Longitudinal Evaluation of Biomechanical Properties of Neoarteries Formed Through Degrading Tissue Engineered Vascular Grafts

Cell-free degrading tissue engineered vascular grafts (TEVGs) elicit successful neoartery development through the effective interplay between graft degradation and extracellular matrix (ECM) deposition. The main mechanism of... [ view full abstract ]

Cell-free degrading tissue engineered vascular grafts (TEVGs) elicit successful neoartery development through the effective interplay between graft degradation and extracellular matrix (ECM) deposition. The main mechanism of ECM formation is through a stress-driven mechanobological response of ECM-producing cells by load transfer through the degrading graft. This work aims to evaluate evolution of biomechanical properties of neoarteries formed through degradation of a bi-layered composite graft: porous poly-glycerol sebacate (PGS) core and electrospun polycaprolactone (PCL) sheath.
Excised neoarteries (n=4) from a rat carotid artery interposition model were obtained at 14, 30 and 90 days post-implantation. Microcomputed tomography (MicroCT) was used to evaluate PGS volume fraction followed by biaxial inflation testing to evaluate passive mechanical properties. Multiphoton microscopy was used to assess collagen fiber density and recruitment with loading.
MicroCT evaluation showed that almost all PGS was degraded by day 14 (fig. 1a). Mechanical testing showed that loss of strength due to this degradation was accompanied by production of collagen fibers to bear load. These collagen fibers exhibited gradual recruitment upon loading. Fig 1b shows the projected multiphoton images of recruited fibers at 20% axial stretch at 120mmHg imaged through the thickness of the neortery at different time points.
Our results showed that the evolution of biomechanical properties of neoarteries was chiefly through the stress-driven production of collagen fibers. A difference in collagen recruitment was observed over time which suggests the presence of multiple remodeling mechanisms likely dependent on initial conditions which are currently under investigation.