PI3Kβ is required for incorporation of new platelets into an existing thrombus under high shear rate in mice and humans. (A) Unlabeled whole blood from p110β^flox/flox control (WT) mice were perfused through a collagen-coated microcapillary at 500 seconds⁻¹. Control blood was then replaced by DIOC₆-labeled platelets in whole blood from p110β^flox/flox control (WT) or PF4-Cre/p110β^flox/flox (p110β^null) mice and was perfused at a high shear rate (4000 seconds⁻¹). Surface covered (%) by fluorescent platelets (1 minute, 4000 seconds⁻¹) was then analyzed using ImageJ software. Results shown are mean ± SEM of 5 experiments. Student t test, ***P < .001. Representative images at the end of the high shear rate are shown for both genotypes. Scale bar, 20 µm. (B) Unlabeled human platelets in whole blood were perfused through a collagen-coated microcapillary at 1500 seconds⁻¹. Control blood was then replaced by DIOC₆-labeled human whole blood treated or not with the PI3Kβ inhibitor AZD6482 and perfused at a high shear rate (4000 seconds⁻¹). Surface covered (%) by fluorescent platelets (2 minutes, 4000 seconds⁻¹) was then analyzed using ImageJ software. Results shown are mean ± SEM of 5 experiments. Student t test, ***P < .001. Representative images at the end of the high shear rate are shown for both conditions. Scale bar, 20 µm.