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BACKGROUND: In recent years, the rapid development of tissue engineering technology provides a new idea for the treatment of intervertebral disc degeneration; that is, biomaterials are used to reconstruct the damaged intervertebral disc structure. OBJECTIVE: To summarize polymer materials which are applicable for intervertebraltissue engineering construction, and overview the advantages, disadvantages and application progress of each material. METHODS: We searched related articles from inception to February 2020 in PubMed, Web of Science and CNKI databases with “polymer, intervertebral disc, tissue engineering, nucleus pulposus, annulus fibrosus” as English and Chinese key words. Initially 189 related articles were searched, and 109 eligible articles were included in final analysis according to inclusion and exclusion criteria. RESULTS AND CONCLUSION: Intervertebral disc is composed of inner soft nucleus pulposus and outer stiff annulus fibrosus. Accordingly, it requires two components with different structures and functions to reconstruct a complete intervertebral disc with tissue engineering method. Chitosan, alginate and hyaluronic acid are considered as optimal materials for nucleus pulposus construction because of their appropriate swelling character and ability of inducing cells to secrete nucleus pulposus matrix. Silk fibroin, collagen, polyethylene glycol, polylactic acid, polyglycolic acid and polycaprolactone with high mechanical strength are suitable for annulus fibrosus construction to bear high loading burden. By further surface modification, these synthesis scaffolds wound show a better cellular compatibility and promote tissue integrity after in vivo implantation.
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Objective To evaluate medium-term valvular functionality after transcatheter pulmonary valve replacement in sheep using a novel polymeric prosthetic pulmonary valve(PPHV). Methods In this study, we designed a novel polymeric trileaflet transcatheter pulmonary valve with a balloon-expandable stent, and the valve leaflet was made of 0. 1mm expanded polytetrafluoroethylene( ePTFE) . We chose bovine pericardium valve as control. Pulmonary valve stents were implanted in situ by right ventricular apical approach in 12 healthy sheep(10 for polymeric valve and 2 for bovine pericardium valve) weighing anaverageof(22.1±2.3)kg. Echocardiography,angiography,64-rowcomputedtomography(CT),andautopsywereusedto assess valvular function 12 weeks after implantation. Results Two PPHVs failed to be implanted in situ of pulmonary valve po-sition. Implantation was successful in the other 10 sheep. One sheep died of pneumonia, and the other 9 sheep survived at the end of follow-up. Echocardiography 12 weeks after implantation showed all the PPHVs exhibited good functionality and no sig-nificant insufficiency. The peak-peak transvalvular pressure gradient of the PPHVs was(28.2 ±8.0)mmHg(16-38 mmHg) (1 mmHg=0. 133 kPa), while that of two bovine pericardium valves were 16 and 21 mmHg. Angiography and CT 12 weeks after implantation demonstrated orthotopic position and normal operation of the valves,and no deformation of the valved stents. Pathological examination of the explanted PPHVs 12 weeks after implantation showed no degradation or damage of the ePTFE leaflets and most of the leaflets were thin and pliable, without significant thrombus or calcification, while visible pannus over-growth was found at the bottom of the valve leaflets, in the commissural areas and on the sealing cuff. Conclusion The medi-um-term effects of the novel ePTFE pulmonary valve after transcatheter pulmonary valve implantation in sheep is good. The no-vel PPHV exhibits good anti-adhesion, anti-degradation, anti-thrombus, anti-calcification performance and good biomechanical property. The hemodynamic parameter of PPHV is comparable to bovine pericardium valve. Optimizing the valve design might eliminate the problem about pannus overgrowth.
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Objective To evaluate valvular functionality after transcatheter pulmonary valve replacement in sheep using a novel polymeric prosthetic pulmonary valve.Methods In this study,we designed a novel polymeric trileaflet transcatheter pulmonary valve with a balloon-expandable stent,and the valve leaflet was made of 0.1 mm expanded polytetrafluoroethylene (ePTFE).We chose bovine pericardium valve as control.Pulmonary valve stents were implanted in situ by right ventricular apical approach in 8 healthy sheep(6 for polymeric valve and 2 for bovine pericardium valve) weighing an average of(22.8 ± 2.2) kg.Angiography was performed after implantation to assess immediate valvular function.Color Doppler echocardiography and 64-row computed tomography were used to assess valvular function 4 weeks after implantation.Results Implantation was successful in 8 sheep.Angiography at implantation showed one polymeric valve was located below the ideal position and most of the stent was in the outflow tract of right ventricle.While,all the other prosthetic valves demonstrated orthotopic position and exhibited normal open and close functionality.Echocardiography 4 weeks after implantation showed all the prosthetic valves exhibited normal functionality and no significant insufficiency.The peak-peak transvalvular pressure gradient of the polymeric valves was (18.8 ± 6.0) mmHg,while that of two bovine pericardium valves were 9 mmHg and 20 mmHg.CT 4 weeks after implantation demonstrated orthotopic position of the stents except the above-mentioned one and all the stents had no deformation.Conclusion The success rate of transcatheter pulmonary valve replacement by right ventricular apical approach is satisfactory.The early valvular functionality of the novel ePTFE pulmonary valve after transcatheter pulmonary valve replacement in sheep is good.