Angiopoietin-1 and its receptor Tie-2 participate in the regulation of capillary-like tubule formation and survival of endothelial cells.
Angiopoietin-1 (Ang-1) and its receptor Tie-2, a trans-membrane tyrosine kinase uniquely expressed by endothelial cells, are shown by null mutation studies to be essential to developmental angiogenesis. The phenotypic abnormalities in these knockout animals suggest that Tie-2 signaling is necessary for the maintenance and expansion of the primitive capillary network. We present in vitro evidence indicating that the Ang-1/Tie-2 system participates in the regulation of capillary tubule formation and is necessary for the survival of confluent endothelial cells. Although recombinant Ang-1, which induces Tie-2 phosphorylation, has no effect on the proliferation of endothelial cells, treatment of confluent adult bovine aortic endothelial cells (ABAE) cells grown on collagen gels with Ang-1 (100 ng/ml) causes the cells to migrate into the collagen gel and form capillary-like tubules. The tubule-forming effect of Ang-1 is similar to the effect caused by FGF-2. A soluble form of the Tie-2 extracellular domain, in fivefold molar excess, blocks Ang-1-induced tubule formation. Specific elimination of Tie-2 protein expression in cultured ABAE cells as a result of transfection with an antisense oligonucleotide causes cell death in a dose-dependent manner (IC(50) = 50 nM). The antisense treatment has no effect on cells that do not express Tie-2. Cells treated with antisense oligonucleotide show a sixfold increase in the rate of apoptosis as assessed by in situ end labeling of fragmented DNA. These findings are consistent with the view that Ang-1/Tie-2 signaling is essential for both angiogenesis and endothelial cell survival.
Hayes
A J
AJ
Lombardi Cancer Center, Georgetown University Medical Center, 3970 Reservoir Road, Washington, DC 20007, USA.
Huang
W Q
WQ
Mallah
J
J
Yang
D
D
Lippman
M E
ME
Li
L Y
LY
D016475:3T3 Cells; D042683:Angiopoietin-1; D000818:Animals; D001483:Base Sequence; D002196:Capillaries / Q000166:cytology / Q000254:growth & development / Q000502:physiology; D002417:Cattle; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000254:growth & development* / Q000502:physiology; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018919:Neovascularization, Physiologic / Q000187:drug effects; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D042787:Receptor, TIE-2; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction
D042683:Angiopoietin-1; C467628:Angpt1 protein, mouse; D008562:Membrane Glycoproteins; D020319:Oligodeoxyribonucleotides, Antisense; D011994:Recombinant Proteins; D020794:Receptor Protein-Tyrosine Kinases; D042787:Receptor, TIE-2