Vein Graft Intimal Hyperplasia Research Articles

Long-Term Engraftment of Bone Marrow-Derived Cells in the Intimal Hyperplasia Lesion of Autologous Vein Grafts

Intimal hyperplasia of autologous vein grafts is a critical problem affecting the long-term patency of many types of vascular reconstruction. Within intimal hyperplasia lesions, smooth muscle cells are a major component, playing an essential role in the pathological process. Given that bone marrow-derived cells may differentiate into smooth muscle cells in the neointima of injured arteries, we hypothesized that the bone marrow may serve as a source for some of the smooth muscle cells within intimal hyperplasia lesions of vein grafts. To test this hypothesis, we used an established mouse model for intimal hyperplasia in wild-type mice that had been transplanted with bone marrow from a green fluorescent protein (GFP+/+) transgenic mouse. High-resolution confocal microscopy analysis performed 2 and 8 weeks after grafting demonstrated expression of GFP in 5.4 +/- 0.8% and 11.9 +/- 2.3%, respectively, of smooth muscle cells within intimal hyperplasia lesions. By 16 weeks, GFP expression in smooth muscle cells was not detected by immunohistochemistry; however, real-time PCR revealed that 20.2 +/- 1.7% of the smooth muscle cells captured from the neointima lesion by laser capture microdissection at 16 weeks contained GFP DNA. Our results suggest that bone marrow-derived cells differentiated into smooth muscle cells within the intimal lesion and may provide a novel clinical approach for decreasing intimal hyperplasia in vein grafts.

Controlled release of small interfering RNA targeting midkine attenuates intimal hyperplasia in vein grafts

Controlled release of small interfering RNA targeting midkine attenuates intimal hyperplasia in vein grafts

Inhibition of vein graft intimal hyperplasia by periadventitial application of hyaluronic acid–carboxymethyl cellulose: An experimental study

Objective. Placement of an external support has been reported to prevent intimal hyperplasia of vein grafts. In this study, we investigated the effect of HA/CMC on intimal hyperplasia in a rabbit model. Design. Right jugular vein to common carotid artery bypass grafting was performed in 24 female New Zealand white rabbits (2.5–3.0 kg). Animals were divided into two groups: control group (n=12) and HA/CMC group (n=12). Absorbable membrane barrier was wrapped around vein grafts in HA/CMC group. In control group, no material was applied following venous graft bypass. Results. At 1 month, in the vein grafts supported with the HA/CMC membrane neointimal thickening was significantly less (109 µm [IQR, 78–166]) compared to the unsupported control grafts (220 µm [IQR; 101–312]; p<0.001). Medial thickening in the HA/CMC group (128 µm [IQR, 101–181]) compared to unsheathed control grafts (182 µm [IQR, 131–255] p<0.001) was also significantly less. Conclusion. Periadventitial placement of HA/CMC as an absorbable membrane inhibits intimal hyperplasia of vein bypass grafts in a rabbit model.

Effect of external stents on prevention of intimal hyperplasia in a canine vein graft model

External stents have been used to reduce intimal hyperplasia of vein grafts. The aim of the present study was to define the size of an external stent appropriate for a particular graft by comparing vein grafts with different sizes of external stents. A series of paired trials was performed to compare femoral vein grafts with different sizes of external stents, where 30 modeled canines were equally divided into three groups: 6-mm external stent vs non-stent control, 4-mm vs 6-mm external stent, and 4-mm vs 8-mm external stent. At day 3 after operation, color Doppler flow imaging (CDFI) was done to observe blood flow in the lumen. Four weeks later, CDFI was re-checked and the veins were harvested, stained and measured. All grafts were patent without formation of thrombosis. External stents significantly reduced intimal thickness of the vein grafts with a 6-mm external stent compared with the vein grafts without external stents (P < 0.05). The vein grafts with the 4-mm external stent had similar intimal, medial and adventitial thicknesses compared with those with the 6-mm external stent and the 8-mm external stent. External stents can reduce intimal hyperplasia of vein grafts. Stents of different diameters exert the similar effect on prevention of intimal hyperplasia.

