全生物化组织工程血管的体外构建

目的 探讨组织工程血管的体外构建:脱细胞血管基质的制备.血管平滑肌细胞和血管内皮祖细胞的体外诱导培养和种植方法.方法 处理猪胸主动脉来获得脱细胞血管基质,采用二步种植法先后种植体外培养的平滑肌细胞和内皮细胞.结果 动脉管壁细胞全部脱除,脱细胞基质胶原蛋白含量与新鲜动脉相似,胶原纤维、弹性纤维呈网状排列,无断裂,基质保持完好.脱细胞血管基质的极限应力比新鲜动脉绀织减小20%[新鲜动脉:(1.1510±1.2870)×10-2,脱细胞血管基质:(0.9215±1.7000)×10-2,t=34.137,P<0.01].种植的平滑肌细胞和内皮细胞生长良好.结论 平滑肌细胞和内皮细胞种植于脱细胞血管基质后生长良好,可体外构建组织工程血管.     

骨髓CD34+细胞种植的覆膜支架应用于静脉系统的初步研究

目的研究骨髓CD34^＋胞种植的覆膜支架在静脉系统应用的前景。方法选杂种犬12条，依支架覆膜不同分成PTFE组和涤纶组，每组实验犬4条、对照犬2条，实验犬采自体骨髓。提取CD34^＋细胞种植覆膜支架，对照犬则采用单纯自体血预凝覆膜支架．用导送系统将覆膜支架置人肾下下腔静脉，术后2周获取标本，观察其通畅率，并分别行光镜、电镜、免疫组化CD34和Ⅷ因子染色，观察新生内膜表面内皮化情况。结果除涤纶组有一条对照犬阻塞外，其他覆膜支架均通畅，光镜、电镜和免疫组化证实两组种植犬覆膜支架腔面覆盖新生内皮细胞，而对照组腔面无内皮细胞存在。结论骨髓CD34^＋细胞种植的阿FE和涤纶覆膜支架在静脉系统能实现腔面的快速内皮化。     

脱细胞血管基质和间充质干细胞构建组织工程血管

目的 探讨利用异种脱细胞血管基质和间充质干细胞体外构建小口径血管移植物的方法.方法 采用去垢剂和胰蛋白酶去除猪髂动脉血管壁的细胞成分,对脱细胞基质进行组织学、力学检测及孔隙率评估.分离培养犬骨髓问充质干细胞,种植到脱细胞基质上,并进一步在搏动性生物反应器内培养,采用HE染色和扫描电镜对构建的组织工程血管进行检测.结果 脱细胞处理后,猪髂动脉的细胞成分完全去除,细胞外基质保存完好,力学强度轻度下降;脱细胞基质的孔隙率为94.9%.间充质干细胞能够种植到脱细胞基质上,在剪切力的作用下细胞基本融合,高度伸长并且其排列与流体的方向一致.结论 小口径血管移植物可以通过将间充质干细胞种植到异种脱细胞血管基质并在搏动性生物反应器内培养的方法进行构建.     

骨髓CD34+细胞人工血管内皮化实验研究

目的探讨骨髓CD34^ 细胞种植的人工血管内皮化和通畅性。方法取犬骨髓,经免疫磁珠分离出CD34^ 细胞,内皮细胞生长因子(vascular endothelial grow factor,VEGF)诱导并扩增;种植聚四氟乙烯(polytetra fluoro ethylene,PTFE)人工血管,再植入犬的下腔静脉和腹主动脉。结果骨髓分离的细胞经流式细胞仪鉴定为CD34^ 细胞,CD34^ 细胞经VEGF诱导培养后经免疫细胞化学和透射电镜检测证实为内皮细胞。内皮化人工血管植入动脉闭塞率0,狭窄率12．5％;人工血管植入静脉闭塞率12．5％,狭窄率25．0％。结论骨髓经免疫磁珠可分离出CD34^ 细胞,CD34^% 细胞经VEGF诱导可定向分化为内皮细胞。骨髓CD34^ 细胞经体外培养种植于PTFE人工血管,获得理想的内皮化和通畅率。     

