Reduction of intimal hyperplasia and enhanced reactivity of experimental vein bypass grafts with verapamil treatment.

Recent studies have shown that calcium antagonists exert an antiatherogenic effect in animals fed cholesterol. Vein graft intimal hyperplasia is believed to be an early event in atherosclerotic lesion formation, which is a significant cause of graft failure. Altered vasoreactivity has also been postulated in the etiology of vein graft failure. Therefore this study examined the effect of verapamil treatment on the development of intimal hyperplasia and the vasoreactivity of experimental vein bypass grafts. The right external jugular vein was grafted into the right carotid artery of 30 male New Zealand white rabbits fed normal rabbit chow. The left external jugular vein was used as the control vein. Fifteen animals received verapamil (1.25 mg/day for 28 days) via the femoral vein by means of an osmotic pump. In 15 control animals the pump contained saline. Plasma verapamil concentration was 50.9 +/- 13.2 ng/mL (x +/- SEM), a dose that showed no effect on either blood pressure, total serum cholesterol, or in vitro platelet aggregation to ADP. Fourteen of fifteen grafts were patent in each group, for a patency rate of 93%. Histologic examination using computer morphometry showed significant reduction of intimal hyperplasia at the proximal, middle, and distal graft segments (p less than 0.05). In addition in vitro isometric tension studies of the vein grafts and control veins showed that verapamil causes enhanced reactivity of both vein grafts and control veins in response to norepinephrine and histamine (p less than 0.05). Reactivity of vein grafts to serotonin was unaltered. While none of the normal veins in the control group responded to serotonin, normal veins treated with verapamil contracted readily in response to serotonin. Endothelial-dependent relaxation to acetylcholine was absent in both control and verapamil-treated vein grafts, while normal veins from both groups responded to the same extent to acetylcholine. Because we could not demonstrate any difference in platelet or endothelium function between untreated and verapamil-treated animals, we examined the direct effect of verapamil on smooth muscle. Verapamil significantly inhibited [3H]-thymidine incorporation into DNA in vascular smooth muscle cells in culture in a dose-dependent manner. Verapamil treatment significantly reduces intimal hyperplasia in experimental vein grafts and inhibits smooth muscle cell proliferation in culture. Furthermore the enhanced reactivity to norepinephrine and histamine in the verapamil-treated vessels has no detrimental effect on the patency rate at 4 weeks. Thus by inhibiting intimal hyperplasia, calcium antagonists may improve the long-term patency of vein bypass grafts.     

Modulation of phosphatidylinositol 3-kinase signaling reduces intimal hyperplasia in aortocoronary saphenous vein grafts

