Figure 4. Numbers of functional HPCs from young and old C57BL/6 mouse BM collected under hypoxia and processed under ambient air or hypoxic conditions.

BM cells were collected and processed as in Figure 1A. Nucleated BM cells were used in an HPC CFU assay stimulated in vitro with EPO, SCF, PWMSCM, and hemin (A, C, and E) and cultured at 5% O₂, with the percentage of HPCs in S-phase defined by a high specific activity tritiated thymidine kill assay (B, D, and F). The numbers of CFU-GM (A and B), BFU-E (C and D), and CFU-GEMM (E and F) were calculated per femur. Data represent the SEM for 10 C57BL/6 mice from 3–4 experiments. **P < 0.01 and ***P < 0.001, by 1-way ANOVA with post hoc Tukey’s multiple-comparison test.