Hypoxia promotes the generation of a versican-rich extracellular matrix by human coronary artery endothelial cells.

Abstract

Normal endothelial cell (EC) function is essential for vascular wall homeostasis, whereas dysfunction increases the risk of cardiovascular disease. Low O2 tension (hypoxia) promotes EC dysfunction and the formation of atherosclerotic plaques. Increasing evidence suggests that hypoxia drives extracellular matrix (ECM) remodeling, an established contributing factor in atherosclerosis. However, the effects of hypoxia on ECs and associated ECM proteins are poorly understood. The aim of this study was to investigate whether the culture of human coronary artery ECs under 1% O2 (hypoxia) alters the ECM generated by these cells, and if this affects HCAEC function. Exposure of HCAECs to 1% O2 resulted in a hypoxic response (HIF-1α stabilization), dysfunction (increased oxidant formation and decreased eNOS), and inflammatory activation (increased IL-6 and ICAM-1 expression). Proteomic analysis of HCAECs cultured under 1% and 20% O2 for 7 days revealed many hypoxia-induced changes to extracellular proteins, particularly increased versican, a key ECM proteoglycan. Increased versican expression and deposition was confirmed at the mRNA and protein level, along with its glycosaminoglycan (chondroitin sulfate) chains and particularly 6-O-sulfated species. This versican-rich ECM showed increased hyaluronan binding and decreased cell adhesiveness, but attached cells proliferated at a greater rate. The generation of a versican-rich ECM under 1% O2 provides a link between hypoxia and atherosclerosis, since versican is reported to accumulate in plaques, where it binds and retains low-density lipoproteins and is involved in inflammatory cell recruitment, thereby potentiating low-density lipoprotein modification and the accumulation of lipid-laden (foam) cells.