Low-oxygen pretreatment enhances endothelial cell growth and retention under shear stress

Oxygen (O(2)) tension is an important factor that regulates endothelial cell (EC) growth and adhesion. We hypothesized that low-O(2) treatment of ECs improves the endothelialization and cell retention upon physiologically relevant perfusion flow, due to enhanced cell proliferation and extracellular matrix (ECM) secretion. We assessed the effects of a low-O(2) tension of 5% O(2) upon growth and ECM production of human umbilical vein ECs (HUVECs), in comparison to their counterparts at 20% O(2) on poly(ethylene terephthalate) (PET) films. Low-O(2) pretreatment at 5% O(2) promoted HUVEC proliferation, ECM secretion, and intercellular adhesion. Cell retentions of the endothelialized PET films formed under 5% and 20% O(2) were analyzed by applying shear stress in the range of 5-20 dyn/cm(2) for up to 24 h under the O(2) of 12% and 20%, mimicking arterial and conventional experimental O(2), respectively. The 5% O(2)-pretreated samples exhibited significantly higher cell retention than their normoxic counterparts at high cell density (>30 x 10(3) cells/cm(2)) over extended exposure time (>12 h) when perfused under both 12% and 20% O(2). The endothelium formed under 5% O(2) maintained its ability to respond to perfusion flow by upregulating nitric oxide and prostacyclin production under both O(2) perfusion conditions. The results indicate that pretreatment at 5% O(2) is an effective strategy to enhance endothelialization of vascular grafts by promoting endothelium formation, cell retention, and function.