Tissue Engineering Small Vascular Graft Of Adventitia Sheathed With Nano Poly ?-caprolactoneon And Intima Coated With Heparin

Objective Small-diameter vascular grafts(SDVGs)(D ? 5mm)are increasingly needed in the clinic for cardiovascular disease,especially in coronary artery surgery and peripheral artery vascular surgery.Total arterial bypass surgery usually has excellent long-term patency rate,but autologous vascular grafts often restricted for the patients' condition.Vascular grafts made from synthetic polymers have shortcomings such as thrombogenecity,intimal hyperplasia,calcification,chronic inflammation and no growth potential.Decellularized xenografts are commonly used as tissue engineering substitutes for vascular reconstructive procedures.Although acellular allogeneic vascular grafts have good histocompatibility and antithrombotic properties,the process of decellularization may damage the biomechanics and accelerate the elastin deformation and degradation,finally resulting in vascular grafts expansion and even aneurysm formation.Here,a new hybrid tissue-engineered vascular graft(HTEV)was developed and composed of natural decellularized small-diameter artery,electrospinning nano-polycaprolactone adventitia sheath,and intima heparin coating.Materials and Methods In the first part of the experiment,decellularized rat aorta(DRA),as a biological vascular scaffold,was made by the rat aorta decellularization with a complex program with detergent and DNAse and RNAse.The effect of decellularization was observed with total DNA assay,and the damage of the fibrogen fiber was evaluated with histology and scanning electron microscope.In the second part,further to prepare a composite type of tissue engineering small caliber vascular scaffold,we used electrospinning nano-polycaprolactone(PCL)to sheath out the decellularized artery to improve the mechanical properties of the DRA.Then the wall thicknesses,suture retention strength,radial and axial tensile testing,burst pressure test of the vessels were measured to characterize the mechanical properties of different types of grafts.In the third part of the experiment,we modified the intima of HTEV scaffold with heparin coating,and verified the incorporation by immunofluorescence and the biocompatibility in vitro.In the fourth part of the experiment,HTEV was implanted inferior to renal artery in rat model in vivo to evaluate the HTEV biological functions.Small animal ultrasound and clear superiority detective CT were performed at six weeks after implantation to measure the blood flow velocity and to observe the vascular morphological and structural changes.The vascular grafts were explanted twelve weeks after implantation,and histology and immunofluorescence were performed to evaluate the vascular structure,endothelial recellularization and inflammation.Results The donor aortic vessels were successfully decellularized with a combination of different detergents and dehydrated under vacuum freeze-drying process.Histopathology and scanning electron microscope displayed the media of decellularized vessels were severely injured.The radial and axial tensile stresses of DRA were significantly reduced after decellularization process.Mechanical testing of scaffolds showed that electrospinning nano-polycaprolactone significantly enhanced the axial strain and burst pressure,which were higher than that of natural rat aortas(NRA),showing excellent biomechanical compliance of HTEV scaffolds.Then the intima of HTEV scaffold was coated with heparin before allograft transplantation.Heparin coating modification significantly reduced the number of platelets that adhered to the HTEV compared with non-heparin DRA,and there were no statistically significant differences between the NRA and HTEV,exhibiting superior biocompatibility.Heparin coating modification promoted the intimal endothelialization of HTEV.Vascular ultrasound and micro-CT angiography showed all grafts were satisfactorily patent after implantation in a rat model for up to 6 weeks.Electrospinning nano-polycaprolactone sheath successfully prevented the occurrence of vasodilation and aneurysm formation after transplantation and reduced inflammatory cell infiltration and induced smooth muscle cells extravascular growth,thereby reducing the intimal hyperplasia.Conclusions Decellularized artery of adventitia sheathed with nano poly ?-caprolactoneon and intima coated with heparin could be used to prepare a kind of new hybrid tissue engineering small caliber vascular graft.ES-PCL sheath greatly increased tensile strength of the hybrid tissue engineering vascular graft,and heparin coating improved the biocompatibility of the HTEV,which provide a new theoretical foundation for the construction of tissue engineering artificial small blood vessels.HTEV with excellent histocompatibility and biomechanics provides a facile and useful technique for the development of SDVGs,and is of great potential clinical application.