人工血管内皮化的研究现状

工血管完整内皮单层的缺乏是导致新内膜增生、血栓形成和感染的主要刺激,因此,人工血管内皮化已成为目前研究的热点,并在许多方面取得了成绩,但是,仍存在许多问题有待解决。     

小口径人工血管的研究进展

为提高小口径人工血管的远期通畅率，一方面需要寻找顺应性更好的材料；另一方面则是在现有人工血管内壁种植内皮细胞。这包括单期种植法，二期种植法以及自体静脉碎片快速种植法。用于种植的内皮细胞可来源于自体静脉、人脐静脉和皮下脂肪微血管。通过在人工血管内壁上衬附可吸收的细胞外黏附蛋白、细胞生长刺激因子，利用生物素与抗生物素蛋白的特异结合能力，或改变植入的内皮细胞的带电性，以及在体外对植入的内皮细胞进行流体切应力锻炼等方法，可以提高内皮细胞的黏附力。植入基因工程改造过的内皮细胞，也是提高小口径人工血管通畅率的一种新尝试。     

小口径人工血管内皮化临床研究现状

冠心病、外周动脉闭塞性疾病、慢性肾功能衰竭建立血液透析通路以及小儿心血管疾病等，这些疾病大多需要小口径血管（直径〈6mm）行动脉移植手术。目前临床上已用的小口径血管移植物包括自体大隐静脉或乳内动脉、涤纶（Dacron）和膨体聚四氟乙烯（ePTFE）人工血管等。自体静脉或动脉移植后虽然能取得较满意的临床疗效，但是因来源有限和供区牺牲大而应用有所限制。在需要行动脉移植手术的患者中，30％以上缺乏适当的自体静脉或动脉移植物。常用的Dacron和ePTFE人工血管在高速血流、低阻力的大、中动脉重建中已取得满意的疗效，     

微血管内皮细胞与人工血管内皮化（综述）

人工血管的应用日趋广泛，如何实现其内皮化是应用的关健。人工血管内皮化的效果决定于三个因素：种植的细胞数、细胞贴壁率、贴壁细胞抗切应力能力。为此，人们进行了内皮细胞获取、培养增殖、微血管内皮细胞获取的研究，尝试了从低密度种植、高密度种植、铺植到离体衬里的一系列内皮化方法，确实了人工血管内皮化的研究的方向：寻求可靠、丰富、方便的细胞来源，建立完善的离体衬里内皮化方法。     

微血管内皮细胞与人工血管内皮化

人工血管的应用日趋广泛,如何实现其内皮化是应用的关键.人工血管内皮化的效果决定于三个因素:种植的细胞数、细胞贴壁率、贴壁细胞抗切应力能力.为此,人们进行了内皮细胞获取、培养增殖、微血管内皮细胞获取的研究,尝试了从低密度种植,高密度种植、铺植(Sodding)到离体衬里(Lining)的一系列内皮化方法,确立了人工血管内皮化的研究的方向:寻求可靠、丰富、方便的细胞来源,建立完善的离体衬里内皮化方法.     

人工血管内皮化的研究进展

人工血管内皮化的研究进展潘明新综述杨继震何红兵审校作者单位：５１０２８２第一军医大学珠江医院普外科血管病研究室众所周知，人工血管置换病变的静脉和口径小于６ｍｍ的动脉，通畅率十分低下。这与人工血管的内表面难以自发形成抗血栓形成的内皮细胞衬里有关。理论上...     

