In vitro anti-PF4 activity of heparin and ODSH. (A) Megakaryocyte colony assay showing the effect of PF4 (25 µg/mL) on colony formation and the effect of heparin (100 IU/mL). N = 4 experiments performed in duplicate. *P = .01 compared with PF4. **P = .01 compared with control. (B) Same as panel A except for ODSH (100 µg/mL). N = 4 experiments performed in duplicate. **P < .001 vs control; *P < .001 vs PF4. (C) Liquid megakaryocyte culture of human CD34⁺ cells in the presence of PF4 (25 µg/mL) ± ODSH (100 µg/mL). N = 6 experiments performed in duplicate. *P < .01 vs PF4; **P < .001 vs control.