The application of tissue-engineered fish swim bladder vascular graft.

Small diameter (< 6 mm) prosthetic vascular grafts continue to show very low long-term patency, but bioengineered vascular grafts show promising results in preclinical experiments. To assess a new scaffold source, we tested the use of decellularized fish swim bladder as a vascular patch and tube in rats. Fresh goldfish (Carassius auratus) swim bladder was decellularized, coated with rapamycin and then formed into patches or tubes for implantation in vivo. The rapamycin-coated patches showed decreased neointimal thickness in both the aorta and inferior vena cava patch angioplasty models. Rapamycin-coated decellularized swim bladder tubes implanted into the aorta showed decreased neointimal thickness compared to uncoated tubes, as well as fewer macrophages. These data show that the fish swim bladder can be used as a scaffold source for tissue-engineering vascular patches or vessels.

Ex Vivo and In Vivo Analysis of a Novel Porcine Aortic Patch for Vascular Reconstruction.

(1) Background: The aim of the present study was the biocompatibility analysis of a novel xenogeneic vascular graft material (PAP) based on native collagen won from porcine aorta using the subcutaneous implantation model up to 120 days post implantationem. As a control, an already commercially available collagen-based vessel graft (XenoSure®) based on bovine pericardium was used. Another focus was to analyze the (ultra-) structure and the purification effort. (2) Methods: Established methodologies such as the histological material analysis and the conduct of the subcutaneous implantation model in Wistar rats were applied. Moreover, established methods combining histological, immunohistochemical, and histomorphometrical procedures were applied to analyze the tissue reactions to the vessel graft materials, including the induction of pro- and anti-inflammatory macrophages to test the immune response. (3) Results: The results showed that the PAP implants induced a special cellular infiltration and host tissue integration based on its three different parts based on the different layers of the donor tissue. Thereby, these material parts induced a vascularization pattern that branches to all parts of the graft and altogether a balanced immune tissue reaction in contrast to the control material. (4) Conclusions: PAP implants seemed to be advantageous in many aspects: (i) cellular infiltration and host tissue integration, (ii) vascularization pattern that branches to all parts of the graft, and (iii) balanced immune tissue reaction that can result in less scar tissue and enhanced integrative healing patterns. Moreover, the unique trans-implant vascularization can provide unprecedented anti-infection properties that can avoid material-related bacterial infections.

Tissue Engineered Small Vessel Conduits - The Anti-Thrombotic Effect of Re-Endothelialization of Decellularized Baboon Arteries: A Preliminary Experimental Study.

BACKGROUND The use of decellularized biological scaffolds for the reconstruction of small-diameter vascular grafts remains a challenge in tissue engineering. Thrombogenicity is an important cause of obstruction in these vessels due to decellularization. Seeding of the decellularized vascular constructs with endothelial cells is therefore a prerequisite for the prevention of thrombosis. The aim of this study was to seed decellularized baboon arteries with endothelial cells and to compare the thrombogenicity to that of decellularized arteries after circulation of blood. MATERIAL AND METHODS Carotid, radial, and femoral arteries (12 arteries in total) were harvested from 2 Papio ursinus baboons. Ten arteries were decellularized. Normal morphology was confirmed in the control vessels. The effect of re-endothelialization was studied in the vessel scaffolds using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Decellularization resulted in vessel scaffolds with well-preserved extracellular matrix and intact basal membranes. Six of the decellularized vessel scaffolds were seeded with viable human umbilical vein endothelial cells (HUVEC). Luminal endothelialization was established after 7 days in a bioreactor and SEM confirmed confluency. Two control, 4 decellularized, and 6 decellularized re-endothelialized vessel scaffolds were studied in an in vitro flow chamber using baboon blood. RESULTS The decellularized arteries showed an absence of endothelial lining, and an intact basement membrane. The seeding process produced a complete endothelial layer on the surfaces of the arteries. After perfusion with whole blood, no thrombi were formed in the control arteries and re-endothelialized vessels. Widespread platelet activation and adhesion occurred in the decellularized vessels despite a relatively intact basal membrane. CONCLUSIONS This study supports the development of re-endothelialized tissue engineered small-vessel conduits.

