重组蛇毒纤溶因子修饰聚氨酯人工血管的犬颈动脉置换实验

目的通过动物实验评价重组蛇毒纤溶因子（recombinant fibrinolytic enzyme factor II，rF II）修饰聚氨酯（polyurethane，PU）人工血管的植入效果。方法采用浸渍．沥滤法制备口径4mmPU微孔人工血管，扫描电镜观察血管管壁微孔大小和形态，用rF II修饰人工血管内腔。取20只体重（20±1）kg的雄性杂种犬制作颈动脉2cm缺损模型，随机分为3组：rF II修饰PU组（n=8）、无rF II修饰PU组（n=6）和膨体聚四氟乙烯（expanded polytetrafluoroethlyene，ePTFE）组（n=6），植入相应人工血管以修复缺损。记录术后动物一般情况；计算术后30d和60d的血管通畅率；测量术后60d人工血管内径，并进行组织学检查和扫描电镜观察。结果制得的PU微孔人工血管内径（3．74±0．06）mm，壁厚0．4～0．6mm，密度0．25g／cm^3，孔隙率79．8％，径向动态顺应性为8．57％／100mmHg。人工血管管壁内，微孔分布均匀，呈开孔结构。外层孔径为（140±41）Ima，内层孔径为（100±3）μm，外层／内层的厚度比约2：1，内腔表面孔径为（40±16）μm。术后颈部切口愈合良好，动物均存活，无并发症发生。术后30d及60d血管通畅率：rF II修饰PU组分别为100％及66．7％，无rF II PU组为66．7％及33．3％，ePTFE组为66．7％及0，堵塞的人工血管在吻合处发现血栓。rFII修饰PU组、无rF II修饰PU组及ePTFE组植入前血管内径分别为（3．74±0．06）、（3．74±0．06）、（4．00±0．03）mm；术后60d内径分别为（4．51±0．05）、（4.31±0．24）、（4．43±0．12）mm；3组间植入前后比较差异均无统计学意义（P〉0．05）。rF II修饰PU组组织学观察，植入15d有血浆蛋白在内腔表面沉积；30d后有少量细胞黏附；60d后新内膜形成。新内膜厚度随植入时间增加而变厚；植入后60 d rF II修饰PU组人工血管近端、中点及远端的新内膜厚度分别为（560±22）、（78±5）、（323±31）μm（P〈0．05）。扫描电镜观察，rF II修饰PU组新内膜表面由扁长形细胞组成，其长轴顺着血流方向排列，与正常颈动脉内腔表面形貌相似。结论rF II修饰PU血管内腔可提高纤溶活性，减少血栓栓塞的发生，有利于提高植入血管的通畅率。     

聚对二氧环己酮缝线编织构建仿生型人工小口径血管支架的实验研究

目的 探讨以聚对二氧环己酮(polydioxanone,PDS)缝线编织网管为中间弹力层,构建仿生型三层小口径血管支架的可行性,并检测其生物力学性能.方法 采用7-0 PDS缝线编织内径为4mm的网管,比较不同的编织结构和编织工艺角对PDS网管生物力学性能的影响.将小肠黏膜下基质包被于PDS支架外表面,以8-0 PDS缝线沿纵轴连续缝合固定,支架内层覆以复合硫酸软骨素共混胶原,真空冷冻干燥.检测血管支架的生物力学性能(爆破压力、抗拉伸能力、顺应性等),并与犬颈总动脉进行比较.方果 选择65°的编织工艺角编织内径为4 mm规则结构的网管,长度为3～5 cm;所制备的人工血管的爆破压为(43,50±8.30)kPa,断裂强度为(19.10±1.56)N,应变率为(42.88±3.16)%,径向顺应性为(5.96±0.87)%/100 mm Hg.方论 以PDS编织网管作为中间弹力层构建的复合型人工小血管支架力学性能满意,可以满足动物体内移植试验的需要.     

