title: In vivo detection of activated platelets allows characterizing rupture of atherosclerotic plaques with molecular magnetic resonance imaging in mice.
abstract: BACKGROUND
  Early and non-invasive detection of platelets on micro atherothrombosis provides a means to identify unstable plaque and thereby allowing prophylactic treatment towards prevention of stroke or myocardial infarction. Molecular magnetic resonance imaging (mMRI) of activated platelets as early markers of plaque rupture using targeted contrast agents is a promising strategy. In this study, we aim to specifically image activated platelets in murine atherothrombosis by in vivo mMRI, using a dedicated animal model of plaque rupture.
  
  
  METHODS
  An antibody targeting ligand-induced binding sites (LIBS) on the glycoprotein IIb/IIIa-receptor of activated platelets was conjugated to microparticles of iron oxide (MPIO) to form the LIBS-MPIO contrast agent causing a signal-extinction in T2*-weighted MRI. ApoE(-/-) mice (60 weeks-old) were fed a high fat diet for 5 weeks. Using a small needle, the surface of their carotid plaques was scratched under blood flow to induce atherothrombosis. In vivo 9.4 Tesla MRI was performed before and repetitively after intravenous injection of either LIBS-MPIO versus non-targeted-MPIO.
  
  
  RESULTS
  LIBS-MPIO injected animals showed a significant signal extinction (p<0.05) in MRI, corresponding to the site of plaque rupture and atherothrombosis in histology. The signal attenuation was effective for atherothrombosis occupying ≥ 2% of the vascular lumen. Histology further confirmed significant binding of LIBS-MPIO compared to control-MPIO on the thrombus developing on the surface of ruptured plaques (p<0.01).
  
  
  CONCLUSIONS
  in vivo mMRI detected activated platelets on mechanically ruptured atherosclerotic plaques in ApoE(-/-) mice with a high sensititvity. This imaging technology represents a unique opportunity for noninvasive detection of atherothrombosis and the identification of unstable atherosclerotic plaques with the ultimate promise to prevent strokes and myocardial infarctions.
authors.affiliation: Department of Radiology/Medical Physics, University Hospital, Freiburg, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: von Elverfeldt
authors.forename: Constantin
authors.initials: C
authors.lastname: von zur Muhlen
authors.forename: Kristina
authors.initials: K
authors.lastname: Wiens
authors.forename: Irene
authors.initials: I
authors.lastname: Neudorfer
authors.forename: Andreas
authors.initials: A
authors.lastname: Zirlik
authors.forename: Mirko
authors.initials: M
authors.lastname: Meissner
authors.forename: Peg
authors.initials: P
authors.lastname: Tilly
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Charles
authors.forename: Christoph
authors.initials: C
authors.lastname: Bode
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Peter
authors.forename: Jean-Etienne
authors.initials: JE
authors.lastname: Fabre
mesh_terms: D000818:Animals; D001665:Binding Sites; D005290:Ferric Compounds; D008024:Ligands; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D057054:Molecular Imaging / Q000379:methods*; D058226:Plaque, Atherosclerotic / Q000175:diagnosis* / Q000503:physiopathology*; D015539:Platelet Activation / Q000502:physiology*; D012421:Rupture; D013927:Thrombosis / Q000150:complications / Q000473:pathology
chemical_list: D005290:Ferric Compounds; D008024:Ligands; C000499:ferric oxide