IGF-1 promotes proplatelet formation. CD34⁺ cells cultured with rhTPO for 10 days were purified for MKs, which were used in subsequent experiments. (A-B) Typical PPF from MKs captured by phase contrast imaging after treatment with 10 or 100 ng/ml rhIGF-1 for 4 days. (C-D) Tubulin cytoskeleton distribution in MKs after rhIGF-1 treatment. MKs were stained with β1-tubulin (green) and DAPI (blue). (E) Immunoblot analysis of β1-tubulin expression in MKs treated with or without rhIGF-1. (F-G) Phospho-Rac1/Cdc42 expression in MKs blocked with 0.5 μM NVP-ADW742, 10 μM LY294002, or 20 μM U0126 and then treated with rhIGF-1 for 15 minutes. (H-I) Number of MKs exhibiting β1-tubulin aggregation (H) and PPFs (I) pre-blocked with 0.5 μM NVP-ADW742, 10 μM LY294002, or 20 μM U0126 for 20 minutes followed by rhIGF-1 treatment. *P < .05, **P < .01.