Pitavastatin Inhibits Intimal Hyperplasia in Rabbit Vein Graft

The autologous saphenous vein graft is currently the most suitable conduit for arterial bypass of the lower limbs. Various approaches have been attempted to control vein graft intimal hyperplasia, and several recent reports have suggested that statin use may be linked to improved patency of vein grafts. In this study, the efficacy of pitavastatin was evaluated on intimal hyperplasia and midkine expression of experimental normocholesterolemic rabbit autologous vein graft. Rabbits were fed regular rabbit chow, and in half of them, pitavastatin (1 mg/kg/d) was administered. A week after starting the treatment, jugular vein was implanted into the carotid artery. At 2 and 4 wk after the operation, vein grafts were harvested, and intimal hyperplasia of vein grafts were assessed. Cell proliferation in neointima was determined by proliferative cell nuclear antigen and Ki-67 stain 2 wk after implantation. In addition, the effect of pitavastatin on midkine, a heparin-binding growth factor, expressed in vein grafts was analyzed by Western blotting. The intimal hyperplasia in the pitavastatin group was significantly suppressed compared with the control group. Both proliferative cell nuclear antigen and Ki-67 labeling index were significantly lower in the pitavastatin group, and pitavastatin significantly reduced midkine expression of vein graft. These results demonstrate the efficacy of pitavastatin in reducing the degree of intimal hyperplasia of rabbit autologous vein grafts under normocholesterolemic condition. The mechanism of inhibition of intimal hyperplasia might be associated with midkine suppression.

Suppression of postoperative intimal hyperplasia of vein grafts with edaravone in rat models - a scanning electron microscope study.

Postoperative intimal hyperplasia, the most common cause of vein graft occlusion, is initiated by endothelial injury. In the present study, the mechanism by which the free radical scavenger edaravone (Radicut, Mitsubishi Tanabe Pharma Co, Japan) protects against endothelial injury in postoperative intimal hyperplasia was investigated. In 18 male Lewis rats, a right epigastric vein graft was interposed into the common femoral artery. Nine rats received a pre-operative intraperitoneal administration of edaravone (3.0 mg/kg, edaravone group) and the other nine rats received an equal volume of saline (saline group). After 1 h, five vein grafts from each group were treated with Verhoeff-van Gieson elastica stain and subjected to a histological examination. The other four vein grafts from each group were examined with an S-800 Hitachi scanning electron microscope (SEM) (Hitachi High-Technologies Co, Japan) at ×1000 magnification, as were three unoperated right epigastric veins (unoperated vein group). The endothelial areas of the vein grafts were measured using computerized planimetry of the SEM images (ImageJ version 1.37, National Institutes of Health, USA). The mean endothelial areas (%) were compared between the two groups. Verhoeff-van Gieson elastica stain revealed no significant differences between the two groups. SEM showed that endothelial cells in the unoperated epigastric vein had a cobblestone-like appearance. In the saline group, the endothelial cells were comb-shaped and had adherent monocytes. In the edaravone group, however, the cobblestone-like appearance of endothelial cells was well preserved, with little monocyte adhesion. Moreover, the mean (± standard error of the mean) endothelial area was significantly higher in vein grafts from the edaravone group than in those from the saline group (74±1.8% versus 56±4.3%, P<0.05), and was similar to those in the unoperated epigastric veins (72±1.9%). These findings show that endothelial injury is present soon after placement of the interposition graft. The authors believe that edaravone suppresses postoperative intimal hyperplasia by alleviating endothelial injury.

