Fibrin clot retraction assay following −889Pl^A2β₃ transduction of thrombasthenic CD34⁺ cells.

The RSΔ9β₃ and EAY115Cβ₃CD34⁺ cells were transduced with −889Pl^A2β₃, induced for 10 to 14 days to form megakaryocytes in vitro, and then examined for the ability to retract a fibrin clot. Cells (1.5 × 10⁶/mL) were resuspended in IMDM containing 60 μg/mL human fibrinogen in a standard aggregometry tube. Clot formation was initiated by the addition of 2.5 U/mL thrombin. Tubes were incubated at 37°C for up to 12 hours and photographed. The β₃-transduced cells were able to mediate clot retraction in vitro similar to the nonthrombasthenic cells (normal control), whereas untransduced patient samples were not able to retract a fibrin clot. A normal control was included for the time each patient sample was assayed.