Figure 2. Effect of aging on the auto-phosphorylation of IGF-IR of bmMSCs. (A) BrdU incorporation analyses. Serum-starved Aged-1 and Aged-2 bmMSCs were examined for the IGF-I-induced DNA synthesis with or without concomitant treatment of AG1024 (1 μM). Relative DNA synthesis was calculated by compared the OD450 readings of the treated cells to that of the untreated (U) cells. (to which a value of 1 was assigned). Data represent the mean ± S.D. from three experiments. Student’s t-test was used to analyze the differences between the groups. (B) Western blot analyses. Serum-starved Aged-1 and Adult-1 cells were treated with 0, 50, and 250 ng/ml of IGF-I for 0, 5, 10, and 20 min. The auto-phosphorylation of IGF-IR was examined. Representative blots are shown. All the signals were compared to that of the untreated cells at time 0 (to which a value of 1 was assigned). Data represent the mean ± S.D. from three experiments. A one-way ANOVA plus Scheffe’s post hoc tests were used to analyze the differences among the untreated and IGF-I-treated groups. *, P<0.05 versus untreated control.