仿生型人工小血管支架的构建与体外力学研究

目的 制备具有三层管壁结构的可降解人工小血管支架,对其生物力学性能进行测试,并与正常生理血管对比以检测其是否符合体内移植试验的要求.方法 以可降解的聚对二氧环己酮(PDS)缝合线编织成网管状织物作为血管内支架,模仿天然血管的三层结构,内层共混硫酸软骨素-胶原,外层包被小肠黏膜下层,缝线加固,构建内径<4 mm的小血管支架,检测血管支架的生物力学性能(爆破压力、抗拉伸能力、顺应性等),并与正常生理血管进行比较.结果 所制备的人工小血管支架平均内径3.83 mm,爆破压为(43.50±8.30)kPa,断裂强度为(19.10±1.56)N,应变率为(42.88±3.16)%,径向顺应性为(5.96±0.87)%/100 mm Hg(1 mm Hg=0.133 kPa).结论 所制备人工血管的力学性能优良,可以满足动物体内移植试验的要求.     

激光微孔脱细胞基质在尿道缺损修复中应用的体外实验研究

目的：研究不同脉宽的超脉冲CO2激光对尿道脱细胞基质的热损伤以及微孔脱细胞基质的生理降解和孔隙率。方法：对尿道脱细胞基质用不同脉宽的CO2激光器进行激光打孔,比较微孔洗涤前后孔径变化,评价热损伤率;并对制备的微孔基质生理降解和孔隙率比较;结果：60ms的超脉冲CO2激光对尿道脱细胞基质的热损伤轻,制备的微孔脱细胞基质生理降解性能和细胞生长增殖生长曲线趋势一致,孔隙率合适。结论：超脉冲CO2激光对尿道脱细胞基质进行精细的加工出合适性能的脱细胞基质。     

三种多孔磷酸钙陶瓷制备方法的比较研究

目的 以磷酸钙双相陶瓷为材料,采用3种成型方法制备多孔生物陶瓷支架,比较不同制备方法所获得的多孔陶瓷的孔结构,为骨组织工程提供适合的支架材料.方法 本实验用不同配比的H2O和SiO2溶胶配制浆料,以添加致孔剂法、冷冻干燥法及有机泡沫浸渍法制备陶瓷坯体,经高温烧结得到多孔双相陶瓷支架.通过扫描电镜(SEM)观察了陶瓷块的孔结构、孔径及孔的连通性.同时,检测了多孔陶瓷的气孔率及力学强度,从而评价其作为骨组织工程支架材料的可行性.结果 本研究采用的3种制备方法获得的多孔陶瓷,均具有连通的孔结构.添加致孔剂法获得陶瓷的孔径为72±30 μm,气孔率为92.3%;冷冻干燥法获得的陶瓷孔径较小(23～47 μm),气孔率为74%～87%;有机泡沫浸渍法制备出的孔径最大(164±46 μm),气孔率为90.2%.力学强度测试结果显示,有机泡沫浸渍法制备的多孔陶瓷的抗压强度最大(71±18 Kpa);添加致孔剂法其次,抗压强度为18±5 Kpa;冷冻干燥法获得的多孔陶瓷抗压强度为14～44 Kpa,抗压强度最低.结论 3种制备方法均能够制备出具有连通孔结构的高气孔率的多孔磷酸钙陶瓷,以有机泡沫浸渍法和添加致孔剂法制备的多孔陶瓷力学强度较高,更适合作为骨组织工程支架材料.     

