SDF-1 promotes survival of sorted clonogenic CD34⁺ progenitors.

PB CD34⁺ cells were purified after overnight incubation on a plastic support (Inc⁺) (A,B) or directly after density gradient separation (Inc⁻) (C,D) and sorted according to CD38 expression: CD34⁺CD38⁻ cells (A,C) and CD34⁺CD38⁺ cells (B,D). The role of exogenous SDF-1 was evaluated on Inc⁺ cells. The role of intracellular SDF-1 was evaluated by adding an anti–SDF-1 neutralizing antibody on Inc⁻ cells. Inc⁺ or Inc⁻ cells (1.5 × 10⁵/mL) were incubated for 72 hours under apoptosis-inducing culture conditions in the presence or not of SDF-1 (0.05 ng/mL) or anti–SDF-1 (10 ng/mL). Cells were harvested, counted, and processed for viability by trypan blue exclusion before plating in duplicate at a density of 2000 cells/mL on semisolid medium. Colonies were scored on day 14. Results are expressed as mean percentages of SDF-1 or anti–SDF-1 untreated control cells (CT) ± SD. Numbers of control colonies, derived from untreated CD34⁺ incubated under apoptosis conditions for 72 hours, were 11.25 ± 4.4 and 37.25 ± 10.2 (BFU-E); 6.50 ± 3.25 and 29 ± 8.5 (CFU-G); 1.5 ± 0.5 and 7.75 ± 2.2 (CFU-M); 2 ± 0.5 and 1.5 ± 0.5 (CFU-GM); 2 ± 1.5 and 0.75 ± 0.25 (CFU-Mix) from Inc⁺CD34⁺CD38⁻ and Inc⁺CD34⁺CD38⁺ cells, respectively, and 31.5 ± 7 and 119.75 ± 50.2 (BFU-E); 33 ± 7.2 and 51 ± 7.3 (CFU-G); 11.5 ± 2 and 23.75 ± 3.6 (CFU-M); 2 ± 1.4 and 5.5 ± 1.5 (CFU-GM); 2.5 ± 0.8 and 2.25 ± 0.4 (CFU-Mix) from Inc⁻CD34⁺CD38⁻ and Inc⁻CD34⁺CD38⁺ cells, respectively. The control plating efficiency (calculated for the total number of colonies) was 1% ± 0.85% and 4.6% ± 2.1% for Inc⁺ and Inc⁻CD34⁺CD38⁻ cells, respectively, and 3.8% ± 0.7% and 11.5% ± 4.4% for Inc⁺ and Inc⁻CD34⁺CD38⁺ cells, respectively (n = 3 independent experiments). The asterisk indicates significant difference from control values, P < .05.