Investigating the structural responses of medial collagen and elastin to traction to elucidate mechanical property differences in porcine aorta and pulmonary artery

Along with the rising interest in regenerative medicine and tissue engineering comes the necessity to gain a deeper understanding of the underlying nature behind the mechanical responses of various soft tissues. This study investigates the differences in mechanical responses of the aorta and pulmonary artery, both of which share similar trilayered structures, by examining how their microstructural architectures influence their response to traction forces. As such, two-photon microscopy was used to visualize elastin and collagen fibers, via two-photon excited autofluorescence and second-harmonic generation respectively, during a mode I tensile fracture test on trouser-shaped specimens harvested from the aorta and pulmonary artery. The tensile tests revealed that while the aorta exhibited significantly higher low-strain elasticity compared to the pulmonary artery (aorta: 184.9 ± 37.4 kPa, pulmonary artery: 25.9 ± 6.0 kPa), both tissues required comparable forces for fracture propagation under mode I fracture (aorta: 7.6 ± 3.4 N, pulmonary artery: 6.3 ± 4.5 N). In this study, the possible reasons behind these mechanical disparities are discussed based on the microscopic images depicting the specimen's histologic structural deformation throughout the tensile test. Elastic responses from the aorta and pulmonary artery were discussed using static images of the elastin and collagen networks taken at a fixed interval during the tensile test. Moreover, this study presents the first successful acquisition of a microscopic video capturing the microstructural failure dynamics during arterial fracture, which served as a basis for discussion on the fracture properties of the aorta and pulmonary artery under mode I loading. These findings offer insights into fracture propagation mechanisms in arteries and underscore the importance of microstructural analysis for elucidating soft tissue biomechanics. STATEMENT OF SIGNIFICANCE: An artery's biomechanical response is essential for its physiological function and is influenced by the vessel's microstructure. While prior studies have focused on the elastic response of the aorta alone, this study examines both elastic and fracture behavior in the aorta and pulmonary artery. Microscopic image sequences capturing elastic and plastic deformation were acquired in both vessels, revealing microstructural differences leading to distinct biomechanical responses. From an engineering perspective, the results show that differences in elastin and collagen organization lead to artery-specific biomechanical properties, indicating that biomechanical models should incorporate vessel-specific structure rather than assuming uniform behavior. Clinically, these differences are relevant for vascular graft design, where matching both mechanical response and structural characteristics may improve performance and durability.