Adaptation-driven optimization strategies in reinforced vascular autografts

Precise medicine strategies for vascular autografts aim to conceive smart and biomechanically mimetic reinforcements able to support the arterialization process of autologous vessels, by bearing systemic loads while fostering virtuous microenvironments conducive to remodeling and growth. However, the mechanical discrepancy between synthetic devices and the biologically active host vessel often determine a conflict between requirements for robust short-term performance and for long-term functionality. Composite architectures should indeed compensate the compliance mismatch between aortic and venous tracts, on a side avoiding aneurysmal dilation and, on the other one, preventing excessive stress-shielding subverting tissue adaptation. Consequently, addressing the mechanical design challenges of reinforced grafts is essential to resolve the trade-off, providing structural support and replicating homeostasis. With this in mind, this work provides insights in the mechanistic interplay between reinforcement and tissue response in autografts, focusing on the effect of reinforcement stiffness on their arterialization. This is achieved by first introducing a mechanobiological model where growth and material remodeling are in full coupling with the nonlinear tissue elasticity, employing ad hoc analytical solutions to study the potential adaptation scenarios emerging from the interaction with implants at varying stiffness. Theoretical projections are then used to tailor a design optimization of reinforcement geometrical and mechanical features, implementing finite-element procedures to analyze the influence of filament number, dimensions and stiffness on realistic meshes. Overall, outcomes suggest how mild stiff reinforcements with mid-density filament architectures offer the most mechanically stable and physiologically consistent solution, opening possible biomechanically-based approaches for enhancing long-stable graft integration.