(A) Western blot analysis showed that the expression of Smad1/5 was significantly reduced by the addition of Noggin in these three groups. No statistical difference was found among these three groups (one-way ANOVA for Smad1/5 expression: F = 1.143, P=0.351, df1/df2 = 2/12, n=5. Control + Noggin vs BMSC-CM + Noggin: P=0.630; Control + Noggin vs BMP + Noggin: P=0.342; BMSC-CM + Noggin vs BMP + Noggin: P=0.163). (B) Quantitative RT-PCR analysis of Id2, Olig1, and Olig2 expression revealed that although the BMP/Smad pathway was completely blocked by Noggin, the expression of Id2, Olig1, and Olgi2 gene expression was still changed by BMSC-CM. No statistical difference was found between the Control and the BMP4 groups (one-way ANOVA for Id2 expression: F = 29.158, P<0.001, df1/df2 = 2/12, n=5; one-way ANOVA for Olig1 expression: F=8.972, P=0.04, df1/df2 = 2/12, n=5; one-way ANOVA for Olig2 expression: F = 9.623, P=0.03, df1/df2 = 2/12, n=5; one-way ANOVA: *P<0.05; NS = P>0.05).