人造血管移植物自然内皮化的研究

一、内皮细胞功能和形态学特征在正常血管内膜除内皮细胞尚有内皮下层和内弹力膜构成.表面与血流接触的一层细胞为内皮细胞,以镶嵌体形式覆盖整个血管内面.内皮细胞形态多不固定.呈扁平、多角形或板状,其超微结构和一般细胞相同,但不发达,而有较多的吞饮小泡.血管内膜生物系统变化是一个复杂的调节,内皮细胞虽然结构简单,功能却相当复杂.除具有屏障功能外,能产生多种生物活性物质,如:前列环素2、组织纤溶酶原活化因子、纤溶酶原活化抑制因子、血栓调变蛋白和c蛋白等,其中前列环素2是一种短效、强力血管扩张剂,具有强烈的抗血小板聚集作用.内皮细胞的表面同血细胞一样带有负电荷,具有抗血小板聚集,防止血液凝固和血栓形成的作用.凝血因子Ⅶ是由内皮细胞合成和分泌的,     

血管内皮祖细胞在人工血管移植后内皮化中的作用机制

血管内皮祖细胞具有高度的分化增殖能力,可以定向分化为成熟内皮细胞,参与体内内皮损伤后的修复和血管再生。研究表明血管内皮祖细胞在人工血管移植后内皮化中也起重要作用,现就近年来的研究进展综述如下。     

体外扩增恒河猴自体内皮细胞人工血管移植研究（二）

目的：为自体内皮细胞移植的临床应用奠定理论基础。方法：将１５只恒河猴随机分为两组。实验组１０例，用衬里有自体静脉内皮细胞的人工血管置换髂总动脉；对照组５例，用未衬里内皮细胞塞外，其余８条人工血管术后四周均保持通畅，内膜下组织碍度为８０±１２μｍ；对照组５条人工血管全部阻塞。结论自体内皮移植可有效地南昌市人工血管的通畅率。     

人大隐静脉内皮细胞种植人工血管的实验研究

目的　探讨人自体静脉内皮细胞移植到人工血管上的可行性。方法　将人大隐静脉内皮细胞在体外扩增培养１３ ．０８ ±１ ．２４ 天, 将扩增培养的内皮细胞衬里用于纤维蛋白胶预衬的膨体聚四氟乙烯（ｅｘｐａｎｄｅｄ ｐｏｌｙｔｅｔｒａｆｌｕｏｒｅｔｈｙｌｅｎｅ ｐａｔｃｈ 〔ＧｏｒｅＴｅｘ〕Ｒ, ｅＰＴＦＥ） 人工血管继续培养９ 天。结果　所培养的细胞为二倍体细胞,纯度为９９ ％ 。原代及传代细胞培养上清液中６酮前列环素（６ｋｅｔｏＰＧＦ１α） 和Ｖｏｎ Ｗｉｌｌｅｂｒａｎｄ 因子（ｖ ＷＦ） 含量差异无显著性意义（ Ｐ＞ ０ ．０５） 。细胞种植后第９ 天人工血管腔面见一层均匀的基质,其表面有一层连续的内皮细胞单层,内皮细胞排列紧密,呈梭形,形态饱满。结论　人自体大隐静脉内皮细胞可有效地移植到人工血管,为人自体细胞内皮化人工血管应用于临床奠定了理论基础。     

小口径脱细胞基质人工血管移植的研究

目的 探讨脱细胞基质( DCM)人工血管用于小口径血管移植的可行性.方法 40条雄性杂种犬随机分为DCM、膨体聚四氟乙烯(ePTFE)人工血管及自体颈外静脉3组行右颈总动脉置换术,彩超监测移植物通畅率.术后4、8周活体取材,标本行苏木素-伊红(HE)、免疫组织化学染色及扫描电镜检查.结果 3组移植物1周通畅率(75.0％、64.3％、100.0％)差异无统计学意义(P＞0.05);自体颈外静脉组4、8周通畅率( 100.0％、88.9％)优于DCM组(56.3％、26.7％)及ePTFE组(57.1％、23.1％,P＜0.05),后两组差异无统计学意义(P＞0.05).DCM人工血管4、8周血栓形成面积小于ePTFE人工血管,吻合口内膜内皮化程度高于后者.结论 小口径DCM人工血管在抑制血栓形成及加快内皮化方面优于ePTFE人工血管.     

