Characterization of Alde-High and Alde-Low EPCs under hypoxic conditions. (A) HUVECs and EPCs were incubated in 20% (left) or 5% (right) oxygen and harvested every 24 hours until the cultures reached confluency. The average cell number in triplicate dishes was determined (mean ± SD) by counting. Note that HUVECs (crisscross) reached a plateau at lower number of cells, and the growth rate of Alde-Low cells (white squares) was faster than that of Alde-High cells (black circles) under normoxic and hypoxic conditions. (B-G) EC tube formation on Matrigel. HUVECs (B,E), Alde-High EPCs (C,F), and Alde-Low EPCs (D,G) were plated on Matrigel and cultured under normoxic (20% O2) or hypoxic (5% O2) conditions for 8 to 12 hours. (H) The number of tubes formed on Matrigel was scored in each field using microscopy and the mean ± SD was obtained from triplicate wells. a indicates HUVECs versus Alde-High EPCs; b, HUVECs versus Alde-Low EPCs; and c, Alde-High versus Alde-Low EPCs; **P < .01.
