Lack of PS in platelets does not affect platelet activation state in steady state, platelet aggregation ex vivo, and platelet-dependent VTE in vivo. (A) PF4 antigen levels in plasma from Pros1^lox/loxPf4-Cre⁻ and Pros1^lox/loxPf4-Cre⁺ mice (ns, not significant; P = .145). Data are expressed as median. The normal range of the PF4 antigen concentration in mouse plasma (0.26-4.70 µg/mL) provided by the manufacturer is indicated in the y-axis by dashed lines. (B) Flow cytometry analysis of CD62p and CD41 on resting and convulxin (10 µg/mL)-activated or thrombin (10 U/mL)-activated platelets. (C) Platelet Function Analyzer-100 closure time using collagen-ADP and collagen-epinephrine (collagen-Epi) cartridges to activate platelets in whole blood from Pros1^lox/loxPf4-Cre⁻ and Pros1^lox/loxPf4-Cre⁺ (n = 5/genotype). Data are expressed as mean ± SEM. (D) Aggregation of washed platelets suspensions were initiated by adding different concentrations of collagen, ADP (in presence of 2 mg/mL fibrinogen), and thrombin. Results are given as mean ± SEM of at least 3 independent experiments; each of them was obtained from platelet pools (n = 4 mice/genotype). (E) Venous thromboembolism model induced by an intravenous injection of collagen-epinephrine in Pros1^lox/loxPf4Cre⁻ (straight line; n = 16) and mice Pros1^lox/loxPf4Cre⁺ (dashed line; n = 13) mice.