Response of BOECs to DDAVP. BOECs derived from a healthy donor (A,B) or the patient heterozygous for p.Tyr1584Cys (C,D) showed VWF strings (indicated by arrowheads) after incubation with 100 μM histamine for 1 hour (A,C), but no strings were seen after stimulation with 1 μM DDAVP (DDAVP) for 2 hours (B,D). Cells were fixed and stained for VWF (green) and β-catenin (red). (Scale bars, 20 μm.) All images were taken by Leica SL confocal laser scanning microscopy with a 63×/1.40 NA oil objective. (E,F) Cells derived from a healthy donor (donor 1) (E) and from the patient heterozygous for p.Tyr1584Cys (F) were cultured in 12-well plates at passage 6. Confluent cell layers were incubated for 60 minutes at 37°C in the absence (Control) or presence (Histamine) of 100 μM histamine or DDAVP (DDAVP) at indicated final concentrations. There was no response to DDAVP. Mean ± SEM indicates variation between triplicate measurements.