Biodegradable, Self-Reinforcing Vascular Grafts for In Situ Tissue Engineering Approaches.

Clinically available small-diameter synthetic vascular grafts (SDVGs) have unsatisfactory patency rates due to impaired graft healing. Therefore, autologous implants are still the gold standard for small vessel replacement. Bioresorbable SDVGs may be an alternative, but many polymers have inadequate biomechanical properties that lead to graft failure. To overcome these limitations, a new biodegradable SDVG is developed to ensure safe use until adequate new tissue is formed. SDVGs are electrospun using a polymer blend composed of thermoplastic polyurethane (TPU) and a new self-reinforcing TP(U-urea) (TPUU). Biocompatibility is tested in vitro by cell seeding and hemocompatibility tests. In vivo performance is evaluated in rats over a period for up to six months. Autologous rat aortic implants serve as a control group. Scanning electron microscopy, micro-computed tomography (µCT), histology, and gene expression analyses are applied. TPU/TPUU grafts show significant improvement of biomechanical properties after water incubation and exhibit excellent cyto- and hemocompatibility. All grafts remain patent, and biomechanical properties are sufficient despite wall thinning. No inflammation, aneurysms, intimal hyperplasia, or thrombus formation are observed. Evaluation of graft healing shows similar gene expression profiles of TPU/TPUU and autologous conduits. These new biodegradable, self-reinforcing SDVGs may be promising candidates for clinical use in the future.

Chorion-derived extracellular matrix hydrogel and fibronectin surface coatings show similar beneficial effects on endothelialization of expanded polytetrafluorethylene vascular grafts.

The endothelium plays an important regulatory role for cardiovascular homeostasis. Rapid endothelialization of small diameter vascular grafts (SDVGs) is crucial to ensure long-term patency. Here, we assessed a human placental chorionic extracellular matrix hydrogel (hpcECM-gel) as coating material and compared it to human fibronectin in-vitro. hpcECM-gels were produced from placental chorion by decellularization and enzymatic digestion. Human umbilical vein endothelial cells (HUVECs) were seeded to non-, fibronectin- or hpcECM-gel-coated expanded polytetrafluorethylene (ePTFE) SDVGs. Coating efficiency as well as endothelial cell proliferation, migration and adhesion studies on grafts were performed. hpcECM-gel depicted high collagen and glycosaminoglycan content and neglectable DNA amounts. Laminin and fibronectin were both retained in the hpcECM-gel after the decellularization process. HUVEC as well as endothelial progenitor cell attachment were both significantly enhanced on hpcECM-gel coated grafts. HUVECs seeded to hpcECM-gel depicted significantly higher platelet endothelial cell adhesion molecule-1 (PECAM-1) expression in the perinuclear region. Cell retention to flow was enhanced on fibronectin and hpcECM-gel coated grafts. Since hpcECM-gel induced a significantly higher endothelial cell adhesion to ePTFE than fibronectin, it represents a possible alternative for SDVG modification to improve endothelialization.