Low-dose niraparib treatment increases platelet production in mice. (A) Schematic outlining niraparib administration: mice were injected intraperitoneally with niraparib or vehicle (dimethyl sulfoxide) at the indicated times. Blood was drawn via tail vein venipuncture and complete blood counts were measured using a Sysmex hematology analyzer. (B) Platelet counts in vehicle- or niraparib-treated mice (50 mg/kg; n = 5 mice per group). (C) MPV in vehicle- or niraparib-treated mice (50 mg/kg; n = 4-5 mice per group). (D) Platelet counts in vehicle- or niraparib-treated mice (25 mg/kg; n = 5 mice per group). (E) MPV in vehicle- or niraparib-treated mice (25 mg/kg; n = 5 mice per group). (F) IPF in vehicle- or niraparib-treated mice (25 mg/kg; n = 5 mice per group). Data in panels B-E are shown as mean ± SD. Two-way ANOVA with Tukey correction was used for multiple comparisons. (G) Frequency of reticulated, TO^high (thiazole orange) platelets in whole blood of vehicle- or niraparib-treated mice (25 mg/kg; n = 5 mice per group). Data are mean ± SD; unpaired, 2-tailed Student t test. (H) Spleen weights from vehicle- or niraparib-treated mice (25 mg/kg) after 3 or 11 days of treatment, as indicated (n = 5 mice per group). Data are mean ± SD; unpaired, 1-way ANOVA with Šidák correction used for multiple comparisons. (I) Hgb in vehicle- or niraparib-treated mice (25 mg/kg). (J) WBC counts in vehicle- or niraparib-treated mice (25 mg/kg; n = 5 mice per group). Data in I-J are mean ± SD; 2-way ANOVA with Tukey correction used for multiple comparisons. fL, femtoliter; Hgb, hemoglobin; IPF, immature platelet fraction; Plt, platelet; WBC, white blood cell.