Celiprolol reduces the intimal thickening of autogenous vein grafts via an enhancement of nitric oxide function through an inhibition of superoxide production

Beta-adrenoceptor antagonist celiprolol has been widely used as an effective antihypertensive agent. Some studies reported that celiprolol enhances nitric oxide production. The purpose of the present study is to examine the effects of celiprolol on vein graft intimal hyperplasia and endothelium-dependent nitric oxide (NO)-mediated relaxation. Japanese white rabbits were randomized to a control group that was fed regular rabbit chow or to a celiprolol group that was fed regular rabbit chow supplemented with 100 mg/body celiprolol sodium. The reversed jugular vein was implanted into the carotid artery. At 2 and 4 weeks after the operation, vein grafts in both groups were harvested, and intimal hyperplasia of the vein grafts was assessed. At 4 weeks after the operation, harvested vein grafts from both the groups were examined on the endothelium-dependent relaxation by application of Ach and were examined to detect for endothelial NO synthase (eNOS) expression and superoxide anion production. Celiprolol inhibited intimal hyperplasia of carotid interposition-reversed jugular vein grafts 4 weeks after implantation (Intima/media index of celiprolol group, 0.48 +/- 0.01 vs control group, 1.07 +/- 0.08, P < .05) and suppressed cell proliferation in the neointima 2 weeks after implantation. In addition, celiprolol significantly enhanced endothelium-dependent NO-mediated relaxation in the vein graft with no change in eNOS expression and a reduction in superoxide production. These novel findings clearly demonstrate that beta-adrenoceptor antagonist celiprolol can suppress intimal hyperplasia of the vein graft, which may be due to the enhancement of nitric oxide function through an inhibition of superoxide production. These results strongly support the clinical usefulness of celiprolol administration for preventing intimal hyperplasia of the vein graft after bypass grafting.

Local shRNA modulation of phosphatidylinositol 3-kinase signaling pathway reduces intimal hyperplasia in vein grafts: experiment with rats

To investigate whether knockdown Pik3cb p110beta subunit by shRNA in autologous vein grafts can reduce intimal hyperplasia. 180 adult SD rats underwent carotid artery bypass graft surgery by using the autologous branch of jugular vein, and they were randomly divided into 6 equal groups: Group A (with the jugular vein grafts treated with 25% Pluronic F-127 only), Group B (with the graft treated with the plasmid encoding shRNA targeting Pik3cb p110beta subunit, pU6-Pik3cb-shRNA-1), Group C (with the graft treated with the plasmid encoding shRNA targeting Pik3cb p110beta subunit, pU6-Pik3cb-shRNA-2), Group D (with the graft treated with the half pU6-Pik3cb-shRNA-1 and pU6-Pik3cb-shRNA-2), and Group E (with the graft treated with the pGenesil-1 scramble shRNA), and Group F (with the jugular vein grafts treated with wortmannin). Specimens of jugular vein graft were harvested 1, 3, 7, 14, and 28 days after surgery to assess the neointimal hyperplasia. Another 18 rats were randomly divided into 6 equal groups as mentioned above to be used in a parallel experiment: 72 h after surgery specimens of jugular vein graft were harvested to undergo fluorescence quantitative real-time PCR and Western blotting to detect the mRNA expression of P13K p110beta subunit and the protein expression of phosphorylated Akt - phospho-Akt (Thr 308) and phospho-Akt (Ser473)-, and mTOR (Ser 2448). And another 9 rats received jugular vein grafts treated with the pGenesil-1 scramble shRNA, and on the postoperative days 1, 2, and 3 respectively 3 rats were killed to undergo fluorescence staining to detect the transfection efficacy. The transfection rate of the plasmid pGenesil-1 was 60% in the vascular smooth muscle cells and 90% in the endothelial cells. The thickness of tunica intima 28 days after the surgery of the pU6-Pik3cb-shRNA-1, pU6-Pik3cb-shRNA-2, 1/2 (shRNA1 + shRNA2), and wortmannin groups were (34.6 +/- 2.7) microm, (39.4 +/- 2.5) microm, (36.7 +/- 2.9) microm, and (40.6 +/- 3.1) microm respectively, all significantly lower than that of the control group (61.8 +/- 4.3 microm, P < 0.05). The expression levels of phospho-Akt (Thr 308), phospho-Akt (Ser 473), and mTOR of the shRNA intervention and wortmannin groups were all down-regulated. Knockdown of Pik3cb in interposition carotid artery branch of jugular vein grafts reduces intimal hyperplasia with the possible mechanism of downregulation of phosphatidylinositol 3-kinase signaling through Akt, with resultant decreases in VASC growth and survival. Modulation of the phosphatidylinositol 3-kinase pathway through knockdown Pik3cb may represent a novel therapy to prevent vein graft intimal hyperplasia after bypass grafting.

