Figure 2.

SSRI (fluoxetine), alone or with G-CSF, hastens recovery from irradiation-induced cytopenia in mice. (A), (B), (D): Horizontal lines represent lower limit of normal range for hemoglobin (11 g/dL), platelets (300 × 10³/mm³), and neutrophils (0.5 × 10³/mm³), and threshold for profound anemia (8 g/dL), in mice.^{7, 8} (A) In vivo rescue experiments with fluoxetine: hemoglobin (g/dL), platelet (10³/mm³), and neutrophil (10³/mm³) levels in WT mice (n = 7) treated with fluoxetine or placebo (control) from D − 1 (ie, 1 day before sublethal irradiation) until end of experiment; data from 3 independent experiments. (B) In vivo rescue experiments with G-CSF, alone or with fluoxetine: hemoglobin (g/dL), platelet (10³/mm³), and neutrophil (10³/mm³) levels in WT mice (n = 5) treated with G-CSF, alone or with fluoxetine, from D − 1 before sublethal irradiation until end of experiment; data from 3 independent experiments. (C) Flow cytometry analysis of hematopoietic progenitor cells in bone marrow of WT mice (n = 5) treated with fluoxetine or placebo (control) from D − 1 before sublethal irradiation. Change over time for erythroid progenitors shown on left; D13 data for all progenitors shown on right. Erythroid progenitors: cKIT⁺, Ter119^+/int, CD71^+/−; proerythroblasts: cKIT⁺, CD71⁺, Ter119^int; EryA: cKIT⁺, Ter119^+/int, CD71⁺, FSC-A^high; EryB: cKIT⁺, Ter119^+/int, CD71^+/int, FSC-A^low.; EryC: cKIT⁺, Ter119^+/int, CD71⁻, FSC-A^low.; megakaryocytes: Ter119⁻, cKIT^+,CD41⁺; granulocyte progenitors: lineage-negative, removal of cKIT⁺CD34⁻cells, maturation from myeloblasts to neutrophils according to cKIT and Ly6G markers (see Supplimentary Fig. 1A). (D) Timing of fluoxetine treatment in rescue experiments in mice: hemoglobin (g/dL), platelet (10³/mm³), and neutrophil (10³/mm³) levels in WT mice (n = 5) treated with placebo (control) or fluoxetine from D − 7 to D0 (ie, day of irradiation), from D − 7 on, or from D − 1 on; data from 3 independent experiments. (E) Hemoglobin, platelet, and neutrophil levels in WT mice (n = 7) treated with placebo (control) or fluoxetine for 0 days, 7 days, 3 weeks, 4 weeks, or 6 weeks, at steady state without any other intervention. (F) Flow cytometry analysis of hematopoietic stem and progenitor cells in bone marrow of WT mice (n = 7) treated with placebo (control) or fluoxetine for 4 weeks, at steady state without any other intervention.

Abbreviations: LSK, Lin⁻, Sca1⁺, CD117⁺cells; LT-HSC and ST-HSC, long-term (LSK, CD150⁺, CD48⁻) and short-term (LSK, CD150⁺, CD48⁺) hematopoietic stem cells; LRP, lineage-restricted progenitors (LSK, CD150⁻, CD48⁺); CMP, common myeloid progenitors (LK, CD34⁺, CD16/32^int); GMP, granulocyte macrophage progenitors (Lin⁻, Sca1⁻, CD117⁺, CD34⁺, CD16/32^high); MEP, megakaryocyte erythroid progenitors (Lin⁻, Sca1⁻, CD117⁺, CD34⁻, CD16/32^low) (see Supplementary Fig. 1B); G-CSF, granulocyte colony-stimulating factor; W, week; WT, wild type.