小口径生物型人工血管移植后的血管壁重构

背景：人工血管相对人体血管最大的优势就是来源丰富,经过生物化改造的人工血管,其特性更接近人体血管,移植后自体化程度也较高。 目的：观察新型小口径生物型人造血管移植后1.5年内不同时期实验犬的生存、生活状况,移植材料的组织相容性、移植血管壁重构的组织病理学变化。 方法：以猪血管为基材,经交联固定,多方位去抗原,共价结合肝素,以及偶联可黏附、富集生长因子的特定多肽等系列生化处理而制成的一种高抗凝的人造血管,管径3.5~4.5 mm。建立犬颈总动脉-人造血管端端连续缝合的动物模型,1.5年内不同时期切取标本,做病理组织学检查。 结果与结论：切取标本发现,移植血管与周围组织粘连少、疏松。病理组织学检查：移植后8周,镜下开始发现宿主组织通过人造血管孔隙长入血管腔内参与移植血管新内膜的形成,移植后12周,镜下于吻合口处,可见新内膜表面有不连续的内皮细胞生长,移植后6个月,通畅的人造血管整段管腔内面均可见内皮细胞生长。移植后12个月,移植血管管壁VG染色尚可见支架层内有大量胶原纤维和毛细血管生长,原先的支架结构已部分被宿主血管壁组织取代。移植后18个月,原先的支架结构已大部分被宿主血管壁组织取代。说明新型小口径生物型人造血管新内膜形成早且完整,自然内皮化相对满意,血管壁重构和血管支架的再生能力强,生物相容和稳定性好。     

小口径生物型人工血管移植后的血管内皮再生

背景：经过生物化改造的人工血管特性更接近人体血管,移植后自体化程度也较高,但人工血管的内皮再生是解决血管长期通畅的关键。 目的：观察新型小口径生物型人造血管移植后不同时期移植材料的组织相容性及移植血管壁内膜再生的组织病理学变化。 方法：建立犬颈总动脉-人造血管端端连续缝合的动物模型。 结果与结论：①光镜：移植后12周于吻合口处见新内膜表面有不连续的内皮细胞生长;移植后6个月通畅的整段管腔内面均可见内皮细胞生长;移植后1.5年管腔通畅,部分内膜组织呈慢性炎症表现。②电镜：移植后12周新生血管内皮细胞排列规则,从吻合口向移植血管中段爬行;移植后6个月内皮细胞从吻合口向移植血管中段爬行,移植血管中段呈跳跃式片状生长的内皮细胞群落,细胞排列更致密,形态更接近成熟血管内皮细胞;移植后1.5年整段血管内壁均有致密内皮细胞覆盖,部分内膜组织呈慢性炎症表现。说明新型小口径生物型人造血管新生内皮形成早,血管内膜重构能力强,生物相容和稳定性好。     

Expression of fibrinolysis activators and their inhibitor in neointima of polyester vascular grafts

The aim of the study was to evaluate dynamic changes in the expression of fibrinolytic system components in neointima forming in polyester vascular grafts.

The study was carried out on 18 mongrel dogs divided into three groups, that underwent replacement of abdominal aorta with a polyester double velour prosthesis. Grafts were removed at 1, 4 and 12 months. The specimens were fixed according to AMeX method. Immunohistochemical labeling for von Willebrand factor (vWf), tissue plasminogen activator (t-PA), urokinase (u-PA), its receptor (u-PAR), plasminogen activator inhibitor type 1 (PAI-1) and D-dimer (DD) was performed.

Increasing intensity of vWf expression on the graft luminal surface was found in successive periods of the study. A light positive t-PA and u-PA staining was shown in neointima at 1 month and its intensity was significantly increased at 4 and 12 months. Expression of u-PAR appeared at 4 months. A light positive PAI-1 and DD staining was demonstrated in neointima in all periods of the study.

The results demonstrated increasing expression of fibrinolysis activators in neointima of polyester vascular grafts. Intensive expression of plasminogen activators, when compared to their inhibitor may reduce thrombotic properties of graft neointima particularly in the late period after prosthesis implantation.     