骨髓CD34~+干细胞种植人工血管应用于血管置换后内皮化和通畅率的研究

目的:探讨骨髓CD34+细胞分别种植于常用膨体聚四氟乙烯(expanded polytera fluoroethylone,ePTFE)人工血管和涤纶人工血管的内皮化程度和通畅率.方法:选杂种犬16条,依人工血管不同分为ePTFE血管实验组(6条)和涤纶皿管实验组(6条)及ePTFE对照组(2条)和涤纶对照组(2条),实验犬采自体骨髓,提取CD34+细胞种植覆膜人工血管,对照犬采用单纯自体血预凝人工血管,将ePTFE或涤纶人工血管分别植入所有实验犬的下腔静脉和腹主动脉.术后第30、60、100天取标本,观察通畅率,并分别用光学显微镜、电子显微镜和免疫组织化学方法观察新生内膜表面内皮化情况.结果:对照组静脉全部阻塞.实验组第30天人工血管腔面新生内膜内皮细胞密度自吻合口向中间方向逐渐减少,第60天的人工血管内皮基本覆盖管壁,第100天人工血管腔面内膜内皮细胞排列均匀完整,而对照组内膜表面无内皮细胞覆盖.结论:经纯化的CD34+细胞种植于ePTFE和涤纶人工血管较未种植的人工血管中远期有较好的内皮化和通畅率.     

骨髓诱导分化内皮细胞构建组织工程心脏瓣膜的实验研究

骨髓基质干细胞（BMSCs）在特定培养条件下能够诱导分化为内皮细胞,是构建组织工程心脏瓣膜（TEHV）较有前景的种子细胞来源.我们研究探讨应用BMSCs诱导分化的内皮细胞和猪去细胞瓣膜支架体外构建TEHV的可行性.     

犬骨髓CD34＋细胞种植人工血管置换后短期内皮化的实验研究

目的：探讨骨髓CD34＋细胞种植于常用膨体聚四氟乙烯（expanded polytera fluoroethylene，ePTFE）人工血管和涤纶人工血管后二者的内皮化程度。方法：选杂种犬8条，依支架覆膜不同分为ePTFE组和涤纶组，每组实验犬2条，对照犬2条。实验犬采自体骨髓，提取CD34＋细胞种植覆膜支架，对照犬采用单纯自体血预凝覆膜支架。将人工血管植入犬的下腔静脉和腹主动脉。在术后第10、30天观察植入的人工血管通畅情况，采用免疫组织化学方法鉴定内膜细胞来源，在光镜和电镜下观察人工血管新生内膜表面内皮化情况。结果：术后第10天实验组与对照组差异无统计学意义；术后第30天腔面新生内膜内皮细胞自人工血管吻合口向中间逐渐减少（P〈0．05）；而对照组内膜表面第10、30天均无内皮细胞覆盖。结论：经纯化的CD34＋细胞种植于ePTFE和涤纶人工血管，均获得理想的内皮化。     

骨髓间充质干细胞复合组织工程化脱细胞真皮基质构建组织工程皮肤

目的：体外培养扩增SD大鼠骨髓间充质干细胞（bone marrow mesenchymal stem cells,BMSCs），复合组织工程化脱细胞真皮基质构建组织工程皮肤，为进一步临床应用奠定基础。方法：将SD大鼠骨髓间充质干细胞进行体外培养扩增后，以生长状态良好的骨髓间充质干细胞接种于制备好的组织工程化脱细胞真皮支架上，进行体外联合培养，构建组织工程皮肤。观察细胞生长情况及组织工程皮肤结构。结果：体外培养的SD大鼠骨髓间充质干细胞生长良好，传代扩增容易，组织工程化脱细胞真皮基质去细胞完全，骨髓间充质干细胞在脱细胞真皮基质中生长良好，可体外构建组织工程皮肤。结论：利用体外扩增培养的骨髓间充质干细胞及制备的组织工程化脱细胞真皮基质可以体外联合构建组织工程皮肤。     