OBJECTIVES: Fifty percent of human aortocoronary saphenous vein grafts are occluded after 10 years. Intimal hyperplasia is an initial step in graft occlusion and consists of vascular smooth muscle cell proliferation. Phosphatidylinositol 3-kinase and its downstream regulator, the inositol 3-phosphatase PTEN (phosphatase and tensin homolog deleted on chromosome 10), are important regulators of vascular smooth muscle cell proliferation, migration, and cell death. This study tests whether overexpression of PTEN in aortocoronary saphenous vein grafts can reduce intimal hyperplasia. METHODS: Adult dogs underwent aortocoronary bypass grafting to the left anterior descending artery by using the autologous saphenous vein. Saphenous vein grafts were treated with phosphate-buffered saline (n = 9), empty adenovirus (n = 8), or adenovirus encoding for PTEN (n = 8). Arteriography at 30 and 90 days assessed saphenous vein graft patency. A subset received saphenous vein grafts treated with a marker transgene (beta-galactosidase, n = 3), empty adenovirus (n = 4), or adenovirus encoding for PTEN (n = 4) and were killed on postoperative day 3 to confirm expression. Vascular smooth muscle cells were isolated from canine saphenous vein infected with adenovirus encoding for PTEN, and immunoblotting and proliferation assays were performed. RESULTS: Saphenous vein graft transgene expression was confirmed by means of immunohistochemistry, immunoblotting, and polymerase chain reaction. Arteriograms revealed all saphenous vein grafts to be patent. Saphenous vein grafts treated with adenovirus encoding for PTEN demonstrated reduced intimal area compared with those treated with empty adenovirus and phosphate-buffered saline (1.39 +/- 0.11 vs 2.35 +/- 0.3 and 2.57 +/- 0.4 mm 2 , P < .05), and the intima/media ratio was lower in saphenous vein grafts treated with adenovirus encoding for PTEN (0.50 +/- 0.05 vs 1.43 +/- 0.18 and 1.11 +/- 0.14, P < .005). PTEN overexpression in vascular smooth muscle cells inhibited platelet-derived growth factor-induced phosphorylation of Akt, a downstream effector of phosphatidylinositol 3-kinase. PTEN-treated vascular smooth muscle cells demonstrated decreased basal, platelet-derived growth factor-stimulated, and serum-stimulated proliferation. CONCLUSION: This study demonstrates that PTEN overexpression in aortocoronary saphenous vein grafts reduces intimal hyperplasia. The mechanism of this antiproliferative effect in vascular smooth muscle cells is likely due to inhibition of phosphatidylinositol 3-kinase signaling through Akt, with resultant decreases in vascular smooth muscle cell growth and survival. Therefore modulation of the phosphatidylinositol 3-kinase pathway through PTEN overexpression might represent a novel therapy to prevent saphenous vein graft intimal hyperplasia after coronary artery bypass grafting.     

Hydrophilic statin suppresses vein graft intimal hyperplasia via endothelial cell-tropic Rho-kinase inhibition

BACKGROUND: Recent studies suggest that statins can protect the vasculature in a manner that is independent of their lipid-lowering activity through inhibition of the small guanosine triphosphate-binding protein, Rho, and Rho-associated kinase. Little information is available on the inhibitory effect of statins on vein graft intimal hyperplasia, the main cause of late graft failure after bypass grafting. We therefore examined the effects of a hydrophilic statin on vein graft intimal hyperplasia in vivo and Rho-kinase activity in vitro. METHODS: In the first experiment, rabbits were randomized to a control group (n = 7) that was fed regular rabbit chow or to a pravastatin group (n = 7) that was fed regular rabbit chow supplemented with 10 mg/kg pravastatin sodium. The branches of the jugular vein were ligated and an approximately 3-cm segment of the jugular vein was taken for an autologous reversed-vein graft. The carotid artery was cut and replaced with the harvested autologous jugular vein. At 2 and 4 weeks after the operation, vein grafts in both groups were harvested, and intimal hyperplasia of the vein grafts was assessed. In the second experiment, human umbilical vein endothelial cells and vascular smooth muscle cells were cultured and then treated with 1 micromol/L and 30 micromol/L pravastatin for 24 hours and harvested. Immunoblotting was performed on the resulting precipitates. Quantitative evaluation of phosphorylated myosin binding subunit and endothelial nitric oxide synthase was performed by densitometric analysis. RESULTS: We demonstrated that oral administration of the hydrophilic statin pravastatin to normocholesterolemic rabbits inhibited intimal hyperplasia of carotid interposition-reversed jugular vein grafts 4 weeks after implantation (pravastatin group, 39.5 +/- 3.5 microm vs control group, 64.0 +/- 7.1 microm; n = 7; P < .05) and suppressed cell proliferation and apoptosis in the neointima 2 weeks after implantation. In addition, we found that pravastatin inhibited Rho-kinase activity and accelerated endothelial nitric oxide synthase expression in human umbilical vein endothelial cells but did not inhibit Rho-kinase activity in vascular smooth muscle cells. CONCLUSIONS: These novel findings clearly demonstrate that a hydrophilic statin can suppress intimal hyperplasia of the vein graft in vivo and also show endothelial cell-tropic inhibition of Rho-kinase in vitro. Furthermore, these results strongly support the clinical use of hydrophilic statins to prevent intimal hyperplasia of the vein graft after bypass grafting. CLINICAL RELEVANCE: Late graft failure caused by neointimal hyperplasia limits the efficacy of vein grafting. Various treatments were examined to reduce neointimal hyperplasia, but a standard clinical treatment has not yet been established. We report here the inhibitory effect of pravastatin on the development of vein graft intimal hyperplasia. In addition, we demonstrate that pravastatin showed endothelial cell-tropic benefits through both the inhibition of Rho-kinase activity and acceleration of eNOS expression in vitro. Because the clinical benefits and safety of pravastatin have been established to a certain extent through long-term clinical usage, pravastatin may soon become standard treatment after vein bypass grafting.     

