IGF-1 promotes the population of CD34⁺cells and the differentiation of MKs. (A) Flow cytometric analysis of the numbers of CD34⁺ cells after stimulation with 10 or 100 ng/mL rhIGF-1 for 7 days in the presence of 20 ng/mL rhSCF. (B) Flow cytometric analysis of CD41⁺ cell counts after 10 or 100 ng/mL rhIGF-1 treatment of 7 days in the presence of 20 ng/mL rhTPO. (C) DNA content assay in CD41⁺ cells after CD34⁺ cells stimulated with 10 or 100 ng/mL rhIGF-1 in the presence of 20 ng/mL rhTPO for 7 days. (D-E) CD41⁺CD42b⁺ expression on CD34⁺ cells treated with or without rhIGF-1 for 7, 10 and 14 days in the presence of 20 ng/mL rhSCF. (F) Western blot analysis of ERK1/2 and Akt phosphorylation in MKs after exposure to 100 ng/mL rhIGF-1 for different times. (G) Phosphorylation of p-ERK1/2 and p-Akt in MKs pretreated with 0.5 μM NVP-ADW742, 10 μM U0126 or 20 μM LY294002 followed by rhIGF-1 treatment of 15 minutes. *P < .05, **P < .01, vs the control; ^#P < .05, ^##P < .01, vs the IGF-1-treated group.