In vivo evaluation of biomimetic fluorosurfactant polymer-coated expanded polytetrafluoroethylene vascular grafts in a porcine carotid artery bypass model

Abstract

The objective of this study was to evaluate the potential for biomimetic self-assembling fluorosurfactant polymer (FSP) coatings incorporating heptamaltose (M7-FSP) to block nonspecific protein adsorption, the cell adhesive RGD peptide (RGD-FSP), or the endothelial cell-selective CRRETAWAC peptide (cRRE-FSP) to improve patency and endothelialization in small-diameter expanded polytetrafluoroethylene (ePTFE) vascular graft implants. ePTFE vascular grafts (4mm in diameter, 5cm in length) were coated with M7-FSP, RGD-FSP, or cRRE-FSP by dissolving FSPs in distilled water and flowing solution through the graft lumen for 24hours. Coatings were confirmed by receding water contact angle measurements on the lumen surface. RGD-FSP and cRRE-FSP grafts were presodded invitro with porcine pulmonary artery endothelial cells (PPAECs) using a custom-designed flow system. PPAEC coverage on the lumen surface was visualized with epifluorescent microscopy and quantified. Grafts were implanted as carotid artery interposition bypass grafts in seven pigs for 33± 2days (ePTFE, n= 3; M7-FSP, n= 4; RGD-FSP, n= 3; cRRE-FSP, n= 4). Patency was confirmed immediately after implantation with duplex color flow ultrasound and at explantation with contrast-enhanced angiography. Grafts were sectioned for histology and stained: Movat pentachrome stain to outline vascular layers, immunofluorescent staining to identify endothelial cells (anti-von Willebrand factor antibody), and immunohistochemical staining to identify smooth muscle cells (anti-smooth muscle α-actin antibody). Neointima to lumen area ratio was determined to evaluate neointimal hyperplasia. Receding water contact angle measurements on graft luminal surfaces were significantly lower (P< .05) on FSP-coated ePTFE surfaces (M7-FSP, 40± 16 degrees; RGD-FSP, 25± 10 degrees; cRRE-FSP, 33± 16 degrees) compared with uncoated ePTFE (126± 2 degrees), confirming presence of the FSP layer. Invitro sodding of PPAECs on RGD-FSP and cRRE-FSP grafts resulted in a confluent monolayer of PPAECs on the luminal surface, with a similar cell population on RGD-FSP (1200± 187 cells/mm(2)) and cRRE-FSP (1134± 153 cells/mm(2)) grafts. All grafts were patent immediately after implantation, and one of three uncoated, two of three RGD-FSP, two of four M7-FSP, and two of four cRRE-FSP grafts remained patent after 1month. PPAEC coverage of the lumen surface was seen in all patent grafts. RGD-FSP grafts had a slightly higher neointima to lumen area ratio (0.53± 0.06) compared with uncoated (0.29±0.15), M7-FSP (0.20± 0.15), or cRRE-FSP (0.17± 0.09) grafts. Biomimetic FSP-coated ePTFE grafts can be used successfully invivo and have potential to support endothelialization. Grafts modified with the M7-FSP and cRRE-FSP showed lower intimal hyperplasia compared with RGD-FSP grafts.