组织工程心脏瓣膜内皮细胞的整合素β1表达

目的体外构建组织工程心脏瓣膜（TEHV）,初步探讨内皮细胞黏附生长的分子机制。方法猪主动脉瓣膜经胰酶-EDTA、表面活性剂、核酸酶处理,去除猪主动脉瓣叶的细胞成分,测定瓣叶脱细胞后的生物力学特性;将扩增的人脐静脉血管内皮细胞（HUVECs）种植在瓣叶上,体外静态构建TEHV,观察内皮细胞的生长状态。消化瓣膜内皮细胞,半定量RT-PCR检测内皮细胞整合素＆mRNA的表达,Western-Blot检测内皮细胞膜上整合素＆蛋白的表达。结果猪主动脉瓣膜中的细胞成分能完全去除,脱细胞瓣叶的生物力学特性同新鲜瓣叶相比无明显变化;种植的HUVECs在瓣叶表面生长状态良好,长成一层连续的细胞层。瓣膜内皮细胞可检测到整合素岛mRNA和蛋白的表达。结论脱细胞猪主动脉瓣膜作为支架,HUVECs做种子细胞可以成功构建TEHV,瓣膜内皮细胞可以表达整合素岛。     

骨髓间充质干细胞复合脱细胞血管基质构建组织工程血管的初步研究

目的：探讨骨髓间充质干细胞复合脱细胞血管基质构建组织工程血管的可行性。方法：采用胰蛋白酶、乙二胺四乙酸和曲拉通X-100对兔主动脉进行脱细胞处理，制备成脱细胞血管基质；体外分离和扩增人骨髓间充质千细胞，并将其作为种子细胞种植于脱细胞血管基质上，复合构建组织工程化人工血管。结果：制备的脱细胞血管基质由胶原、弹力纤维等组成，未见细胞成分残留；体外扩增的人骨髓间充质干细胞种植于脱细胞血管基质上可生长增殖。结论：骨髓间充质干细胞与脱细胞血管基质支架材料复合可成功构建组织工程血管，有望为血管缺损的修复提供一种全新的技术方法和手段。     

Mesenchymal stem cell-based tissue engineering of small-diameter blood vessels

The aim of the study was to construct small-diameter vascular grafts using canine mesenchymal stem cells (cMSCs) and a pulsatile flow bioreactor. cMSCs were isolated from canine bone marrow and expanded ex vivo. cMSCs were then seeded onto the luminal surface of decellularized arterial matrices, which were further cultured in a pulsatile flow bioreactor for four days. Immunohistochemical staining and scanning electron microscopy was performed to characterize the tissue-engineered blood vessels. cMSCs were successfully seeded onto the luminal surface of porcine decellularized matrices. After four-day culture in the pulsatile flow bioreactor, the cells were highly elongated and oriented to the flow direction. Immunohistochemistry demonstrated that the cells cultured under pulsatile flow expressed Von Willebrand factor, an endothelial cell marker. In conclusion, cMSCs seeded onto decellularized arterial matrices could differentiate into endothelial lineage after culturing in a pulsatile flow bioreactor, which provides a novel approach for tissue engineering of small-diameter blood vessels.     

Differentiation of hematopoietic stem cells into hepatocytes in liver fibrosis in rats

It has been reported that hematopoietic stem cells (HSC) can differentiate into hepatocytes in the normal liver and in some pathologic environments. The aim of this study was to investigate whether HSC can differentiate into hepatocytes in cases of established liver fibrosis. Rat liver fibrosis was induced by subcutaneous injection of tetrachloride (CCl4). Thy+ CD3- CD45RA- HSC in bone marrow cells, which had been enriched by fluorescence-activated cell sorting (FACS), were labeled with PKH26-GL, and autologously transplanted into CCl4-treated rats. The expressions of albumin (Alb), cytokeratin 8 (CK8), and alpha-smooth muscle actin (SMA) were determined by immunofluorescence methods. The PKH26-GL labeled Thy+ CD3- CD45RA- HSC expressed the hepatocyte-specific markers Alb and CK8, but did not express alpha-SMA in liver fibrosis. Thy+ CD3- CD45RA- HSC differentiated into hepatocytes, but not into hepatic stellate cells. In conclusion, autologous stem cell transplantation may be helpful to treat hepatic fibrosis.     

