title: Biomechanics and gene expression in abdominal aortic aneurysm.
abstract: OBJECTIVE
  The aim of the study was to detect inter-relations between the mechanical conditions and material properties of abdominal aortic aneurysm (AAA) wall and the underlying local gene expression of destabilizing inflammatory, proteolytic, and structural factors.
  
  
  METHODS
  During open surgery, 51 tissue samples from 31 AAA patients were harvested. Gene expression of collagen types I and III, inflammatory factors CD45 and MSR1, proteolytic enzymes matrix metalloproteinases 2 and 9, and tissue inhibitor of matrix metalloproteinase 1 was analyzed by reverse transcription-polymerase chain reaction. Material properties of corresponding AAA tissue samples were assessed by cyclic sinusoidal and destructive testing. Local mechanical conditions of stress and strain were determined by advanced nonlinear finite element analysis based on patient-specific three-dimensional AAA models derived from preoperative computed tomography data.
  
  
  RESULTS
  In the AAA wall, all parameters analyzed were significantly expressed at the messenger RNA level. With respect to mechanical properties of the aneurysmatic wall, expression of collagen III correlated with the stiffness parameter α (r = -0.348; P = .017), and matrix metalloprotease 2 correlated with the stiffness parameter β and wall strength (r = -0.438 and -0.593; P = .005 and P < .001). Furthermore, significant relationships were observed between local AAA diameter and the expression of CD45, MSR1, and tissue inhibitor of matrix metalloproteinase 1 (r = 0.285, 0.551, 0.328; P < .05). However, we found no inter-relation of local calculated wall stresses and strains with gene expression.
  
  
  CONCLUSIONS
  Our results show for the first time that gene expressions of destabilizing factors within AAA tissue might be correlated to geometric and mechanical properties of the AAA wall. However, we found no influence of local mechanical conditions on gene expression of these factors. Therefore, these preliminary results are still ambiguous.
authors.affiliation: Department of Vascular and Endovascular Surgery, Technische Universität, Munich, Germany. Electronic address: christian.reeps@googlemail.com.
authors.forename: Christian
authors.initials: C
authors.lastname: Reeps
authors.affiliation: Mechanics & High Performance Computing Group, Technische Universität, Munich, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kehl
authors.affiliation: Department of Vascular and Endovascular Surgery, Technische Universität, Munich, Germany.
authors.forename: Fadwa
authors.initials: F
authors.lastname: Tanios
authors.affiliation: Institute for Computational Mechanics, Technische Universität, Munich, Germany.
authors.forename: Jonas
authors.initials: J
authors.lastname: Biehler
authors.affiliation: Department of Vascular and Endovascular Surgery, Technische Universität, Munich, Germany.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Pelisek
authors.affiliation: Institute for Computational Mechanics, Technische Universität, Munich, Germany.
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Wall
authors.affiliation: Department of Vascular and Endovascular Surgery, Technische Universität, Munich, Germany.
authors.forename: Hans-Henning
authors.initials: HH
authors.lastname: Eckstein
authors.affiliation: Mechanics & High Performance Computing Group, Technische Universität, Munich, Germany.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Gee
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000737:chemistry* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging / Q000235:genetics* / Q000503:physiopathology*; D001027:Aortography / Q000379:methods; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D005260:Female; D020342:Finite Element Analysis; D005786:Gene Expression Regulation; D005819:Genetic Markers; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D066253:Vascular Remodeling / Q000235:genetics*
chemical_list: D005819:Genetic Markers; D012333:RNA, Messenger