title: Single and combined effects of alphavbeta3- and alpha5beta1-integrins on capillary tube formation in a human fibrinous matrix.
abstract: The fibrinous exudate of a wound or tumor stroma facilitates angiogenesis. We studied the involvement of RGD-binding integrins during tube formation in human plasma-derived fibrin clots and human purified fibrin matrices. Capillary-like tube formation by human microvascular endothelial cells in a 3D plasma-derived fibrinous matrix was induced by FGF-2 and TNF-alpha and depended largely on cell-bound u-PA and plasmin activities. While tube formation was minimally affected by the addition of either the alphavbeta3-integrin inhibiting mAb LM609 or the alpha5-integrin inhibiting mAb IIA1, the general RGD-antagonist echistatin completely inhibited this process. Remarkably, when alphavbeta3- and alpha5beta1-integrins were inhibited simultaneously, tube formation was reduced by 78%. It was accompanied by a 44% reduction of u-PA antigen accumulation and 41% less production of fibrin degradation products. alphavbeta5-integrin-blocking antibodies further enhanced the inhibition by mAb LM609 and mAb IIA1 to 94%, but had no effect by themselves. alphav-specific cRGD only inhibited angiogenesis when alpha5beta1-integrin was simultaneously blocked. Endostatin mimicked the effect of alpha5beta1-integrin and inhibited tube formation only in the presence of LM609 or cRGD (73 and 80%, respectively). Comparable results were obtained when purified fibrin matrices were used instead of the plasma-derived fibrinous matrices. These data show that blocking of tube formation in a fibrinous exudate requires the simultaneous inhibition of alphavbeta3- and alpha5beta1-integrins. This may bear impact on attempts to influence angiogenesis in a fibrinous environment.
authors.affiliation: Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Centre Amsterdam, Amsterdam, The Netherlands.
authors.forename: Nancy
authors.initials: N
authors.lastname: Laurens
authors.forename: Marten A
authors.initials: MA
authors.lastname: Engelse
authors.forename: Clarissa
authors.initials: C
authors.lastname: Jungerius
authors.forename: Clemens W
authors.initials: CW
authors.lastname: Löwik
authors.forename: Victor W M
authors.initials: VW
authors.lastname: van Hinsbergh
authors.forename: Pieter
authors.initials: P
authors.lastname: Koolwijk
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000494:pharmacology*; D002196:Capillaries / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D004338:Drug Combinations; D004353:Drug Evaluation, Preclinical; D043169:Endostatins / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D005109:Extracellular Matrix / Q000737:chemistry; D005337:Fibrin / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D039081:Integrin alpha5beta1 / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000502:physiology; D039302:Integrin alphaVbeta3 / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000502:physiology; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D009842:Oligopeptides / Q000378:metabolism; D011485:Protein Binding; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
chemical_list: D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D004338:Drug Combinations; D043169:Endostatins; D039081:Integrin alpha5beta1; D039302:Integrin alphaVbeta3; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid; D005337:Fibrin; D014568:Urokinase-Type Plasminogen Activator