Norepinephrine reuptake inhibition promotes mobilization in mice: potential impact to rescue low stem cell yields

Abstract

The mechanisms mediating hematopoietic stem and progenitor cell (HSPC) mobilization by G-CSF are complex. We have found previously that G-CSF-enforced mobilization is controlled by peripheral sympathetic nerves via norepinephrine (NE) signaling. In the present study, we show that G-CSF likely alters sympathetic tone directly and that methods to increase adrenergic activity in the BM microenvironment enhance progenitor mobilization. Peripheral sympathetic nerve neurons express the G-CSF receptor and ex vivo stimulation of peripheral sympathetic nerve neurons with G-CSF reduced NE reuptake significantly, suggesting that G-CSF potentiates the sympathetic tone by increasing NE availability. Based on these data, we investigated the NE reuptake inhibitor desipramine in HSPC mobilization. Whereas desipramine did not by itself elicit circulating HSPCs, it increased G-CSF-triggered mobilization efficiency significantly and rescued mobilization in a model mimicking "poor mobilizers." Therefore, these data suggest that blockade of NE reuptake may be a novel therapeutic target to increase stem cell yield in patients.

Figures

Figure 1

The G-CSF receptor is expressed on peripheral sympathetic neurons and its stimulation reduces norepinephrine (NE) uptake. (A) Immunofluorescence staining for the G-CSF receptor (G-CSF-R; Cy3 top panel) or tyrosine hydroxylase (TH; Alexa 647, bottom panel) in sections of murine SCSG neurons. Images were acquired with a 40×/1.4 oil objective in a Zeiss AX10 microscope and a Coolsnap HQ2 camera (Fisher) at room temperature. Images were aquired using Slidebook 5.0 (3I). Purified rabbit immunoglobulin (TH) and isotype control (G-CSFR) are shown in insets. (B) G-CSF-R mRNA expression was assessed by RT-PCR in SCG neurons and whole BM. (C) SCSGs were cultured in medium containing PBS (n = 6), desipramine (DES; n = 6) at a concentration of 10μM, or 50 ng of G-CSF alone (n = 5) or in combination with anti–G-CSFR Ab (1 μg/mL; n = 3). *P < .05; **P < .005.

Figure 2

The NE reuptake inhibitor desipramine enhances G-CSF–triggered HSC/progenitor mobilization. (A) Treatment scheme of 8-week-old male C57BL/6 mice for HSPC mobilization using G-CSF in combination with desipramine. (B-C) Absolute numbers of CFU-Cs (B) or LSKF cells (C) in the peripheral blood of mice mobilized with G-CSF alone (G) or in combination with desipramine (G+D), respectively (n = 4-5). (D) Gating strategy and representative dot plots to determine LSKF numbers in the peripheral blood of mice mobilized with G-CSF alone or in combination with desipramine, respectively. (E) Long-term culture-initiating cells per milliliter in the blood of mice mobilized as in panel A (n = 4-5). (F) Experimental design to assess the effect of desipramine on G-CSF–induced mobilization in poor mobilizer mice. (G) LSKF cells per femur (n = 12-14) in poor mobilizer mice. (H-I) CFU-Cs (H) and LSKF cells (I) after mobilization in the peripheral blood of poor mobilizer mice (n = 8-7). Dashed lines indicate the mobilization values in nonirradiated mice as determined in panels B and C. *P < .05; **P < .005.