title: Endothelial beta1 integrins regulate sprouting and network formation during vascular development.
abstract: beta1 integrins are important regulators of vascular differentiation and development, as their endothelial-specific deletion results in embryonic lethality. In the present study, we investigated the molecular mechanisms underlying the prominent vascular abnormalities that occur in the absence of beta1 integrins. Because of the early embryonic lethality of knockout mice, we studied endothelial cell and vessel development in beta1-integrin-deficient murine embryonic stem cells to gain novel insights into the role of beta1 integrins in vasculo-angiogenesis. We found that vessel development was strongly defective in the mutant embryoid bodies (EBs), as only primitive and short sprouts developed from clusters of vascular precursors in beta1 integrin(-/-) EBs, whereas complex network formation of endothelial tubes was observed in wild-type EBs. The vascular defect was due to deficient beta1 integrin expression in endothelial cells, as its endothelial-specific re-expression rescued the phenotype entirely. The mechanism responsible for defective vessel formation was found to be reduced endothelial cell maturation, migration and elongation. Moreover, the lower number of endothelial cells in beta1 integrin(-/-) EBs was due to an increased apoptosis versus proliferation rate. The enhanced apoptosis and proliferation of beta1 integrin(-/-) endothelial cells was related to the elevation of peNOS and pAKT signaling molecules, respectively. Our data demonstrate that endothelial beta1 integrins are determinants of vessel formation and that this effect is mediated via different signaling pathways.
authors.affiliation: Institute of Physiology I, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Malan
authors.forename: Daniela
authors.initials: D
authors.lastname: Wenzel
authors.forename: Annette
authors.initials: A
authors.lastname: Schmidt
authors.forename: Caroline
authors.initials: C
authors.lastname: Geisen
authors.forename: Axel
authors.initials: A
authors.lastname: Raible
authors.forename: Birgit
authors.initials: B
authors.lastname: Bölck
authors.forename: Bernd K
authors.initials: BK
authors.lastname: Fleischmann
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Bloch
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001808:Blood Vessels / Q000196:embryology* / Q000378:metabolism; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D002478:Cells, Cultured; D047108:Embryonic Development / Q000235:genetics / Q000502:physiology; D042783:Endothelial Cells / Q000378:metabolism / Q000502:physiology; D004730:Endothelium, Vascular / Q000196:embryology / Q000502:physiology; D005109:Extracellular Matrix / Q000378:metabolism / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D019012:Integrin beta1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018919:Neovascularization, Physiologic / Q000235:genetics*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D030781:Organisms, Genetically Modified
chemical_list: D019012:Integrin beta1; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse