title: Noninvasive assessment of angiogenesis by ultrasound and microbubbles targeted to alpha(v)-integrins.
abstract: BACKGROUND
  Noninvasive methods for characterizing neovessel formation during angiogenesis are currently lacking. We hypothesized that angiogenesis could be imaged with the use of contrast-enhanced ultrasound (CEU) with microbubbles targeted to alpha(v)-integrins.
  
  
  RESULTS
  Microbubbles targeted to alpha(v)-integrins were prepared by conjugating echistatin (MB(E)) or monoclonal antibody against murine alpha(v) (MB(alpha)) to their surface. Control microbubbles (MB(c)) were also prepared. The microvascular behavior of these microbubbles was assessed by intravital microscopy of the cremaster muscle in mice treated for 4 days with sustained-release FGF-2. Microvascular retention was much greater (P<0.01) for MB(E) (11+/-6 mm(-3)) and MB(alpha) (10+/-7 mm(-3)) than that for MB(c) (1+/-1 mm(-3)). Retained MB(E) and MB(alpha) attached directly to the microvascular endothelial surface. Microbubble retention in 4 control mice was minimal. Subcutaneous matrigel plugs enriched with FGF-2 were created in 12 mice and studied 10 days later. Neovessels within the matrigel stained positive for alpha(v)-integrins. CEU demonstrated greater (P<0.01) acoustic intensity for MB(E) (16.0+/-5.9 U) and MB(alpha) (17.0+/-5.5 U) compared with MB(c) (5.8+/-2.6 U). The signal from targeted microbubbles (MB(E) and MB(alpha)) correlated well (r=0.90) with the matrigel blood volume determined by CEU perfusion imaging.
  
  
  CONCLUSIONS
  CEU with microbubbles targeted for alpha(v)-integrins may provide a noninvasive method for assessing therapeutic angiogenesis.
authors.affiliation: Cardiovascular Imaging Center, Cardiovascular Division, University of Virginia, Charlottesville 22908, USA.
authors.forename: Howard
authors.initials: H
authors.lastname: Leong-Poi
authors.forename: Jonathan
authors.initials: J
authors.lastname: Christiansen
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Klibanov
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Kaul
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Lindner
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001808:Blood Vessels / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000254:growth & development*; D002478:Cells, Cultured; D003094:Collagen; D004338:Drug Combinations; D004730:Endothelium, Vascular / Q000000981:diagnostic imaging; D039564:Integrin alphaV / Q000032:analysis* / Q000276:immunology; D036341:Intercellular Signaling Peptides and Proteins; D007797:Laminin; D051379:Mice; D008833:Microcirculation / Q000000981:diagnostic imaging; D018613:Microscopy, Confocal; D018482:Muscle, Skeletal / Q000098:blood supply; D018919:Neovascularization, Physiologic; D010455:Peptides; D011509:Proteoglycans; D014463:Ultrasonography / Q000379:methods*
chemical_list: D000911:Antibodies, Monoclonal; D004338:Drug Combinations; D039564:Integrin alphaV; D036341:Intercellular Signaling Peptides and Proteins; D007797:Laminin; D010455:Peptides; D011509:Proteoglycans; C057986:echistatin; C059485:matrigel; D003094:Collagen