Rapid endothelialization of microporous vascular prostheses covered with meshed vascular tissue: a preliminary report

The aim of our study was to induce rapid endothelialization of vascular prostheses which replace malfunctioning blood vessels. We developed a technique of meshing a section of autologous arterial or venous tissue, wrapping it around a porous vascular prosthesis and fixing it with a running suture. This combination was used to replace a 1 cm segment of rat abdominal aorta. The implanted specimens were harvested after 8, 16, 24 or 135 d and evaluated for cellular ingrowth and endothelial coverage with light and scanning electron microscopy. All grafts were patent when harvested. Cells of the meshed tissue were observed to migrate through the pores in the prosthetic wall to cover the luminal surface. The presence of meshed vascular tissue around the prosthesis resulted in complete endothelialization within 24 d and sometimes within 8 d after implantation. This endothelial layer is still present after 135 d. In control prostheses without meshed vascular tissue, complete endothelialization takes at least 42 d. We conclude that the application of meshed vascular tissue around porous vascular prostheses results in patent prostheses with a rapidly formed and long-term surviving endothelium layer.     

Evaluation of urokinase-type plasminogen activator and its receptor in neointima of polyester vascular grafts

The aim of the study was to assess the expression of urokinase-type plasminogen activator (uPA) and its receptor (uPAR) in neointima of polyester vascular grafts. Anastomotic areas were examined at 1, 4 and 12 months after prosthesis implantation in dogs, as well as in human vascular grafts. Immunohistochemistry was performed for uPA and uPAR. Graft neointima in dogs was positively stained for uPA with increased intensity at 4 and 12 months, whereas uPAR expression appeared at 4 and its intensity was increased at 12 months. Intensive uPA and positive uPAR labeling was shown in human grafts. The results demonstrated that in the early period of the healing process of polyester vascular grafts only uPA is present in the neointima in the region of the graft to adjacent artery anastomosis, whereas in healed grafts in dogs and humans uPAR is found as well.     

The role of an endothelial cell lining in limiting distal anastomotic intimal hyperplasia of 4-mm-I.D. Dacron grafts in a canine model.

The effect of an endothelial cell (EC) lining on intimal hyperplasia at the distal anastomosis of Dacron grafts was assessed in a canine model. Enzymatically derived autologous EC were used to seed 14 to 17 cm long, 4 mm I.D., knitted Dacron aortoiliac grafts implanted in an end-to-side manner in six dogs (Group I). Unseeded grafts were similarly implanted in six control dogs (Group II). All animals received acetylsalicylic acid (325 mg po qd) 24 h prior to graft placement and for 2 weeks postoperatively. Distal anastomotic intimal hyperplasia (AIH) and luminal surface EC coverage were quantitated at the conclusion of a 16-week study period. Patency for Group I and Group II grafts were 90% and 55%, respectively (p = 0.07). Maximum AIH, defined as the maximum reduction of luminal cross-sectional area at the distal anastomosis, was not significantly different between Group I (13.1 +/- 8.0%) and Group II (15.1 +/- 7.3%) conduits. However, AIH was inversely related to the extent of luminal EC coverage (r = -0.6, p less than 0.05), thus greater endothelialization was associated with decreased AIH. These data support the idea that EC coverage of the luminal surface of prosthetic vascular grafts may limit the development of AIH.     

A new vascular prosthesis coated with polyamino-acid urethane copolymer (PAU) to enhance endothelialization

Clinically available synthetic ePTFE vascular grafts frequently fail when used for small-diameter arterial substitution. The lower long-term patency of ePTFE grafts is due mainly to thrombogenicity and poor healing. We developed a new small-diameter (1.5-mm) ePTFE vascular prosthesis coated with polyamino-acid urethane copolymer (PAU) to enhance endothelialization. Coating with PAU made the hydrophobic ePTFE vascular graft hydrophilic. Scanning electron microscopy (SEM) observation showed that PAU was homogeneously coated on the ePTFE graft while maintaining the graft's porous structure. Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectra showed PAU was present on graft inner surfaces. Noncoated and PAU-coated ePTFE vascular grafts were implanted into the rat abdominal aorta and evaluated within 1 week and at 8 weeks after implantation. We evaluated the extent of neoendothelialization by SEM, light microscopy, and immunohistochemical staining. Noncoated grafts showed partial endothelialization at proximal and distal areas of grafts but none at midsection. One-percent PAU-coated grafts showed incomplete neoendothelialization, but endothelial cells were observed in the midsection of grafts. Three-percent PAU-coated ePTFE grafts showed complete endothelialization with typical endothelial cell layers under SEM and histologic observation. Immunohistochemical staining also showed that an endothelial cell lining positively reacted with anti-von Willebrand factor (endothelial cell marker) antibody. We conclude that PAU-coated ePTFE vascular grafts enhance endothelialization.     

