264 publications from this institution
Ascending thoracic aortic aneurysm (ATAA) has been associated with diminished biomechanical strength and disruption in the collagen fiber microarchitecture. Additionally, the congenital bicuspid aortic valve (BAV) leads to a distinct extracellular matrix structure that may be related to ATAA development at an earlier age than degenerative aneurysms arising in patients with the morphological normal tricuspid aortic valve (TAV). The purpose of this study was to model the fiber-reinforced mechanical response of ATAA specimens from patients with either BAV or TAV. This was achieved by combining image-analysis derived parameters of collagen fiber dispersion and alignment with tensile testing data. Then, numerical simulations were performed to assess the role of anisotropic constitutive formulation on the wall stress distribution of aneurysmal aorta. Results indicate that both BAV ATAA and TAV ATAA have altered collagen fiber architecture in the medial plane of experimentally-dissected aortic tissues when compared to normal ascending aortic specimens. The study findings highlight that differences in the collagen fiber distribution mostly influences the resulting wall stress distribution rather than the peak stress. We conclude that fiber-reinforced constitutive modeling that takes into account the collagen fiber defect inherent to the aneurysmal ascending aorta is paramount for accurate finite element predictions and ultimately for biomechanical-based indicators to reliably distinguish the more from the less 'malignant' ATAAs.
Aortic disease is a significant cause of death in developed countries. The most common forms of aortic disease are aneurysm, dissection, atherosclerotic occlusion and ageing-induced stiffening. The microstructure of the aortic tissue has been studied with great interest, because alteration of the quantity and/or architecture of the connective fibres (elastin and collagen) within the aortic wall, which directly imparts elasticity and strength, can lead to the mechanical and functional changes associated with these conditions. This review article summarizes the state of the art with respect to characterization of connective fibre microstructure in the wall of the human aorta in ageing and disease, with emphasis on the ascending thoracic aorta and abdominal aorta where the most common forms of aortic disease tend to occur.
Cardiovascular disease remains the number one cause of death in the United States. Most current surgical procedures to alleviate this disease rely on the availability of suitable small diameter vascular grafts, which are constrained by several limitations. Tissue engineering brings new hope to this field, but still faces many challenges. This review focuses on the molecular aspects of the different components of vascular tissue engineering. The topics addressed include the cell type, extracellular matrix, and physical and biochemical stimulation with respect to their role in the development of a tissue engineered vascular graft.
One of the major failings in vascular tissue engineering is the limited capacity of autologous differentiated cells to reconstitute tissues. A logical solution is to use multipotent progenitor cells, which in vascular treatments have been underutilized. Although biochemical stimulation has been explored to differentiate bone marrow-derived progenitor cells (BMPCs) to smooth muscle cells (SMCs), the use of biomechanical forces in differentiation remains unexplored. The purpose of this work was to explore the effects of cyclic strain alone on BMPC morphology, proliferation, and differentiation. BMPCs were isolated from rat bone marrow and, after 7 days in culture, the cells grew in distinct multilayered colonies. BMPCs were stimulated with 10% strain at 1 Hz for 7 days. Observations showed that cyclic strain inhibited proliferation (p < 0.05) and caused alignment of the cells (p < 0.05) and of the F-actin cytoskeleton perpendicular to the direction of strain. In addition, cyclic strain resulted in expression by the cells of vascular smooth muscle alpha-actin and h1-calponin. This work demonstrates the potential of physiologic biomechanical stimulation in the differentiation of BMPCs to SMCs, and this could have important implications for vascular tissue engineering and other therapies in which cell sourcing is a major concern.
Abstract Abdominal aortic aneurysm (AAA) is a condition whereby the terminal aorta permanently dilates to dangerous proportions, risking rupture. Rupture of AAA is a significant cause of death in this country that is generally avoided by surgical repair. In order to improve our understanding and diagnosis of this disease, we call upon first principles of finite elasticity. We use such principles to estimate the AAA wall strength and acting wall stress, which in turn allow evaluation of an individual aneurysm’s risk of rupture. In this paper, we summarize the work that has been performed to date in applying finite elasticity to abdominal aortic aneurysm research.
