Migration of hematopoietic progenitor cells through Matrigel and the effect of MMP inhibitors. (A) Migration of CD34⁺ cells isolated from steady-state BM and G-CSF–mobilized PB are shown (left bars). Migration of CD34⁻ MNC obtained from the same sources is also presented (right bars). Graph bars show a significant difference between BM and PB CD34⁺ cells (P < .0001) in the percentage of migration, which is expressed as the mean ± SD (n = 3 for BM and n = 5 for PB), whereas the percentage of migration between the MNC was not statistically different (P= .7). (B) Plating efficiency of PB CD34⁺ cells that migrated through Matrigel compared with that of nonmigrating cells. Equal numbers of cells (1 × 10³ cells/mL) from the upper (nonmigrating) and lower (migrating) compartments of Boyden chambers were plated in quadruplicate and colonies were scored for CFU-GM, BFU-E, CFU-GEMM, and CFU-MK after 14 days of incubation at 37°C and 5% CO₂. (C) Effect of MMP inhibitors on the in vitro migration of PB CD34⁺ cells. The final concentrations ofo-phenanthroline, anti-MMP-2, anti-MMP-9, rhTIMP-1, and rhTIMP-2 and the preincubation conditions are described in Materials and Methods. The basal migration of PB CD34⁺ cells was set at 100% (control) and the percentages of migration in the presence of the various inhibitors are represented as the mean ± standard deviation from duplicate experiments relative to the control.