Romiplostim induces a reduction of GPVI and GPIb-IX-V complex expression. (A) Flow cytometric experiment showing in both WT mice and Myh9^−/− mice a reduced surface expression of GPVI and GPIb-IX-V complex during romiplostim treatment (i-iv), whereas expression of GPIIbIIIa (v) remained normal. Blood samples were taken after 28 days of romiplostim treatment. Results are expressed as the mean fluorescent intensity ± SEM (n = 8 for GPVI and n = 4 for other proteins). (B) Western blot analysis showing total GPVI, GPIbβ, and GPIIIa expression (lysate from a pool of 8-10 mice, after 1 month of treatment, representative of 2 separate experiments). (C) Flow cytometric experiment showing absence of P-selectin exposure or Jon/A-PE labeling after romiplostim treatment (n = 4-5). (D) Bleeding time, measured by the tail tip sectioning, was not reduced in Myh9^−/− mice treated with romiplostim for 1 month, whereas it was increased in treated WT mice.