Stimulation of megakaryocyte colony formation from human CD34⁺ cells by NIP-004. (A) Morphology of CFU-MK colonies obtained from human BM-derived CD34⁺ cells treated with 1 μg/mL NIP-004. CFU-MKs were visualized with AP-labeled antibody against human CD41. Polyploid megakaryocytes are shown in detail in the right panel. Bar, 200 μm. (B) The number of CFU-MKs from human BM-, CB-, and PB-derived CD34⁺ cells treated with 1 to 3 μg/mL NIP-004 was similar to that with 10 ng/mL rhTPO. Results are expressed as mean ± SEM from 4 independent experiments (BM) or mean ± SD from 2 independent experiments (CB and PB). NC indicates negative control; T, 10 ng/mL rhTPO; NIP₁,1 μg/mL NIP-004; NIP₃,3 μg/mL NIP-004.