A Novel Hybrid Silk Fibroin/Polyurethane Arteriovenous Graft for Hemodialysis: Proof-of-Concept Animal Study in an Ovine Model

To solve the problem of vascular access failure, a novel semi-degradable hybrid vascular graft, manufactured by electrospinning using silk fibroin and polyurethane (Silkothane), has been previously developed and characterized in vitro. This proof-of-concept animal study aims at evaluating the performances of Silkothane grafts in a sheep model of arteriovenous shunt, in terms of patency and short-term remodeling. Nine Silkothane grafts are implanted between the common carotid artery and the external jugular vein of nine sheep, examined by palpation three times per week, by echo-color Doppler every two weeks, and euthanized at 30, 60, and 90 days (N = 3 per group). At sacrifice, grafts are harvested and submitted for histopathology and/or scanning electron microcopy (SEM). No cases of graft-related complications are recorded. Eight of nine sheep (89%) show 100% primary unassisted patency at the respective time of sacrifice (flow rate 1.76 ± 0.61 L min−1, one case of surgery-related thrombosis excluded). Histopathology and SEM analysis evidence signs of inflammation and pseudointima inside the graft lumen, especially at the venous anastomosis; however, endoluminal stenosis never impairs the functionality of the shunt and coverage by endothelial cells is observed. In this model, Silkothane grafts grant safety and 100% patency up to 90 days.