Longitudinal study of the mechanical properties of rat abdominal aortas incubated in ex vivo conditions

抄録

Aortic disease is often associated with tissue degradation. However, the changes in the mechanical properties of the aorta occurring in accordance with tissue degradation remain unclear. This study explored the time course of the natural decay of aortic tissues in terms of mechanical and histological properties. Aortas excised from mice were incubated under ex vivo conditions, and their mechanical properties were assessed using a pressure–diameter test. Two linear lines were fitted to the pressure–diameter curve; the pressure at which the lines crossed was defined as the “collagen recruitment pressure”. During incubation, the aortas suddenly changed in stiffness, and the collagen recruitment pressure dropped abruptly. These rapid changes occurred significantly earlier under an intraluminal pressure of 0 than 100 mmHg. Histological examination revealed the loss of elastic laminas (ELs) and smooth muscle cells in the aorta, coinciding with the changes in mechanical properties. Thus, the rapid change was caused by sudden structural failure of the ELs, in which damage accumulated at the microscopic level over the incubation period. Additionally, the tissue degradation rate was dependent on the mechanical environment. These findings provide insight into the etiology of aortic diseases.