两种非吸收性肌腱缝线的对比研究

目的 对两种常用非吸收性肌腱缝线的生物力学特性及组织相容性进行对比研究,为临床肌腱修复术的缝线选择提供实验依据.方法 取3-0 TICRON聚酯缝线和3-0真丝缝线各100根,分为两组.A组:3-0 TICRON聚酯缝线；B组:3-0真丝缝线.将2组缝线各80根分别随机埋入40只SD大鼠腹部皮下,术后1、2、3、4周各组取材,对缝线周围组织进行形态学观察及HE染色,观察缝线周围炎性反应程度及缝线与周围组织粘连程度；对缝线进行生物力学测定,测定缝线初始张力强度及术后4个时间点的张力强度.结果 A组术后1、2周时缝线周围炎性反应明显,3、4周时炎性反应逐渐减轻至消退.B组术后各个时间段缝线周围炎性反应均较A组严重,并且炎性反应消退慢.3-0 TICRON聚酯缝线的初始张力强度为(19.02±0.63)N、机体内4周维持张力强度为(17.80±0.64)N,大于3-0真丝缝线的初始张力强度(15.40± 0.44)N和机体内4周维持张力强度(9.79±0.54)N,并且3-0 TICRON聚酯缝线张力强度的衰减速度小于3-0真丝缝线.结论 3-0TICRON聚酯缝线组织相容性好,局部炎性反应轻,抗张力强度维持时间长,衰减速度慢,修复肌腱断裂比3-0真丝缝线理想.     

应用钛环钉行人工血管旁路术的实验研究

目的　探讨应用钛环钉行人工血管旁路术后人工血管及髂动脉腔表面内皮细胞形态学变化。方法　选用14 只健康雄性恒河猴,用3 mm 直径的ePTFE 人工血管置换左髂总动脉,近端用60 无创缝线吻合,远端用73Ⅱ型血管吻合器吻合。术后4 周,取出吻合口行光镜及电镜检查。结果　钛环钉组血管损伤反应轻,吻合口有完整内膜覆盖;而缝线组损伤反应重,吻合口内膜覆盖不完整,有血栓样组织沉积。结论　钛环钉组吻合口在术后4 周均形成完整的内膜,对预防吻合口早期血栓形成及晚期内膜增生有重要意义     

抗菌性负压封闭吸引材料的研制

目的 制备具有抗菌性等生物活性的聚乙烯醇/壳聚糖复合泡沫材料,并优化生产工艺,使材料具有更理想的孔径、孔隙率及弹性.方法 采用混合溶解、乳化发泡、缩醛固定、烘干固化、去酸去醛法制备聚乙烯醇/壳聚糖复合泡沫材料,采用观察测量、重量法、力学测试、细菌培养法检测10组材料的孔径、孔隙率、力学性能及抗菌性.结果 研制材料的孔径约增大0.267 mm、孔隙率约增大7%,弹性约增强0.120 MPa,材料具有明显的抗菌性,抗菌强度随壳聚糖的含量增加而增强.结论 研制的聚乙烯醇/壳聚糖复合泡沫材料孔径、孔隙率及弹性更为理想,并具有抗菌性.     

PLLA细胞支架的制备方法及形态结构的研究

目的 以聚乳酸为基质材料,分别用三种不同的方法,制备了细胞支架,并比较了制备方法对支架孔结构的影响.方法 分别用溶剂浇铸/致孔剂溶出法、固-液相分离法、液-液相分离法,制得了PLLA的多孔支架,测定其孔隙率及平均孔径,并观察其微观结构.结果 溶液浇铸/致孔剂溶出法可以调节致孔剂的用量及颗粒大小,制得符合设计要求的孔隙率及孔径的细胞支架.固-液相分离法结合致孔剂的溶出,可以获得孔径大于200 μm并且提高孔与孔之间贯通的支架.液-液相分离法通过调节相分离条件,可以制得最大孔径在300 μm～400 μm的细胞支架,大大超过文献报道的只有120 μm孔径.结论 三种制备方法均可得到组织工程用的细胞支架,可以按需控制孔隙率及孔径,溶剂浇铸/致孔剂溶出法只限于制得板状支架,固-液相分离和液-液相分离则不受限制,并且孔径可以达到200 μm以上.     

