Fiber micro-architecture in the longitudinal-radial and circumferential-radial planes of ascending thoracic aortic aneurysm media |
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Authors: | Alkiviadis Tsamis Julie A. Phillippi Ryan G. Koch Salvatore Pasta Antonio D'Amore Simon C. Watkins William R. Wagner Thomas G. Gleason David A. Vorp |
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Affiliation: | 1. Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States;2. Department of Cardiothoracic Surgery, University of Pittsburgh, Pittsburgh, PA, United States;3. Department of Surgery, University of Pittsburgh, Pittsburgh, PA, United States;4. Center for Vascular Remodeling and Regeneration, University of Pittsburgh, Pittsburgh, PA, United States;5. Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA, United States;6. McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, United States;g Fondazione Ri.MED, Palermo, Italy;h DICGM University of Palermo, Palermo, Italy |
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Abstract: | It was recently demonstrated by our group that the delamination strength of ascending thoracic aortic aneurysms (ATAA) was lower than that of control (CTRL, non-aneurysmal) ascending thoracic aorta (ATA), and the reduced strength was more pronounced among bicuspid (BAV) vs. tricuspid aortic valve (TAV) patients, suggesting a different risk of aortic dissection for BAV patients. We hypothesized that aortic valve morphologic phenotype predicts fiber micro-architectural anomalies in ATA. To test the hypothesis, we characterized the micro-architecture in the longitudinal-radial (Z-RAD) and circumferential-radial (Θ-RAD) planes of human ATA tissue that was artificially dissected medially. The outer and inner-media of CTRL-ATA, BAV-ATAA and TAV-ATAA were imaged using multi-photon microscopy in the Z-RAD and Θ-RAD planes to observe collagen and elastin. Micrographs were processed using an image-based tool to quantify several micro-architectural characteristics. In the outer-media of BAV-ATAA, elastin was more undulated and less aligned about the Θ-axis when compared with CTRL-ATA, which is consistent with increased tensile stretch at inflection point of Θ-strips of adventitial-medial half of BAV-ATAA (1.28) when compared with CTRL-ATA (1.13). With increasing age, collagen became more undulated about the Z-axis within the outer-media of TAV-ATAA, and elastin became more oriented in the Z-axis and collagen less radially-oriented within the inner-media of TAV-ATAA. This discrepancy in the micro-architecture with fibers in the inner layers being more stretched and with disrupted radially-oriented components than fibers in the outer layers may be associated with the development, progression and vascular remodeling in aneurysms arising in TAV patients. |
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Keywords: | Human ascending thoracic aortic aneurysm Elastin Collagen Micro-architecture Multi-photon microscopy Dissection |
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