title: Murine ultrasound imaging for circumferential strain analyses in the angiotensin II abdominal aortic aneurysm model.
abstract: OBJECTIVE
  The underlying causes of abdominal aortic aneurysms (AAAs) remain obscure, although research tools such as the angiotensin II (Ang II) apolipoprotein E-deficient (apoE(-/-)) mouse model have aided investigations. Longitudinal imaging and determination of biomechanical forces in this small-scale model have been difficult. We hypothesized that high-frequency ultrasound biomicroscopy combined with speckle-tracking analytical strategies can be used to define the role of circumferential mechanical strain in AAA formation in the Ang II/apoE(-/-) mouse model of AAAs. We simultaneously examined dietary perturbations that might impact the biomechanical properties of the aortic wall, hypothesizing that the generalized inflammatory phenotype associated with diet-induced obesity would be associated with accelerated loss of circumferential strain and aneurysmal aortic degeneration.
  
  
  METHODS
  Receiving either a 60 kcal% fat Western diet or standard 10 kcal% fat normal chow, Ang II-treated apoE(-/-) mice (n = 34) underwent sequential aortic duplex ultrasound scan imaging (Vevo 2100 System; VisualSonics, Toronto, Ontario, Canada) of their entire aorta. Circumferential strains were calculated using speckle-tracking algorithms and a custom MatLab analysis.
  
  
  RESULTS
  Decreased strains in all aortic locations after just 3 days of Ang II treatment were observed, and this effect progressed during the 4-week observation period. Anatomic segments along the aorta impacted wall strain (baseline highest in ascending aorta; P < .05), whereas diet did not. At 2 and 4 weeks, there was the largest progressive decrease in strain in the paravisceral/supraceliac aorta (P < .05), which was the segment most likely to be involved in aneurysm formation in this model.
  
  
  CONCLUSIONS
  In the Ang II/apoE(-/-) aneurysm model, the aorta significantly stiffens (with decreased strain) shortly after Ang II infusion, and this progressively continues through the next 4 weeks. High-fat feeding did not have an impact on wall strain. Delineation of biomechanical factors and AAA morphology via duplex scan and speckle-tracking algorithms in mouse models should accelerate insights into human AAAs.
authors.affiliation: Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, Mass., USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Favreau
authors.forename: Binh T
authors.initials: BT
authors.lastname: Nguyen
authors.forename: Ian
authors.initials: I
authors.lastname: Gao
authors.forename: Peng
authors.initials: P
authors.lastname: Yu
authors.forename: Ming
authors.initials: M
authors.lastname: Tao
authors.forename: Jacob
authors.initials: J
authors.lastname: Schneiderman
authors.forename: Glenn R
authors.initials: GR
authors.lastname: Gaudette
authors.forename: C Keith
authors.initials: CK
authors.lastname: Ozaki
mesh_terms: D000818:Animals; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D004041:Dietary Fats / Q000008:administration & dosage; D004195:Disease Models, Animal; D018450:Disease Progression; D008297:Male; D051379:Mice; D033401:Microscopy, Acoustic; D013314:Stress, Mechanical; D018616:Ultrasonography, Doppler, Duplex
chemical_list: D004041:Dietary Fats