人工血管移植动静脉瘘术后超声检测价值

目的 探讨彩色多普勒超声对人工血管移植动静脉瘘及其并发症的检测价值.方法 对18例人工血管移植动静脉瘘术后4～6周的患者,应用彩色多普勒超声测量动脉侧吻合口和移植人工血管动脉端内径、峰值流速和血流量,同时对上肢出现不适症状患者进行超声检测.结果 术后4～6周彩色多普勒超声显示吻合口和移植人工血管血流充盈良好,动脉侧吻合口内径、峰值流速和血流量分别为(3.61±0.68)mm、(298.56±93.42)cm/s、(583.62±216.77) ml/min;人工血管动脉端内径、峰值流速和血流量分别为(4.47±0.61)mm、(219.37±68.42)cm/s、(325.23±117.12)ml/min.7例患者手术侧上肢出现不适症状,超声检查发现1例血清肿;3例移植血管血栓;1例假性动脉瘤;2例单纯性皮下组织水肿.结论 超声对人工血管移植动静脉瘘术后人工血管及其并发症的检测有重要的临床应用价值.     

Comparative In vitro evaluation of two different preparations of small diameter polyurethane vascular grafts

Polyurethane (PU) frequently has been used to manufacture small diameter vascular grafts due to its good bicompatibility. In this study, sponge PU small diameter vascular grafts were fabricated from Pellethane 2103, as well as a self-synthesized PU, by utilization of a salt casting technique and by varying the salt/polymer ratios. Two types were made; one of them had a thin solid layer on the outer surface. The inner surface was identical and was coated with gelatin crosslinked by epoxide. Tensile properties, compliance, platelet activation, and endothelial cell attachment were evaluated in vitro. It was found that for the grafts with an outer nonporous coating, compliance could not be estimated from modulus due to anisotropy. The most compliance-matched grafts were made of self-synthesized polyurethane with a salt/polymer ratio 4 to 8 or Pellethane with a ratio 6 to 8 without the outer nonporous coating. The former had better elongation. Self-synthesized PU had lower platelet adhesion as well as more endothelial attachment than Pellethane. Porosity activated platelets strongly and reduced endothelial adhesion unless the surface was modified by the crosslinked gelatin layer. It was concluded that PU synthesized in our lab with a salt/polymer ratio of at least 4 and coated with epoxy crosslinked gelatin was a better substrate for preparation of small diameter vascular grafts.     

重组蛇毒纤溶因子修饰聚氨酯人工血管的犬颈动脉置换实验

OBJECTIVE: To evaluate the implantation effect of artificial vascular grafts with recombinant fibrinolytic enzyme factor II (rF II)-immobilized lumina in animal test. METHODS: Four mm internal diameter (ID) polyurethane (PU) artificial vascular grafts were prepared by dipping and leaching method. The micro-pore size and morphology of the graft walls were observed by SEM. The graft lumina were immobilized with rF II. Twenty hybrid male dogs [weighing (20 +/- 1) kg] were used for animal model of carotid artery defect and were randomly divided into 3 groups: rF II -immobilized PU group, no rF II -immobilized PU group and expanded polytetrafluoroethylene (ePTFE) group. The vascular grafts were implanted for repairing injured segments of carotid artery in dogs. The general health state of animals was recorded. At 30 days and 60 days, the patency rate of every group was calculated. At 60 days IDs were measured, cell proliferation in neointima was inspected by light microscope, morphology on neointima was observed by SEM. RESULTS: The ID of the PU vascular grafts was (3.74 +/- 0.06) mm, wall thickness was 0.4-0.6 mm, the wall density was 0.25 g/cm3, the porosity was 79.8%, racical compliance was 8.57%/100 mmHg. In the wall, micropores were well distributed and opened-pores structure was observed. Pore size was (140 +/- 41) microm in the outside layer, pore size was (100 +/- 3) microm in the inside layer, thickness ratio of outside / inside layers was 2 : 1, the pore size was (40 +/- 16) microm on the lumina surface. After operation the wounds on neck healed, all the animals survived and had no complication. At 30 days and 60 days after implantation, the patency rate for rF II -immobilized PU group were 100% and 66.7%, for no rF II -immobilized PU group were 66.7% and 33.3%, and for ePTFE group were 67.7% and 0 respectively, but at 60 days there were thrombosis at anastamotic sites of some grafts occluded. Before operation the IDs for rF II-immobilized PU group, no rF II -immobilized PU group and ePTFE group were (3.74 +/- 0.06), (3.74 +/- 0.06) and (4.00 +/- 0.03) mm, at 60 days after operation the IDs were (4.51 +/- 0.05), (4.31 +/- 0.24) and (4.43 +/- 0.12) mm respectively, showing no statistically significant differences between 3 groups (P > 0.05). Histological inspection indicated that at 15 days a layer of plasma protein deposited on the lumina, at 30 days some cells adhered to the lumina, at 60 days neointima could be observed on the lumina. Thickness of the neointima became larger with implantation time. At 60 days neointima thickness at proximal end, middle site and distal end of graft were (560 +/- 22), (78 +/- 5) and (323 +/- 31) microm respectively for rF II -immobilized PU group. The results of SEM showed that neointima surface consisted of flat and long cells which long axes ranged with blood flow direction and was similar to lumina morphology of carotid artery of dog. CONCLUSION: Immobilization of rF II to lumina of grafts could enhance fibrinolytic activity and inhibited formation of thrombo-embolia which led to an increase in patency rate after implantation.     

