In vivo depletion of macrophages with clodronate-loaded liposomes mobilizes HSCs. (A) Effect of a 2-day treatment with clo-lip and PBS-lip on the number of BM F4/80⁺Ly-6G⁻CD11b⁺ (F⁺G⁻), F4/80⁺Ly-6G⁺CD11b⁺ (F⁺G⁺) macrophages and F4/80⁻Ly-6G⁺CD11b⁺ (F⁻G⁺) granulocytes measured by flow cytometry. The 2 dot-plots illustrate the loss of F⁺G⁺. Data are mean ± SD of 4 mice per group. (B) Effect of liposomes on the number of circulating Lin⁻Sca1⁺KIT⁺ HSPCs and CFCs. Data are mean ± SD of 4 mice per group. (C) Mobilization of long-term reconstituting HSCs in competitive repopulation assay. Test donor CD45.2⁺ mice were injected with clo-lip for 2 or 4 days, or PBS-lip for 4 days. Next, 50 μL blood was transplanted in competition with 200 000 competing CD45.1⁺ BM cells into lethally irradiated CD45.1⁺ recipients. Donor CD45.2⁺ contribution was measured in CD45⁺ leukocytes, myeloid, B, and T cells 16 weeks after transplantation. Contribution was estimated to be positive when the proportion of CD45.2⁺ donor cells was above 0.5% in each lineage. ***P < .001, **P < .01, and *P < .05 between PSB-lip– and clo-lip–treated mice.