聚氨酯涤纶复合人工血管顺应性研究

目的 分析不同应用环境对聚氨酯涤纶复合人工血管顺应性的影响。方法 通过改变测试中的频率和压力模拟人工血管不同应用环境,对3种不同直径的聚氨酯涤纶复合人工血管在恒定压力不同频率,以及恒定频率不同压力下的顺应性进行测试,使用t检验分析测试结果的差异性。结果 本研究中使用的3种直径的聚氨酯涤纶复合人工血管,在恒定压力不同频率的测试中,顺应性测试值均随着频率的增大而减小(P<0.05);在恒定频率不同压力的测试中,顺应性测试值随着压力的增大而减小(P<0.05)。结论 聚氨酯涤纶复合人工血管的顺应性结果明显受到应用环境的影响,并且这种影响呈规律性变化。在人工血管的生产、质控以及临床使用中应充分考虑预期使用部位的特性,以提高临床使用过程中人工血管与人体的适配性。     

小口径医用聚氨酯人造血管径向顺应性研究

目的 比较小口径医用聚氨酯人造血管在干法制作与湿法制作方法下的微观形态和径向顺应 性,探讨管径大小、管壁厚度对血管顺应性的影响,分析接枝血管中不同部位的顺应性差别。 方法 通过在玻璃棒模具上复合均匀厚度的聚氨酯膜,制作出小口径聚氨酯人造血管。在自 行搭建的顺应性测试回路装置中测试得到压力与直径的关系,依据ISO7198国际标准计算 出人造血管的径向顺应性。结果 干法制作的聚氨酯人造血管表面与截面均很致密,湿法制 作的聚氨酯人造血管的截面呈微孔结构;随着人造血管管径的增大,顺应性逐渐增大;随着 管壁厚度的增加,顺应性逐渐减小;人造血管的接口处的径向顺应性波动较中间处大;湿法 制作的人造血管顺应性要优于干法制作的人造血管顺应性。结论：医用聚氨酯制作的小口径 人造血管具有良好的径向顺应性,是很有前景的小口径血管代用品材料;影响顺应性不匹配 的因素有很多,还需做进一步的研究。     

顺应性测试条件对纺织人工血管径向顺应性的影响

目的 分析纺织人工血管试样的预加张力和测试位置,探讨影响人工血管径向顺应性的因素。方法 基于人工血管动态顺应性测试仪,通过变化试样轴向预加张力以及调整试样直径测试观察点位置,对3种内直径8 mm的纺织人工血管试样,测试不同脉动压力值及其所对应的径向直径值。根据ISO 7198-1998顺应性计算方法,获得不同实验条件下的径向顺应性值。结果 随着预加张力的增大,3种纺织人工血管径向顺应性也随之增大,当预加张力达到500~550 mN时,径向顺应性值达到最大（1.03~1.72）%/100 mmHg（1 mmHg=0.133 kPa）,之后随着预加张力的增大而降低。此外,PET波纹化经编人工血管的径向顺应性值显示波谷径向顺应性值略大于波峰,而波峰的径向顺应性值稳定性好于波谷。结论 预加张力和测试位置对纺织人工血管径向顺应性有较大的影响,在测试时应给试样的预加张力为500~550 mN,对于波纹化纺织人工血管应选择波峰处为测试位置,结果更加稳定,数据更加可靠。     

小口径微孔聚氨酯人工血管的动物体内植入研究

将内径4mm的聚氨酯微孔人工血管植入Beagle狗体内，置换一段腹主动脉，研究血管内腔的内皮细胞化过程。该小口径血管具有以下特点：内腔偶联水蛭素以增加抗血栓性；顺应性接近天然血管；血管内表面孔径为40μm，并且管壁的孔径由内到外呈梯度增大。植入初始，人工血管内腔先吸附血浆纤维蛋白。14d见有少量梭形内皮样细胞生成。41d后形成完整内膜，由表面的内皮细胞单层和其下的平滑肌细胞组成。90d后生成稳定的内膜，平均厚度223μm。偶联水蛭素组和无偶联水蛭素组的通畅率分别为88．9％和75．0％。结果表明，改善抗血栓性、顺应性和微观结构可提高小口径人工血管的性能，有效促进内腔自然内皮细胞化，显著提高长期通畅率。     

