Figure 1. Short-duration, low-dose DFO treatment is sufficient to induce EPC senescence and cell cycle arrest. (A) DFO increased the percentage of SA-βGal activity-positive cells in a dose- and time-dependent manner. Late EPCs were treated with the indicated concentration (μM) of DFO for two, four or six days. Cells were fixed, stained with X-gal and quantified. ** P < 0.01 compared with the untreated group. N=3. (B) DFO increased the proportion of cells remaining in the G0 and G1 phases. The representative cell cycle analysis demonstrates that when different concentrations (0, 1 and 3 μM) of DFO were applied to the same clone of EPCs, there were graded increases in the percentages of cells from the same passage in G0 and G1 arrest, along with reduced percentages of cells in G2 and M phase. The experiment was repeated with three different clones of EPCs with similar results.