A new cell culture system has been developed that reflects the vascular microenvironment. By means of this system the cultured cells are exposed not only to shear stress by the circulating culture medium, but also to an oxygen concentration gradient and certain critical blood components such as low-density lipoprotein (LDL) and monocytes. DNA microarray analysis was performed for human umbilical vein endothelial cells cultured in this system in the absence and presence of laminar flow at a low shear stress, 0.2 dyn/cm(2). In addition to shear stress, either an oxygen concentration gradient, or LDL (1 mg/ml), or both were applied. Many Nrf-2-regulating genes, such as heme oxygenase 1, NAD(P)H quinone oxidoreductase 1, solute carrier family 7 No. 11, and glutamate-cysteine ligase modifier subunit, were induced by laminar flow at very low shear stress regardless of the additional conditions. Certain genes were specifically affected by exposure to the oxygen gradient and/or LDL under shear stress, but the degree was very low. These results suggest that shear stress is the most critical factor affecting gene expression in endothelial cells and that Nrf-2-regulating proteins may contribute to protecting endothelial cells against other vascular stress. This system should provide highly relevant and useful information about both vascular physiology and pathology, in the latter on such urgent matters as the specific steps involved in atherogenesis.