New prostheses for use in bypass grafts with special emphasis on polyurethanes

Vascular bypass procedures using traditional prosthetic grafts such as polytetrafluoroethylen (PTFE) and polyethylene tetraphthlate (Dacron) are prone to failure when used in low flow states such as in below knee bypass and when the diameter of the graft is less than 6 mm. A major factor in this is compliance mismatch between the graft and the diseased vessel, which may cause intimal hyperplasia at the distal anastomosis. PTFE and Dacron are rigid grafts with poor compliance. By improving the compliance of the prosthetic graft it is hoped that patency will improve. Recent advances in polyurethane chemistry have developed materials that do not degrade and which allow compliance matching of the graft to the patient's vasculature. It is now possible to manufacture biologically and haemodynamically compatible grafts with small diameter from these polyurethane graft materials. This review will focus on the lack of compliance in current vascular bypass grafts and the promise of the new polyurethane polymers in a new generation of small-bore bypass grafts.     

Improved retention of endothelial cells seeded on polyurethane small-diameter vascular grafts modified by a recombinant RGD-containing protein

Sponge-type small-diameter vascular grafts were fabricated from a medical-grade polyurethane, Pellethane 2363-80A, by utilization of a salt casting technique. The grafts were compliance matched with a storage modulus of 0.53 +/- 0.08 MPa. The luminal surface of grafts was modified with a thin layer ( approximately 40 micro m) of gelatin crosslinked by epoxide. Then a special Arg-Gly-Asp (RGD)-containing recombinant protein, named CBD-RGD (cellulose binding domain RGD-containing protein), was coated onto the gelatin layer. The platelet adhesion and activation on such a gelatin/CBD-RGD modified surface was significantly reduced. Human umbilical vein endothelial cells were seeded more efficiently onto the modified grafts. There was also a substantial reduction in the subsequent loss of cells from the graft surface following perfusion in vitro. The cell number retained on the modified graft was enhanced by three times after 1 h of perfusion, and by eight times after 3 h of perfusion (retention rate approximately 63%). The retention after 3 h of perfusion could be further increased to nearly 100% if the lined endothelium on gelatin/CBD-RGD modified graft was cultured for another week before perfusion. The modified surface was also shown to help canine external jugular vein endothelial cells to maintain the round cell morphology in vitro.     

