Construction of Oriented Structure in Inner Surface of Small-Diameter Artificial Blood Vessels:A Review

There is an urgent need for small-diameter artificial blood vessels in clinic.Physical,chemical and biological factors should be integrated to avoid thrombosis and intimal hyperplasia after implantation and to promote successful fabrication of small-diameter artificial blood vessels.From a physical perspective,the internal oriented structures of natural blood vessels plays an important role in guiding the directional growth of cells,improving the blood flow environment,and promoting the regeneration of vascular tissue.In this review,the effects of the oriented structures on cells,including endothelial cells(ECs),smooth muscle cells(SMCs)and stem cells,as well as the effect of the oriented structures on hemodynamics and vascular tissue remodeling and regeneration are introduced.Various forms of oriented structures(fibers,grooves,channels,etc.)and their construction methods are also reviewed.Conclusions and future perspectives are given.It is expected to give some references to relevant researches.

Weavability of β-Hydroxybutyrate and β-Hydroxyvalerate Copolymers( PHBV ) /PLA Used in Artificial Blood Vessels

The β-hydroxybutyrate and β-hydroxyvalerate copolymers( PHBV) /polylactic acid( PLA) is a new biocompatible material,which is developed through bacterial fermentation in vivo systems.The PHBV / PLA material could be used to make continuous filaments.However,features of artificial blood vessels,especially small diameter vascular grafts made of PHVB / PLA materials are not known.This research are to evaluate and improve weavability of the PHBV / PLA material, and to explore feasibility of using it in artificial blood vessels.Preliminary results showed that weavability of PHBV / PLV was not good,but its weavability could be improved by using methods of weak chemical,such as sizing.In this research,scanning electron microscope( SEM) was adopted to evaluate weavability of PHBV / PLV after sizing and observe surfaces of yarns and fabrics.Also,in order to set proper parameters in heat settings,differential scanning calorimetry( DSC) was used to identify glass transition temperature.

Design and Development of PHBV/PLA Artificial Blood Vessels

In the research,a β-hydroxybutyrate and β-hydroxyvalerate copolymer(PHBV)/polylactic acid(PLA)artificial blood vessel was designed and developed,and it was also implanted in vivo for a period of time to observe its biocompatibility and degradation performance.The results showed that the developed PHBV/PLA artificial blood vessel could be used to replace the natural blood vessel,but its degradation rate was too fast and the mechanical supporting force was insufficient.Thus,properties of the PHBV/PLA need to be further improved.

Simulation and preparation of novel medium convex artificial blood vessel for reducing compliance mismatch

Compliance mismatch between artificial blood vessel and host vessel can cause abnormal hemodynamics and is the main mechanical trigger of intimal hyperplasia(IH)after transplantation.To explore the specific effects of the degree of compliance mismatch on hemodynamics,the concept of“compliance mismatch degree”was defined in this paper.Numerical results showed that when the compliance mismatch degree was less than-22.21%or more than 3.16%,the minimum WSS in the anastomotic site was less than the safety threshold of 0.5 Pa,which is easy to induce IH.In addition,the compliance mismatch caused different radial displacements first,which in turn affected the hemodynamics.Inspired by this,a novel medium convex artificial blood vessel was proposed,and the simulation results theoretically validated its desired effect on reducing the compliance mismatch.An increase of 0.22 mm in the diameter of the artificial blood vessel corresponded to a decrease of 0.88%in compliance mismatch degree.The feasibility of preparing real medium convex artificial blood vessel was also investigated.The PLCL medium convex artificial blood vessel with good mechanical properties was prepared by dip-coating and electrospinning composite method.These findings are valuable for the design and preparation of novel artificial blood vessel which can make up for the mismatch of compliance.

Approaches to reconstruction of inferior vena cava by ex vivo liver resection and autotransplantation in 114 patients with hepatic alveolar echinococcosis

BACKGROUND Hepatic alveolar echinococcosis(AE)is most commonly found in retrohepatic inferior vena cava(RHIVC).Ex vivo liver resection and autotransplantation(ELRA)can better realize the radical resection of end-stage hepatic AE with severely compromised hepatocaval confluences,and reconstruction of the affected vessels.Currently,there is a scarcity of information regarding RHIVC reconstruction in ELRA.AIM To propose reasonable RHICV reconstruction strategies for ex vivo liver resection and autotransplantation.METHODS We retrospectively summarized the clinical data of 114 patients diagnosed with hepatic AE who treated by ELRA in our department.A total of 114 patients were divided into three groups according to the different reconstruction methods of RHIVC:Group A with original RHIVC being repaired and reconstructed(n=64),group B with RHIVC being replaced(n=43),and group C with RHIVC being resected without reconstruction(n=7).The clinical data of patients,including the operation time,anhepatic phase,intraoperative blood loss,complications and postoperative hospital stay,were analyzed and the patients were routinely followed up.The normally distributed continuous variables were expressed as means±SD,whereas the abnormally distributed ones were expressed as median and analyzed by analysis of variance.Survival curve was plotted by the Kaplan-Meier method.RESULTS All patients were routinely followed up for a median duration of 52(range,12-125)mo.The 30 d mortality rate was 7.0%(8/114)and 7 patients died within 90 d.Among all subjects,the inferior vena cava(IVC)-related complication rates were 17.5%(11/63)in group A and 16.3%(7/43)in group B.IVC stenosis was found in 12 patients(10.5%),whereas thrombus was formed in 6 patients(5.3%).Twenty-two patients had grade III or higher complications,with the complication rates being 17.2%,16.3%,and 57.1%in the three groups.The average postoperative hospital stay in the three groups was 32.3±19.8,26.7±18.2,and 51.3±29.4 d(P=0.03),respectively.CONCLUSION ELRA can be considered a safe and feasible option for end-stage hepatic AE patients with RHIVC infiltration.The RHIVC reconstruction methods should be selected appropriately depending on the defect degree of AE lesions in IVC lumen.The RHIVC resection without any reconstruction method should be considered with caution.