Responsiveness of vein bypass grafts to stimulation with norepinephrine and 5-hydroxytryptamine

The in vitro reactivity of vein bypass grafts to norepinephrine (NE) and 5-hydroxytryptamine (5-HT) was studied in 20 rabbits undergoing bypass grafting. In these animals the right external jugular vein was grafted into the right carotid artery. The cumulative dose-response to NE and 5-HT of rings of vein grafts 2, 4, and 6 weeks after insertion was compared with that of rings from the normal contralateral jugular vein by means of an organ bath to measure changes in isometric tension. With NE there was no significant difference in the response of vein grafts harvested at 2 weeks and control veins. However, at 4 and 6 weeks there was a progressive decrease in the sensitivity of the grafts to NE. The difference in ED50 values (ED50 defined as concentration of agonist required to elicit 50% of the maximal response) between control veins and vein grafts at 4 weeks was twofold and at 6 weeks it was fivefold. None of the control veins responded to 5-HT stimulation. However, the vein grafts contracted with 5-HT, exhibiting sigmoid dose-response curves. The vein grafts showed intimal hyperplasia, which was maximal after 4 weeks. These results show that vein grafts undergo a progressive decrease in their sensitivity to norepinephrine and develop a marked, sustained increase in sensitivity to 5-HT. This finding is in contrast to previous observations in intimal hyperplastic rabbit aorta, suggesting a fundamental difference in the functional expression of arterial and venous intimal hyperplasia.     

Development of a method to prevent degenerative changes of the vein graft for arterial reconstruction]

Autologous vein graft is frequently used for arterial reconstruction in vascular surgery. Its' long-term patency rate, however, is low because of the degenerative changes of the vein wall. Of the basis of our hypothesis that the degenerative changes are mainly caused by an over-distension of vein wall in arterial system, in this study, autologous vein grafts of rabbit (N = 56) were implanted in the carotid arteries. To prevent overdistension, some of the grafts were covered with prosthesis which was made of microporous, compliant biodegradable polyurethane and were compared with those without prosthesis. The integrity of the architecture of the vein wall covered with prosthesis was well preserved at 6 weeks after implantation, where the biodegradation of prosthesis induced an optimal arterialization of the vein grafts. The results indicate that this method may prevent the degenerative changes of vein wall such as fibrosis and intimal hyperplasia, which would cause poor long-term patency of vein graft used for arterial reconstruction.     

Adenoviral activin A expression prevents vein graft intimal hyperplasia in a rat model

Autologus vein grafts are used for coronary artery and infra-inguinal bypass procedures. Although initially successful, long-term patency rates are limited by lumen occlusion due to neointima formation by smooth muscle cell hyperplasia. Gene therapy to prevent this smooth muscle cell proliferation has been studied extensively with limited success. Activin A, a member of the transforming growth factor-beta super family, promotes the contractile phenotype of smooth muscle cells. Maintaining the contractile phenotype could be a novel strategy to prevent intimal hyperplasia. In an epigastric vein-to-common femoral artery interposition grafts rat model, activin A over-expression resulted in a significant decrease in intimal cross-sectional area and percentage stenosis as compared to the control group. BrdU staining identified lower proliferation rates of the smooth muscle cells in the group treated with activin A. We report for the first time evidence that activin A can diminish vein graft failure in a rat model supporting a novel strategy to prevent intimal hyperplasia.     