Estrogen-TNF interactions and vascular inflammation

cardiovascular disease (CVD), especially coronary heart disease (CHD), is by far the leading cause of death in women ([29][1], [40][2]). As the prevalence of these diseases increases after menopause, much effort has been devoted to determining whether endogenous estrogen confers a protective effect

Controlled release of small interfering RNA targeting midkine attenuates intimal hyperplasia in vein grafts

Intimal hyperplasia is a major obstacle to patency after vein grafting. Despite of a diverse array of trials to prevent it, a satisfactory therapeutic strategy for clinical use has not been established. However, sufficient inhibition of early stages of intimal hyperplasia may prevent this long-term progressive disease. Midkine (MK) is a heparin-binding growth factor that was originally discovered as the product of a retinoic acid-responsive gene. We previously demonstrated that MK-deficient mice exhibit a striking reduction of neointima formation in a restenosis model, which is reversed on systemic MK administration. In this study, we evaluated a strategy of using small interfering RNA (siRNA) targeting MK as a therapy for vein graft failure. We first made a highly effective siRNA to rabbit MK. Jugular vein-to-carotid artery interposition vein grafts, which are applied to a low flow condition, were made in Japanese white rabbits. Small interfering RNA mixed with atelocollagen was administrated to the external wall of grafted veins. Cy3-conjugated stabilized siRNA was used to confirm its stability and successful transfer into the vein graft wall. Neointimal hyperplasia was evaluated 4 weeks after the operation. The proliferation index and leukocyte infiltration were determined. MK expression was induced and reached the maximum level 7 days after operation. Fluorescence of Cy3-labeled siRNA could be detected in the graft wall even 7 days after operation. Knockdown of the gradually increasing expression was achieved by perivascular application of siRNA using atelocollagen. The intima-media ratio and the intima thickness at 28 days after grafting were both reduced >90% by this treatment compared with controls. This phenomenon was preceded by significant reductions of inflammatory cell recruitment to the vessel walls and subsequent cell proliferation in MK siRNA-treated grafts. These results suggest that midkine is a candidate molecular target for preventing vein graft failure. Furthermore, for clinical applications of siRNA, a single intraoperative atelocollagen-based nonviral delivery method could be a reliable approach to achieve maximal function of siRNA in vivo. This strategy may be a useful and practical form of gene therapy against human vein graft failure.

Perivenous Application of Fibrin Glue as External Support Enhanced Adventitial Adenovirus Transfection in Rabbit Model

Placement of an external support has been reported to prevent intimal hyperplasia of vein grafts. However, it's application limited by potential complications. Peri-adventitial gene delivery is a promising alternative therapy to reduce intimal hyperplasia, but it is limited by low and transient levels of gene transfection. To get more effective inhibition of intimal hyperplasia and to avoid the limitations associated with these two approaches, a study was undertaken to investigate whether mixing adenovirus with fibrin glue may increase the level and prolong the time period of gene expression. Right jugular vein to common carotid artery interposition grafting was performed in 36 male New Zealand white rabbits (2.5-3.0 kg) and the animals were divided into four groups: control group (n = 6); fibrin glue group (n = 6); Ad-GAL group (n = 12); fibrin glue/Ad-GAL group (n = 12). Commercially available fibrin glue and adenovirus expressing the gene for beta-galactosidase (Ad-GAL) was applied separately or in mixing around vein grafts. At 7th day and 14th day after implantation, the grafts were harvested to evaluate transfection rate. At 28th day the grafts were harvested for morphometric analysis. Compared with weak staining in 2.1 +/- 0.5% in Ad-GAL alone grafts, a high level of beta-Galactosidase staining was evident in 13.2 +/- 4.6% in fibrin glue/Ad-GAL grafts at 7th day (P < 0.001). At 14th day, almost no staining (0%) was detected in Ad-GAL alone grafts. However, there was still a relative high level staining (6.3 +/- 3.8%) in fibrin glue/Ad-GAL grafts (P < 0.001 versus Ad-GAL alone group). At 28th day, a statistically significantly decrease in neointimal area (0.68 +/- 0.06 mm(2)versus 1.00 +/- 0.08 mm(2), P < 0.05) was shown in fibrin glue grafts compared with unsupported vein grafts (control group). The same statistically significantly difference was also existed in fibrin glue/Ad-GAL group and unsupported group in neointimal area (0.66 +/- 0.07 mm(2), P < 0.05). A novel method of adventitial gene delivery using fibrin glue as external support is proposed. Fibrin glue may be an ideal candidate for controlled release delivery that would facilitate adventitial gene transfer.