Reconstrucción de la vía aérea principal mediante el uso de prótesis sintéticas integrables / Reconstruction of the main airway through the use of integrable synthetic prosthesis

Uno de los principales problemas que plantea el tratamiento quirúrgico de las lesiones traqueales es la limitación existente en la longitud del segmento que es posible resecar. Actualmente, se puede extirpar con seguridad el 50% de la tráquea como máximo. Lesiones más extensas no se pueden beneficiar de este tratamiento y es necesario utilizar técnicas alternativas, en la mayoría de los casos paliativas. Una posible solución a este problema es la interposición de algún elemento que sustituya el segmento traqueal resecado. Se ha realizado un estudio experimental en animales, sustituyendo segmentos traqueales de distinta longitud por prótesis cilíndricas de politetrafluoroetileno. Posteriormente, se ha realizado un seguimiento y sacrificio de los animales estudiando los cambios histológicos. Los resultados obtenidos muestran la posibilidad técnica de la sustitución de la vía aérea por segmentos de material protésico. En el seguimiento evolutivo de los animales, parece existir una relación directa entre la longitud del implante y la aparición de estenosis traqueal a dicho nivel, tanto en los estudios morfológicos macroscópicos como en los estudios realizados con microscopía óptica. Sin embargo, por el momento, la mortalidad perioperatoria es elevada y, si bien se puede atribuir a la curva de aprendizaje, la traslación de los resultados a una posible práctica clínica no es recomendable

One of the main problems arising from the surgical treatment of tracheal lesions is the existing limitation in the length of segment that can be resected. Currently, a maximum of 50% of the trachea can be safely removed. More extensive lesions cannot benefit from this treatment and alternative techniques must be used, which are palliative in most cases. The interposition of an element which substitutes the segment of resected trachea is a possible solution for this problem. An experimental animal study has been conducted, substituting tracheal segments varying in length with cylindrical polytetrafluoroethylene prostheses. Later, a follow-up was done and the animals were sacrificed to study histological changes. The results show the technical possibility of substituting the airway with segments of prosthetic material. In the monitoring of the animals, there seems to be a direct relationship between the length of the implant and the appearance of tracheal stenosis at the implant site, both in the macroscopic morphological studies and the studies completed with optical microscopy. However, for the time being, perioperative mortality is high and, although it can be attributed to the learning curve, applying the results to possible clinical practice is not recommended

Three-Layered PCL Grafts Promoted Vascular Regeneration in a Rabbit Carotid Artery Model.

In this study, a three layered poly (ε-caprolactone) (PCL) graft (tPCL) was fabricated by electrospinning PCL and electrospraying poly (ethylene oxide) (PEO), which has a thin dense inner layer, a loose middle layer, and a dense outer layer. Regular PCL grafts (rPCL) with only a dense layer were used as control. In vivo evaluation was performed in rabbit carotid artery. Enhanced cell infiltration, rapid regeneration of endothelium and smooth muscle layers, and increased elastin deposition were observed within the tPCL graft wall. After 3 months, tPCL grafts showed faster PCL degradation than the rPCL grafts. Infiltrated macrophages in the tPCL grafts secreted higher level of monocyte chemoattractant protein-1 (MCP-1) and vascular endothelial growth factor (VEGF) which enhanced vascular regeneration. In conclusion, the tPCL graft may be a useful vascular prosthesis and worth for further investigation.

Evaluation in vivo of autologous cell derived vein grafts based on tissue engineering concept.

AIM: Aim of the study was to construct and evaluate of autologous cell derived vein grafts based on tissue engineering concept. METHODS: In this study, we constructed venous grafts (VGs) in 12 days based on tissue engineering concept. We draw out 8-12 mL of bone marrow from the intended recipient canines (N.=8) to culture and expand endothelial progenitor cells (EPCs). After having been labeled with PKH26-GL, the cells were seeded onto the luminal surface of decellularized scaffolds (DSs) with single, rotative method for 4 hours. Following static culture for 24-72 hours, the hybrids were implanted to recipient canine inferior vena cava. Non-seeded DSs (N.=4) were performed as control. RESULTS: Angiography disclosed that patent number of test (control) group were 7/7 (2/4), 6/6 (2/2) and 4/4 (1/2) at postoperative 10 days, 4 weeks and 12 weeks, respectively. At 12 weeks, confluenced endothelial cells which covered the whole inner luminal surface of the explants were detected. Meanwhile, fibroblasts and α-actin positive cells in the matrices were found. PKH26-GL labeled EPCs sustained on the luminal surface accompanied by newly formed endothelial cells. However, the explants in both groups showed partial stenosis. CONCLUSION: These results indicate that such constructed VGs based on autologous bone marrow-derived EPCs and porcine DSs are promising and deserve to further improvement and testing.

