title: In vivo isotopically labeled atherosclerotic aorta plaques in ApoE KO mice and molecular profiling by matrix-assisted laser desorption/ionization mass spectrometric imaging.
abstract: BACKGROUND
  The ability to quantify rates of formation, regression and/or remodeling of atherosclerotic plaque should facilitate a better understanding of the pathogenesis and management of cardiovascular disease. In the current study, we coupled a stable isotope labeled tracer protocol with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to examine spatial and temporal lipid dynamics in atherosclerotic plaque.
  
  
  METHODS
  To promote plaque formation in the aorta region, ApoE KO mice were fed a high cholesterol diet (0.15% cholesterol) and orally dosed with (2,2,3,4,4,6-d(6))-cholesterol over several weeks. Tissue sections of ~10 µm thickness were analyzed by MALDI-MSI using matrix deposition by either chemical sublimation or acoustic droplet ejection.
  
  
  RESULTS
  MALDI-MSI yielded distinct spatial distribution information for a variety of lipid classes including specific lysophosphatidylcholines typically associated with atherosclerosis-related tissue damage such as phospholipase 2 (Lp-PLA(2)) that mediate chemotactic responses to inflammation (e.g. LPC 16:0, LPC 18:0 and LPC 18:1) as well as free cholesterol and cholesteryl esters that contribute to atheroma formation. MALDI mass spectra acquired from aorta tissue sections clearly distinguished non-esterified and esterified versions of (2,2,3,4,4,6-d(6))-cholesterol within aortic plaque regions and showed distinct spatial accumulation of the cholesterol tracer.
  
  
  CONCLUSIONS
  The ability to couple stable isotope based protocols with MALDI-MSI enables a novel strategy to characterize the effects of therapeutic treatments on atherosclerotic plaque formation, regression and potential remodeling of the complex lipid components with high chemical specificity and spatiotemporal information.
authors.affiliation: Merck & Co., Inc, Merck Research Laboratories, Kenilworth, NJ, 07033, USA.
authors.forename: Jose
authors.initials: J
authors.lastname: Castro-Perez
authors.forename: Nathan
authors.initials: N
authors.lastname: Hatcher
authors.forename: Nana
authors.initials: N
authors.lastname: Kofi Karikari
authors.forename: Sheng-Ping
authors.initials: SP
authors.lastname: Wang
authors.forename: Vivienne
authors.initials: V
authors.lastname: Mendoza
authors.forename: Henry
authors.initials: H
authors.lastname: Shion
authors.forename: Alan
authors.initials: A
authors.lastname: Millar
authors.forename: John
authors.initials: J
authors.lastname: Shockcor
authors.forename: Mark
authors.initials: M
authors.lastname: Towers
authors.forename: David
authors.initials: D
authors.lastname: McLaren
authors.forename: Vinit
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authors.lastname: Shah
authors.forename: Stephen
authors.initials: S
authors.lastname: Previs
authors.forename: Karen
authors.initials: K
authors.lastname: Akinsanya
authors.forename: Michele
authors.initials: M
authors.lastname: Cleary
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Roddy
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Johns