Gene delivery to aortocoronary saphenous vein grafts in a large animal model of intimal hyperplasia

OBJECTIVE: More than 50% of aortocoronary saphenous vein grafts are occluded 10 years after surgery. Intimal hyperplasia is an initial, critical step in the progression toward occlusion. To date, no clinically relevant large animal models of aortocoronary saphenous vein graft intimal hyperplasia have been fully characterized. Gene therapy holds promise as a novel treatment for aortocoronary saphenous vein graft intimal hyperplasia. The 2 objectives of this study are to characterize a canine model of aortocoronary saphenous vein graft intimal hyperplasia and to demonstrate that ex vivo gene delivery is possible in these grafts using adenoviral vectors. METHODS: Ten dogs underwent aortocoronary bypass grafting using saphenous veins. Six dogs underwent serial arteriograms to monitor graft patency. On postoperative day 90, the dogs were killed and their grafted and nongrafted saphenous veins were studied histologically. Four dogs underwent the same procedure, but their saphenous veins were treated with 1 x 10(12) total viral particles of a replication-deficient, recombinant adenovirus containing beta-galactosidase (n = 2) or the beta-adrenergic receptor kinase carboxyl terminus (n = 2). These animals were killed on postoperative day 7 for determination of transgene expression. RESULTS: All grafts were demonstrated patent by arteriogram before the animals were killed. The mean intimal area of the saphenous vein grafts was increased when compared with that of the nongrafted saphenous veins (2.83 mm(2) vs 0.09 mm(2), P <.0008). Adenoviral-treated saphenous vein grafts demonstrated positive transgene expression either by X-gal staining (beta-galactosidase) or Northern analysis (beta-adrenergic receptor kinase carboxyl terminus). CONCLUSION: This study characterizes a clinically relevant canine model of aortocoronary saphenous vein graft intimal hyperplasia. In addition, it demonstrates that adenoviral vectors can be delivered ex vivo to the saphenous vein graft vessel wall at subphysiologic distension pressures. This model may be used in future studies to manipulate molecular targets critical in aortocoronary saphenous vein graft intimal hyperplasia.     

Pro-UK基因抑制静脉移植物细胞增生的实验研究

目的：探讨Ｐｒｏ－ｕｋ基因对静脉桥移植物细胞增生的影响。方法：３００￣３５０ｇ Ｗｉｓｔａｒ大鼠４２只,取下双鼠颈静脉,两端阻断后,用含Ａｄｖ５－ＣＭＶ／Ｐｒｏ－ＵＫ质粒（治疗组,２１只）的溶液扩张静脉,使溶液在静脉 腔内滞留３０分钟降温末然后置于同一大鼠的颈总动脉。术后２８天,取静脉移植物行尿激酶原活性测定,观察Ｐｒｏ－ＵＫ表达（２６５ｉｕ／ｇｔｉｓｓｕｅ）,对照组未测到Ｐｒｏ－ＵＫ活性。虽然两     

Inhibition of subintimal hyperplasia of autologous vein bypass grafts by nimodipine in rats: a placebo-controlled study.

An arterial bypass may be required for the management of neoplastic or cerebrovascular disease. When an arterial graft is not suitable, autologous vein grafts are the most commonly used conduits; however, as many as 20% of the vein grafts used in vascular surgery may occlude as a result of subintimal hyperplasia. Although the mechanism initiating subintimal hyperplasia remains unclear, it is known that subintimal hyperplasia is dependent upon smooth muscle cell proliferation and migration from the media to the intimal layer. The present study focused on the prevention of smooth muscle cell proliferation using a calcium antagonist. Forty rats received an autologous vein bypass graft from the jugular vein to reconstruct the abdominal aorta. They were randomly divided into two groups of 20 rats each. Animals in the treated group received a calcium antagonist (nimodipine), and those in the control group received a placebo. Nine months after grafting, the group receiving the calcium antagonist presented no or only slight sub intimal hyperplasia as compared with the placebo-treated group (P less than 0.001). These data suggest that a calcium antagonist could be used for the prevention of venous graft disease.     

