Effects of cytokine combinations on the cell cycle and early apoptosis of irradiated umbilical cord blood AC133+ cells

The cell cycle and early apoptosis of 2.5 Gy 6 MV-X ray irradiated umbilical cord blood AC133+ cells cultured with cytokine combinations (IL-3 + FL + SCF) were immunolabelled and analyzed by flow cytometry at d 0, 1, 2, 3 and 7. The result of flow cytometry analysis showed that majority of irradiated umbilical cord blood AC133+ cells were in G0/G1 phase of the cell cycle at d 0. Under the influence of cytokine combinations (IL-3 + FL + SCF), nearly 50% of cells were in S phase on 3rd day. AC133+ cells irradiated were in vitro incubated in the medium without cytokines, nearly all cells died by apoptosis. However, when we incubated cells with cytokine combinations (IL-3 + FL + SCF), (38.0 ± 6.8)% of cells were saved from apoptosis at d 2. The more percent of saved AC133+ cells became to proliferate with the extension of culture. In short, cytokine combinations (IL-3 + FL + SCF) could have a key role to protect irradiated cells and partially avoid induction of apoptosis by ionizing radiation in hematopoietics stem/progenitor cells. (authors)