SDF-1 counteracts apoptosis-associated nuclear DNA degradation in PB Inc⁺CD34⁺ cells.

PB CD34⁺ cells purified immediately after density gradient separation (Inc⁻) or after incubation on a plastic support (Inc⁺) were incubated (1 × 10⁵ cells/mL) under apoptosis-inducing culture conditions (serum- and cytokine-free medium [IMDM]). Freshly isolated cells (A) or cells harvested after a 4-day incubation (B) were processed for apoptosis assessment by “sub-G₁ peak” detection as indicated in “Materials and methods.” The biologic effect of SDF-1 on apoptosis was evaluated by adding rhSDF-1α at various concentrations (0.01, 0.05, 0.1, 0.5 ng/mL) to the culture medium. The percentages of sub-G₁apoptotic cells shown for each histogram are for one experiment representative of the 3 performed. The logarithm fluorescence of PI is expressed in channel numbers. Maximal effect of SDF-1 was obtained for 0.5 ng/mL in Inc⁻ cells and for 0.05 ng/mL in Inc⁺ cells.