SDF-1 stimulates colony formation by PB Inc⁺ CD34⁺ progenitor cells released from quiescence by anti–TGF-β antibody treatment.

PB Inc⁺ CD34⁺ cells, purified after overnight incubation on a plastic support were incubated for 48 hours in serum-free liquid culture medium without cytokine (Stem α A) containing or not containing anti–TGF-β antibody (5 μg/mL) or its isotype IgY control (5 μg/mL). Cells were harvested, counted, and plated in duplicate at a density of 500 cells/mL on methylcellulose medium containing IL3, IL6, IL11, SCF, G-CSF, GM-CSF, and Epo (Stem α ID) in the presence or absence of SDF-1 at various concentrations. Colonies were scored on day 18. (A) Data are expressed as mean percentages of SDF-1 untreated control cells (CT) ± SD calculated by subtracting the percentage of colonies obtained with control CD34⁺cells not treated with anti–TGF-β antibody from that for anti–TGF-β-treated CD34⁺ cells. Control (not treated with SDF-1) colony numbers were 25.4 ± 2.5 (CFU-G); 4.3 ± 1.2 (CFU-M); 1.2 ± 0.6 (CFU-GM); 6.6 ± 1.2 (CFU-Mix); 66 ± 1.6; and 16.6 ± 2 (mature and immature BFU-E, respectively). The control plating efficiency, calculated on the total number of colonies was 37.9% ± 3.3% (n = 3 independent experiments). Photomicrographs of (B) CFU-M and (C) CFU-Mix from anti–TGF-β antibody-treated CD34⁺ cells incubated (B1 and C1) without or (B2 and C2) with SDF-1, × 40. An asterisk indicates significant differences from control values: * .001 < P < .05; ** .0001 < P < .001; *** P < .0001.