Intramural Distribution of Elastic Moduli in Thoracic Aortas and Its Relationship to Histology. Comparison between Porcine and Bovine Thoracic Aortas.

Local elastic moduli in the wall of porcine thoracic aortas were measured in the axial, circumferential, and radial directions by the pipette aspiration method. The local elastic moduli in the three directions were found to be independent of wall position. Then, histological analysis using color classification based on Mahalanobis' generalized distance was performed to quantitatively assess the correlation between elastic moduli and histology. Porcine thoracic aortas had a typical layered structure. The area fraction values, i.e., the percentage area of three structural components, elastin, collagen fibers and smooth muscle cells, were almost uniform in the wall. On the other hand, the moduli in bovine aortas reported previously decreased significantly from the inner to the outer sides of the wall. The histological structure was not homogeneous, that is, large clusters of smooth muscle cells existed in the outer side. These results suggest that the intramural distributions of elastic moduli are closely correlated with the histological structure.