Microscopic Mechanical Analysis of Aortic Wall: Estimation of Stress in the Intramural Elastic Laminas and Smooth Muscle Cells in a Physiological State

It is well known that the artery walls change their dimensions and mechanical properties adaptively in response to the mechanical environment they are exposed to [1]. Because mechanical adaptation of the artery wall is driven by the smooth muscle cells (SMCs) in its media, it is crucial to know the mechanical environment of SMCs in the wall to reveal the details of the adaptation mechanism. Mechanical stress applied to the SMCs in the media should be different from that applied to the wall, because at a microscopic level, the media has a highly heterogeneous structure composed of various materials with different elastic modulus. For example, aortic media has a layered structure of a lamellar unit, a pair of elastic lamina (EL) mainly composed of elastin and a smooth muscle-rich layer mainly composed of SMCs and collagen [2], and Young’s modulus of elastin, SMCs, and collagen is about 0.6MPa, 10kPa, and 1GPa, respectively [3]. Such heterogeneity should cause complex distribution of stress and strain depending on the histological structure both in the unloaded state and in the physiological state [4].