Department of Biomedical Engineering, Yale University, New Haven, CT, USA.
Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
Biomech Model Mechanobiol. 2019 Feb;18(1):203-218. doi: 10.1007/s10237-018-1077-9. Epub 2018 Sep 24.
We recently developed an approach to characterize local nonlinear, anisotropic mechanical properties of murine arteries by combining biaxial extension-distension testing, panoramic digital image correlation, and an inverse method based on the principle of virtual power. This experimental-computational approach was illustrated for the normal murine abdominal aorta assuming uniform wall thickness. Here, however, we extend our prior approach by adding an optical coherence tomography (OCT) imaging system that permits local reconstructions of wall thickness. This multimodality approach is then used to characterize spatial variations of material and structural properties in ascending thoracic aortic aneurysms (aTAA) from two genetically modified mouse models (fibrillin-1 and fibulin-4 deficient) and to compare them with those from angiotensin II-infused apolipoprotein E-deficient and wild-type control ascending aortas. Local values of stored elastic energy and biaxial material stiffness, computed from spatial distributions of the best fit material parameters, varied significantly with circumferential position (inner vs. outer curvature, ventral vs. dorsal sides) across genotypes and treatments. Importantly, these data reveal an inverse relationship between material stiffness and wall thickness that underlies a general linear relationship between stiffness and wall stress across aTAAs. OCT images also revealed sites of advanced medial degeneration, which were captured by the inverse material characterization. Quantification of histological data further provided high-resolution local correlations among multiple mechanical metrics and wall microstructure. This is the first time that such structural defects and local properties have been characterized mechanically, which can better inform computational models of aortopathy that seek to predict where dissection or rupture may initiate.
我们最近开发了一种方法，通过结合双向拉伸-扩张测试、全景数字图像相关和基于虚功原理的反演方法，来描述小鼠动脉的局部非线性各向异性力学特性。这种实验计算方法是针对假设壁厚均匀的正常小鼠腹主动脉进行说明的。然而，在这里，我们通过添加光学相干断层扫描（OCT）成像系统来扩展我们之前的方法，该系统允许局部重建壁厚。然后，使用这种多模态方法来描述两种基因修饰小鼠模型（原纤维蛋白 1 和弹性蛋白 4 缺乏）的升主动脉瘤（aTAA）中的材料和结构特性的空间变化，并将其与血管紧张素 II 输注的载脂蛋白 E 缺乏和野生型对照升主动脉进行比较。从空间分布最佳拟合材料参数计算得出的存储弹性能量和双向材料刚度的局部值，在基因型和处理之间，沿周向位置（内曲率与外曲率、腹侧与背侧）变化显著。重要的是，这些数据揭示了材料刚度与壁厚之间的反比关系，这是 aTAA 中刚度与壁应力之间的一般线性关系的基础。OCT 图像还显示了中膜退化的晚期部位，这些部位被反演材料特征所捕获。组织学数据的定量分析进一步提供了多个力学指标和壁微观结构之间的高分辨率局部相关性。这是第一次从力学角度对这些结构缺陷和局部特性进行了描述，这可以更好地为主动脉病变的计算模型提供信息，这些模型试图预测夹层或破裂可能开始的位置。
