Urokinase receptor expression on human microvascular endothelial cells is increased by hypoxia: implications for capillary-like tube formation in a fibrin matrix

Blood. 2000 Oct 15;96(8):2775-83.

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)

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / biosynthesis
  • Antigens, CD / genetics
  • Cell Hypoxia
  • Cell Survival
  • Cells, Cultured
  • Culture Media
  • Culture Media, Conditioned
  • DNA, Complementary / genetics
  • Endothelial Growth Factors / pharmacology
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / metabolism*
  • Extracellular Matrix
  • Fibrin
  • Fibrinolysin / physiology
  • Fibroblast Growth Factor 2 / pharmacology
  • Gene Expression Regulation / drug effects
  • Humans
  • Hypoxia / physiopathology*
  • Integrin alphaV
  • Integrins / antagonists & inhibitors
  • Integrins / immunology
  • Lymphokines / pharmacology
  • Morphogenesis / physiology
  • Neovascularization, Pathologic / physiopathology*
  • Oxygen / pharmacology
  • Proto-Oncogene Proteins / physiology
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Receptor Protein-Tyrosine Kinases / antagonists & inhibitors
  • Receptor Protein-Tyrosine Kinases / immunology
  • Receptor Protein-Tyrosine Kinases / physiology
  • Receptors, Cell Surface / biosynthesis*
  • Receptors, Cell Surface / genetics
  • Receptors, Growth Factor / antagonists & inhibitors
  • Receptors, Growth Factor / immunology
  • Receptors, Urokinase Plasminogen Activator
  • Receptors, Vascular Endothelial Growth Factor
  • Receptors, Vitronectin / antagonists & inhibitors
  • Receptors, Vitronectin / immunology
  • Tumor Necrosis Factor-alpha / pharmacology
  • Urokinase-Type Plasminogen Activator / physiology
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factor Receptor-1
  • Vascular Endothelial Growth Factors

Substances

  • Antigens, CD
  • Culture Media
  • Culture Media, Conditioned
  • DNA, Complementary
  • Endothelial Growth Factors
  • Integrin alphaV
  • Integrins
  • Lymphokines
  • PLAUR protein, human
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • Receptors, Cell Surface
  • Receptors, Growth Factor
  • Receptors, Urokinase Plasminogen Activator
  • Receptors, Vitronectin
  • Tumor Necrosis Factor-alpha
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors
  • integrin alphaVbeta5
  • Fibroblast Growth Factor 2
  • Fibrin
  • Receptor Protein-Tyrosine Kinases
  • Receptors, Vascular Endothelial Growth Factor
  • Vascular Endothelial Growth Factor Receptor-1
  • Fibrinolysin
  • Urokinase-Type Plasminogen Activator
  • Oxygen