Selective homing of CD34⁺ cells in a CXCR4-dependent manner.

PKH26-labeled CD34⁺ cells were injected into NOD/SCID mice, either untreated or after blocking with 10 μg mAb for human CXCR4 per 10⁶ cells, as indicated. (A) The number of homing PKH26⁺ cells in the murine tissues 4 and 8 hours after transplantation is shown. Cells from the same organs of noninjected mice were used as a negative control. (B) Human progenitor cells in the BM or spleen of transplanted mice 8 hours after transplantation. Number of human colonies per total BM of one mouse. Data represent mean ± SE from 6 experiments, n = 9 mice/group, *P < .05. (C) Nonirradiated NOD/SCID mice were injected with 1 μg human SDF-1 directly into the BM of the femur (upper panel) or into the spleen (lower panel). Mice were further transplanted immediately with 1 × 10⁶ CD34⁺ cells/mouse either untreated (ii) or preincubated with antihuman CXCR4 mAb (iii). Noninjected organs were used as a negative control (i). Data indicate number of human cells per 10⁶ acquired cells. A representative experiment from 3 performed is shown. Similar results (P < .05) were obtained in all 3 experiments performed, n = 12 mice. (D) Enriched CD34⁺ cells were incubated for 48 hours with 50 ng/mL SCF+IL-6 and assayed for migration levels (i). NOD/SCID mice were transplanted with stimulated or unstimulated cells. Murine BM and spleen were harvested 16 hours later and assayed for the growth of human colonies (ii). Data shown is from 4 experiments, n = 8 mice.