Autologous endothelial progenitor cells transplantation promoting endothelial recovery in mice

Transplantation of endothelial progenitor cells (EPCs) restores endothelial function. The present study was designed to determine the effect of autologous EPCs transplantation on the regeneration of endothelium in mice. Mice splenectomy was performed 14 days before carotid artery injury, and mononuclear cells were isolated and cultured in endothelial growth media for 7 days. EPCs were confirmed by immunostaining (CD31, endothelial nitric oxide synthase (eNOS) and double positive for 1,1'dioctadecyl-3,3,3',3-tetramethylindocarbocyanine (DiI)-low-density lipoprotein and ulex europaeus agglutinin (UEA)). Cell counts and fluorescence-activated cell sorting for stem cell marker were performed. 1 x 10(6) 4-,6-Diamidino-2-phenylindole- labeled EPCs or saline were injected through tail vein after wire injury. Two weeks after transplantation, cell tracking and immunohistochemical staining showed homing and incorporation of labeled EPCs in injury artery. Administration of EPCs enhanced reendothelialization (P < 0.05) after 1 week and inhibition of neointima formation at 3 weeks compared with that of saline (P < 0.05, n = 6). These data demonstrate that delivery of autologous EPCs is associated with accelerated reendothelialization and reduced neointimal formation. Thus, delivery of autologous EPCs represents an important vasculoprotective approach to attenuate the response to acute vascular injury.     

Decellularized vein as a potential scaffold for vascular tissue engineering

PURPOSE: Current strategies to create small-diameter vascular grafts involve seeding biocompatible, compliant scaffolds with autologous vascular cells. Our purpose was to study the composition and strength of decellularized vein to determine its potential as a vascular tissue-engineering scaffold. METHODS: Intact human greater saphenous vein specimens were decellularized by using sodium dodecyl sulfate (SDS). Residual cellular and extracellular matrix composition was studied with light and electron microscopy as well as immunohistochemistry. Burst and suture-holding strength was measured in vitro by insufflation and pull-through techniques. To assess initial handling and durability of decellularized vein in vivo, a canine model was developed wherein decellularized canine jugular veins were implanted as carotid interposition grafts in recipient animals. After two weeks of arterial perfusion, these grafts were studied with duplex imaging and histologic methods. RESULTS: Human saphenous vein decellularized by using SDS was devoid of endothelial cells and >94% of the cells resident within the vein wall. Collagen morphology appeared unchanged, and elastin staining decreased only slightly. Basement membrane collagen type IV remained intact. Compared with fresh vein, decellularized vein had similar in vitro burst (2480 +/- 460 mm Hg vs 2380 +/- 620 mm Hg; P >.05) and suture-holding (185 +/- 30 gm vs 178 +/- 66 gm; P >.05) strength. Decellularized canine vein functioned well in vivo without dilation, anastomotic complication, or rupture over 2 weeks of arterial perfusion. CONCLUSIONS: Vein rendered acellular with SDS has well-preserved extracellular matrix, basement membrane structure, and strength sufficient for vascular grafting. These properties suggest proof of concept for its use as a scaffold for further vascular tissue engineering. CLINICAL RELEVANCE: The following research examines the creation of a new small-diameter bypass graft. It is clinically relevant to patients who need distal arterial bypass, coronary artery bypass, or hemodialysis access, but who do not have adequate autologous vein for their surgeries. Future investigations will involve further tissue engineering of this vascular scaffold (eg, autologous endothelial seeding of its lumen) and testing the clinical usefulness of the completed graft.     

Tissue engineering of heart valves in vivo using bone marrow-derived cells

In this study, we tissue-engineered heart valves in vivo using autologous bone marrow-derived cells (BMCs). Canine BMCs were differentiated into endothelial cell (EC)-like cells and myofibroblast (MF)-like cells. Decellularized porcine pulmonary valves were seeded with BMCs and implanted to abdominal aorta and pulmonary valve of bone marrow donor dogs. Histological examination of the explants identified the regeneration of valvular structures expressing CD31 and smooth muscle alpha-actin, indicating the presence of EC-like and MF-like cells in the grafts at 3 and 1 week, respectively, after implantation. Fluorescent microscopic examinations identified the presence of fluorescently labeled cells in the explants, indicating that the implanted BMCs survived and participated in the heart valve reconstitution. This study reports, for the first time, on tissue engineering of heart valve in vivo using BMCs.     

