title: Formation of the collateral circulation is regulated by vascular endothelial growth factor-A and a disintegrin and metalloprotease family members 10 and 17.
abstract: BACKGROUND
  The density of native (preexisting) collaterals varies widely and is a significant determinant of variation in severity of stroke, myocardial infarction, and peripheral artery disease. However, little is known about mechanisms responsible for formation of the collateral circulation in healthy tissues.
  
  
  OBJECTIVE
  We previously found that variation in vascular endothelial growth factor (VEGF) expression causes differences in collateral density of newborn and adult mice. Herein, we sought to determine mechanisms of collaterogenesis in the embryo and the role of VEGF in this process.
  
  
  RESULTS
  Pial collaterals begin forming between embryonic day 13.5 and 14.5 as sprout-like extensions from arterioles of existing cerebral artery trees. Global VEGF-A overexpressing mice (Vegf(hi/+)) formed more, and Vegf(lo/+) formed fewer, collaterals during embryogenesis, in association with differences in vascular patterning. Conditional global reduction of Vegf or Flk1 only during collaterogenesis significantly reduced collateral formation, but now without affecting vascular patterning, and the effects remained in adulthood. Endothelial-specific Vegf reduction had no effect on collaterogenesis. Endothelial-specific reduction of a disintegrin-and-metalloprotease-domain-10 (Adam10) and inhibition of γ-secretase increased collateral formation, consistent with their roles in VEGF-induced Notch1 activation and suppression of prosprouting signals. Endothelial-specific knockdown of Adam17 reduced collateral formation, consistent with its roles in endothelial cell migration and embryonic vascular stabilization, but not in activation of ligand-bound Notch1. These effects also remained in adulthood.
  
  
  CONCLUSIONS
  Formation of pial collaterals occurs during a narrow developmental window via a sprouting angiogenesis-like mechanism, requires paracrine VEGF stimulation of fetal liver kinase 1-Notch signaling, and adult collateral number is dependent on embryonic collaterogenesis.
authors.affiliation: Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Lucitti
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Mackey
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Morrison
authors.forename: Jody J
authors.initials: JJ
authors.lastname: Haigh
authors.forename: Ralf H
authors.initials: RH
authors.lastname: Adams
authors.forename: James E
authors.initials: JE
authors.lastname: Faber
mesh_terms: D051722:ADAM Proteins / Q000502:physiology*; D000072197:ADAM10 Protein; D000072198:ADAM17 Protein; D053829:Amyloid Precursor Protein Secretases / Q000502:physiology*; D000818:Animals; D003097:Collateral Circulation / Q000235:genetics / Q000502:physiology*; D055785:Gene Knockdown Techniques / Q000379:methods; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D051881:Receptor, Notch1 / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000235:genetics / Q000502:physiology*
chemical_list: D008565:Membrane Proteins; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D040301:Vascular Endothelial Growth Factor Receptor-2; D053829:Amyloid Precursor Protein Secretases; D051722:ADAM Proteins; D000072197:ADAM10 Protein; C491234:Adam10 protein, mouse; D000072198:ADAM17 Protein; C000606463:Adam17 protein, mouse