Quantification of P-SMAD1/5 expression during collagen-induced arthritis (CIA) by Western blot. (a) Western blot for P-SMAD1/5 and SMAD5 on mouse whole knee extracts at different time points in CIA, normalized to wet weight (n = 3 sets of pooled knees per time point). (b) Positive control of Western blot for P-SMAD1/5 and SMAD5 on C2C12 cells unstimulated or stimulated with bone morphogenetic protein-2 (BMP2) (300 ng/mL) for 30 minutes. Ten micrograms of protein was loaded. (c) Analysis of the activation of the BMP signaling pathway, which was measured as the inverted density of P-SMAD1/5 bands (normalized to density of SMAD5 bands) (n = 3 sets of 3 pooled knees per time point). Data are presented as mean ± standard deviation. P-SMAD, phosphorylated Smad family members; SMAD, Smad family members.