Reduction of vein graft intimal hyperplasia and preservation of endothelium-dependent relaxation by topical vascular endothelial growth factor

Purpose: Recent evidence suggests that vascular endothelial growth factor (VEGF), in addition to stimulating angiogenesis, also serves a repair/maintenance or survival function, modulating various aspects of endothelial cell function. This study was designed to examine the effect of VEGF pretreatment in a model of vein graft intimal hyperplasia. Methods: Reversed jugular vein–to–common carotid artery interposition grafts were constructed in New Zealand White rabbits. Vein conduits were immersed in solution containing 500 mg rhVEGF165 or saline solution for 20 minutes before implantation. Twenty-eight days later the vein grafts and contralateral control jugular veins were harvested for either histologic or isometric tension studies. Results: VEGF-treated vein grafts showed a 23% reduction in intimal area (0.76 ± 0.07 mm² vs 0.98 ± 0.06 mm²; p = 0.028) and a 30% reduction in intimal thickness (62 ± 6 μm vs 89 ± 5 μm; p = 0.001) when compared with control grafts. After precontraction with norepinephrine, the maximal relaxation to acetylcholine (endothelium-dependent, receptor-mediated agonist) for control vein grafts was 0%, whereas for VEGF-treated vein grafts it was 25% ± 9% (p < 0.05 vs control grafts). The maximal relaxation to the calcium ionophore A23187 (endothelium-dependent, receptor-independent agonist) was also greater in VEGF-treated grafts than in control grafts (172.3% ± 19.4% vs 122.5% ± 13.7%; p < 0.05). There was no difference in the response to sodium nitroprusside (endothelium-independent agonist) between the two groups. Conclusions: A single topical application of VEGF before implantation reduces intimal hyperplasia and improves endothelial function in a rabbit vein graft model. Further evaluation of this simple strategy to improve vein graft patency appears warranted. (J Vasc Surg 1998;27:167-73.)     

大鼠自体移植静脉差异表达microRNA及其生物信息学分析

目的：通过分析大鼠自体移植静脉microRNA（miRNA）表达谱,探讨miRNA对移植静脉内膜增生的调控机制。 方法：将SD大鼠自体颈外静脉移植到肾下腹主动脉制作静脉移植模型,分别术后3、14 d取移植静脉,以正常SD大鼠颈外静脉为对照,提取总RNA后用高通量测序技术检测miRNA表达谱,筛选差异表达miRNA并预测其靶基因,进行靶基因的GO富集分析和KEGG富集分析。 结果：与正常静脉比较,术后14 d的移植静脉差异表达miRNA总数为265,其中表达上调的miRNA有183个,表达下调的miRNA有82个;术后14 d与术后3 d的移植静脉间比较,差异表达的miRNA总数158,其中表达上调的miRNA有94个,表达下调的miRNA有64个。miRNA靶基因GO功能分析显示,富集的基因主要参与了DNA转录过程的调节、细胞间信号转导的调控和蛋白质磷酸化过程的调节;KEGG通路分析显示,富集的信号通路主要有MAPK信号通路、cAMP信号通路、Wnt信号通路、紧密连接、cGMP-PKG信号通路。 结论：miRNA通过复杂的调控网络参与移植静脉内膜增生的生物学过程。所发现的miRNA及其调控网络可能为移植静脉内膜增生的机制研究与干预提供参考。     

Pre- vs postoperative pharmacologic inhibition of platelets: effect on intimal hyperplasia in canine autogenous vein grafts.

