title: In vivo imaging of macrophages during the early-stages of abdominal aortic aneurysm using high resolution MRI in ApoE mice.
abstract: BACKGROUND
  Angiotensin II (ANG II) promotes vascular inflammation and induces abdominal aortic aneurysm (AAA) in hyperlipidemic apolipoprotein E knock-out (apoE(-/-)) mice. The aim of the present study was to detect macrophage activities in an ANG II-induced early-stage AAA model using superparamagnetic iron oxide (SPIO) as a marker.
  
  
  RESULTS
  Twenty-six male apoE(-/-) mice received saline or ANG II (1000 or 500 ng/kg/min) infusion for 14 days. All animals underwent MRI scanning following administration of SPIO with the exception of three mice in the 1000 ng ANG II group, which were scanned without SPIO administration. MR imaging was performed using black-blood T2 to proton density -weighted multi-spin multi-echo sequence. In vivo MRI measurement of SPIO uptake and abdominal aortic diameter were obtained. Prussian blue, CD68,α-SMC and MAC3 immunohistological stains were used for the detection of SPIO, macrophages and smooth muscle cells. ANG II infusion with 1000 ng/kg/min induced AAA in all of the apoE(-/-) mice. ANG II infusion exhibited significantly higher degrees of SPIO uptake, which was detected using MRI as a distinct loss of signal intensity. The contrast-to-noise ratio value decreased in proportion to an increase in the number of iron-laden macrophages in the aneurysm. The aneurysmal vessel wall in both groups of ANG II treated mice contained more iron-positive macrophages than saline-treated mice. However, the presence of cells capable of phagocytosing haemosiderin in mural thrombi also induced low-signal-intensities via MRI imaging.
  
  
  CONCLUSIONS
  SPIO is taken up by macrophages in the shoulder and the outer layer of AAA. This alters the MRI signaling properties and can be used in imaging inflammation associated with AAA. It is important to compare images of the aorta before and after SPIO injection.
authors.affiliation: Department of Cardiology, Zhongda Hospital, Medical School of Southeast University, Nanjing, Jiangsu, China.
authors.forename: Yuyu
authors.initials: Y
authors.lastname: Yao
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yefei
authors.initials: Y
authors.lastname: Li
authors.forename: Zulong
authors.initials: Z
authors.lastname: Sheng
authors.forename: Song
authors.initials: S
authors.lastname: Wen
authors.forename: Genshan
authors.initials: G
authors.lastname: Ma
authors.forename: Naifeng
authors.initials: N
authors.lastname: Liu
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
authors.forename: Gao-Jun
authors.initials: GJ
authors.lastname: Teng
mesh_terms: D000804:Angiotensin II / Q000009:adverse effects*; D000818:Animals; D017544:Aortic Aneurysm, Abdominal / Q000139:chemically induced / Q000473:pathology*; D001057:Apolipoproteins E / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism; D003911:Dextrans; D004195:Disease Models, Animal; D006801:Humans; D008055:Lipids / Q000032:analysis; D008264:Macrophages / Q000187:drug effects / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010587:Phagocytosis / Q000187:drug effects
chemical_list: D001057:Apolipoproteins E; D016207:Cytokines; D003911:Dextrans; D008055:Lipids; D058185:Magnetite Nanoparticles; D000804:Angiotensin II; C065507:ferumoxides