Figure 2.

Stromal-derived SDF-1 is a chemoattractant for human and mouse hematopoietic progenitor cells. (A) Chemotaxis assay of cord blood (CB) CD34⁺ cells in response to various concentration of SDF-1 (10, 30, 100, 300, 1,000 ng/ml). Results represent the average and the range of three experiments performed in duplicates. Data are expressed as the percent of input cells that migrated. The percentage of migration of CB CD34⁺ to undiluted MS-5 supernatant in the same experiments was used as control and is shown as a bar diagram on the right (n = 3). (B) Chemotactic response to SDF-1 of clonogenic progenitors (CFC). The graph shows the number of CFU-GM, BFU-E, and CFU-MIX progenitors from human CB CD34⁺ cells that migrated to 300 ng/ml of SDF-1 or control media in a chemotaxis assay. (C) Transendothelial chemotaxis in vitro of human bone marrow (BM) or mobilized peripheral blood (PB) CD34⁺ cells in response to different concentration of SDF-1. Results show the average and the range of three experiments performed in duplicates. (D) Transendothelial chemotaxis of mobilized PB CD34⁺ cells in response to SDF-1 or to various chemoattractants and cytokines at the concentrations described in the Materials and Methods. (E) Transendothelial chemotaxis in vitro of the mouse progenitor cell lines FDCP-MIX and M1 in response to SDF-1. (F). In vivo delivery of SDF-1 into mouse spleens increases the seeding of intravenously transplanted FDCP-MIX cells in this organ. Experimental mice were injected intrasplenically with SDF-1 and control mice were injected with MIP-1α or with PBS and then transplanted i.v. with PKH-26-labeled FDCP-MIX cells, as described in Materials and Methods (three experimental mice and three control mice per experiment; three separate experiments performed). 3 h after the injection, mice were killed and 5 × 10⁵ splenocytes plated in duplicate in a clonogenic assay for FDCP-MIX. After 72 h, the plates were counted on an inverted fluorescent microscope and scored for the number of fluorescent colonies. Results show the significant increase in FDCP-MIX clonogenic precursors per SDF-1 injected spleens relative to control injected spleens. Data shown are from three experiments: *P <0.005.