title: Interaction of biomechanics with extracellular matrix components in abdominal aortic aneurysm wall.
abstract: OBJECTIVE
  Little is known about the interactions between extracellular matrix (ECM) proteins and locally acting mechanical conditions and material macroscopic properties in abdominal aortic aneurysm (AAA). In this study, ECM components were investigated with correlation to corresponding biomechanical properties and loads in aneurysmal arterial wall tissue.
  
  
  METHODS
  Fifty-four tissue samples from 31 AAA patients (30♂; max. diameter Dmax 5.98 ± 1.42 cm) were excised from the aneurysm sac. Samples were divided for corresponding immunohistological and mechanical analysis. Collagen I and III, total collagen, elastin, and proteoglycans were quantified by computational image analysis of histological staining. Pre-surgical CT data were used for 3D segmentation of the AAA and calculation of mechanical conditions by advanced finite element analysis. AAA wall stiffness and strength were assessed by repeated cyclical, sinusoidal and destructive tensile testing.
  
  
  RESULTS
  Amounts of collagen I, III, and total collagen were increased with higher local wall stress (p = .002, .017, .030, respectively) and strain (p = .002, .012, .020, respectively). AAA wall failure tension exhibited a positive correlation with collagen I, total collagen, and proteoglycans (p = .037, .038, .022, respectively). α-Stiffness correlated with collagen I, III, and total collagen (p = .011, .038, and .008), while β-stiffness correlated only with proteoglycans (p = .028). In contrast, increased thrombus thickness was associated with decreased collagen I, III, and total collagen (p = .003, .020, .015, respectively), and AAA diameter was negatively associated with elastin (p = .006).
  
  
  CONCLUSIONS
  The present results indicate that in AAA, increased locally acting biomechanical conditions (stress and strain) involve increased synthesis of collagen and proteoglycans with increased failure tension. These findings confirm the presence of adaptive biological processes to maintain the mechanical stability of AAA wall.
authors.affiliation: Department of Vascular and Endovascular Surgery, Klinikum rechts der Isar, Technische Universität München, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Tanios
authors.affiliation: Mechanics & High Performance Computing Group, Technische Universität München, Germany.
authors.forename: M W
authors.initials: MW
authors.lastname: Gee
authors.affiliation: Department of Vascular and Endovascular Surgery, Klinikum rechts der Isar, Technische Universität München, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Pelisek
authors.affiliation: Mechanics & High Performance Computing Group, Technische Universität München, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Kehl
authors.affiliation: Institute for Computational Mechanics, Technische Universität München, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Biehler
authors.affiliation: Department of Vascular and Endovascular Surgery, Klinikum rechts der Isar, Technische Universität München, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Grabher-Meier
authors.affiliation: Institute for Computational Mechanics, Technische Universität München, Germany.
authors.forename: W A
authors.initials: WA
authors.lastname: Wall
authors.affiliation: Department of Vascular and Endovascular Surgery, Klinikum rechts der Isar, Technische Universität München, Germany.
authors.forename: H-H
authors.initials: HH
authors.lastname: Eckstein
authors.affiliation: Department of Vascular and Endovascular Surgery, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: christian.reeps@googlemail.com.
authors.forename: C
authors.initials: C
authors.lastname: Reeps
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000737:chemistry* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017544:Aortic Aneurysm, Abdominal / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology*; D001019:Aortic Rupture / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D001027:Aortography / Q000379:methods; D001696:Biomechanical Phenomena; D018450:Disease Progression; D016326:Extracellular Matrix Proteins / Q000032:analysis*; D005260:Female; D020342:Finite Element Analysis; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D012307:Risk Factors; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D059289:Vascular Stiffness
chemical_list: D016326:Extracellular Matrix Proteins
keywords: AAA; Biomechanics; Collagen; ECM; Elastin; Proteoglycans