Tissue Engineering and Regenerative Medicine

The in vitro simulation of physiological mechanical conditioning through bioreactors plays a pivotal role in the development of functional tissue-engineered blood vessels. Thus, we developed a scaffold-specific fluid-structure interaction (FSI) model under pulsatile perfusion provided by a bioreactor in order to estimate the flow rate that ensures physiological circumferential deformations (εcirc) and wall shear stresses (WSS) on cells seeded on the tubular scaffold. The 2D-axial symmetric FSI model,computed by COMSOL Multiphysics 4.4, represents two domains: The former schematizes decellularized swine artery scaffold,defined as a linear viscoelastic material characterized by its elastic modulus and shear relaxation modulus, previously obtainedby uniaxial stretch tests. The latter domain represents the culture medium, defined as an isotropic, homogeneous, incompressible and Newtonian fluid. A pulsatile and parabolic velocity profile is prescribed at the model inlet, while calculated pressure is prescribed at the scaffold outlet. The pressure is estimated at the scaffold end by solving boundary ordinary differential equations, in relation to construct deformations and to the bioreactor downstream lumped-parameter hydraulic circuit. Our results indicate that the FSI-simulated εcirc-max and εcirc-min are statistically comparable to the experimentally estimated values at the considered flow rate, showing the maximum around 10%. The computed WSS values are in the range of 0.175-2.940 dyne/cm2. Both εcirc (≤10%) and WSS (≤20 dyne/cm2) fall within the physiological range for vascular cells. Therefore,the in silico FSI model well describes scaffold mechanical conditioning when subjected to pulsatile perfusion, properly driving its’ in vitro physiological maturation using scaffold mechanical properties obtained experimentally.