Figure 6. Hypothesis-Driven Studies to Improve Evolving Linearized Stiffness.
Values of circumferential (left) and axial (right) linearized stiffness, computed at in vivo values of circumferential and axial stretch, are contrasted between the simulated TEVGs (lines) and native inferior vena cava (solid symbols). All simulations are for experimental scaffold parameters ε = 80% and ω* = 1.4, with the baseline case from Figures 2 and 3 indicated by the solid black curve for comparison. The top row shows potential effects of reducing the rate at which the polymer loses load-bearing integrity via ξp ∈ [0.01cp, 0.3cp], the middle row shows potential effects of decreasing the survival fraction of ECM constituents produced during the inflammatory period, and the bottom row shows a single case wherein all deposited matrix has the same mechanical properties of the native vein. Of particular note (top row), tuning the polymer degradation rate could result in a linearized stiffness that is more consistent throughout the evolution of the graft (i.e., less of a valley at B and less of a peak at C), albeit still at overall higher biaxial values than native. Indeed, only if all newly deposited matrix has properties identical to native can the graft evolve to become truly normal after the polymer degrades, though in all cases the polymer creates a “compliance mismatch” with the native host vessels early on.