Abstract 5423: Adaptation to Oxygen Deprivation in Human Pluripotent Stem Cells, Endothelial Progenitors, and Endothelial Cells
Hypoxia plays an important role during vascular development and regeneration through accumulation of hypoxia-inducible factor 1 alpha (HIF-1alpha) and activation of downstream pathways. We sought to explore the in vitro response of cultures of human embryonic stem cells (hESCs), induced pluripotent stem cells (iPSCs), human endothelial progenitor cells (hEPCs), and human umbilical cord vein endothelial cells (HUVECs) to normoxic and hypoxic oxygen tensions. We first measured cell growth and dissolved O2 (DO) in media of adherent cultures in atmospheric oxygen, physiological oxygen (5% O2) and hypoxic conditions (1% O2). Higher aerobic metabolism was observed in both hESCs and iPSCs cultured in atmospheric oxygen, while hESCs and iPSCs cultured in 5% and 1% O2 had slower or no cell growth, respectively. At each oxygen tension, feeder-free cultured iPSCs were found to consume higher amount of oxygen than feeder-free cultured hESCs. Transport analysis revealed that the oxygen uptake rate (OUR) of hESCs, iPSCs and HUVECs was low as DO availability decreased, whereas the OUR of hEPCs was found to be low only in 1% O2. Next, we examined HIF-1alpha accumulation and the expression of target genes, including VEGF and angiopoietins (angiogenesis), Glut-1 (metabolism), Bnip3 (autophagy) and Bnip3L (apoptosis). Accumulation of HIF-1alpha was detected in all four cell lines cultured in 1% O2. Corresponding upregulation of VEGF, ANGPT2 and GLUT-1 was observed in response to HIF-1alpha accumulation, while upregulation of ANGPT1 was detected only in hESCs. Upregulation of BNIP3 and BNIP3L was detected in hESCs after being cultured for five hours in 5% and 1% O2, which levels corresponded to decreased and no cell growth, respectively. Flow cytometric analysis revealed changes in cell cycle in response to 5% and 1% oxygen tensions. These results demonstrate different cell responses to physiological and hypoxic environments, recognizing that continuous on-line measurements and control over oxygen environments during SC cultures will make it possible to derive desirable cellular responses.