[Patent ductus arteriosus in the dog: a retrospective study of clinical presentation, diagnostics and comparison of interventional techniques in 102 dogs (2003-2011)]. / Persisterende ductus arteriosus bij de hond: een retrospectieve studie naar klinische presentatie, diagnostiek, en vergelijking van toegepaste therapeutische mogelijkheden bij 102 honden (2003-2011).

A left-to-right shunting patent ductus arteriosus (PDA) is a common congenital heart defect in dogs. If it is left uncorrected, life expectancy in most cases is decreased due to the development of left-sided congestive heart failure. The aim of this study was to describe the dogs diagnosed with PDA in the Utrecht University Companion Animal Clinic from 2003 to 2011. The medical records of 102 patients were retrieved, and the clinical presentation and outcome of PDA closure by surgical ligation or transarterial catheter occlusion (TCO) were reviewed. In the TCO group, the result of coiling was compared with the placement of an Amplatz Canine Duct Occluder (ACDO). A predisposition to PDA was found in the German Brak, Stabyhoun, and Schapendoes. Dogs treated with surgical ligation were significantly older and heavier than those treated with TCO; within the TCO group, dogs treated with ACDO were significantly older and heavier The initial success rate (complete disappearance of the audible murmur in a patient that survived the procedure) was not significantly different between the different treatment modalities. Major complications were more common with surgical ligation, but the incidence of minor complications was not significantly different. There was no diference in survival between dogs treated with surgical ligation and dogs treated with TCO. This study shows a previously unreported predisposition to PDA in certain breeds. Both surgical ligation and TCO are suitable techniques for PDA closure, although major complications were more common with surgical ligation. ACDO appears to be the method with the least complications and thus can be considered the safest method.

Transarterial ductal occlusion using the Amplatz Canine Duct Occluder in 40 dogs.

OBJECTIVES: Describe the result of patent ductus arteriosus (PDA) occlusion using the Amplatz Canine Duct Occluder (ACDO) in 40 dogs. ANIMALS, MATERIAL AND METHODS: Records of the first 41 dogs at Texas A&M University in which ductal occlusion with an ACDO was attempted were reviewed. RESULTS: Appropriate device release was achieved in 40 of 41 dogs. Post-release angiography in 39 dogs documented complete occlusion in 27 dogs, trivial residual flow in 7, mild residual flow in 1 and moderate residual flow in 4; angiography was not recorded in one dog. The following day transthoracic color Doppler echocardiography documented complete occlusion in all 40 dogs. One dog required a larger device than could be deployed through the largest sheath accommodated by the femoral artery and the PDA was subsequently closed by surgical ligation. CONCLUSIONS: Ductal occlusion using an ACDO has a high rate of initial and 24-h complete occlusion. Ductal occlusion using an ACDO is a safe and efficacious therapy for PDA in dogs. This report confirms the positive clinical outcome of the original report in a large cohort of dogs.

Transvenous occlusion of patent ductus arteriosus in 56 consecutive dogs.

OBJECTIVE: Document safety and efficacy of transvenous catheter occlusion of patent ductus arteriosus (PDA) over a wide range of ductal and patient sizes. ANIMALS, MATERIALS AND METHODS: Retrospective study of fifty-six consecutive dogs referred to Colorado State University with diagnosis of PDA. All cases utilized the transvenous approach, via the femoral vein. Occlusion was achieved using a coil (Flipper) in dogs with PDA minimal dimension of 4 mm, or if a coil was unstable following deployment. RESULTS: Ductal occlusion was achieved using the transvenous route alone in 54/56 dogs (96.4%). Occlusion was achieved using detachable Flipper coils in 39/42 dogs (92.9%) in which coil occlusion was attempted, with 38/39 dogs (97.4%) requiring only a single coil. In 16 dogs, occlusion was achieved using an Amplatzer duct occluder or vascular plug. Post-procedure residual ductal flow was absent or only mild in 36/39 (92.3%) dogs in which it was assessed. Procedural mortality rate was 1.7%, and major complication rate 7.0%. CONCLUSION: Transcatheter occlusion via a transvenous approach is a safe and effective method for treating PDA in dogs and is useful for small dogs (<2.5 kg).

