HSPC radiation resistance increased by HIF-1α protein stabilization in vivo. Mice were treated with saline or DMOG for 18 days, irradiated with 9.0 Gy, and the BM harvested 7 weeks later (see timeline in Figure 5A). Shown are the numbers of LKS⁺48⁻ HSCs, LKS⁺48⁺ lineage-restricted HPCs, and LKS⁻ myeloid progenitors (A) and total CFCs and CFU-GMs (B) in mouse BM 50 days after 9.0 Gy of irradiation. Data are shown as the means ± SD from 6 mice per group. (C) Competitive repopulation assay at day 36 (week 5) after 9.0Gy irradiation following a pre-treatment with DMOG or saline for 18 days (see timeline in Figure 5A). BM cells from 10 CD45.2⁺ donor mice per treatment group were pooled within each treatment group. A total of 200 000 CD45.2⁺ BM cells from each treatment group were transplanted with 200 000 competitive whole BM cells from untreated congenic B6.SJL CD45.1⁺ mice into 9 lethally irradiated CD45.1⁺ recipients. (C) Percentages of CD45.2⁺ donor contribution in total CD45⁺ leukocytes, CD11b⁺ myeloid cells, B220⁺ B cells, and CD3⁺ T cells 16 weeks after transplantation. Data are shown as the means ± SD from 9 mice per group. Each symbol represents an individual recipient mouse, bars are averages, dotted lines represent the 0.5% CD45.2⁺ threshold above which chimerism was considered to be positive. (D) Percentage of CD45.2⁺ donor leukocytes in the blood at 8, 12, and 16 weeks after transplantation. Each line represents an individual mouse (black lines are DMOG-treated donors; gray lines are saline-treated donors). (E) Number of RUs/femur from donor chimerism at 16 weeks after transplantation. (F) Comparison of RUs/femur in mice treated with DMOG or saline before (Figure 4C) and 50 days after (Figure 6C) 9.0 Gy of irradiation. Data are shown as the means ± SD from 9 mice per group. Significance levels were calculated using a t test (A-B) or a Mann-Whitney test (C,E,F). NS indicates not significant.