Healing pattern of small caliber dacron grafts in the baboon: an animal model for the study of vascular prostheses

Although dogs have been used widely to study the healing of large caliber synthetic grafts, hypercoagulability probably makes the dog a poor model for studies of small caliber vascular prostheses. The baboon's coagulation system is similar to man's, but large caliber baboon grafts were reported to endothelialize rapidly. In this study the healing pattern of 4 mm internal diameter Dacron carotid interposition grafts in baboons was determined using specimens harvested at time points between 2 weeks and 18 months post-implantation and examined with light and scanning electron microscopy. The luminal surface of baboon grafts in the acute healing phase (less than 1 month) was comparable to that reported in the literature for dogs. Baboon grafts did not completely endothelialize until 10-12 weeks post-implantation. For work with small caliber vascular prostheses, the dog appears to have no advantage over the baboon as an animal model on the basis of graft healing.     

Superhydrophobic modification fails to improve the performance of small diameter expanded polytetrafluoroethylene vascular grafts.

To determine whether superhydrophobic modification of small diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts improves the performance of these grafts, we assessed neointima formation and platelet deposition in standard and superhydrophobic modified ePTFE grafts. Standard and superhydrophobic vascular grafts were implanted in the carotid arteries of two rabbits and two pigs. Furthermore, standard and superhydrophobic vascular patches were implanted in the carotid arteries of seven pigs. After 4 weeks of implantation all patches were removed and histomorphometric data were analyzed. The early thrombotic effect of superhydrophobic modification was examined by quantifying platelet glycoprotein receptor IIIa deposition onto each type of vascular graft after 15 min of in vitro circulation with human blood. All superhydrophobic and standard ePTFE vascular grafts occluded 15 min to 1 h after implantation in both rabbit and pig carotid arteries. All implanted patches remained patent and were completely covered by endothelium. Superhydrophobic modification of ePTFE vascular grafts did not lead to less neointima formation and resulted in significantly more platelet deposition than did standard ePTFE vascular grafts. Thus, superhydrophobic modification does not improve the performance of small diameter ePTFE vascular grafts.     

Induction of neointima formation by platelet derived angiogenesis fraction in a small diameter, wide pore, PTFE graft.

Enhancement of endothelialization and patency of a small diameter (2 mm), wide pore, PTFE graft was attempted by coating the luminal surface with a platelet derived angiogenesis fraction (PDAF) and implanting it in a rat model. PDAF was delivered to the grafts by combining it with a carrier polymer. PDAF-treated grafts were initially implanted in the retroperitoneum for 21 days followed by removal of one for histology and in situ end to side bypass to the infrarenal aorta for the other. Vascularized grafts were examined at 14 days for patency and 100 days for patency and histology. Significant differences were noted in transmural ingrowth of capillaries and tissue at 21 days post implantation in PDAF-treated versus untreated grafts. Similarly, near significance was noted in capillary ingrowth and significance was noted in tissue ingrowth at 100 days in PDAF-treated grafts. Despite favorable trends particularly early in the time course, no significant differences in graft patency, endothelialization, or hydroxyproline content was demonstrated between PDAF-treated and untreated grafts. Results of this preliminary study are encouraging for further study of PDAF-treated PTFE grafts and the potential that rapid vascularized neointima formation results improved in graft patency rates.     

Formation of a multilayer cellular lining on a polyurethane vascular graft following endothelial cell sodding.

Small-diameter (less than 6 mm) clinically available vascular grafts often fail due in part to the inherent thrombogenicity of artificial polymers. Transplantation of endothelial cells onto the lumen of these vascular grafts has been suggested as one method to overcome this thrombogenicity. We have developed a compliant polyurethaneurea (PEUU) 4-mm graft with a luminal surface modified by a glow discharge gas plasma. Autologous microvessel endothelial cells were isolated from canine falciform ligament fat, were transplanted onto the luminal surface of the grafts using an intraoperative isolation and sodding technique, and both endothelial-cell-treated and non-cell-treated grafts were placed as bilateral carotid interposition grafts in a canine model. After 5 weeks of implantation, explanted control (non-cell-treated) grafts exhibited a deposition of platelets, white cells and fibrin characteristic of a thrombogenic surface. MVEC sodded grafts exhibited a multicellular lining within but distinct from the lumen of the PEUU graft. The blood-contacting surface of this lining exhibited an antithrombogenic endothelial cell monolayer. We suggest that the PEUU graft supported the initial deposition of MVEC and development of and endothelial cell lining. During the 5 weeks of implantation this lining continued to proliferate and detached from the PEUU graft substratum. The final neocellular lining exhibited a luminal diameter and histological features similar to a native artery.     