Development of a composite degradable/nondegradable tissue-engineered vascular graft

The present study aimed to determine the feasibility of constructing a reinforced autologous vascular graft by combining the advantages of fibrin gel as an autologous cell carrier material with the inherent mechanical strength of an integrated mesh structure. It was hypothesized that the mesh and dynamic culture conditions could be combined to generate mechanically stable and implantable vascular grafts within a shorter cultivation period than traditional methods. A two-step moulding technique was developed to integrate a polyvinylidene fluoride (PVDF) mesh (pore size: 1-2 mm) in the wall of a fibrin-based vascular graft (I.D. 5 mm) seeded with carotid myofibroblasts. The graft was cultured under increasing physiological flow conditions for 2 weeks. Histology, burst strength, and suture retention strength were evaluated. Cell growth and tissue development was excellent within the fibrin gel matrix surrounding the PVDF fibers, and tissue structure demonstrated remarkable similarity to native tissue. The grafts were successfully subjected to physiological flow rates and pressure gradients from the outset, and mechanical properties were enhanced by the mesh structure. Mean suture retention strength of the graft tissue was 6.3 N and the burst strength was 236 mm Hg. Using the vascular composite graft technique, the production of tissue engineered, small-caliber vascular grafts with good mechanical properties within a conditioning period of 14 days is feasible.     

Microporous, complaint, biodegradable vascular grafts for the regeneration of the arterial wall in rat abdominal aorta

Microporous, complaint, biodegradable vascular grafts prepared from mixtures of polyurethane (PU) and poly-L-lactic acid (PLLA) can function as temporary scaffolds for the regeneration of the arterial wall in small-caliber arteries. This study was undertaken to determine the most suitable composition for PU/PLLA vascular grafts to ensure an optimal regeneration. Four types of PU/PLLA vascular grafts differing in percent weight of the PU/PLLA mixture, molecular weight of PLLA, and pore size were implanted into the abdominal aorta of rats (n = 32). Six weeks after implantation two implants of each graft type were evaluated by means of scanning electron microscopy and six implants were evaluated by means of light microscopy. In two types of the PU/PLLA vascular grafts, both of which were prepared from a 95%/5% weight PU/PLLA mixture with PLLA of molecular weight 500,000 but which had a different pore size, there was (I) absence of aneurysm formation and maintenance of arterial implant pulsations, (II) regeneration of a complete antithrombogenic neointima, (III) regeneration of a neomedia of comparable thickness to the media of normal rat abdominal aorta with the regeneration of elastic laminae almost throughout its thickness, and (IV) regeneration of a sufficiently supporting neoadventitia. These results demonstrate that a 95%/5% weight PU/PLLA mixture with PLLA of molecular weight 500,000 is the most suitable composition for PU/PLLA vascular grafts to ensure an optimal regeneration of a neoarterial wall that is of sufficient strength, compliance, and thromboresistance to function as a small-caliber arterial substitute. Pore size of these PU/PLLA grafts does not affect regeneration.     

Nitric oxide-releasing biopolymers inhibit thrombus formation in a sheep model of arteriovenous bridge grafts

OBJECTIVES: Nitric oxide (NO), produced by normal vascular endothelial cells, reduces platelet aggregation and thrombus formation. NO-releasing biopolymers have the potential to prolong vascular graft and stent patency without adverse systemic vasodilation. METHODS: 5-mm polyurethane vascular grafts coated with a polymer containing the NO-donor dialkylhexanediamine diazeniumdiolate were implanted for 21 days in a sheep arteriovenous bridge-graft model. RESULTS: Eighty percent (4/5) of grafts coated with the NO-releasing polymer remained patent through the 21 day implantation period, compared to fifty percent (2/4) of sham-coated grafts and no (0/3) uncoated grafts. Thrombus-free surface area (+/-SEM) of explanted grafts was significantly increased in NO-donor coated grafts (98.2% +/- 0.9%) compared with sham-coated (79.2% +/- 8.6%) and uncoated (47.2% +/- 5.4%) grafts ( P = .00046). Examination of the graft surface showed no adherent thrombus or platelets and no inflammatory cell infiltration in NO-donor coated grafts, while control grafts showed adherent complex surface thrombus consisting of red blood cells in an amorphous fibrin matrix, as well as significant red blood cell and inflammatory cell infiltration into the graft wall. CONCLUSION: In this study we determined that local NO release from the luminal surface of prosthetic vascular grafts can reduce thrombus formation and prolong patency in a model of prosthetic arteriovenous bridge grafts in adult sheep. These findings may translate into improved function and improved primary patency rates in small-diameter prosthetic vascular grafts.     

