Accelerated hematopoietic recovery in HO-1^+/− mice treated with 5-FU and reconstitution in recipients of large numbers of HO-1^+/− BM cells. (A) Leukocyte counts of HO-1^+/− mice after myelotoxic injury. HO-1^+/− or HO-1^+/+ mice (n = 10) were treated with a single dose of 5-FU (150 mg/kg intraperitoneally), and leukocyte counts in the peripheral blood were performed at different time points after treatment and are shown as a mean (± SD) percentage of normal leukocyte count. (B,C) Hematopoietic engraftment from HO-1–deficient BM cells in lethally irradiated recipients. BM cells (5 × 10⁶) from luc⁺HO-1^+/− or luc⁺HO-1^+/+ mice were transferred into lethally irradiated recipients (n = 4) and hematopoietic engraftment was monitored by BLI. Representative BLI images of the recipients of luc⁺HO-1^+/− or luc⁺HO-1^+/+ cells at day 18 are displayed at the same scale (B). Time course of hematopoietic reconstitution, as measured by whole-body bioluminescent intensity (mean ± SD, photons/s) over time (C). (D) Representative FACS plots and (E) relative trend of CFSE⁺Lin⁻Sca-1⁺ cell distribution versus number of cell division in vivo. Nucleated BM cells (1 × 10⁷) from either HO-1^+/− or HO-1^+/+ mice were labeled by CFSE (1 μM) and transferred into lethally irradiated recipients. Cells recovered from the BM of the recipients 48 hours after transfer were pooled (3 mice/group) and costained by antibodies against lineage markers and Sca-1. The number of cell divisions and cell distribution were analyzed by CFSE intensity after gating for the Lin⁻Sca-1⁺ population. Values are absolute (D) or relative (E) mean percentages (n = 4) of cells undergoing different numbers of cell divisions from 2 different experiments.