骨髓基质干细胞与软骨脱细胞基质多孔支架异位构建组织工程化软骨的实验研究

目的 探讨骨髓基质干细胞(bone marrow mesenchymal stem cells,BMSCs)与软骨脱细胞基质多孔支架(cartilage ECM-derived porous scaffold,CEDPS)在裸鼠体内异位构建软骨的可行性,并建立利用PKH26荧光和分子荧光活体成像系统无创评估组织工程化细胞-支架复合体在体内生长情况的新方法.方法 PKH26荧光标记成软骨诱导的BMSCs,接种入CEDPS支架,体外进行电镜、Desd/Live荧光染色观察,然后植入裸鼠背部,4周后利用分子荧光活体成像系统无创伤性评估组织工程化组织在裸鼠体内生长情况,取材进行组织学以及Ⅱ型胶原免疫荧光检测,与荧光图像比较.结果 体外培养的BMSCs-CEDPS复合体电镜检查结果表明随着培养时间的增加,细胞在支架中增殖显著,细胞基质分泌增加,Dead/Live染色表明BMSCs在支架内部活性良好.4周后活体荧光示踪显示BMSCs在支架内生长良好,无扩散趋势,BMSCs-CEDPS复合体在裸鼠体内生成软骨样组织,番红"O"、甲苯胺蓝染色、Ⅱ型胶原免疫组化染色阳性,免疫荧光检查表明构建的软骨样组织内的细胞来源为接种的PKH26标记的BM-SCs.结论 利用BMSCs和CEDPS支架能够在裸鼠皮下异位构建类软骨样组织.PKH26标记与分子荧光活体成像系统结合,能够无创伤性评估组织工程化组织的种子细胞在动物体内生长情况与转归.     

Biological vascularized matrix for bladder tissue engineering: matrix preparation, reseeding technique and short-term implantation in a porcine model

PURPOSE: We generated a vascularized, autologous, reseeded bladder substitute and evaluated immediate vascularization and perfusion of the graft after implantation to the recipient organism in a porcine model. MATERIAL AND METHODS: Acellular matrix was processed from porcine small bowel segments by subsequent mechanical, chemical and enzymatic decellularization, preserving the jejunal arteriovenous pedicles. In 2 separate steps the matrix was reseeded with primary bladder smooth muscle cells (SMCs) and urothelial cells (UCs), and its vascular structures were resurfaced with endothelial progenitor cells (EPCs). To evaluate graft perfusion short-term implantation was performed. RESULTS: The acellular scaffold was successfully repopulated with multilayers of ingrowing SMCs and superficial UCs. After reseeding the jejunal arteriovenous pedicles with EPCs and cultivation for 3 weeks the larger vessels as well as the intramural scaffold capillary network were repopulated with cell monolayers expressing endothelial specific proteins. Perfusion stagnation and implant thrombosis occurred within 30 minutes after the implantation of acellular scaffolds not reseeded with EPCs. In the EPC reseeded group the vascular system revealed intact perfusion and no relevant thrombus formation was observed after 1 or 3 hours. CONCLUSIONS: The current study of successful SMC and UC reseeding, vessel resurfacing with EPCs and short-term vascular patency represents the promising in vitro and in vivo basis for further evaluation of this biological vascularized matrix in chronic long-term large animal implantation experiments.     

Small-diameter blood vessels engineered with bone marrow-derived cells

OBJECTIVE: The objective of this study is to investigate if bone marrow-derived cells (BMCs) regenerate vascular tissues and improve patency in tissue-engineered small-diameter (internal diameter = 3 mm) vascular grafts. SUMMARY BACKGROUND DATA: BMCs have demonstrated the ability to differentiate into endothelial-like cells and vascular smooth muscle-like cells and may offer an alternative cell source for vascular tissue engineering. Thus, we tissue-engineered small-diameter vascular grafts with BMCs and decellularized arteries. METHODS: Canine BMCs were differentiated in vitro into smooth muscle alpha-actin/smooth muscle myosin heavy-chain-positive cells and von Willebrand factor/CD31-positive cells and seeded onto decellularized canine carotid arteries (internal diameter = 3 mm). The seeded grafts were implanted in cell donor dogs. The vascular-tissue regeneration and graft patency were investigated with immunohistochemistry and angiography, respectively. RESULTS: The vascular grafts seeded with BMCs remained patent for up to 8 weeks in the canine carotid artery interposition model, whereas nonseeded grafts occluded within 2 weeks. Within 8 weeks after implantation, the vascular grafts showed regeneration of the 3 elements of artery (endothelium, media, and adventitia). BMCs labeled with a fluorescent dye prior to implantation were detected in the retrieved vascular grafts, indicating that the BMCs participated in the vascular tissue regeneration. CONCLUSIONS: Here we show that BMCs have the potential to regenerate vascular tissues and improve patency in tissue-engineered small-diameter vascular grafts. This is the first report of a small-diameter neovessel engineered with BMCs as a cell source.     

