Quantitative polymerase chain reaction of different bone morphogenetic protein (BMP) ligands in synovium and cartilage during collagen-induced arthritis. Relative expression of BMP subfamily members BMP2 and BMP4 (green), BMP6 and BMP7 (red), GDF5 (dashed blue), and noggin (black) (upper panel) and TNFα (lower panel) at different time points in collagen-induced arthritis synovium (left) and cartilage (right) towards day 0, no immunisation. Expression was normalized to GAPDH. (n = 3 sets of 2 pooled mice per time point.) Data are presented as mean relative expression. GAPDH, glyceraldehydes-3-phosphate dehydrogenase; GDF5, growth and differentiation factor-5; TNFα, tumor necrosis factor-alpha.