Several clinical studies have shown that pharmacologic inhibition of platelets can increase the patency of vascular grafts, but only if platelet-inhibition is initiated before surgery. This study was performed to compare the efficacy of pre- vs postoperative platelet-inhibition on the development of intimal hyperplasia in canine autogenous vein grafts. Reversed femoral veins were used to bypass the ligated femoral arteries in 15 dogs. End-to-side anastomoses were constructed. Eleven dogs were treated with aspirin (325 mg QD) and dipyridamole (25 mg BID). In six dogs treatment was begun 48 hours preoperatively and continued for 3 months. In five other dogs treatment was begun 48 hours after surgery and was continued for 3 months. In 4 control dogs no antiplatelet treatment was given. Excision of the vein grafts 3 months after surgery disclosed reduced intimal hyperplasia (p < 0.05) in the grafts excised from all of the treated animals as compared with those obtained from the control animals. However, there was no difference in intimal hyperplasia observed in the dogs treated both pre- and postoperatively (11 grafts) as compared with those treated only postoperatively (9 grafts). These data demonstrate that it is not necessary to begin antiplatelet therapy preoperatively in order to inhibit intimal hyperplasia. They also suggest that preoperative antiplatelet therapy may improve early graft patency by directly preventing thrombosis, not by inhibiting the development of intimal hyperplasia.     

Therapeutic approach against intimal hyperplasia of vein grafts through endothelial nitric oxide synthase/nitric oxide (eNOS/NO) and the Rho/Rho-kinase pathway

Late graft failure of autologous vein grafts is associated with intimal hyperplasia resulting from the migration and proliferation of vascular smooth muscle cells (VSMCs). Endothelial nitric oxide synthase (eNOS) is an enzyme that synthesizes nitric oxide (NO). An impairment of NO-mediated vasorelaxation and increases in cell proliferation occurs in vein grafts after the surgery and these pathophysiological changes cause intimal thickening. The Rho/Rho-kinase pathway negatively regulates eNOS and is involved in intimal hyperplasia. Several studies have been conducted with the goal of controlling intimal hyperplasia targeting eNOS/NO and the Rho/Rho-kinase pathway. The oral administration of drugs, such as Rho-kinase inhibitor, l-arginine, beta-blocker and statins, significantly suppressed intimal thickening in animal models. This study revealed that statins upregulate eNOS through Rho-kinase inhibition to suppress intimal hyperplasia. The intraluminal gene transfer of eNOS inhibited intimal hyperplasia, thereby reducing the cell proliferation. These approaches are thus considered to be potentially promising therapeutic modalities for graft failure.     

Reinforced long saphenous vein bypass graft for infrainguinal reconstruction procedures: case series and literature review

Poor rehabilitation rates and the high-cost of managing postamputation patients justify an aggressive revascularization policy in critical lower limb ischemia. Endovascular therapy is our first choice for limb salvage in these patients. However there are patients for whom endovascular therapy is not feasible. When bypass is necessary, autologous vein is a superior conduit to synthetic material. However, varicosities usually contraindicate autologous vein bypass because of the risk of aneurysm formation, rupture and increased intimal hyperplasia compared with nonvaricose venous grafts. We report the use of varicosed long saphenous vein (LSV) with external Dacron support in infrainguinal bypass procedures for limb salvage, where endovascular therapy was not feasible. The external Dacron tube was not brought close to the distal anastomotic area itself. With a mean follow-up of 18 months, duplex ultrasonography and computed tomography angiography showed no evidence of stenosis of the reinforced vein segments or aneurysmal degeneration of the residual vein. External reinforcement with Dacron prosthesis allows the use of autogenous greater saphenous veins with varicose dilatation without compromising graft patency and limb salvage.     

Effect of AP-1 decoy using hemagglutinating virus of Japan-liposome on the intimal hyperplasia of the autogenous vein graft in mongrel dogs

Intimal hyperplasia is the leading cause of late vein graft failure. Smooth muscle cell proliferation and migration is the underlying mechanism. Pharmacological approaches to prolong vein graft patency have produced limited results. AP-1 proteins play a role in the expression of many genes involved in cellular proliferation and cell cycle progression. Previously we reported inhibition of vascular smooth muscle cell migration, proliferation, and intimal hyperplasia in the balloon-injured rat carotid artery using an AP-1 decoy with HVJ-liposomes. In this report, we evaluated the effect of the AP-1 decoy on intimal hyperplasia in a large animal model. The jugular vein was transfected with hemagglutinating virus of Japan-liposomes containing the AP-1 decoy or scrambled oligonucleotides. An interposition graft was performed with the pretreated jugular vein between the transected femoral arteries. The graft was harvested at 16 weeks after the procedure. The intimal area was compared: the intimal area of the AP-1 decoy-treated versus control group was 47.3 +/- 15.2 versus 102.3 +/- 15.9 (P < .05), respectively. In conclusion, AP-1 decoy using HVJ-liposomes effectively prevented intimal hyperplasia of an autogenous vein graft in mongrel dogs.     