外周血内皮祖细胞种植小径聚氨酯人工血管及流体切应力处理的实验研究

本研究收集健康成人骨髓单个核细胞,用血管内皮生长因子等加以诱导分化,通过荧光显微镜和荧光免疫标记等方法观察和鉴定诱导后的细胞。之后将诱导分化的内皮祖细胞种植到聚氨酯小径人工血管表面,予以15 dyn／cm2的流体切应力处理,并用扫描电镜观察。结果发现外周血单个核细胞诱导分化成为内皮祖细胞,ac- LDL及lectin抗体荧光标记阳性。扫描电镜下,未种植细胞的聚氨酯小径人工血管表面孔径大小比较适合内皮祖细胞爬行;静态种植细胞后,人工血管表面内皮祖细胞排列不整齐;切应力条件下种植细胞后,人工血管表面内皮祖细胞排列较为整齐。因此,在体外能将外周血单个核细胞诱导分化成为内皮祖细胞,内皮祖细胞是小径人工血管内皮化的理想种子细胞。流体切应力对小径聚氨酯人工血管表面内皮祖细胞的生长排列有着良好的机械塑形作用。     

流体剪应力调节内皮化小径聚氨酯人工血管抗血栓特性的体外研究

研究不同流体剪应力条件下,内皮化小径聚氨酯人工血管分泌一氧化氮(Nitrogen monoxide, NO)和前列环素(Prostaglandin I2, PGI2)水平的变化,从而为剪应力处理调节内皮化小径聚氨酯人工血管抗血栓特性提供实验依据.分离健康成人外周血的单个核细胞并诱导分化成内皮祖细胞,通过相差显微镜和免疫荧光标记等方法对诱导分化后的细胞进行形态学观察和鉴定.种植内皮祖细胞到小径聚氨酯人工血管表面后,将内皮化小径聚氨酯人工血管分为静态组、低剪应力组(5 dynes/cm2)、中剪应力组(15 dynes/cm2)和高剪应力组(25 dynes/cm2)4个不同处理组,之后用硝酸还原酶法和酶联免疫吸附法测定不同时间点培养液中NO和6-keto-PGF1α(6-keto-prostaglandin F1α,6-keto-PGF1α)的水平.外周血单个核细胞分化成为内皮祖细胞,倒置荧光显微镜下呈典型的"纺锤样"梭形细胞, ac-LDL吞噬及lectin抗体荧光标记双阳性,FLK-1和vWF免疫荧光抗体染色均为阳性.流体剪应力增加种植人工血管表面内皮祖细胞NO和6-keto-PGF1α的产生,并且这种作用与剪应力大小呈正相关.因此,提高流体剪应力明显促进内皮祖细胞NO和PGI2等抗血栓物质的分泌,提示流体剪应力可改善内皮化小径聚氨酯人工血管抗血栓特性.     

小口径人工血管的研究现状及展望

近年来,由于心血管疾病发生率逐渐上升,临床上对再生血管的需求日益增加。目前,大口径人工血管(直径>6 mm)已成功应用于临床,小口径人工血管(直径<6 mm)由于血栓形成、内膜增生、炎症反应和顺应性差导致血流动力学改变等原因,使其移植后远期通畅率低,距离临床应用尚有一段距离。其中,快速内皮化、抑制血栓形成及与自体血管相匹配的顺应性仍是解决问题的关键。本文简述制备小口径人工血管常用材料及技术的特点,重点讨论提高人工血管生物相容性和顺应性的策略,并对未来的研究工作进行展望。     

不同轴向伸长率下兔股动、静脉的顺应性变化

目的：探讨不同轴向伸长率下兔股动、静脉的顺应性变化,以及对临床修复血管损伤时方法选择的影响。方法：以兔正常股动、静脉血管标本为研究对象,通过血管压力－轴向应变试验及检测血管轴向伸长率,获取兔正常股动、静脉顺应性变化规律。结果：顺应性不仅与压力有关,而且同轴向伸长率有关,在内压强为动脉血压时,兔股动脉血管在伸长率为１．９时比其正常生理伸长率１．５８下的横截面积减少４０％。静脉也有相似变化规律。结论：     

