Mean telomere length and telomerase activity of human umbilical vein endothelial cells (HUVECs) cultured in hypoxic conditions were measured. Subtelomeric methylation status of these cells was assessed by genomic Southern blot with telomere DNA probe using methylation-sensitive and -insensitive isoschizomers, MspI and HpaII.
The telomerase activity in HUVECs correlated inversely with the oxygen concentration. Mild hypoxia (10 or 15%oxygen) increased the telomere lengths, whereas the telomere lengths did not appear to change when <1%O2. The subtelomere of the shortest telomere range was methylated the most at 1%O2.
Subtelomeric hypermethylation of short telomeres at 1%O2 compared to milder hypoxia implied that the subtelomeric hypermethylation may yield telomere stability and favor the cell survival of short telomere-bearing cells.