Effect of porosity on small-diameter vascular graft healing

Experimental studies have reported that complete healing of small-diameter expanded polytetrafluoroethylene (ePTFE) grafts occurs only if the porosity of the graft is increased, thereby allowing ingrowth of perigraft capillaries yielding endothelial cells. This study investigates the effects of varied graft porosity on the healing characteristics of 2-mm internal diameter (ID) ePTFE grafts interposed in the rabbit common carotid artery. Four groups were evaluated: Group A (n = 8) standard (30-microm pores) ePTFE grafts; Group B (n = 8) increased porosity (60-microm pores) ePTFE grafts; Group C (n = 8) standard ePTFE; and Group D (n = 8) 60-microm ePTFE external graft surface was externally coated with an impermeable layer of polyurethane. Patency was 100% for all groups at 8 weeks. At explantation, the neointima was composed of primarily modified smooth muscle cells. Endothelial cells were only identified at the perianastomotic region using the endothelial cell-specific antibody CD31. The impermeable external polyurethane coating of ePTFE grafts had no effect on neointima formation, regardless of porosity.     

An integrated approach to the design and engineering of hybrid arterial prostheses

Purpose: A newly devised hybrid small-caliber graft was developed. The graft consisted of three components: a microporous polyurethane graft (inside diameter 3 mm; length 5 cm) with compliance close to that of a natural artery; an artificial basement membrane composed of a complex gel of type I collagen and dermatan sulfate, which showed enhanced adhesion and growth of endothelial cells (ECs) and reduced adhesion of platelets in vitro; and an autogenous EC monolayer with high degrees of cell-substrate and cell-cell interactions, which was performed before implantation.Methods: Twenty EC-seeded grafts were implanted bilaterally into carotid arteries of dogs without anticoagulant. The implantation period was up to 26 weeks.Results: The overall patency rate for seeded grafts was 75%. The percentage of endothelial coverage of seeded grafts was 98% as implanted, 92% at 2 weeks, and 100% after 12 weeks. The mean intimal thickness of grafts was around 80 μm at 12 weeks. Little additional increase was observed at 26 weeks.Conclusions: It appears that the complete endothelialization as implanted, high cell-to-substrate adhesive strength that resists hydrodynamic shear stress, and biomechanical compatibility of the polyurethane graft functioned cooperatively to provide a vascular graft with high antithrombogenicity and minimal hyperplasia. The integrated approach of combining biomechanical and cellular engineering designs leading to an important functional smaller-caliber graft is discussed. (J VASC SURG 1994;19:658-67.)     

In vivo study of an elastomer end-coated polytetrafluoroethylene vascular prosthesis.

Polyurethane end-coated polytetrafluoroethylene (PTFE) grafts (elastomer PTFE grafts) were implanted in 12 female adult mongrel dogs to assess patency, intimalization, tissue incorporation, and technical suitability of the material as a vascular graft. Each dog had bilateral aortoiliac grafts placed, one a standard PTFE and the other an elastomer PTFE graft. The length of the grafts was 7-8 cm and the diameter was 6 mm. The grafts were harvested at intervals to 120 days postoperatively. The elastomer PTFE grafts showed superior longitudinal elasticity, retention of shape, and no graft tearing with suture tension; however, no significant difference in bleeding was noted at the anastomoses between the standard and elastomer PTFE grafts. Satisfactory patency was obtained with both standard (8/10) and elastomer PTFE grafts (9/10) at 90-120 days. No significant difference in the thickness of intima and the length of pannus ingrowth was noted between the standard and elastomer PTFE grafts. No outer tissue incorporation was seen at the elastomer-treated graft segments as opposed to the well-incorporated untreated segments. In conclusion, elastomer end-coating of a PTFE vascular prosthesis provided excellent handling characteristics without detracting from patency; however, the lack of outer tissue incorporation may be a potential disadvantage in its clinical use.