腔内隔绝术用覆膜支架顺应性的研究意义及进展

小口径人工血管与宿主血管间顺应性不匹配,是导致其植入后远期通畅率低的重要因素;而目前已有文献证明,腔内隔绝术用覆膜支架(SG)与宿主血管间顺应性不匹配,也是引起术后远期滑移、内漏、血流紊乱等并发症的原因。但是,这一领域的研究十分有限。综述SG顺应性的评价方法,包括通过SG体积、压力的变化计算其体积顺应性,或通过脉搏波速和瘤体压力间接反映SG的顺应性。关于SG顺应性的研究主要包括:验证SG的植入对宿主血管的影响,不同结构SG对宿主血管的影响,以及顺应性随疲劳时间推移的可能变化。同时,对改变结构优化SG顺应性进行简要综述。     

不同轴向伸长率下兔股动、静脉的顺应性变化

研究轴向应变对血管顺应性的影响 ,明确能否通过调节吻合张力建立顺应性一致的静脉移植修复动脉缺损模型。取一段做完轴向拉伸实验的血管 (兔股动、静脉分别为 13、12条 ) ,测量不同伸长率下的压力—容积曲线 ,换算为压力—标准容积曲线 ,用幂函数 P=M1 × [еM2 ( v- v0 ) - 1]进行拟合 ,用多项式 M=a1 λ5+a2 λ4 +a3λ3+aλ2 +a5λ+a6 拟合 M- λ数据。由 P=M1 × [еM2 ( v- v0 ) - 1]得出在动脉平均压 (11.78KPa)下血管顺应性 dv/ dp=1/ (M1 ×M2 +11.78M2 )。由张力 T与伸长率 λ的单值对应关系建立起 T与顺应性 dv/ dp的单值对应关系 ,发现在张力 1.19g时 ,在动脉平均压下 ,动静脉的顺应性一致 ,为 0 .0 31,其所对应的动静脉伸长率为 :1.6 7及 1.32     

Electrospun biodegradable elastic polyurethane scaffolds with dipyridamole release for small diameter vascular grafts

Acellular biodegradable small diameter vascular grafts (SDVGs) require antithrombosis, intimal hyperplasia inhibition and rapid endothelialization to improve the graft patency. However, current antithrombosis and antiproliferation approaches often conflict with endothelial cell layer formation on SDVGs. To address this limitation, biodegradable elastic polyurethane urea (BPU) and the drug dipyridamole (DPA) were mixed and then electrospun into a biodegradable fibrous scaffold. The BPU would provide the appropriate mechanical support, while the DPA in the scaffold would offer biofunctions as required above. We found that the resulting scaffolds had tensile strengths and strains comparable with human coronary artery. The DPA in the scaffolds was continuously released up to 91 days in phosphate buffer solution at 37 °C, with a low burst release within the first 3 days. Compared to BPU alone, improved non-thrombogenicity of the DPA-loaded BPU scaffolds was evidenced with extended human blood clotting time, lower TAT complex concentration, lower hemolysis and reduced human platelet deposition. The scaffolds with a higher DPA content (5 and 10%) inhibited proliferation of human aortic smooth muscle cell significantly. Furthermore, the DPA-loaded scaffolds had no adverse effect on human aortic endothelial cell growth, yet it improved their proliferation. The attractive mechanical properties and biofunctions of the DPA-loaded BPU scaffold indicate its potential as an acellular biodegradable SDVG for vascular replacement.     

促进内皮细胞在小口径人工血管表面的黏附方法探讨

人工血管内皮化是解决人工血管移植体内后血栓形成和提高远期通畅率的最有前途的途径之一.为了使内皮细胞在小口径人工血管表面形成一层完整的覆盖并减少血栓形成,一般采用对人工血管做黏附基底预处理、在生物反应器中对人工血管进行三维流动培养、对内皮细胞进行基因修饰以及改变内皮细胞的带电性质等方法.本文对此方面的研究进展进行了综述,初步探讨了促进内皮细胞在小口径人工血管表面黏附的方法.     