In vivo evaluation of hydrophobic and fibrillar microporous polyetherurethane urea graft

Mitrathane hydrophobic and fibrillar microporous prosthesis was implanted as infrarenal arterial substitute in dogs; it was evaluated in terms of patency rates, healing characteristics and biostability. Segments of grafts were implanted in duplicate for a period of implantation of 24 h, 1 wk, 1 month and 6 month. Two control grafts from the Ontario Research Foundation were implanted: one for 1 month, the other for six month. All except the two Mitrathane grafts implanted for 6 month were patent at death. The Mitrathane grafts showed kinking at one and 6 month post-implantation. The ORF graft implanted for 1 month was found crinkled in its mid-section and the external capsule was ruptured in the graft implanted for 6 month, without crinkling. Histological studies showed fibrin deposits on the flow surface and infiltration of blood elements into the wall of the Mitrathane grafts implanted for 24 h and 1 wk. A thin internal capsule was present on the graft flow surface of both types of graft tested 1 month post-implantation; scanning electron microscopy revealed the presence of endothelial-like cells on the luminal surface, particularly in the vicinity of the anastomoses. At 6 month, the Mitrathane grafts were occluded by a thick thrombus originating from the anastomoses, while the ORF graft showed infiltration of collagen through the polyurethane fibrillar structure of the wall with an endothelial-like lining covering the flow surface in the vicinity of both anastomoses.     

Improved endothelialization and reduced thrombosis by coating a synthetic vascular graft with fibronectin and stem cell homing factor SDF-1α

Failure of synthetic small-diameter vascular grafts is determined mainly by the lack of endothelial cells, as these cells inhibit thrombosis and intimal hyperplasia. Coating of graft material with homing factors for circulating stem cells has the potential to improve endogenous endothelialization of these grafts and to reduce graft failure. Synthetic knitted polyester grafts (6mm diameter) were coated with FN and SDF-1α before surgical interposition in the carotid artery of sheep. Similar uncoated vascular grafts were implanted in the contralateral side as internal controls. To study the early attraction of stem cells, grafts were implanted in a first series of nine sheep and explanted after 1 or 3 days. In coated grafts, four times higher fractions of CD34(+) and three to four times higher fractions of CD117(+) cells adhering to the vessel walls were found than in control grafts (P<0.05). When such coated and non-coated grafts were implanted in 12 other sheep and explanted after 3 months, all coated grafts were patent, while one control graft was occluded. EcNOS staining revealed that FN-SDF-1α coating significantly increased coverage with endothelial cells from 27 ± 4% of the graft to 48 ± 4% compared with the controls (P=0.001). This was associated with a significant reduction of intimal hyperplasia (average thickness 1.03 ± 0.09 mm in controls vs. 0.69 ± 0.04 mm in coated grafts; P=0.009) and significantly less adhesion of thrombotic material in the middle part of the graft (P=0.029). FN-SDF-1α coating of synthetic small-caliber vascular grafts stimulated the attraction of stem cells and was associated with improved endothelialization and reduced intimal hyperplasia and thrombosis.     

Design considerations for a small bore vascular prosthesis

No synthetic prosthesis has yet been found which can satisfactorily be used as a substitute for saphenous veins in vascular surgery. One explanation for the lack of success is that their properties and behaviour do not mimic those of the arteries they replace. The essential features for a successful vascular prosthesis, over and above biocompatibility, are a low friction non-thrombogenic flow surface, mechanical (elastic) behaviour that matches natural artery and dimensions that approximate the host vessels. This will allow a high velocity of flow with low impedance. A prosthesis with this specification would avoid the problems of flow disturbances and reflection at the anastomoses, pulse wave damping and large pressure gradients, all of which reduce pulsatile energy. We have designed a vascular prosthesis based upon the above criteria. It has an internal diameter of 4 mm and a wall thickness of 1 mm. Its geometry makes it kink resistant and a good match for tibial and coronary arteries. The prosthesis is made from polyurethane and its mechanical properties, which approximate to those of peripheral arteries, are achieved via a mechanism of internal wall compression rather than external circumferential expansion. To assess the in-vivo potential of this prosthesis, 21 grafts were implanted in 11 sheep, replacing a section of carotid artery with a 6 cm long prosthesis. All 21 grafts were patent after 3 months. One graft was removed for histological examination. 16 of the remaining 20 grafts were patent after 7 months. Problems associated with thrombosis were not encountered and we conclude that this prosthesis shows good potential as a small bore vascular substitute.     