Vascular ultrasound studies for the non-invasive assessment of vascular flow and patency in experimental surgery in the pig.

Vascular ultrasound is a reliable non-invasive tool used for the routine assessment of vascular flow and patency in human recipients. We describe the use at three different time points (immediately, 1 week and 4 weeks postsurgery) of ultrasound studies and its validation by angiographic studies in 37 swine undergoing carotid graft replacement. We calculated predictive values (>92%), sensitivity (>85%) and specificity (>92%) with high results at all time points. Ultrasound appeared as an accessible non-invasive technique, providing rapid, safe, repeatable and reliable results. It is an excellent alternative to angiography, avoiding risks inherent to invasive methods and therefore contributing to animal welfare.

Histological study of right ventricle-pulmonary artery valved conduit implantation (RPVC) in dogs with pulmonic stenosis.

We examined whether right ventricle-pulmonary artery valved conduit (RPVC) implantation can overcome the disadvantages of current procedures for pulmonic stenosis (PS). We histologically evaluated the feasibility of RPVC using a homograft in PS model dogs. Eight dogs underwent pulmonary artery banding (PAB) and then 12 weeks later were assigned to PAB (n=4) or PAB+RPVC (n=4) groups. Dogs in the PAB group received no treatment throughout the experimental period, whereas the PAB+RPVC group underwent RPVC. At 1 year after PAB, hearts and conduits were explanted from euthanized dogs and histologically evaluated. The ratios (%) of myocardial fibrosis on right ventricle (RV) epicardial, median and endocardial layers were significantly lower in the PAB+RPVC, than in the PAB group. The ratio of myocardial fibrosis on left ventricular (LV) epicardial and endocardial layers were significantly lower in the PAB+RPVC, than in the PAB group. Neo-intimal thickness in the anastomosis areas of the Denacol and PAB+RPVC groups was 42.77 +/- 30.19 and 88.30 +/- 27.24 microm, respectively, with no significant differences between the groups. Calcification and neo- intima hypertrophy were not obvious in the valve area. Immunohistological staining showed that the internal surface of the anastomosis and intermediate areas were positive for endothelial cells. We concluded that RPVC using a bioprosthetic graft can apparently overcome the disadvantages of current procedures for pulmonic stenosis.

Cardiovascular effects of right ventricle-pulmonary artery valved conduit implantation in experimental pulmonic stenosis.

Right ventricle (RV)-pulmonary artery (PA) valved conduit (RPVC) implantation decreases RV systolic pressure in pulmonic stenosis (PS) by forming a bypass route between the RV and the PA. The present study evaluates valved conduits derived from canine aortae in a canine model of PS produced by pulmonary artery banding (PAB). Pulmonary stenosis was elicited using PAB in 10 conditioned beagles aged 8 months. Twelve weeks after PAB, the dogs were assigned to one group that did not undergo surgical intervention and another that underwent RPVC using denacol-treated canine aortic valved grafts (PAB+RPVC). Twelve weeks later, the rate of change in the RV-PA systolic pressure gradient was significantly decreased in the PAB+RPVC, compared with the PAB group (60.5 +/- 16.7% vs. 108.9 +/- 22.9%; p<0.01). In addition, the end-diastolic RV free wall thickness (RVFWd) was significantly reduced in the PAB+RPVC, compared with the PAB group (8.2 +/- 0.2 vs. 9.4 +/- 0.7 mm; p<0.05). Thereafter, regurgitation was not evident beyond the conduit valve and the decrease in RV pressure overload induced by RPVC was confirmed. The present results indicate that RPVC can be performed under a beating heart without cardiopulmonary bypass and adapted to dogs with various types of PS, including "supra valvular" PS or PS accompanied by dysplasia of the pulmonary valve. Therefore, we consider that this method is useful for treating PS in small animals.

An experimental study of apico-aortic valved conduit (AAVC) for surgical treatment of aortic stenosis in dogs.