Mechanical Properties of Small-diameter Superfine Silk Powder/Polyurethane Vascular Graft Reinforced by Tubular Knitted Fabric

In this paper, a kind of composite microtube, which is made from superfine silk powder and polyurethane, reinforced by polyster and spandex tubular fabrics, was examined. The cross-section of composite microtubes were microporous, and micropores were uniform distributed, the inner surface was relatively smooth. The results showed that the wall thickness of composite microtubes increased, which led to the strength,the breaking work and the initial modulus incresead; that the spandex content increased brought about the initial modulus and the breaking work decreased, but the breaking extension and the breaking load were firstly increased and then decreased; and all the mechanical properties decreased as the SFSP content increased.     

基于弹性小球动态平衡的血管中心线和直径的测量

血管中心线及直径的测量是血管类疾病诊断和微创介入治疗的重要依据.当前研究主要依据图像细化算法,但是细化算法缺乏计算结果的一致性.提出一种基于弹性小球动态平衡的血管中心线和直径的测量方法.首先在血管内部以交互的方式输入一条多段线(polyline)来确定感兴趣的血管部位,然后对多段线离散化为一组点,通过对离散点逐步膨胀为小球以及在小球与血管壁碰撞的两个力影响下,对小球和多段线同时变形,最后在平衡状态下得到的多段线即是血管中心线,小球直径就是该处血管直径.实验中,通过对模拟血管图像和临床DSA图像的量化测量及与常用方法对比,表明所提出算法能够精确地得到血管中心线与血管直径.     

Effects of an Artery/Vascular Graft Compliance Mismatch on Protein Transport: A Numerical Study

Small-diameter vascular graft failure by intimal hyperplasia and thrombosis may result from flow disturbances and disruption of chemical transport in the fluid at the distal anastomosis, because of compliance mismatch between the graft and host artery. In previous studies. lower-than-normal wall shear stress (WSS), particle trapping, and high particle residence times were observed at the distal anastomosis due to a pulsatile tubular expansion effect caused by nonuniform radial deformations. This study was undertaken to examine effects of compliance and radius mismatch on the distribution of a model protein released at the graft-fluid interface. Finite element simulations of end-to-end vascular grafting were performed under pulsatile flow, using fluid-structure coupling to give physiologic wall displacements. Results showed that protein is convected smoothly downstream in a uniform compliant tube. A compliance mismatch disturbed the transport, causing positive and negative gradients in the concentration profile at the distal anastomosis. This was seen when the graft and artery radii were matched at zero pressure and at mean arterial pressure; low WSSs were only observed in the former case. Thus the distal intimal hypertrophy seen in noncompliant grafts may be caused partly by decreased WSS, and partly by concentration gradients of dissolved chemicals affecting chemotaxis of cells.     

Study of a Novel Small Caliber Vascular Graft in a Canine Model with Optical and Scanning Electron Microscopy

A novel biological small-diameter vascular graft was evaluated in a canine model. 3 cm long segments with 4 mm I. D. were implanted end-to-end in the carotid position of 12 dogs for 6 months. Color Doppler sonography was performed at the first week post-operation, and angiography was then administered to 9 grafts at 4th week, 12th week and 24th week respectively to monitor the graft pantency and blood flow characteristics. Vascular samples containing the grafts were collected at 1st week, 8th week, 12th week and 24th week after implantation. Morphological changes of the grafts were observed by optical and scanning electron microscopic （SEM） studies and compared with that of the original prosthesis and the normal host vessel. All grafts were patent throughout the experiment except one graft. Histopathology and SEM demonstrated both a nearly complete inner capsule of varied thickness lining the graft luminal surface and connective tissue adventitia formation at one-week post-operation. The neointima became confluent at 8 weeks and then compact but had no signs of hyperplasia up to 12 weeks; meanwhile on the neointimal surface newly grown endothelial-like cells were migrating from the stoma to the middle portion. The grafts also illustrated endothelialization in many ＂islands＂ in the mid-segment luminal surface of the grafts. In addition, the closer distance the cells towards the stoma were, the more morphological similarity the cells with the normal endothelial were. Taken together, the biological vascular graft remained patent for 24 weeks as a carotid prosthesis, characterized by the early and complete neointima formation plus endothelialization starting before 12 weeks post grafting. Therefore, the graft seems suitable for reconstruction of vascular lesions in dogs. Further studies may be carried out to extend the graft application for the clinical use.