Inhibition of mTORC1 suppresses age-associated elevation of MK size and platelet activation in mice. (A) VWF immunohistochemistry (IHC) staining of femur bone sections from 4- or 16-month-old mice. Bar represents 100 μm. Quantification of MK sizes (average area per MK) is illustrated (n = 10). Values represent means ± SEM; *P < .05. (B) FACS analysis of MKs from 16-month-old mice treated with rapamycin (1.5 mg/kg per day) for 2 months for mTORC1 activity (P-S6) (n = 10). MFI values are presented as means ± SEM; **P < .01. (C) VWF IHC staining of femur bone sections from 16-month-old mice treated with rapamycin (1.5 mg/kg per day) for 2 months (n = 10). Bar represents 100 μm. Quantification of average area per MK is illustrated. *P < .05. (D) PF4 enzyme-linked immunosorbent assay (ELISA) analysis of plasma from 4- or 16-month-old mice treated with rapamycin (1.5 mg/kg per day) for 2 months (n = 10). Values represent means ± SEM; **P < .01. (E) FACS analysis of platelets incubated with 0.2 U/mL thrombin for 15 minutes at room temperature from mice described in panel D for platelet integrin αIIbβ3 activation and quantification illustrated (n = 10). Values represent means ± SEM; *P < .05; ***P < .001. (F) Adenosine 5′-diphosphate–induced (20 μM) platelet aggregation in platelet-rich plasma from mice described in panel D (n = 10). Values represent means ± SEM; *P < .05.