Endothelial cell seeding of a 4-mm I.D. polyurethane vascular graft

We evaluated the extent (luminal coverage) of the endothelial cell (EC) lining/neointimal development and the thromboresistance of electrostatically EC seeded small diameter ChronoFlex-polyurethane vascular grafts. The evaluation consisted of harvesting autologous, canine jugular vein ECs, electrostatically seeding the polyurethane grafts (4-mm I.D., length = 6 cm) with the harvested ECs, implanting the grafts in a canine femoral artery model for four to six weeks, and excising the grafts for histological and scanning electron microscopy evaluations. Results of the histological evaluation (mid-graft region only) indicated that electrostatic EC seeding led to neointimal development and to minimal to no thrombus formation within the EC seeded grafts. The unseeded control grafts resulted in no neointimal development and substantial thrombus formation on the graft luminal surfaces. Scanning electron microscopy examination demonstrated a mature, confluent endothelium with a "cobblestone" appearance on the EC seeded graft luminal surface after six weeks. We conclude that electrostatic EC seeding enhanced the development of a neointima and reduced the incidence of thrombosis in polyurethane grafts implanted in a canine femoral artery model.     

Long-term results of tissue-engineered small-caliber vascular grafts in a rat carotid arterial replacement model

The concept of tissue engineered small-caliber vascular grafts (TE-SCVGs) is theoretically ideal. In this study, we evaluated the long-term (more than 1?year) course of TE-SCVGs using a rat carotid arterial replacement model. We fabricated a TE-SCVG scaffold (0.7?mm in diameter) with electrospun nano-scale fibers. Poly-??-caprolactone was used as a biodegradable polymer. These artificial vessels were then used in carotid arterial replacement performed on Sprague?CDawley rats. The implanted grafts were removed at an early phase (1, 2, 6?weeks), middle phase (12, 24?weeks), and late phase (48, 72?weeks) after implantation. Twenty-nine patent grafts from among the 40 implanted grafts (patency 72.5?%) could be evaluated. No aneurysm formation was observed during the follow-up period. Endothelial cells positive for immunostaining with von Willebrand factor were found to be already attached to the inner surface of the TE-SCVGs in the early phase. The percentage of smooth muscle cell specific marker (??-smooth muscle actin and calponin with fluorescent immunostaining) positive cells, which seemed to be mesenchymal cells in the graft wall, increased with time, while, in contrast, the scaffold material decreased. Even after 72?weeks, however, although the scaffold material had degraded, it had not disappeared completely. These results show that the novel TE-SCVGs we developed were still functioning in the rat carotid arterial circulation after more than 1?year. However, further investigations will be required with regard to regeneration of the SMC layer and the complete degradation of graft materials.     

Explant pathology study of decellularized carotid artery vascular grafts

The purpose of this study was to evaluate the morphologic findings in small-diameter freeze-dried decellularized carotid artery grafts implanted in goats as carotid artery interposition grafts for 6-7 months. Unimplanted decellularized carotid artery grafts did not contain intact cells; however, remnants of smooth muscle cells were present in the media. The extracellular matrix was well preserved. All decellularized grafts were patent at explant, without significant dimensional changes or aneurysm formation. Their luminal surfaces were lined by a thin neointima, consisting of myofibroblasts, collagen, and a discontinuous layer of endothelial cells. Histologic evidence of calcification within the explants was not observed; however, electron microscopy showed calcification of minute remnants of cell membranes. Inflammatory cells were not present in the graft wall. Host cell migration was greatest in the adventitia along the length of the graft. Migration of host cells into the media was more apparent close to the anastomoses, forming cellular nests rich in extracellular proteoglycans, whereas cell migration into areas subjacent to the lumen was minimal. Ingrowth of host blood vessels was not observed. These results demonstrate satisfactory structural and morphologic features of a decellularized carotid artery small-diameter graft implanted for up to 7 months.     