In vitro endothelialization of small-caliber vascular grafts

To establish the conditions for achieving immediate and complete endothelial cell coverage of the luminal surfaces of small-caliber (internal diameter:4 mm) vascular grafts in vitro, the attachment and spread of endothelial cells cultured from human umbilical veins to expanded polytetrafluoroethylene (PTFE) and knitted Dacron grafts was studied. Cell number was quantified by fluorescent measurements of deoxyribonucleic acid. The completeness of cell coverage and cell junction formation were assessed by means of both scanning and transmission electron microscopy. Cell attachment was compared after expanded PTFE or knitted Dacron grafts were precoated with gelatin, laminin, fibronectin, fibrin, or collagen, singly or in combination. Saturation cell attachment of 3.5 +/- 0.7 X 10(5) cm-2 was completed within 15 minutes when (1) type I collagen was used to form the substrate matrix, (2) human umbilical vein endothelial cells were suspended in phosphate-buffered saline solution supplemented with calcium and magnesium, and (3) the suspended cell number was greater than or equal to 5 X 10(5). In contrast, attachment to untreated or laminin-treated surfaces was 1.3 +/- 0.33 X 10(5) cells cm-2 and attachment to fibrin- or fibronectin-treated surfaces was 2.8 +/- 0.47 and 2.4 +/- 1.1 cells X 10(5) cm-2, respectively. However, to produce a confluent flow surface, the attached cells required several hours in culture medium to spread completely. Maintenance of confluent cell coverage on the graft surface for 3 days in vitro was achieved by means of continuous perfusion with oxygenated tissue culture medium RPMI-1640-HEPES supplemented with 20% fetal bovine serum. We conclude that optimum immediate confluent endothelial coverage of small-caliber vascular grafts requires a high concentration of cells, attachment to collagen-precoated grafts, and several hours of incubation in complete culture medium.     

Fibroblast and vascular endothelial growth factor coating of decellularized vascular grafts stimulates undesired giant cells and graft encapsulation in a rat model

Replacing an infected prosthesis with a bioimplant provides a hopeful alternative in septic vascular surgery. The objective of this study was to determine the effect of fibroblast endothelial growth factors (FGF) and vascular endothelial growth factors (VEGF) coating on a decellularized vascular graft in a rat model and the possible impact on recellularization processes. Rat aortas were decellularized, crosslinked with genipin, and coated with poly-(D, L) lactide containing either FGF or VEGF. Observation periods were 6 and 12 weeks. Surprisingly, we found moderate accumulation of giant cells around the grafts that contained poly-(D, L) lactide acid. FGF and VEGF grafts showed massive stimulation of giant cells and eosinophils leading to complete graft encapsulation (P < 0.05). Pseudointmal hyperplasia was significantly increased in the FGF group (P < 0.05). Both results can only be interpreted as very negative. We achieved a situation in diametric opposition to that which we had hoped for. These data demonstrate that the use of growth factors may produce harmful side effects.     

Administration of granulocyte colony-stimulating factor enhances endothelialization and microvessel formation in small-caliber synthetic vascular grafts

OBJECTIVE: The purpose of this study was to determine whether systemic administration of granulocyte colony-stimulating factor (G-CSF) would promote endothelialization for small-caliber Dacron vascular grafts. METHODS: We implanted 4-mm preclotted Dacron grafts in both carotids of 12 dogs. For a fair comparison, all dogs had a comparable platelet aggregation profile with platelet aggregation scores less than 30. Five dogs served as controls, and the others were given 7-day subcutaneous injections of G-CSF (10 microg/kg per day), starting on the seventh postoperative day. The effect of G-CSF was evaluated by white blood cell count, which showed a 3.7-fold (+/- 2.7-fold) increase at the end of treatment. Grafts were harvested at 4 weeks. All G-CSF grafts were patent, and one control occluded. Endothelial-like cell coverage averaged 80.8% on G-CSF grafts, but only 35.6% for control grafts (P <.0004). With the exclusion of the anastomotic pannus healing factor, the difference in endothelial-like cell coverage was even greater (68.5% vs 9.8%; P <.0001). Immunocytochemical staining and electron microscopy studies demonstrated endothelial cells. Light microscopy also showed that there were more microvessels on and in the G-CSF grafts than in the control grafts. This study suggests that G-CSF can enhance early endothelialization of small-caliber vascular grafts. Further studies to determine the proper dosage and timing are needed before clinical application can be recommended.     

