Hypoxia-induced apoptosis in endothelial cells and embryonic stem cells

Background: To evaluate the influence of hypoxia and molecular events in endothelial and embryonic stem cells. Materials and Methods: Human umbilical vein endothelial cells (HUVECs) and mouse embryoid body (EB) cells were subjected to hypoxic conditions for different time courses. DNA fragmentation assay, quantification of apoptotic cells by TUNEL assay measured by flowcytometry, and Western blot analysis for the molecular events of apoptosis were performed. Results: DNA fragmentation could be identified under hypoxic conditions in HUVECs and mouse EBs. The DNA fragmentation increased when the hypoxic interval was extended. In situ internucleosomal DNA fragmentation-TUNEL assay also found that the percentages of apoptotic cells increased gradually in HUVECs and mouse EBs when the hypoxic interval was extended. Furthermore, the levels of expression of p53 and Bax both increased in hypoxic conditions. Conclusions: Hypoxia increases both HUVEC and mouse EB apoptosis, which is associated with increase in p53/Bax expression.