Figure 4. Effect of DCN overexpression on the DNA synthesis and IGF-IR auto-phosphorylation of adult bmMSCs. (A) Western blot analyses of DCN and IGF-IR levels in cells overexpressing DCN. Adult-1 cells were infected with Lenti virus to generate DCN-overexpressing (DCN) and empty vector control (EV) cells. The DCN and IGF-IR protein levels of the parental Aged-1, DCN, and EV cells are shown. (B) BrdU incorporation analyses. Serum-starved parental, DCN, and EV cells were examined for DNA synthesis induced by IGF-I (50 and 200 ng/ml). The DNA syntheses in these cells were compared to that of the untreated parental cells (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-1-treated groups. *, P<0.05 versus untreated control. Student’s t-test was used to analyze the differences between the groups. (C) Western blot analyses of IGF-IR auto-phosphorylation in cells overexpressing DCN. Serum-starved DCN and EV cells were either treated with varying doses of IGF-I for 5 min or left untreated, and the IGF-IR auto-phosphorylation in response to IGF-I was examined by Western blot analyses. The difference in the response rates between DCN and EV cells was analyzed by linear regression.