Abstract 351: Collagen Alignment Correlates with Differential Biaxial Stiffness in Nonhuman Primate Carotid and Femoral Arteries
Introduction: There are known differences in arterial compliance in different regions of the arterial tree. These differences are thought to be determined by pressure and flow demands of their capacitance artery and their respective tissue bed perfusion requirements, and they may play a role in certain arteries having a greater or lesser prevalence of disease as well as favorable response to intervention. Both the femoral and carotid arteries are susceptible to peripheral arterial disease. Here we define the differences in compliance and analyze the microstructural collagen alignment between these arteries to assess the hypothesis that arterial stiffness, defined as the inverse of compliance, will correlate with collagen alignment.
Methods: In-vitro biaxial mechanical tests using a custom system were performed on carotid and femoral arteries excised from non-human primates at necroscopy. Pressure-diameter and force-axial stretch responses were measured, and the arterial compliance (C, units of %/mmHg x 10-2) at the physiological pressure range to calculate the axial stretch. To characterize the microstructure, planar sections of the arteries were imaged under two-photon confocal microscopy. Three-dimensional, z-stack images were taken at two different locations across the medial thickness for each artery. The images were post-processed using a fast Fourier transform analysis to the quantify fiber angle distributions. Circular descriptive statistics was then used to calculate a fiber dispersion index (FDI), where 0≤FDI≤1. FDI=0 signifies random fiber dispersion and FDI=1 signifies complete circumferential fiber alignment. T-test statistical analysis was used to compare groups. P<.05 was considered significant.
Results: Biaxial testing identified femoral arteries as being more than twice as stiff as the carotid artery (P=.01; Figure). Microstructural fiber analysis demonstrated significantly increased collagen alignment in the femoral compared to carotid artery (FDI=0.31, n=4 for femoral versus FDI=0.26, n=4 for carotid, p=0.03).Conclusion: Arterial stiffness in the femoral and carotid artery of nonhuman primates correlates with collagen alignment in the vessel media. The absence of a cellular requirement in the observed mechanical behavior of these arteries suggests that not only matrix composition but also alignment contribute to arterial stiffness. Differential arterial responses to procedures, particularly those endovascular in nature, may be expected by these results.
- © 2012 by American Heart Association, Inc.