Low-Oxygen Pretreatment Enhances Endothelial Cell Growth and Retention Under Shear Stress

Abstract

Oxygen (O₂) tension is an important factor that regulates endothelial cell (EC) growth and adhesion. We hypothesized that low-O₂ 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-O₂ tension of 5% O₂ upon growth and ECM production of human umbilical vein ECs (HUVECs), in comparison to their counterparts at 20% O₂ on poly(ethylene terephthalate) (PET) films. Low-O₂ pretreatment at 5% O₂ promoted HUVEC proliferation, ECM secretion, and intercellular adhesion. Cell retentions of the endothelialized PET films formed under 5% and 20% O₂ were analyzed by applying shear stress in the range of 5–20 dyn/cm² for up to 24 h under the O₂ of 12% and 20%, mimicking arterial and conventional experimental O₂, respectively. The 5% O₂–pretreated samples exhibited significantly higher cell retention than their normoxic counterparts at high cell density (>30 × 10³ cells/cm²) over extended exposure time (>12 h) when perfused under both 12% and 20% O₂. The endothelium formed under 5% O₂ maintained its ability to respond to perfusion flow by upregulating nitric oxide and prostacyclin production under both O₂ perfusion conditions. The results indicate that pretreatment at 5% O₂ is an effective strategy to enhance endothelialization of vascular grafts by promoting endothelium formation, cell retention, and function.