The in vivo performance of small-caliber nanofibrous polyurethane vascular grafts

Abstract

BackgroundIn a previous in vitro study, we confirmed that small-caliber nanofibrous polyurethane (PU) vascular grafts have favorable mechanical properties and biocompatibility. In the present study, we examined the in vivo biocompatibility and stability of these grafts.MethodsForty-eight adult male beagle dogs were randomly divided into two groups receiving, respectively, polyurethane (PU) or polytetrafluoroethylene (PTFE) grafts (n = 24 animals / group). Each group was studied at 4, 8, 12, and 24 weeks after graft implantation. Blood flow was analyzed by color Doppler ultrasound and computed tomography angiography. Patency rates were judged by animal survival rates. Coverage with endothelial and smooth muscle cells was characterized by hematoxylin-eosin and immunohistological staining, and scanning electron microscopy (SEM).ResultsPatency rates were significantly higher in the PU group (p = 0.02 vs. PTFE group). During the first 8 weeks, endothelial cells gradually formed a continuous layer on the internal surface of PU grafts, whereas coverage of PTFE graft by endothelial cells was inhomogeneous. After 12 weeks, neointimal thickness remained constant in the PU group, while PTFE group showed neointimal hyperplasia. At 24 weeks, some anastomotic sites of PTFE grafts became stenotic (p = 0.013 vs. PU group). Immunohistological staining revealed a continuous coverage by endothelial cells and an orderly arrangement of smooth muscle cells on PU grafts. Further, SEM showed smooth internal surfaces in PU grafts without thrombus or obvious neointimal hyperplasia.ConclusionsSmall-caliber nanofibrous PU vascular grafts facilitate the endothelialization process, prevent excessive neointimal hyperplasia, and improve patency rates.

Promoting Endothelialization of Polymeric Cardiovascular Biomaterials

“…Additionally, a functioning endothelium shields the underlying smooth muscle cells from factors in the blood stream and locally produces antiproliferative agents . In recent years, polyurethane grafts have shown promise in this space due to their more acceptable mechanical properties when compared to native vasculature …”

“…[14] In recent years, polyurethane grafts have shown promise in this space due to their more acceptable mechanical properties when compared to native vasculature. [34,35]…”

Polymers in Cardiology

“…PUR, due to their excellent hemocompatibility well-established as scaffold materials for vascular grafts [26][27][28][29], can be synthesized by a stepwise addition reaction, therefore called step-growth polymerization, between isocyanate and alcohol bifunctional monomers. In addition to the mentioned polyaddition and as a further type of step-growth polymerizations polycondensation reactions are generally used for the synthesis of polyesters.…”

Computational study on the haemodynamic and mechanical performance of electrospun polyurethane dialysis grafts

“…Electrospun polyurethane (ePU) has emerged as a possible substitute to ePTFE for vascular grafts (Hu et al 2012). Since ePU can be manufactured over a large range of mechanical properties (Montini-Ballarin et al 2016), resulting grafts can be tuned to better match the mechanical properties of native veins, thereby minimising graft-vein compliance mismatch.…”

“…Since ePU can be manufactured over a large range of mechanical properties (Montini-Ballarin et al 2016), resulting grafts can be tuned to better match the mechanical properties of native veins, thereby minimising graft-vein compliance mismatch. Furthermore, since the grafts are spun, they exhibit a fibrous structure that closely resembles native extracellular matrix (Hu et al 2012). This structure allows for better graft endothelialisation compared to ePTFE grafts, which enhances the graft's biocompatibility (Hu et al 2012).…”