A new valved conduit was developed using a canine aortic valve. The bioprosthetic valve was fixed with glutaraldehyde and epoxy compound (Denacol-EX313/810). A vascular graft composed of ultra-fine polyester fiber (10 mm in diameter, 200 mm in length) was used. Four dogs underwent apico-aortic valved conduit (AAVC) implantation and aortic banding (bypass group, BG), while another 4 dogs underwent aortic banding without AAVC implantation (control group, CG). Cardiac catheterization and angiocardiography were performed for assessment of hemodynamics 2 weeks and 6 months after surgery. Left ventricular systolic pressure, left ventricular end-diastolic pressure and the left ventricular-aortic pressure gradient differed significantly (P<0.01) between the BG and CG dogs. Left ventricular angiocardiography showed patency of the valved conduit in all the BG dogs. Echocardiography was performed before and 2, 4 and 6 months after surgery, and showed that while pressure overload caused concentric myocardial hypertrophy in the CG dogs, the left ventricle dilated eccentrically in the BG dogs. Furthermore, relief of left ventricular pressure overload by AAVC was maintained.

A long term comparison between Denacol EX-313-treated bovine jugular vein graft and ultrafine polyester fiber graft for reconstruction of tight ventricular outflow tract in dogs.

A Denacol EX-313 (Denacol)-treated bovine venous graft and an ultrafine polyester fiber (UFPF) graft were transplanted as patch graft into the right ventricular outflow tract under extracorporeal circulation in six dogs each experimentally. Hemodynamics in right heart and histological findings around the graft were compared between both groups over a period of one year after grafting. Pressure measurements and angiocardiography were performed through a cardiac catheter. Right ventricular pressure, pulmonary artery pessure, and right ventricle to pulmonary artery gradient were within normal limits in both groups at 1, 2, 3, 4, 6, and 12 months or more after grafting. No difference were seen between the values for the Denacol and the UFPF group. Histologically, the medial surface at the site of grafting was covered with vascular endothelial cells at one month after grafting in both groups. The density of the vascular endothelial cells increased with time after grafting, showing no clear difference between the two groups. Subendothelial layers comprised of collagen fibers, elastic fibers, and inflammatory cells decreased with time in both groups, but there was less cell infiltration in the Denacol group than in the UFPF group at all time points after grafting. In addition, the central cut thickness value of the graft tended to be thinner in the Denacol group than in the UFPF group at all observation time points after grafting. In the Denacol group, very slight metaplasia of cartilage was noted in a portion of the graft margin at six months or more after grafting, but no other abnormalities were observed. These results suggest that the Denacol-treated bovine venous graft has better grafting characteristics than the UFPF graft with easier intra-operative handlings and less tissue reactions after grafting.

Permanent implantation of a reinforced polytetrafluoroethylene vascular graft for treatment of artificial defects of the teat cistern mucosa in cows.

OBJECTIVE: To evaluate use of a reinforced polytetrafluoroethylene vascular graft for treatment of an artificial defect of mucosa of the teat cistern in lactating cows. DESIGN: Prospective study. ANIMALS: 9 clinically normal lactating dairy cows. PROCEDURE: A 20-mm wide circumferential area of mucosa was sharply excised from the cistern of 1 teat on each cow 10 days after spontaneous calving, and the lesion was covered by a graft. After 14 days of passive milk drainage, routine milking was resumed. Follow-up examinations were performed during the next 2 lactation periods and included evaluation of wound healing, location and sonographic appearance of the implant, milk flow and yield, and somatic cell counts. Cows were slaughtered, and teats and mammary glands were examined microscopically. RESULTS: Implants had partially to totally collapsed within 30 to 90 days. Milk flow was significantly increased by day 15 of the first lactation, but decreased significantly by day 300 of lactation 1. At the end of lactation 1, milk flow had ceased in 3 out of 7 quarters. Only 3 of 9 quarters drained through grafted teats were milkable at the end of the study. Somatic cell counts of these quarters were significantly increased in the first lactation period. At necropsy, 2 grafts were in the teat cistern, but only 1 was incorporated into the mucosa by connective tissue. The mucosa was thickened in all teats with grafts, and there was epithelial metaplasia and granulation tissue proliferation. CLINICAL RELEVANCE: Use of a polytetrafluoroethylene graft can preserve patency in the first lactation period. However, the graft may not be sufficiently incorporated into the mucosa if routine machine milking is resumed 2 weeks after implantation. )

Implantation of a reinforced polytetrafluoroethylene vascular graft for treatment of obstructions of the teat and mammary gland cisternae in cattle.