Balloon catheter injury and vein graft morphology and function

Endovascular interventions to salvage failing vein bypass grafts are often associated with suboptimal outcomes. This study examines the effect of experimental vein graft catheter injury on vein graft morphology and vasomotor function. Thirty New Zealand white rabbits underwent a right common carotid interposition vein bypass graft. Ten grafts were harvested at 14 days, 10 were harvested at 28 days, and 10 had a balloon catheter injury induced at 14 days (4 F Fogarty catheter, 0.6 to 0.75 ml water inflation, 3 passes) and these 10 grafts were harvested after an additional 14 days. Morphologic and morphometric determinations (n=5) or in vitro contractile studies (n=5) were performed on segments of the vein grafts. Intimal thickness, without any intervention, increased by 84% from 14 to 28 days (p<0.01), whereas catheter injury at 14 days induced a twofold increase (p<0.001) in the formation of intimal hyperplasia by 28 days. Scanning electron microscopy demonstrated near-complete endothelial denudation after balloon catheter injury. In the 14- and 28-day control vein grafts, and in the balloon-injured vein grafts, the vascular surfaces had confluent endothelial linings. However, the ultrastructural features of the endothelial cells were group specific. Transmission electron microscopy of the same specimens confirmed this. There were no significant differences in contractility between the 28-day control and the catheter-injured vein grafts. This study demonstrates that balloon catheter injury doubles the rate at which intimal hyperplasia develops in vein grafts without significantly altering the physiologic phenotype of the smooth muscle cells as defined by their vasomotor function.Supported by United States Public Health Service grants HL 15448 and HL 12486. Dr. Davies is supported by a National Institutes of Health Fogarty International Research Fellowship (TW 04810) and is the recipient of a Royal College of Surgeons in Ireland Surgical Travelling Fellowship and a Trinity College Dublin Postgraduate Scholarship. Dr. Dalen is the recipient of an award from the Fulbright Foundation in Norway and is supported by a stipend from the Norwegian Research Council. Dr. Svendsen is supported by the Blix Family Foundation for Medical Research.     

Radiation therapy induced modulation of wound healing at experimental vein graft anastomoses.

OBJECTIVES: The aim of this study was to investigate if radiation therapy (RT) favorably modulates wound healing at vein graft anastomoses. MATERIALS AND METHODS: Jugular vein grafts were sewn into carotid arteries in 32 rats which were randomly divided into two groups: RT (gamma source, 14 Gray, n=16) and control (C, sham irradiation, n=16). Grafts and adjacent arteries were analyzed at 2 (n=8) and 8 weeks (n=8) by histology, immunohistochemistry, and morphometry. RESULTS: Although, RT did not reduce the overall occurrence of intimal hyperplasia, the distribution differed. RT led to a reduction of intimal hyperplasia in arterial segments (median: C: 41.873 microm2; RT: 6.452 microm2, p < 0.0007). In contrast, RT augmented intimal hyperplasia in vein grafts (median: C: 30.287 microm2; RT: 90.455 microm2, p < 0.014). Vein graft diameters after RT were enlarged (median: C: 2.098 microm; RT: 3.381, p < 0.031). Over 80% of the cells were of mesenchymal origin in both groups. CONCLUSIONS: RT reduced intimal hyperplasia in arterial segments. However, RT led to graft dilatation and increased intimal hyperplasia in vein grafts. RT did not favorably modulate the vascular wound healing response in this model.     

