title: Urokinase receptor expression on human microvascular endothelial cells is increased by hypoxia: implications for capillary-like tube formation in a fibrin matrix.
abstract: Hypoxia stimulates angiogenesis, the formation of new blood vessels. This study evaluates the direct effect of hypoxia (1% oxygen) on the angiogenic response of human microvascular endothelial cells (hMVECs) seeded on top of a 3-dimensional fibrin matrix. hMVECs stimulated with fibroblast growth factor-2 (FGF-2) or vascular endothelial growth factor (VEGF) together with tumor necrosis factor-alpha (TNF-alpha) formed 2- to 3-fold more tubular structures under hypoxic conditions than in normoxic (20% oxygen) conditions. In both conditions the in-growth of capillary-like tubular structures into fibrin required cell-bound urokinase-type plasminogen activator (uPA) and plasmin activities. The hypoxia-induced increase in tube formation was accompanied by a decrease in uPA accumulation in the conditioned medium. This decrease in uPA level was completely abolished by uPA receptor-blocking antibodies. During hypoxic culturing uPA receptor activity and messenger RNA (mRNA) were indeed increased. This increase and, as a consequence, an increase in plasmin formation contribute to the hypoxia-induced stimulation of tube formation. A possible contribution of VEGF-A to the increased formation under hypoxic conditions is unlikely because there was no increased VEGF-A expression detected under hypoxic conditions, and the hypoxia-induced tube formation by FGF-2 and TNF-alpha was not inhibited by soluble VEGFR-1 (sVEGFR-1), or by antibodies blocking VEGFR-2. Furthermore, although the alpha(v)-integrin subunit was enhanced by hypoxia, blocking antibodies against alpha(v)beta(3)- and alpha(v)beta(5)-integrins had no effect on hypoxia-induced tube formation. Hypoxia increases uPA association and the angiogenic response of human endothelial cells in a fibrin matrix; the increase in the uPA receptor is an important determinant in this process. (Blood. 2000;96:2775-2783)
authors.affiliation: Gaubius Laboratory TNO-PG, Leiden, The Netherlands.
authors.forename: M E
authors.initials: ME
authors.lastname: Kroon
authors.forename: P
authors.initials: P
authors.lastname: Koolwijk
authors.forename: B
authors.initials: B
authors.lastname: van der Vecht
authors.forename: V W
authors.initials: VW
authors.lastname: van Hinsbergh
mesh_terms: D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics; D015687:Cell Hypoxia; D002470:Cell Survival; D002478:Cells, Cultured; D003470:Culture Media; D017077:Culture Media, Conditioned; D018076:DNA, Complementary / Q000235:genetics; D016228:Endothelial Growth Factors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005109:Extracellular Matrix; D005337:Fibrin; D005341:Fibrinolysin / Q000502:physiology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D039564:Integrin alphaV; D016023:Integrins / Q000037:antagonists & inhibitors / Q000276:immunology; D008222:Lymphokines / Q000494:pharmacology; D009024:Morphogenesis / Q000502:physiology; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D010100:Oxygen / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000502:physiology; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000235:genetics; D017978:Receptors, Growth Factor / Q000037:antagonists & inhibitors / Q000276:immunology; D055293:Receptors, Urokinase Plasminogen Activator; D040262:Receptors, Vascular Endothelial Growth Factor; D019030:Receptors, Vitronectin / Q000037:antagonists & inhibitors / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014568:Urokinase-Type Plasminogen Activator / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A; D040281:Vascular Endothelial Growth Factor Receptor-1; D042442:Vascular Endothelial Growth Factors
chemical_list: D015703:Antigens, CD; D003470:Culture Media; D017077:Culture Media, Conditioned; D018076:DNA, Complementary; D016228:Endothelial Growth Factors; D039564:Integrin alphaV; D016023:Integrins; D008222:Lymphokines; C524898:PLAUR protein, human; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017978:Receptors, Growth Factor; D055293:Receptors, Urokinase Plasminogen Activator; D019030:Receptors, Vitronectin; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C064660:integrin alphaVbeta5; D016222:Fibroblast Growth Factor 2; D005337:Fibrin; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D040281:Vascular Endothelial Growth Factor Receptor-1; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator; D010100:Oxygen