Hemocompatible polyurethane/gelatin-heparin nanofibrous scaffolds formed by a bi-layer electrospinning technique as potential artificial blood vessels

In this paper,a scaffold,which mimics the morphology and mechanical properties of a native blood vessel is reported.The scaffold was prepared by sequential bi-layer electrospinning on a rotating mandrel-type collector.The tubular scaffolds(inner diameter 4 mm,length 3 cm)are composed of a polyurethane(PU)fibrous outer-layer and a gelatin-heparin fibrous inner-layer.They were fabricated by electrospinning technology,which enables control of the composition,structure,and mechanical properties of the scaffolds.The microstructure,fiber morphology and mechanical properties of the scaffolds were examined by means of scanning electron microscopy(SEM)and tensile tests.The PU/gelatinheparin tubular scaffolds have a porous structure.The scaffolds achieved a breaking strength(3.7±0.13 MPa)and an elongation at break(110±8%)that are appropriate for artificial blood vessels.When the scaffolds were immersed in water for 1 h,the breaking strength decreased slightly to 2.2±0.3 MPa,but the elongation at break increased to 145
21%.In platelet adhesion tests the gelatin-heparin fibrous scaffolds showed a significant suppression of platelet adhesion.Heparin was released from the scaffolds at a fairly uniform rate during the period of 2nd day to 9th day.The scaffolds are expected to mimic the complex matrix structure of native arteries,and to have good biocompatibility as an artificial blood vessel owing to the heparin release.

History,progress and future challenges of artificial blood vessels:a narrative review

Cardiovascular disease serves as the leading cause of death worldwide,with stenosis,occlusion,or severe dysfunction of blood vessels being its pathophysiological mechanism.Vascular replacement is the preferred surgical option for treating obstructed vascular structures.Due to the limited availability of healthy autologous vessels as well as the incidence of postoperative complications,there is an increasing demand for artificial blood vessels.From synthetic to natural,or a mixture of these components,numerous materials have been used to prepare artificial vascular grafts.Although synthetic grafts are more appropriate for use in medium to large-diameter vessels,they fail when replacing small-diameter vessels.Tissue-engineered vascular grafts are very likely to be an ideal alternative to autologous grafts in small-diameter vessels and are worthy of further investigation.However,a multitude of problems remain that must be resolved before they can be used in biomedical applications.Accordingly,this review attempts to describe these problems and provide a discussion of the generation of artificial blood vessels.In addition,we deliberate on current state-of-the-art technologies for creating artificial blood vessels,including advances in materials,fabrication techniques,various methods of surface modification,as well as preclinical and clinical applications.Furthermore,the evaluation of grafts both in vivo and in vitro,mechanical properties,challenges,and directions for further research are also discussed.

Electrospun fiber membrane with asymmetric NO release for the differential regulation of cell growth

The high incidence of cardiovascular disease has led to significant demand for synthetic vascular grafts in clinical applications.Anti-proliferation drugs are usually loaded into devices to achieve desirable anti-thrombosis effects after implantation.However,the non-selectiveness of these conventional drugs can lead to the failure of blood vessel reconstruction,leading to potential complications in the long term.To address this issue,an asymmetric membrane was constructed through electro-spinning techniques.The bilayer membrane loaded and effectively released nitric oxide(NO),as hoped,from only one side.Due to the short diffusion distance of NO,it exerted negligible effects on the other side of the membrane,thus allowing selective regulation of different cells on both sides.The released NO boosted the growth of endothelial cells(ECs)over smooth muscle cells(SMCs)-while on the side where NO was absent,SMCs grew into multilayers.The overall structure resembled a native blood vessel,with confluent ECs as the inner layer and layers of SMCs to support it.In addition,the membrane preserved the normal function of ECs,and at the same time did not exacerbate inflammatory responses.By preparing this material type that regulates cell behavior differentially,we describe a new method for its application in the cardiovascular field such as for artificial blood vessels.

Numerical simulation to study the impact of compliance mismatch between artificial and host blood vessel on hemodynamics

Small-diameter artificial blood vessels are prone to cause intimal hyperplasia(IH)after transplantation,which leads to restenosis and low long-term patency rates.The main biomechanical factor for IH formation is the compliance mismatch between the artificial and host blood vessels which can cause abnormal hemodynamics.Although there have been many studies on vascular compliance mismatches,however,little attention has been paid to the effect of the degree of compliance mismatch between graft and the host vessel on hemodynamics.At present,the research on compliance mismatch between the artificial and host blood vessels is still very limited,especially with regard to the specific impact of the compliance mismatch degree on hemodynamics.Therefore,three end-to-end anastomosis models(the compliance of the artificial blood vessel is lower than,similar to,and higher than that of the host blood vessel,called model 1,model 2,model 3,respectively)were constructed and simulated in this study.Simulation results showed that the radial displacement difference between the artificial and host blood vessels were 0.281 mm,0.183 mm and 0.485 mm in model 1,model 2 and model 3,respectively.A low-velocity recirculation zone near the distal anastomosis was formed in model 1 which resulted in excessively low TAWSS(9.261 E-5Pa)and high OSI(0.497).Similarly,a low-velocity recirculation zone near the proximal anastomosis was formed in model 3 and lead to low TAWSS(6.007 E-4Pa)and high OSI(0.480).However,there was no low-velocity recirculation zone near the anastomosis stoma in model 2.The results are instructive for the design and preparation of artificial blood vessels.