To evaluate the number of circulating progenitor cells after mobilization, a colony-forming cell assay was employed. Red blood cells (RBCs) were lysed with BD Pharm Lyse buffer (BD Biosciences, San Jose, CA; http://www.bdbiosciences.com). Nucleated cells were subsequently washed twice and used for colony-formation assays. Briefly, cells were resuspended in methylcellulose base media provided by the manufacturer (R&D Systems, Inc., Minneapolis, MN; http://www.rndsystems.com) supplemented with granulocyte macrophage colony-stimulating factor (GM-CSF, 25 ng/ml) plus interleukin-3 (IL-3, 10 ng/ml) for colony forming units (CFU) granulocyte/macrophage (GM), granulocyte colony stimulating factor (G-CSF, 20 ng/ml) for CFU-granulocyte (G), macrophage colony stimulating factor (M-CSF, 10 ng/ml) for CFU macrophage (M), erythropoietin (EPO, 5 unit/ml, Stem cell Tech, http://www.stemcell.) plus stem cell factor (SCF, 5 ng/ml) for burst-forming units (BFU-E), and thrombopoietin (TPO, 100 ng/ml) for CFU-megakaryocytes (Megs). All growth factors were purchased from the same company unless otherwise mentioned. Cultures were incubated for 7 days, at which time they were scored under an inverted microscope for the number of each colonies.