Fig. 2

SB-505124 and (5Z)-7-Oxozeaenol do not affect constitutively active activin receptor-like kinase 1 (ALK1) whereas LDN-193189 does. a Primary bovine chondrocytes were transfected with either constitutively active ALK1 (caALK1) or caALK5 and 2 days later treated with inhibitors for 1 h. A virus overexpressing LacZ was used as control. Efficiency of overexpression was visualized on western blot by staining for the HA-tag attached to the caALKs. kDa kilodalton. b Quantification of the pSmad1/5 and pSmad2 signal (as shown in a) in three experiments; ^# p ≤ 0.001 compared to unstimulated. pSmad levels were normalized to vinculin levels and plotted as a relative amount in arbitrary units (AU) compared to the control group; ^§ p ≤ 0.01 compared to unstimulated; **p ≤ 0.01; ***p ≤ 0.001. c Dose-response effect of LDN-193189 on transforming growth factor β1 (TGFβ1) signaling in primary chondrocytes. pSmad levels were normalized to glyceraldehyde-3-phosphate dehydrogenase (Gapdh) levels and indicated as a relative amount in AU compared to the control group. d Primary chondrocytes were incubated for 1 h with LDN-193189 and subsequently stimulated for 1 h with 1 ng/ml (78 pM) TGFβ1, 25 ng/ml (1.94 nM) recombinant human bone morphogenic protein 2 (rhBMP2), 25 ng/ml (3.06 nM) bone morphogenic protein 7 (BMP7) or 1 ng/ml (83 pM) bone morphogenic protein 9 (BMP9). pSmad levels were normalized to Gapdh levels and indicated as a relative amount in AU compared to the control group