Regional mechanical characterization of pulmonary arteries can be useful in the development of computational models of pulmonary arterial mechanics.
We performed a biomechanical and microstructural characterization study of porcine pulmonary arteries, inclusive of the main, left, and right pulmonary arteries (MPA, LPA, and RPA, respectively).
The specimens were initially stored at −20 °C and allowed to thaw for 12–24 h prior to testing. Each artery was further subdivided into proximal, middle, and distal regions, leading to ten location-based experimental groups. Planar equibiaxial tensile testing was performed to evaluate the mechanical behavior of the specimens, from which we calculated the stress at the maximum strain (S55), tensile modulus (TM), anisotropy index (AI), and strain energy in terms of area under the stress-strain curve (AUC). Histological quantification was performed to evaluate the area fraction of elastin and collagen content, intima-media thickness (IMT), and adventitial thickness (AT). The constitutive material behavior of each group was represented by a five-constant Holzapfel-Gasser-Ogden model.
The specimens exhibited non-linear stress-strain characteristics across all groups. The MPA exhibited the highest mean wall stress and TM in the longitudinal and circumferential directions, while the bifurcation region yielded the highest values of AI and AUC. All regions revealed a higher stiffness in the longitudinal direction compared to the circumferential direction, suggesting a degree of anisotropy that is believed to be within the margin of experimental uncertainty. Collagen content was found to be the highest in the MPA and decreased significantly at the bifurcation, LPA and RPA. Elastin content did not yield such significant differences amongst the ten groups. The MPA had the highest IMT, which decreased concomitantly to the distal LPA and RPA. No significant differences were found in the AT amongst the ten groups.
The mechanical properties of porcine pulmonary arteries exhibit strong regional dissimilarities, which can be used to inform future studies of high fidelity finite element models.
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The authors would like to thank Dr. Mirunalini Thirugnanasambandam for developing the MATLAB script for constitutive modeling, Dr. Hai-Chao Han for providing access to the planar biaxial testing equipment, and Dr. Gabriela Romero-Uribe for lending her microscopy equipment.
Research funding was provided in part by National Institutes of Health award No. R01HL121293 and American Heart Association award No. 16CSA28480006. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health and the American Heart Association. The authors have no other conflicts of interest to disclose. This research involved animal tissue specimens, but not actual animal subjects. The UTSA Institutional Biosafety Committee approved the protocol for acquisition and use of the specimens. No human participants were used in this study; hence, no informed consent was required.
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Pillalamarri, N., Patnaik, S., Piskin, S. et al. Ex Vivo Regional Mechanical Characterization of Porcine Pulmonary Arteries. Exp Mech 61, 285–303 (2021). https://doi.org/10.1007/s11340-020-00678-2
- Pulmonary arterial mechanics
- Pulmonary hypertension
- Planar biaxial tension
- Constitutive modeling