Linking the Region-Specific Tissue Microstructure to the Biaxial Mechanical Properties of the Porcine Left Anterior Descending Artery

Abstract

Coronary atherosclerosis is the main cause of death worldwide. Advancing the understanding of coronary microstructure-based mechanics is fundamental for the development of therapeutic tools and surgical procedures. Although the passive biaxial properties of the coronary arteries have been extensively explored, their regional differences and the relationship between tissue microstructure and mechanics have not been fully characterized. In this study, we characterized the passive biaxial mechanical properties and microstructural properties of the proximal, medial, and distal regions of the porcine left anterior descending artery (LADA). We also attempted to relate the biaxial stress-stretch response of the LADA and its respective birefringent responses to the polarized light for obtaining information about the load-dependent microstructural variations. We found that the LADA extensibility is reduced in the proximal-to-distal direction and that the medial region exhibits more heterogeneous mechanical behavior than the other two regions. We have also observed highly dynamic microstructural behavior where fiber families realign themselves depending on loading. In addition, we found that the microstructure of the distal region exhibited highly aligned fibers along the longitudinal axis of the artery. To verify this microstructural feature, we imaged the LADA specimens with multi-photon microscopy and observed that the adventitia microstructure transitioned from a random fiber network in the proximal region to highly aligned fibers in the distal region. Our findings may offer new perspectives for understanding coronary mechanics and aid in the development of tissue-engineered vascular grafts, which are currently limited due to their mismatch with native tissue in terms of mechanical properties and microstructural features.

Funding Information: We would also like to acknowledge the American Heart Association Scientist Development Grant Award (16SDG27760143) and the Presbyterian Health Foundation Team Science Grant. S.A.P.-C. was supported in part by the Alumni Fellowship from the Graduate College at the University of Oklahoma. D.W.L. was supported by the National Science Foundation Graduate Research Fellowship (GRF 2019254233).

Declaration of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence (bias) the work reported in this manuscript.

Keywords: coronary artery biomechanics, polarized spatial frequency domain imaging, planar biaxial testing, multi-photon microscopy, collagen and elastin microstructure