OBJECTIVE: To evaluate use of an artificial vascular graft as treatment for obstructions of the teat and mammary gland cisternae in lactating cattle. DESIGN: Prospective clinical study. ANIMALS: 14 lactating dairy cows. PROCEDURE: After physical examination that included palpation, ultrasonography, evaluation of milk flow, and California mastitis test, each cow underwent surgical excision of obstructive tissue and implantation of a reinforced polytetrafluoroethylene vascular graft. Milk drained passively for 10 to 14 days after surgery. Follow-up evaluation was performed by telephone questionnaire of owners 1, 6, and 12 months after surgery regarding somatic cell count, time needed to milk affected quarter, compared with that of the contralateral quarter, and frequency of mastitis. After the subsequent nonlactation period and calving, milk flow was tested, using a quarter milking machine, and ultrasonographic examination of the affected teat was performed. RESULTS: Milk could be obtained from affected quarters from all cows 14 days after surgery, from 13 (93%) cows 1 month after surgery, from 10 (71%) cows 6 months after surgery, and from 3 (21%) cows 12 months after surgery, but milk flow in these 3 cows was considerably reduced. This technique failed because of collapse of the implant (4 cows), chronic mastitis (1), migration of the implant (4), and ingrowth of obstructive tissue between the distal aspect of the implant and the ridges of mucous membrane that radiate from the internal orifice of the streak canal (4), or a combination of these. CLINICAL IMPLICATIONS: Implantation of this vascular graft is a useful technique to restore teat patency for 6 months. A longer period of passive drainage of milk appears necessary for sufficient ingrowth of the graft. Lesions that extend to the distal most aspect of the teat cistern have a poor prognosis, because this area cannot be sufficiently overlapped by the graft.

[Palliative treatment of tetralogy of Fallot using a PTFE (polytetrafluoroethylene) vascular graft]. / Palliative Behandlung von Fallotscher Tetralogie mit einer PTFE-(Polytetrafluorethylene-) Gefässprothese.

The application of a PTFE (polytetrafluorethylene) vascular graft for palliative surgical treatment in a case of tetralogy of Fallot in a dog is described. The surgical procedure took place after an attempt to perform a Blalock anastomosis failed. The surgical technique, the postoperative care and the outcome are presented. The technique and its indications are discussed.

Prosthetic microvenous grafting in the rat femoral vein.

Male Wistar rats were used to evaluate microvenous prosthetic grafting techniques and microvenous prostheses in the femoral vein. With the end-to-end technique to implant microvenous prostheses, there was extensive exposure of vessel wall collagen especially at the suture sites. Thrombus formation then led to complete occlusion in all but one of the 32 prostheses 60 min after implantation. However, with the sleeve anastomotic technique there was only minimal exposure of collagen and minimal thrombus accumulation. Fifty-nine of the 64 microvenous prostheses implanted with the sleeve technique were patent after 1 day, 1, 3, 6, and 12 weeks (patency rate 92%). All patent microvenous prostheses were completely covered by an endothelial layer after 3 weeks. It was concluded that the rat is an appropriate experimental laboratory animal for evaluating new grafting techniques with microvenous prostheses and that the sleeve anastomotic technique gives the highest patency rates with microvenous prostheses.

[New experimental rabbit model with PTFE grafts interpositioned in infrarenal abdominal aorta--influence of hyperlipidemia in prosthetic grafts].

The major obstacle to clinical application of artificial blood vessel grafts with inside diameter of less than 4 mm is neogenic intimal hypertrophy at anastomotic sites. With the aim of preventing this artificial blood vessel graft anatomotic intimal hypertrophy, attempts have been made to improve surgical techniques and develop new materials for sutures and the grafts themselves. In the assessment of the preventive effects of various measures on anastomotic intimal hypertrophy, it is desirable to minimize variation in preoperative arteriosclerotic changes and uniform hemodynamics after vessel replacement surgery among the subjects. The present authors succeeded in creating an infrarenal abdominal aorta replacement model that meets these requirements using rabbits, and conducted experiments using this model to assess the effects of hyperlipidemia on anastomotic intimal hypertrophy. The anastomotic intimal hypertrophy lesion in the present rabbit infrarenal abdominal aorta replacement model is both morphologically and histologically similar to that found in human artificial blood vessel graft anastomotic sites. In addition, this model permits the easy obtain of animals showing the same hemodynamic status after vascular surgery. For these reasons, the present model is expected to serve well as an experimental model of artificial blood vessel graft anastomotic intimal hypertrophy.