体外培养血管平滑肌细胞与内皮细胞增殖的影响

目的 研究在外体培养条件下兔血管内皮细胞条件培养基（ＥＣＣＭ）、内皮素－１（ＥＴ－１）、内皮素转化酶抑制剂（Ｅｎ－ｄｏｔｈｅｌｉａｌ－ｃｏｖｅｒｔｉｎｇ ｅｎｚｙｍｅ ｉｎｈｉｂｉｔｏｒ）Ｐｈｏｓｐｈｏｒａｍｉｄｏｎ对血管平滑肌细胞（ＳＭＣ）增殖的影响,同时研究了血管平滑肌细胞条件培养基（ＳＭＣＣＭ）对血管内皮细胞（ＥＣ）增殖方面的影响。方法 ＥＣ和ＳＭＣ均来源于兔主动脉,在获得了ＥＣ和ＳＭＣ的条     

The sartorius muscle flap: an important adjunct for complicated femoral wounds involving vascular grafts

Introduction

Femoral wound complications can threaten vascular grafts. Muscle flaps can be used to facilitate soft-tissue coverage and graft salvage. We report a series of sartorius flaps performed by vascular surgeons in the treatment of complicated femoral wounds.

Methods

Rotational sartorius flaps were performed to attempt salvage of underlying vascular grafts. We reviewed a prospective database to determine the outcomes of sartorius flaps on facilitating wound healing and graft salvage and patency.

Results

From 2005 to 2008, 21 sartorius flaps were performed in infected or threatened femoral wounds. Original operations included femoral endarterectomy with patch repair in 8, aortofemoral graft in 6, axillofemoral graft in 4, and femoral-distal bypass in 3 patients. Complete wound healing occurred in 18 patients (86%). Primary wound closure was achieved in 7 patients. Secondary wound closure was achieved in 11 patients with mean healing time of 2.3 months. All vascular reconstructions remained patent at the 9.5-month follow-up.

Conclusions

Sartorius muscle flaps are effective at facilitating complicated femoral wound healing while maintaining graft salvage and patency.     

Effect of tapered grafts on hemodynamics and flow rate in dialysis access grafts

AIM: Aside from the high incidence of venous stenosis, high-output failure and peripheral steal syndromes remain serious problems of vascular access. Meanwhile commercial tapered grafts are available to address this topic, but little is known about its effect neither on graft flow nor on hemodynamics. METHODS: Anastomotic models were constructed using a clear silicon elastomer. The arterial anastomosis was shaped in two ways: 1) like a direct connection of artery and 7-mm graft and 2) with a 4-mm diameter segment between artery and graft. Hemodynamic measurements were performed in a pulsatile flow circuit to simulate blood flow at physiological conditions. Flow patterns were obtained by direct dye injection. Additionally, the correlation between the length of narrow segment and mean arterial pressure was investigated. RESULTS: In all models using a 4-mm segment, the oscillating anastomotic vortex was disappeared. This vortex was shifted to the area behind the well-rounded expansions of the graft demonstrating a new separation region, but the flow direction was constant during the whole simulated cycle. At identical pressure rates and waveforms the length of narrow segment determined the graft flow rate directly (e.g., at mean pressure 100 mmHg, flow reduction up to 28% in 4-mm segments, and up to 55% in 3-mm segments). CONCLUSION: These findings indicate that taper is an important consideration in the design of vascular access grafts.