Cellular, molecular and immunological mechanisms in the pathophysiology of vein graft intimal hyperplasia

Coronary artery disease, leading to myocardial infarction and ischaemia, affects millions of persons and is one of the leading causes of morbidity and mortality worldwide. Invasive techniques such as coronary artery bypass grafting are used to alleviate the sequelae of arterial occlusion. Unfortunately, restenosis or occlusion of the grafted conduit occurs over a time frame of months to years with a gradual reduction in patency, especially in vein grafts. The events leading to intimal hyperplasia (IH) formation involve numerous cellular and molecular components. Various cellular elements of the vessel wall are involved as are leucocyte-endothelial interactions that trigger the coagulation cascade leading to localized thrombus formation. Subsequent phenotypic modification of the medial smooth muscle cells and their intimal migration is the basis of the lesion formation that is thought to be propagated by an immune-mediated reaction. Despite intense scrutiny, the pathophysiology of IH remains an enigma. Although several growth factors, cytokines and numerous other biomolecules have been implicated and their relationship to prohyperplasia pathways such as the phosphatidyl-inositol 3-kinase (PI3K)-Akt pathway has been established, many pieces of the puzzle are still missing. An in-depth understanding of early vein graft adaptation and progression is necessary to improve the long-term prognosis and develop more effective therapeutic measures. In this review, we have critically evaluated and summarized the literature to elucidate and interlink the numerous established and emerging factors that play a key role in the development of IH leading to vein graft restenosis.

Perivenous application of fibrin glue prevents the early injury of jugular vein graft to arterial circulation in rabbits

Placement of an external support has been reported to prevent intimal hyperplasia of vein grafts. However, it is limited by potential complications. In the present study, we investigated the effect of fibrin glue on preventing vein graft failure as perivenous application. Twenty-four rabbits were divided into non-supported group (n = 12) and fibrin glue group (n = 12). All animals underwent unilateral jugular vein into common carotid artery interposition grafting and then fibrin glue was applied as perivenous support. Samples of tissues were harvested after 4 weeks. The vein grafts with fibrin glue demonstrated a statistically significant decrease in proliferating cell nuclear antigen in the medial/intimal region [13.38% (11.26% - 15.11%)] compared with non-supported vein grafts [31.22% (27.15% - 35.98%)] (P < 0.001). Light microscopy showed remarkable attenuation of endothelial cell loss and numerous microvessels in neoadventitia in the fibrin glue group compared with the non-supported group. The smooth muscle cells migrated into adventitia significantly in fibrin glue group, whereas the smooth muscle cells migrated into intima in non-supported group. Conclusion Perivenous support of vein graft with fibrin glue in vivo can attenuate the severe injury encountered in the non-supported vein grafts exposed to artery.

Tu-P10:471 NFKB-induced gene expression in vein graft intimal hyperplasia

Tu-P10:471 NFKB-induced gene expression in vein graft intimal hyperplasia

Influence of Losartan, an angiotensin receptor antagonist, on neointimal proliferation in cultured human saphenous vein.

