Fig. 2.

Inhibition of DNA methylation is associated with increased GDF5 expression in human articular chondrocytes (HACs). a Effect of AZA treatment on GDF5 expression. HACs from four OA patients were cultured in 5 µM AZA dissolved in 50 % acetic acid or 50 % acetic acid alone (control) for three passages and gene expression measured after the third passage. b GDF5 expression in HACs transfected with siRNAs against the DNA methyltransferase enzymes and the non-targeting control siRNA. Four wells of a 96-well plate were transfected per siRNA for three independent experiments. The percentage of siRNA-mediated inhibition of expression relative to the control siRNA is stated for each enzyme. GDF5 expression levels were normalised to 18s and control-treated cells and those transfected with the control siRNA given an arbitrary value of 1. Error bars denote standard error of the mean. *p < 0.05, **p < 0.01, Mann–Whitney U test