Fig. 5. Migration of BM cells to mature muscle cells is independent of SDF-1 and CXCR4 but requires c-met expression. GFP-expressing BM cells (500,000 per well) were placed in the upper chamber of transwells. (A) Migration of CD45⁺ cells and CFU towards MS-5 stroma (i) and C2C12 myotubes (ii) was tested in the absence (stromal cells or muscle cells alone) and presence of SDF-1-neutralizing antibody (white and black bars, respectively), and following treatment of BM with CXCR4-blocking antibody (hatched bars). (B,C) Migration of CD45⁺ cells and progenitors derived from whole BM cells (untreated) and BM cells treated with c-met-blocking antibody (white and black bars, respectively) was examined in response to HGF or bFGF alone (B or C, respectively). Random migration controls consisted of media without HGF or bFGF as indicated (gray bars). (D) The ability of c-met-blocking antibody to inhibit the migration of BM-derived CD45⁺ cells and CFU was determined by placing untreated and anti-c-met-treated BM-MNCs (white and black bars, respectively) in the upper chamber of transwell assays containing MS-5 stromal cells (i) or C2C12 myotubes (ii) in the lower chambers. Pooled results of five separate experiments are given as the percentage of CD45⁺ cells or CFUs that had initially been loaded in the upper chamber (input), and which had then migrated to the lower chamber. (E) Analysis of c-met expression on CD45⁺ cells (gated) engrafting recipient mice transplanted with donor GFP⁺ BM cells, n=3. Significant differences of migration in the absence of antibody or of the percentage of cells migrating to media alone were determined by using Student's t-test (^*P0.05).