Figure 3. Hypoxia induced senescence. (A) HUVECs were cultured in normoxic conditions (i) or under hypoxic conditions (0.5% oxygen) for 5 days and then stained for SA-β-gal and Eosin counter-staining (ii). Bar=100μm. (B) The number of senescent cells per random field was counted after 5 days treatment at different oxygen tensions. The number of senescent cells at each oxygen tension is normalised to the number of cells in normoxic conditions using matched lines (mean of four experiments per oxygen tension ± SD. * P<0.05, paired Student's t-test). (C) Cell growth was compared at normoxia (squares), 1% oxygen (circles) and 0.5% oxygen (triangle) for 5 days. Cells were seeded 24 hours (Day −1) prior to being placed into the hypoxic incubator on day 0 (mean of four experiments per oxygen tension ± SD. *** P<0.001, paired Student's t-test). (D) HUVECs were untreated (i) or treated with 10μM DFO for 72 hrs (ii) then fixed and stained for SA-β-gal. This is a representative of 3 HUVEC lines. Bar=100μm.