Bellini C, Ferruzzi J, Roccabianca S, Di Martino E S, Humphrey J D
Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT, 06511, USA.
Ann Biomed Eng. 2014 Mar;42(3):488-502. doi: 10.1007/s10439-013-0928-x. Epub 2013 Nov 7.
Through mechanobiological control of the extracellular matrix, and hence local stiffness, smooth muscle cells of the media and fibroblasts of the adventitia play important roles in arterial homeostasis, including adaptations to altered hemodynamics, injury, and disease. We present a new approach to model arterial wall mechanics that seeks to define better the mechanical environments of the media and adventitia while avoiding the common prescription of a traction-free reference configuration. Specifically, we employ the concept of constituent-specific deposition stretches from the growth and remodeling literature and define a homeostatic state at physiologic pressure and axial stretch that serves as a convenient biologically and clinically relevant reference configuration. Information from histology and multiphoton imaging is then used to prescribe structurally motivated constitutive relations for a bi-layered model of the wall. The utility of this approach is demonstrated by describing in vitro measured biaxial pressure-diameter and axial force-length responses of murine carotid arteries and predicting the associated intact and radially cut traction-free configurations. The latter provides a unique validation while confirming that this constrained mixture approach naturally recovers estimates of residual stresses, which are fundamental to wall mechanics, without the usual need to prescribe an opening angle that is only defined conveniently on cylindrical geometries and cannot be measured in vivo. Among other findings, the model suggests that medial and adventitial stresses can be nearly uniform at physiologic loads, albeit at separate levels, and that the adventitia bears increasingly more load at supra-physiologic pressures while protecting the media from excessive stresses.
通过对细胞外基质的力学生物学控制，进而控制局部硬度，中膜的平滑肌细胞和外膜的成纤维细胞在动脉稳态中发挥重要作用，包括对血流动力学改变、损伤和疾病的适应性反应。我们提出了一种模拟动脉壁力学的新方法，该方法旨在更好地定义中膜和外膜的力学环境，同时避免采用无牵引参考构型这一常见设定。具体而言，我们采用生长和重塑文献中特定成分沉积拉伸的概念，并定义了在生理压力和轴向拉伸下的稳态，将其作为一个方便的、与生物学和临床相关的参考构型。然后，利用组织学和多光子成像信息为动脉壁的双层模型规定基于结构的本构关系。通过描述体外测量的小鼠颈动脉双轴压力-直径和轴向力-长度响应，并预测相关的完整和径向切割的无牵引构型，证明了该方法的实用性。后者提供了一种独特的验证方式，同时证实了这种约束混合物方法能够自然地恢复对残余应力的估计，而残余应力是壁力学的基础，通常无需规定仅在圆柱几何形状上方便定义且无法在体内测量的开口角度。在其他发现中，该模型表明，在生理负荷下，中膜和外膜应力虽处于不同水平但可近乎均匀，并且在超生理压力下，外膜承受的负荷越来越大，同时保护中膜免受过大应力。
