title: Fourier Transform Infrared Spectroscopic Imaging-Derived Collagen Content and Maturity Correlates with Stress in the Aortic Wall of Abdominal Aortic Aneurysm Patients.
abstract: Abdominal aortic aneurysm (AAA) is a degenerative disease of the aorta characterized by severe disruption of the structural integrity of the aortic wall and its major molecular constituents. From the early stages of disease, elastin in the aorta becomes highly degraded and is replaced by collagen. Questions persist as to the contribution of collagen content, quality and maturity to the potential for rupture. Here, using our recently developed Fourier transform infrared imaging spectroscopy (FT-IRIS) method, we quantified collagen content and maturity in the wall of AAA tissues in pairs of specimens with different wall stresses. CT scans of AAAs from 12 patients were used to create finite element models to estimate stress in different regions of tissue. Each patient underwent elective repair of the AAA, and two segments of the AAA tissues from anatomic regions more proximal or distal with different wall stresses were evaluated by histology and FT-IRIS after excision. For each patient, collagen content was generally greater in the tissue location with lower wall stress, which corresponded to the more distal anatomic regions. The wall stress/collagen ratio was greater in the higher stress region compared to the lower stress region (1.01 ± 1.09 vs. 0.55 ± 0.084, p = 0.02). The higher stress region also corresponded to the location with reduced intraluminal thrombus thickness. Further, collagen maturity tended to decrease with increased collagen content (p = 0.068, R = 0.38). Together, these results suggest that an increase in less mature collagen content in AAA patients does not effectively compensate for the loss of elastin in the aortic wall, and results in a reduced capability to endure wall stresses.
authors.affiliation: Department of Mechanical Engineering, Temple University, Philadelphia, PA, USA.|Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Rabee
authors.initials: R
authors.lastname: Cheheltani
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Pichamuthu
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Jayashree
authors.initials: J
authors.lastname: Rao
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.|McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Justin S
authors.initials: JS
authors.lastname: Weinbaum
authors.affiliation: Department of Mechanical Engineering, Temple University, Philadelphia, PA, USA.
authors.forename: Mohammad F
authors.initials: MF
authors.lastname: Kiani
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.|McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.|Department of Surgery, Department of Cardiothoracic Surgery, and Center for Vascular Remodeling and Regeneration, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Vorp
authors.affiliation: Department of Bioengineering, Temple University, Philadelphia, PA, USA. npleshko@temple.edu.
authors.forename: Nancy
authors.initials: N
authors.lastname: Pleshko
mesh_terms: D001012:Aorta, Abdominal / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000503:physiopathology / Q000601:surgery; D003094:Collagen / Q000032:analysis / Q000378:metabolism*; D004549:Elastin / Q000032:analysis / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism / Q000473:pathology; D006801:Humans; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013314:Stress, Mechanical
chemical_list: D003094:Collagen; D004549:Elastin
keywords: Aneurysm; Collagen; Extracellular matrix; FTIR; Stress