BMP-2 and BMP-7 proteins, then cultured for the designated time periods. Col2α1 mRNA and col1α1 mRNA were normalized to 18S RNA respectively. Data are expressed as col2α1 mRNA (A) and col1α1 mRNA (B) changes compared to the respective control for each time point ± SD for three independent experiments. Comparison groups are illustrated as data sets. Ranges in values are over the three time points. A: Sets 1 versus 2: range 29–37%, (all P ≤ 0.0097). Sets 1 versus 3: range 1.76-fold (P = 0.0018) to 8.85-fold (P = 0.0050). Sets 3 versus 4: range 32% (P < 0.0001) to 59% (P < 0.0001). Sets 1 versus 5: range 71% (P = 0.0001) to 93% (P ≤ 0.0001). Sets 5 versus 6: range 25–41% (all P ≤ 0.0001). B: Sets 1 versus 2: range 1.49- to 1.68-fold (all P ≤ 0.0238). Sets 1 versus 3: range 22% (P = 0.0222) at day 2, NS at day 4 to 2.67-fold (P = 0.0015) at day 6. Sets 3 versus 4: range 1.70- to 2.09-fold (all P < 0.0001). Sets 1 versus 5: range 80% (P = 0.0001) to 97% (P < 0.0001). Sets 5 versus 6: range 1.21- to 2.00-fold (all P ≤ 0.0147).