Department of Mechanical Engineering, Boston University, 110 Cummington Mall, Boston, MA, 02215, USA.
Department of Biomedical Engineering, Boston University, 110 Cummington Mall, Boston, MA, 02215, USA.
Biomech Model Mechanobiol. 2021 Feb;20(1):93-106. doi: 10.1007/s10237-020-01370-z. Epub 2020 Jul 23.
The artery relies on interlamellar structural components, mainly elastin and collagen fibers, for maintaining its integrity and resisting dissection propagation. In this study, the contribution of arterial elastin and collagen fibers to interlamellar bonding was studied through mechanical testing, multiphoton imaging and finite element modeling. Steady-state peeling experiments were performed on porcine aortic media and the purified elastin network in the circumferential (Circ) and longitudinal (Long) directions. The peeling force and energy release rate associated with mode-I failure are much higher for aortic media than for the elastin network. Also, longitudinal peeling exhibits a higher energy release rate and strength than circumferential peeling for both the aortic media and elastin. Multiphoton imaging shows the recruitment of both elastin and collagen fibers within the interlamellar space and points to in-plane anisotropy of fiber distributions as a potential mechanism for the direction-dependent phenomena of peeling tests. Three-dimensional finite element models based on cohesive zone model (CZM) of fracture were created to simulate the peeling tests with the interlamellar energy release rate and separation distance at damage initiation obtained directly from peeling test. Our experimental results show that the separation distance at damage initiation is 80 μm for aortic media and 40 μm for elastin. The damage initiation stress was estimated from the model for aortic media (Circ: 60 kPa; Long: 95 kPa) and elastin (Circ: 9 kPa; Long: 14 kPa). The interlamellar separation distance at complete failure was estimated to be 3 - 4 mm for both media and elastin. Furthermore, elastin and collagen fibers both play an important role in bonding of the arterial wall, while collagen has a higher contribution than elastin to interlamellar stiffness, strength and toughness. These results on microstructural interlamellar failure shed light on the pathological development and progression of aortic dissection.
动脉依赖于层间结构成分，主要是弹性蛋白和胶原纤维，以维持其完整性并抵抗夹层的扩展。在这项研究中，通过力学测试、多光子成像和有限元建模研究了动脉弹性蛋白和胶原纤维对层间结合的贡献。在猪主动脉中膜和纯化的弹性蛋白网络的环向（Circ）和纵向（Long）方向上进行了稳态剥离实验。与模式 I 失效相关的剥离力和能量释放率对于主动脉中膜来说要比弹性蛋白网络高得多。此外，对于主动脉中膜和弹性蛋白来说，纵向剥离的能量释放率和强度都高于环向剥离。多光子成像显示了层间空间内弹性蛋白和胶原纤维的募集，并指出纤维分布的面内各向异性可能是剥离试验中与方向相关的现象的潜在机制。基于断裂的内聚区模型（CZM）创建了三维有限元模型，以模拟剥离试验，直接从剥离试验中获得层间能量释放率和损伤起始时的分离距离。我们的实验结果表明，损伤起始时的分离距离对于主动脉中膜为 80μm，对于弹性蛋白为 40μm。从模型中估计了损伤起始时的应力，对于主动脉中膜（Circ：60kPa；Long：95kPa）和弹性蛋白（Circ：9kPa；Long：14kPa）。估计了完全失效时的层间分离距离对于中膜和弹性蛋白均为 3-4mm。此外，弹性蛋白和胶原纤维都在动脉壁的结合中起着重要作用，而胶原纤维对层间刚度、强度和韧性的贡献高于弹性蛋白。这些关于微观层间失效的结果揭示了主动脉夹层的病理发展和进展。
