Figure 3. Estrogen Promotes HSPC Regeneration After Irradiation.

(A) Bone marrow cellularity (A), LSK frequencies (B), and total numbers of LSK cells (C) were analyzed at 3, 5, 7, and 14 days after 600cGy of TBI. E2 treatment significantly accelerated the recovery of bone marrow cellularity, and the frequencies and the total numbers of LSK cells. (B–C) Frequencies (B) and total numbers (C) of LSK cells in the bone marrow drop significantly 14 days after 600cGy of irradiation; this affect is rescued by E2 treatment in wild-type mice but not in ERα-deficient mice (n = 7 over four independent experiments). (D) Competitive transplantation assays using 5 × 10⁵ WBM cells from Ubc-GFP⁺ unirradiated mice (green lines) or sublethally irradiated, oil-treated mice (black lines) or sublethally irradiated E2-treated mice (red lines) along with competitor cells (n = 8, two donors, four recipients per donor). E2 pretreatment significantly rescued the ability of WBM cells to reconstitute the myeloid cells, platelets, and red blood cells after irradiation. (E–G) Bone marrow cellularity (E), LSK frequencies (F), and total numbers of LSK cells (G) in the bone marrow are significantly lower 14 days after 600cGy of irradiation (IR) compared to unirradiated mice (Un). This effect is rescued by E2 treatment in wild-type mice but not in ERα-deficient mice (n = 7, four independent experiments). All data represent mean ±standard deviation; *p<0.05; **p<0.01; and ***p<0.001 by Student’s t-test in (A–D), and by ANOVA in (E–G).

Figure 3—figure supplement 1. Regeneration of HSPCs after irradiation by E2 stimulation.

(A) Gating schemes to identify LSK cells and lineage^-Sca-1^-c-kit⁺myeloid progenitor (MP) cells in unirradiated mice and irradiated mice treated with oil or E2. (B) Frequencies of MP cells and (C) LSK cells in unirradiated and irradiated animals, with or without E2 treatment. 3 month old male mice were sublethally irradiated (600cGy) followed by oil or E2 administration every other day. Both MP and LSK frequency are severely reduced following irradiation. Whereas MP frequency is unaffected by E2 treatment, LSK frequency is significantly increased. (D) Depletion of bone marrow cellularity after irradiation was significantly rescued by E2. (E) Total numbers of LSK cells found in the long bones of sublethally irradiated mice given E2 after irradiation. All data represent mean ±standard deviation; *p<0.05; ***p<0.001, two-way ANOVA. MP frequency (F) and MP numbers (G) were assessed following sublethal TBI. Although MP frequency is unchanged, the total numbers of MPs are increased by E2 treatment at day 14. **p<0.01, Student’s t test. (H) MP frequency at day 14 post-TBI in Oil and E2 treated WT and ERα-deficient mice. **p<0.01, two-way ANOVA. (I) Apoptosis rates were analyzed after sublethal TBI in lineage^- BM cells in Oil and E2 treated WT males. *p<0.05; **p<0.01, two-way ANOVA.