FVIII Y1680F variant binds to VWF strings when expressed by BOECs or exogenously added. (A) Nontransduced, FVIII-YFP-, and FVIII-YFP Y1680F-transduced BOECs were stimulated with 100μM histamine at 2.5 dyne/cm2, fixed and stained for VWF (red) and FVIII (green). (B) Nontransduced BOECs were stimulated with 100μM histamine at 2.5 dyne/cm2 followed by perfusion with 5 U/mL purified FVIII-YFP or 5 U/mL FVIII-YFP Y1680F. Cells were fixed and stained for VWF (red) and FVIII (green). Scale bars represent 20 μm.