Figure 3. Scf from LepR⁺ stromal cells, but not endothelial cells, is necessary for hematopoietic regeneration and mouse survival after irradiation.

(a–f) White blood cell (a) red blood cell (b), and platelet counts (c), as well as bone marrow (two femurs and two tibias per mouse) cellularity (d) and numbers of Lineage⁻Sca-1⁺c-kit⁺ cells (e) and CD150⁺CD48⁻Lineage⁻Sca-1⁺c-kit⁺ HSCs (f) from paired Tie2-cre; Scf^GFP/fl mice and Scf^GFP/fl controls that were non-irradiated (Con) or analyzed 2 or 4 weeks after irradiation and bone marrow transplantation. n=5 mice/genotype/condition from 3 independent experiments. HSCs could not be detected at 2 weeks after irradiation. Two-way ANOVAs with Sidak’s multiple comparisons tests (a-e) or two-tailed Student’s t-tests with Holm-Sidak’s multiple comparisons test (f) were used to assess differences between Tie2-cre; Scf^GFP/fl and Scf^GFP/fl mice.

(g) 10⁶ donor bone marrow cells from the indicated primary recipient mice were transplanted 4 weeks after irradiation along with recipient-type competitor cells into irradiated secondary recipient mice (n=12 recipient mice/genotype from 3 independent experiments). Differences were assessed using two-way ANOVAs with Sidak’s multiple comparisons tests.

(h–m) White blood cell (h) red blood cell (i), and platelet counts (j), as well as bone marrow cellularity (k) and numbers of LSK cells (l) and HSCs (m) from paired Lepr-cre; Scf^GFP/fl mice and Scf^GFP/fl controls that were non-irradiated (Con) or analyzed at 2 or 4 weeks after irradiation and bone marrow transplantation (n=5 mice/genotype/condition from 3 independent experiments). Two-way ANOVAs with Sidak’s multiple comparisons tests (h-l) or two-tailed Student’s t-tests with Holm-Sidak’s multiple comparisons test (m) were used to assess the statistical significance of differences between Lepr-cre; Scf^GFP/fl and Scf^GFP/fl mice.

(n) 10⁶ donor bone marrow cells from the indicated primary recipient mice were transplanted 4 weeks after irradiation along with recipient competitor cells into irradiated secondary recipient mice (n=12 recipient mice/genotype from 3 independent experiments). Differences were assessed using two-way ANOVAs with Sidak’s multiple comparisons test (*P<0.05, **P<0.01, ***P<0.001).

(o) Mouse survival after irradiation and transplantation of 2×10⁵ whole bone marrow cells (n=20 mice/genotype/condition from 5 independent experiments). The Gehan-Breslow-Wilcoxon test was used to assess statistical significance.

All data in Figure 3 represent mean±SD.