Tissue engineering of small-diameter vascular grafts by endothelial progenitor cells seeding heparin-coated decellularized scaffolds

Successful construction of a small-diameter bioartificial vascular graft remains a great challenge. This study reports on novel tissue engineering vascular grafts (TEVGs) constructed by endothelial progenitor cells and heparin-coated decellularized vessels (DV). The DVs were fabricated from canine carotid arteries with observable depletion of cellular components. After heparin coating, the scaffolds possessed excellent antithrombogeneity. Canine endothelial progenitor cells harvested from peripheral blood were expanded and seeded onto heparin-coated DVs and cocultured in a custom-made bioreactor to construct TEVGs. Thereafter, the TEVGs were implanted into the carotid arteries of cell-donor dogs. After 3 months of implantation, the luminal surfaces of TEVGs exhibited complete endothelium regeneration, however, only a few disorderly cells and thrombosis overlaid the luminal surfaces of control DVs grafts, and immunofluorescent staining showed that the seeded cells existed in the luminal sides and the medial parts of the explanted TEVGs and partially contributed to the endothelium formation. Specifically, TEVGs exhibited significantly smaller hyperplastic neointima area compared with the DVs, not only at midportion (0.64 ± 0.08 vs. 2.13 ± 0.12 mm(2) , p < 0.001), but also at anastomotic sites (proximal sites, 1.03 ± 0.09 vs. 3.02 ± 0.16 mm(2), p < 0.001; distal sites, 1.84 ± 0.15 vs. 3.35 ± 0.21 mm(2), p < 0.001). Moreover, TEVGs had a significantly higher patency rate than the DVs after 3 months of implantation (19/20 vs. 12/20, p < 0.01). Overall, this study provided a new strategy to develop small-diameter TEVGs with excellent biocompatibility and high patency rate.     

Evaluation of electrostatically endothelial cell seeded expanded polytetrafluoroethylene grafts in a canine femoral artery model

(1) PURPOSE: The purpose of this study was to evaluate the extent (luminal coverage) of the endothelial cell (EC) lining/neointimal development and the thromboresistance of electrostatically EC seeded small diameter e-PTFE vascular grafts. (2) METHODS: This evaluation consisted of harvesting autologous, canine jugular vein ECs, electrostatically EC seeding the e-PTFE grafts (4 mm GORE-TEX, Length = 6 cm), implanting the grafts in a canine femoral artery model for six weeks, and excising the graft for histological and scanning electron microscopy evaluations. (3) RESULTS: The results of the histological evaluation (mid-graft region only) indicated that the electrostatic EC seeding significantly affected neointimal development (p < 0.01) and the degree of thrombus formation (p < 0.001) within the EC seeded grafts versus the untreated control grafts. Scanning electron microscopy examination demonstrated a mature, confluent endothelium with a "cobblestone" appearance on the EC seeded graft luminal surface. The control grafts demonstrated an equal distribution of SMCs through the graft wall while the electrostatically EC seeded graft sections exhibited an uneven SMC cellular distribution which was skewed toward the graft luminal surface. (4) CONCLUSIONS: The presence of electrostatic EC seeding significantly (p < 0.01) enhanced the development of a neointima and reduced the incidence of thrombosis in e-PTFE grafts implanted in a canine femoral artery model. Results of the mid-graft SMC migration measurements indicate that the electrostatic EC seeding had a significant (p < 0.001) impact on the acute healing of the standard wall e-PTFE vascular graft specimens.     

Introducing a selectively biodegradable filament wound arterial prosthesis: a short-term implantation study.

This article introduces a new compliant and selectively biodegradable filament wound vascular graft and reports the findings of a short-term implantation study. A basic feature of filament winding is its ability to tailor and better control the mechanical properties of the prosthesis, so that a closer match with the anisotropic properties of native arteries is achieved. The elastomeric vascular grafts comprise poly(ether urethane urea) fibers (Lycra) embedded in a two-component matrix consisting of poly(ether urethane) (Pellethane) and a highly flexible poly(ethylene glycol)/poly(lactic acid) biodegradable segmented copolymer (PELA). Typical tensile modulus values fall in the few megapascals (MPa) range, this being comparable to that of natural arteries. The wound graft exhibits excellent handling and suturability characteristics as well as enhanced burst strength. Furthermore, due to its biodegradable constituent, the prosthesis combines minimal intraoperative blood loss and high healing porosity. The graft displays initially negligible in vitro water permeation, which increases gradually with time. In this short-term study, the prostheses were implanted in the canine carotid, and their biological performance was compared to that of expanded Gore-Tex. The luminal surface of the wound grafts was coated with a thin layer of pseudointima, strongly adhered to the prosthesis surface. Contrasting with the very stiff Gore-Tex grafts, the filament wound prostheses retained their high compliance, being highly pulsatile upon explanation. Histological studies fully corroborated these findings, underscoring the healing properties of these new filament wound vascular prostheses.