猪主动脉脱细胞基质的简化制备及生物学评价

目的应用酶法制备猪主动脉脱细胞基质，并评价其生物学性能。方法取新鲜屠宰的16根肉猪降主动脉，长10～12cm，应用0．1％胰蛋白酶和0．01％EDTA于37℃震荡条件下脱除细胞成分，HE和Masson染色行脱细胞基质的组织学观察，扫描电镜和透射电镜观察超微结构改变。应用单轴拉伸方法比较脱细胞前和脱细胞后48、96和120h时材料两断端厚度、极限抗张强度（ultimate tension stress，UTS）和断裂伸长率（strain of failure，SOF），绘制应力-应变曲线。取成年杂种犬3只，体重20～30kg，雌雄不限。将脱细胞前后片状主动脉基质埋植于犬脊柱两侧皮下，分别于埋植后1、3和6周取材，行HE染色观察，参照半定量的Wakitani评分法，对取材时的大体形态、浸润细胞种类和数量、新生血管等指标进行比较，观察宿主炎性细胞反应和脱细胞基质变化。将犬内皮细胞种植于猪脱细胞基质，HE染色和扫描电镜观察细胞相容性。结果HE染色和电镜检查显示在96h可将新鲜猪主动脉细胞成分脱除，Masson染色显示细胞外纤维成分保留完整。脱细胞前后的动脉基质厚度、UTS和SOF差异均无统计学意义（P〉0．05），但UTS显示降低趋势，SOF则呈现增加趋势，应力-应变曲线呈现力学强度降低和延展性增加的变化趋势。犬皮下埋植，各组脱细胞标本炎性细胞浸润明显减轻，6周时以成纤维细胞浸润为主，且基质中见新生毛细血管。半定量组织学评分，在大体观察、浸润细胞种类和数量方面与脱细胞前比较有统计学意义（P〈0．05）；新生血管数量比较，差异无统计学意义（P〉0．05）。HE染色和扫描电镜显示种植的内皮细胞可在基质表面形成单细胞层。结论应用0．1％胰蛋白酶和0．01％EDTA持续振荡96h制备的猪主动脉脱细胞基质，在生物力学、免疫原性和细胞相容性方面可满足血管组织工程的需要。     

Endothelial cell seeding of expanded polytetrafluoroethylene vena cava conduits: effects on luminal production of prostacyclin, platelet adherence, and fibrinogen accumulation

The blood-surface interface of 12 mm ID x 5 cm ePTFE vena cava conduits, unseeded (n = 8) and seeded (n = 8) with enzymatically derived autologous endothelial cells, was studied in a canine model at 4 and 12 weeks after graft implantation. Acetylsalicylic acid (325 mg each day) and Coumadin (prothrombin time 1.4 to 1.7 times the control value) were administered preoperatively and continued 4 weeks postoperatively. Platelets labeled with 111In and 125I-labeled fibrinogen were administered 24 hours before graft removal. Luminal platelet adherence, expressed as 10(6) platelets/cm2 of graft surface, was 8.9 +/- 5.6 vs. 56.4 +/- 8.0 (p less than 0.008) and 4.0 +/- 0.9 vs. 12.4 +/- 2.3 (p less than 0.005) in seeded vs. unseeded grafts at 4 and 12 weeks, respectively. Luminal fibrinogen deposition, expressed in micrograms per square centimeter of graft surface, was 11.8 +/- 2.2 vs. 32.0 +/- 2.0 (p less than 0.06) and 6.1 +/- 2.4 vs. 12.4 +/- 6.3 (p less than 0.005) in seeded vs. unseeded grafts at 4 and 12 weeks, respectively. Cumulative 4- and 12-week luminal production of 6-keto-PGF1 alpha from seeded and unseeded grafts represented 11% and 5%, respectively, of that produced from the native iliac vein. Luminal endothelial cell coverage was 71% +/- 22% vs. 33% +/- 9% and 79% +/- 8% vs. 55% +/- 8% (p less than 0.05) in seeded and unseeded grafts at 4 and 12 weeks, respectively. Although endothelialization was not complete in seeded vena cava grafts, it is clear that seeded prostheses exhibited improved thromboresistance compared with unseeded conduits.