Bone marrow HSPC counts and platelets recover after short-term niraparib treatment. (A) Time course of platelet counts in vehicle- and niraparib-treated mice (25 mg/kg). Mice were followed and platelet counts measured for 47 days after treatment cessation (n = 4-5 mice per group). Data are mean ± SD; 2-way ANOVA with Tukey correction for multiple comparisons. (B) Absolute counts of HSPC populations 47 days after cessation of niraparib or vehicle treatment were quantified by flow cytometry using the panel outlined in supplemental Figure 2 (n = 4-5 mice per group). Data are mean ± SD; unpaired, 2-tailed Student t test. (C) Platelet aggregation after stimulation with CRP (1 μg/mL) or thrombin (0.5 U/mL) was measured 47 days after cessation of niraparib or vehicle treatment (n = 4-5 mice per group). Data are mean ± SD; unpaired, 2-tailed Student t test. (D) Platelets were left resting or activated with indicated agonists and MFI of P-selectin and αIIbβ3 integrins was measured on platelets in whole blood isolated from niraparib- or vehicle-treated mice (n = 4-5 mice per group). Data are mean ± SD; multiple t tests were used. CRP, collagen-related peptide; LT-HSC, long-term HSC; ST-HSC, short-term HSC.