Transient elastic support for vein grafts using a constricting microfibrillar polymer wrap

Abstract

Arterial vein grafts (AVGs) often fail due to intimal hyperplasia, thrombosis, or accelerated atherosclerosis. Various approaches have been proposed to address AVG failure, including delivery of temporary mechanical support, many of which could be facilitated by peri-vascular placement of a biodegradable polymer wrap. The purpose of this work was to demonstrate that a polymer wrap can be applied to vein segments without compromising viability/function, and to demonstrate one potential application; i.e., gradually imposing the mid-wall circumferential wall stress (CWS) in wrapped veins exposed to arterial levels of pressure.Poly(ester urethane)urea, collagen, and elastin were combined in solution, and then electrospun onto freshly-excised porcine internal jugular vein segments. Tissue viability was assessed via Live/ Dead™ staining for necrosis, and vasomotor-challenge with epinephrine and sodium nitroprusside for functionality. Wrapped vein segments were also perfused for 24-hrs within an ex vivo vascular perfusion system under arterial conditions (pressure=120/80 mmHg; flow=100 mL/min), and CWS was calculated every hour.Our results showed that the electrospinning process had no deleterious effects on tissue viability, and that the mid-wall CWS vs. time profile could be dictated through the composition and degradation of the electrospun wrap. This may have important clinical applications by enabling the engineering of an improved AVG.

The Use of Natural Polymers in Tissue Engineering: A Focus on Electrospun Extracellular Matrix Analogues

“…The polymer wrap proved to be efficient in adding structural support, as electrospun porcine internal jugular veins appeared to be less stiff than sham controls when exposed to arterial conditions for 24 hours (pulsatile pressure of 120/80 mmHg and a mean perfusate flow of 100 mL/min). In addition, as confirmed by a live/dead assay, the electrospinning process had no deleterious effects on tissue viability [89].…”

“…Collagen:elastin:PLLA and collagen:elastin:PCL scaffolds maintained their original diameters over the 2 months without contraction or swelling, and had only reduced to 90.1% and 87.4% of their initial diameters, respectively. El-Kurdi et al electrospun a poly(ester urethane) urea, collagen and elastin blend from HFP onto freshly excised porcine internal jugular vein segments to further enhance the structural integrity of the vein [89]. Histological and SEM images verified a strong attachment of the polymer wrap to the adventitial surface of the vein.…”

Computational Simulation of the Adaptive Capacity of Vein Grafts in Response to Increased Pressure

“…Given this finding, and motivated by some prior empirical (e.g., Ref. [46]) and computational (e.g., Refs. [36,54]) studies, we then explored possible advantages of increasing the pressure gradually rather than abruptly, as occurs during surgical procedures when the arterial clamps are released.…”

“…This situation is analogous to a step change in pressure. A biodegradable coating on the graft could be envisioned that would expose the vein to a gradual increase in pressure [46,47], mimicking numerical experiment 2. Observations from this experiment could have potential implications in the design of synthetic sheaths and alternate clinical procedures.…”

Mechanical behavior of bilayered small-diameter nanofibrous structures as biomimetic vascular grafts

“…Vacular grafts were simulated using an isotropic linearelastic mechanical model (El-Kurdi et al, 2008;Vorp et al, 1995). Some simplifications were taken as described elsewhere: the vascular graft geometry was idealized as two/ three concentric incompressible, homogeneous, isotropic, linear-elastic layers with perfect adherence (Fig.…”