Tissue-Engineered Carotid Artery Interposition Grafts Demonstrate High Primary Patency and Promote Vascular Tissue Regeneration in the Ovine Model

Abstract

Tissue-engineered vascular graft for the reconstruction of small arteries is still an unmet clinical need, despite the fact that a number of promising prototypes have entered preclinical development. Here we test Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)Poly(ε-caprolactone) 4-mm-diameter vascular grafts equipped with vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and stromal cell-derived factor 1α (SDF-1α) and surface coated with heparin and iloprost (PHBV/PCL[VEGF-bFGF-SDF]Hep/Ilo, n = 8) in a sheep carotid artery interposition model, using biostable vascular prostheses of expanded poly(tetrafluoroethylene) (ePTFE, n = 5) as a control. Primary patency of PHBV/PCL[VEGF-bFGF-SDF]Hep/Ilo grafts was 62.5% (5/8) at 24 h postimplantation and 50% (4/8) at 18 months postimplantation, while all (5/5) ePTFE conduits were occluded within the 24 h after the surgery. At 18 months postimplantation, PHBV/PCL[VEGF-bFGF-SDF]Hep/Ilo grafts were completely resorbed and replaced by the vascular tissue. Regenerated arteries displayed a hierarchical three-layer structure similar to the native blood vessels, being fully endothelialised, highly vascularised and populated by vascular smooth muscle cells and macrophages. The most (4/5, 80%) of the regenerated arteries were free of calcifications but suffered from the aneurysmatic dilation. Therefore, biodegradable PHBV/PCL[VEGF-bFGF-SDF]Hep/Ilo grafts showed better short- and long-term results than bio-stable ePTFE analogues, although these scaffolds must be reinforced for the efficient prevention of aneurysms.

Controlled and Synchronised Vascular Regeneration upon the Implantation of Iloprost- and Cationic Amphiphilic Drugs-Conjugated Tissue-Engineered Vascular Grafts into the Ovine Carotid Artery: A Proteomics-Empowered Study

“…Among the most frequent complications of TEVG implantation are thrombosis, aneurysms, neointimal hyperplasia, calcification, atherosclerosis, and infection [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Previously, our group reported an efficient approach for increasing haemocompatibility and thrombosis prevention by immobilising an anticoagulant heparin and a vasodilator/antiplatelet drug, iloprost, to the luminal surface of PCL-based TEVGs [ 25 ]. Further, we have developed an anti-aneurysmatic PCL sheath attached to the TEVG outer surface by fused deposition modeling, a method employing 3D printing extrusion [ 60 ].…”

“…By this design, we were able to evaluate the extent of tissue remodeling and the balance between physiological and pathological remodeling during the degradation of TEVGs and their replacement by regenerating vascular tissue, having the intact contralateral carotid artery as the gauge. The efficacy of iloprost has been shown in one of the previous papers by our group [ 25 ], and thence we focused on tissue remodeling and vascular regeneration features rather than on the modification efficiency.…”

“…The proximal segment was fixed in two changes of 10% neutral phosphate buffered formalin (B06-003, ErgoProduction, Saint Petersburg, Russia) for 24 h at 4 °C, embedded into paraffin (Histomix Extra, 10342, ErgoProduction, Saint Petersburg, Russia), and cut (8 µm sections) on a microtome (Microm HM 325, Thermo Scientific, Waltham, MA, USA) as previously described [ 25 ]. To ensure proper histological examination, we prepared 8 sections, evenly distributed across the entire excised segment, per slide.…”

“…The second midgraft segment was fixed in 10% neutral phosphate buffered formalin (B06-003, ErgoProduction, Saint Petersburg, Russia), postfixed and stained in 1% phosphate buffered osmium tetroxide (OsO 4 , 19110, Electron Microscopy Sciences, Hatfield, PA, USA), dehydrated in ascending ethanol series (Kemerovo Pharmaceutical Plant, Kemerovo, Russia) and isopropanol (06-002, ErgoProduction, Saint Petersburg, Russia), stained in 2% alcoholic uranyl acetate (22400-2, Electron Microscopy Sciences, Hatfield, PA, USA), impregnated with acetone (6-09-20-03-83, EKOS-1, Moscow, Russia): epoxy resin (1:1) and epoxy resin (Araldite 502, 13900, Electron Microscopy Sciences, Hatfield, PA, USA), embedded into epoxy resin, grinded, polished, counterstained with Reynolds’s lead citrate (17810, Electron Microscopy Sciences, Hatfield, PA, USA), sputter coated with carbon (Leica EM ACE200, Leica Microsystems, Wetzlar, Germany) and visualised by means of backscattered scanning electron microscopy (S-3400N, Hitachi, Tokyo, Japan) in accordance with an EM-BSEM (embedding and backscattered scanning electron microscopy) procedure as previously described [ 25 , 35 ].…”

“…Clots within the scaffold promote microbial adhesion in cases of transient bacteriemia similar to the infective endocarditis scenario [ 23 ], and vascular graft infection might further enhance thrombosis [ 24 ]. Previously, we attached an anticoagulant, heparin, and a vasodilator/antiplatelet drug, iloprost, to the luminal surface of PCL-based TEVGs and reached 50% patency in the ovine model 18 months postimplantation, also demonstrating complete vascular regeneration at the implantation site [ 25 ]. Other groups have also reported efficiency of heparin conjugation for preventing thrombotic complications upon the TEVG implantation into sheep [ 26 , 27 ] and swine [ 28 ].…”