Figure 4

(A) Survival in C57BL/6 male mice following 8.0 Gy total body irradiation (TBI). A single dose of JNJ-26366821 at 1 mg/kg (■) or saline as a vehicle (□) was administered 24 h post-TBI to C57BL/6 male mice. Kaplan–Meier survival curves were plotted using GraphPad software; n = 24 mice per group and trend in survival is compared between vehicle and drug-treated groups (Log-rank test p < 0.0001). Percent survival on day 30 post-TBI is shown at the end of each curve. (B–E) The non-irradiated naïve group was compared with the irradiated groups (saline and JNJ-26366821). (B) Peripheral blood cell counts on day 30 post-TBI (8 Gy). White blood cells (WBC), neutrophils (NEU), lymphocytes (LYM), red blood cells (RBC) and platelets (PLT) were measured. (C) Recovery of femoral bone marrow was estimated by Colony forming Unit assay. On day 30 post-TBI (8 Gy), the JNJ-26366821 group had significant recovery (p = 0.01) compared to saline group. (D) Serum levels of FLT3-L on day 30 post-TBI (8 Gy) were measured by ELISA showing recovery by JNJ-26366821 treatment. Data represented are mean ± standard error of the mean (SEM) for n = 3 mice. (E) Recovery of cellularity of sternal bone marrow was determined on day 30 post-TBI (8 Gy). The number of megakaryocytes were counted in all three groups. The JNJ-26366821 group showed significant recovery (p < 0.05) compared to saline group. Significant difference (p < 0.001–0.05) by t-test is indicated with an asterisk (*). (F) Representative sternal bone marrow sections are shown for naïve, irradiated saline and JNJ-26366821 groups. Green arrows indicate megakaryocytes. Figures were plotted using GraphPad Prism 9 software V9.0.2; www.graphpad.com.