Spatial Variation in Aorta Composition and Correlation with Mechanical Properties

Aorta is composed of distinct anatomical layers and components with different mechanical characteristics. Understanding and characterization of the interactions between aorta building blocks and their mechanical properties enable us to quantify changes that may occur in the material behavior of aorta as a result of cardiovascular diseases. In the present work the microstructural and components´ heterogeneity along the porcine thoracic aorta wall thickness was studied with histology and infrared spectroscopy, and the changes were correlated to the mechanical properties along the wall thickness determined from nanoindentation tests. Two layers of equal thickness were distinguishable based on the radial variations in the instantaneous Young´s modulus E, elastic lamellae density (ELD) as calculated from histology, and the total amount of protein as determined from infrared spectroscopy. The results showed that compared with the inner half, the outer half layer is stiffer, elastic lamellae are denser and total protein content is higher. ELD and total protein are strongly correlated with mechanical properties. It is likely that disruption of this balance has a major effect on cardiovascular health and disease.