Meso-Structural Characterization and Modeling of Arterial Tissue Subjected to intermittent hypobaric Hypoxia
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In Chilean mining, a significant fraction of operations is conducted at altitudes close to 3500 m above sea level, where exposure to hypoxia directly affects workers’ cardiovascular function. Recent studies indicate that hypoxia can induce alterations in the mechanical biomarkers of the aorta [1]. Given the hyperelastic and anisotropic nature of the arterial extracellular matrix (ECM), primarily governed by the orientation of collagen fibers, this work integrates equibiaxial tensile testing and multiphoton microscopy (MPM) to probabilistically model the fibrillar architecture and characterize the mechanical adaptation of the aorta under intermittent hypoxia conditions [2]. Thoracic aortic tissue was harvested from rats subjected to intermittent hypoxia and normoxic conditions and experimentally characterized using equibiaxial tensile tests. To obtain the probability functions associated with collagen fiber waviness and preferred orientation, MPM was performed on unloaded, formalin-fixed samples, enabling a detailed structural characterization of the arterial extracellular matrix and the extraction of geometric parameters and collagen fiber distribution functions in the reference configuration. The combination of the biaxial testing protocol with MPM enables a comprehensive characterization of the arterial ECM by incorporating mesostructural parameters into the constitutive model proposed by Sacks [2]. This study evaluates hypoxia-induced differences in the structural components of the tissue, with particular emphasis on the collagen. The biaxial tests confirm the anisotropic behavior of the aorta and allow for the estimation of stiffness in both low and high-strain regimes. MPM reveals variations in collagen content, orientation, and waviness among the different experimental groups. Finally, these results are implemented in a finite element code (VULCAN) to computationally validate the effects of hypoxia and assess its mechanical impact under a pressurized state.
