Morphological and morphometric aspects of the equine aortic valve: New insights for comparative studies in mammals

New data on the equine aortic valve obtained using advanced techniques is especially important given the greater availability of animal models for translational research. Here we characterized the morphological and morphometric aspects of the equine aortic valve from 60 healthy hearts collected at equine abattoirs. The valve cusps were analyzed by light and scanning electron microscopy, and the morphometric data were analyzed using ImageJ software in Fiji version 1.51 J. The aortic semilunar cusps were partially translucent and white with grayish nuances. As revealed under light microscopy, both sides of the valve cusps were coated with endothelial cells, and the body was composed of a fibromolecular arrangement of type I and III collagen and elastin, as well as an extracellular matrix rich in cells. The mean total area of the left semilunar valve was 8.9 cm² and the valve contained a mean of eight tendinous bundles; the mean total area of the right semilunar valve was 10.1 cm² and it contained six tendinous bundles. The septal semilunar valve was, on average, 9.9 cm² and contained nine tendinous bundles. In both cusps, the relative elastin ranged from 10.9% to 12.6%, and collagen from 41.5% to 48.8%, with no significant differences between the cusps. The morphological and morphometric aspects of the equine aortic valve are similar among the previously described mammalian species, indicating that the characteristics observed in this study are remarkably conserved among genera throughout the evolutionary process. This has contributed to an increased availability of viable animal models for translational studies.