肝素对自体移植静脉内膜增殖的影响

目的 探讨肝素对移植静脉内膜增殖的影响。方法 建立大鼠自体静脉移植模型;将颈静脉内侧支移植于髂总动脉,应用肝素,每日２次,皮下注射５天。移植后２８天,应用病理形态学及ＰＣＮＡ免疫组织化学,通过计算机图像定量分析,观察其对移植静脉内膜平滑肌细胞增殖的影响。结果 肝素治疗组和空白对照组移植静脉段内膜增厚程度,ＰＣＮＡ阳性细胞数无差异。结论 肝素对移植静脉内膜增殖无作用,对受损的动脉内膜平滑肌细胞增殖有     

Antisense oligonucleotides to c-fos and c-jun inhibit intimal thickening in a rat vein graft model.

BACKGROUND: C-fos and c-jun are 2 immediate early genes that have been implicated in the stimulation of vascular smooth muscle cell proliferation and migration. In previous experiments in our laboratory with a rat vein graft model a 2- to 3-fold increase of messenger RNA of c-fos and c-jun were noted 1 hour after vein graft perfusion. Because c-fos and c-jun are up-regulated after the perfusion of vein grafts, the purpose of this study was to delineate the temporal expression of c-fos and c-jun protein and to study the effect of antisense oligonucleotides (ASO) to c-fos and c-jun on intimal thickening observed in this model. METHODS: Sprague-Dawley rats underwent bilateral interposition femoral artery grafts with use of the superficial epigastric vein, which was harvested from 15 minutes up to 2 weeks and analyzed by Western blot for Fos and Jun protein. Additional rats underwent bypasses and at the time of the procedure 1 graft was treated with a pluronic gel containing an ASO to c-fos, c-jun, or sense and the contralateral side was treated with pluronic gel only. The vein grafts were harvested 2 weeks after the procedure and perfusion fixed. After longitudinal sectioning, the intimal and total wall thicknesses were measured in the perianastamotic and midgraft regions by a morphometric digitizing microscope and the statistics were analyzed by a paired Student's t test. RESULTS: Protein analysis by Western blot showed that c-fos levels rose quickly within 2 hours and leveled at 6 hours 40-fold above basal levels after vein graft perfusion. Similarly, c-jun levels rose 10-fold above basal levels after 15 minutes and peaked at 2 hours 120-fold above basal levels. The treatment of the vein grafts with these ASOs resulted in a reduction of about 30% in the thickness of the intimal layer and the total wall thickness in both the perianastomotic and the midgraft regions, which was statistically significant different from control veins. CONCLUSION: These results indicate a possible therapeutic role for ASO to immediate early genes in the treatment of vein graft intimal hyperplasia.     

Rapid,arteriovenous graft failure due to intimal hyperplasia: a porcine,bilateral, carotid arteriovenous graft model

BACKGROUND: The loss of patency constitutes the major complication of arteriovenous (AV) polytetrafluoroethylene hemodialysis grafts. In most cases, this graft failure is due to intimal hyperplasia at the venous outflow tract, including proliferation of vascular, smooth muscle cells and fibroblasts with deposition of extracellular matrix proteins. Thus far, procedures developed for improving patency have proven unsuccessful, which can be partly explained by the lack of relevant animal models. For this purpose, we developed a porcine model for AV graft failure that will allow the assessment of promising therapeutic strategies in the near future. MATERIALS AND METHODS: In 14 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein using expanded polytetrafluoroethylene. Two, 4 or 8 weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis. RESULTS: From 2 weeks onwards, a thick neo-intima developed at the venous anastomosis, predominantly consisting of alpha-actin-positive vascular smooth muscle cells (VSMC). Intimal area increased over time, coinciding with a decreased graft flow. Grafts remained patent for at least 4 weeks. At 8 weeks, patency rates declined to less than 50% due to thrombus formation superimposed on progressive neo-intima formation. CONCLUSIONS: Implantation of an AV graft between the carotid artery and jugular vein in pigs causes a rapid neo-intimal response, accompanied by a loss of patency of 50% at 8 weeks after surgery. This model offers a suitable tool to study local interventions aimed at the improvement of AV graft patency rates.