A fiber-progressive-engagement model to evaluate the composition, microstructure, and nonlinear pseudoelastic behavior of porcine arteries and decellularized derivatives.

The theoretical fiber-progressive-engagement model was proposed to describe the pseudoelastic behavior of an artery pre- and post-decellularization treatments. Native porcine arteries were harvested and decellularized with 0.05% trypsin for 12 h. The uniaxial tensile test data were fitted to the fiber-progressive-engagement model proposed herein. The effects of decellularization on the morphology, structural characteristics, and composition of vessel walls were studied. The experimental stress-strain curve was fitted to the model in the longitudinal and circumferential direction, which demonstrated the adequacy of the proposed model (R2>0.99). The initial and turning strains were similar in the longitudinal and circumferential directions in the aorta, suggesting the occurrence of collagen conjugation in both directions. Discrepancies in the initial and turning strain and initial and stiff modulus in both directions in the coronary artery revealed the anisotropic features of this vessel. Decellularization induced a decrease in the initial and turning strains, a slight change in the initial modulus, and a substantial decrease in the stiffness modulus. The decrease in the initial and turning strain can be attributed to the loss of waviness of collagen bundles because of the considerable decrease in elastin and glycosaminoglycan contents. This simple non-linear model can be used to determine the fiber modulus and waviness degree of vascular tissue. Based on these results, this mechanical test can be used as a screening tool for the selection of an optimized decellularization protocol for arterial tissues. STATEMENT OF SIGNIFICANCE: Decellularized vascular graft has potential in clinical application, such as coronary artery bypass surgery, peripheral artery bypass surgery or microsurgery. An ideal decellularization protocol requires balance in cell removal efficiency and extracellular matrix preserving. Both biochemical and biomechanical properties are crucial to the success of scaffold in cell seeding and animal study. A comprehensive understanding of the composition, microstructure, and mechanical behavior of the arterial wall is the key to the development of decellularized vascular grafts. For this purpose, we proposed this "Fiber-Progressive-Engagement" model to evaluate the microstructure, composition and mechanical properties of porcine coronary artery. The model provides a new perspective regarding the non-linear behavior of arterial tissue and its decellularized derivatives. It can be widely applied to different types of tissues, as demonstrated in the aorta and coronary artery. This model has several advantages; it provides an improved fit of non-linear curves (R2>0.99), can be used to elucidate the pseudoelastic properties of porcine vascular tissues using the concept of fiber engagement, and can estimate an elastic modulus with greater accuracy (compared to the graphical estimation or calculation by simple linear fittings), as well as to plot typical stress-strain curves.