Enforced expression of SDF-1 by BMSSCs mediates cell survival. (A) Proliferation studies were performed by plating high SDF-1–expressing BMSSCs and vector control cell lines in triplicate wells at a density of 5 × 103 cells/well in 96-well plates in regular growth medium for 5 days. Single-cell suspensions were then prepared by trypsin/EDTA digest and counted to assess the total number of cells. (B) Parallel cultures were established in the presence of interleukin 4 (IL-4; 30 ng/mL), and the percentage of apoptotic cells was measured by using trypan blue exclusion. (C) The histogram represents the level of cell surface annexin V staining (solid line) by control cell lines compared with the isotype-matched control antibody (dotted line) cultured in the presence of IL-4. A representative image is shown of the intensity of fluorescence staining on living cells in situ (× 100). (D) The histogram represents the level of cell surface annexin V staining (solid line) by high SDF-1–expressing BMSSC lines compared with the isotype-matched control (dotted line) cultured in the presence of IL-4. A representative image is shown of the intensity of fluorescence staining on living cells in situ (× 100). The data represent the mean values ± standard errors of triplicate experiments. Statistical differences (*) of P < .05 between the SDF-1 high–expressing BMSSC lines and corresponding controls were determined by using the unpaired t test.
