Morphology of Weibel-Palade bodies upon expression of untagged FVIII and VWF. (A) HEK293 cells were transfected with untagged FVIII (left panel), untagged VWF (middle panel), or both (right panel). Cells were stained for FVIII (green) using monoclonal antibody EL14 and for VWF (red) using monoclonal antibody CLB-RAg20. Shown is the merge of double-fluorescent detection of representative 3-dimensional projections (Z-stacks 0.4 μm). The scale bar represents 10 μm. (B) HUVECs (control) were transduced with untagged FVIII (C). Cells were stained for VWF (red, left panel) and FVIII (green, middle panel) using antibodies as in panel A. The right panel represents the merge of double-fluorescent detection. Regions of colocalization are represented in yellow. The scale bar represents 20 μm. The inset shows the vesicle morphology.