Transplanted BM-derived ALDH^hi cells are recruited to the ischemic limb. (A,B) Representative FACS showing removal of noncellular events (R1) and selection of ALDH^hiFe[750]^lo (R2 = 47.3% ± 9.9%) and ALDH^hiFe[750]^hi (R3 = 22.5% ± 6.5%) nanoparticle-labeled cells (n = 5). (C) Prussian blue staining of sorted ALDH^hiFe[750]^hi cells shows cytoplasmic accumulation of iron nanoparticles. (D) Recruitment of ALDH^hiFe[750]^hi cells to the site of ischemic injury 24 to 48 hours after transplantation demonstrated by Kodak multimodal imaging. Intense signal beside mouse limb represents internal standard for Fe[750] fluorescence. (E) Two days after MNC injection, CD45⁺ cells (brown) were detected near arterioles (, inset), and GUSB⁺ human cells (red) that were negative for CD45 expression were detected adjacent to muscle fibers () in the ischemic limb. (F) Human cells were not detected in the ischemic limbs of mice transplanted with BM ALDH^lo cells. (G) After injection of ALDH^hi cells, GUSB⁺CD45⁻ human cells were detected adjacent to vascular structures and muscle fibers as early as 2 days after transplantation and remained for up to 30 days after transplantation (). (H,I) Transplantation of ALDH^hiFe[750]^hi cells produced increased fluorescence in the ischemic limb at 1 and 7 days. Fluorescent signal was cleared from the ischemic limb by 14 days after transplantation (n = 3).