An organ culture of human saphenous vein was used as a model of vein graft intimal hyperplasia and the potential of Losartan, an angiotensin II receptor antagonist, to inhibit neointimal proliferation was investigated. Median (range) neointimal thickness was reduced from 17 (16-19) to 11 (8-18) microns in veins cultured with Losartan (median difference 5 (95 per cent confidence interval 2-8) microns). A similar decrease in the median neointimal proliferation index was seen from 21 (range 14-47) to 15 (range 5-31) per cent (median difference 8 per cent (95 per cent confidence interval 5-11 per cent)). These results demonstrate that angiotensin II receptor antagonists may be of therapeutic value for the modulation of vein graft intimal hyperplasia.

Anti‐proliferative and anti‐inflammatory effects of topical MAPK inhibition in arterialized vein grafts

Vein graft failure following bypass surgery is a frequent and important clinical problem. The vascular injury caused by arterialization is responsible for vein graft intimal hyperplasia, a lesion generated by medial smooth muscle cell proliferation and migration into the intima, increased extracellular matrix deposition, and formation of a thick neointima. Development of the neointima into a typical atherosclerotic lesion and consequent stenosis ultimately result in vein graft failure. Endothelial damage, inflammation, and intracellular signaling through mitogen-activated protein kinases (MAPKs) have been implicated in the early stages of this process. We therefore investigated the effects of topical inhibition of ERK-1/2 MAPK activation on vascular cell proliferation and apoptosis, and on the inflammatory response in a canine model of vein graft arterialization. For this purpose, vein grafts were incubated with the MEK-1/2 inhibitor, UO126, ex vivo for 30 min before grafting. This treatment effectively abolished arterialization-induced ERK-1/2 activation, decreased medial cell proliferation, and increased apoptosis. UO126 treatment also inhibited the vein graft infiltration by myeloperoxidase-positive inflammatory cells that follows vein graft arterialization. Thus, topical ex vivo administration of MAPK inhibitors can provide a pharmacological tool to prevent or reduce the vascular cell responses that lead to vein graft intimal hyperplasia and graft failure.

The clopidogrel after surgery for coronary artery disease (CASCADE) randomized controlled trial: clopidogrel and aspirin versus aspirin alone after coronary bypass surgery [NCT00228423

BackgroundSaphenous vein graft disease remains a major limitation of coronary artery bypass graft surgery. The process of saphenous vein intimal hyperplasia begins just days after surgical revascularization, setting the stage for graft atherosclerotic disease and its sequalae. Clopidogrel improves outcomes in patients with atherosclerotic disease, and is effective at reducing intimal hyperplasia in animal models of thrombosis. Therefore, the goal of this study will be to evaluate the efficacy of clopidogrel and aspirin therapy versus aspirin alone in the prevention of saphenous vein graft intimal hyperplasia following coronary artery bypass surgery.MethodsPatients undergoing multi-vessel coronary artery bypass grafting and in whom at least two saphenous vein grafts will be used are eligible for the study. Patients will be randomized to receive daily clopidogrel 75 mg or placebo, in addition to daily aspirin 162 mg, for a one year duration starting on the day of surgery (as soon as postoperative bleeding has been excluded). At the end of one year, all patients will undergo coronary angiography and intravascular ultrasound assessment of one saphenous vein graft as selected by randomization. The trial will be powered to test the hypothesis that clopidogrel and aspirin will reduce vein graft intimal hyperplasia by 20% compared to aspirin alone at one year following bypass surgery.DiscussionThis trial is the first prospective human study that will address the question of whether clopidogrel therapy improves outcomes and reduces saphenous vein graft intimal hyperplasia following cardiac surgery. Should the combination of clopidogrel and aspirin reduce the process of vein graft intimal hyperplasia, the results of this study will help redefine modern antiplatelet management of coronary artery bypass patients.

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

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. 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. 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. 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. 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.

Suppression of postoperative intimal hyperplasia of vein graft with edaravone in a rat model

Postoperative intimal hyperplasia is still the major cause of vein graft occlusion. No medicine, however, can suppress the development of postoperative intimal hyperplasia. Since June 2001, edaravone has been commercially available as the free radical scavenger for acute cerebral infarction. In addition, it is well known that edaravone in lower dosage also suppresses injury to endothelial cells of vessels in vitro. In this study we evaluated the effect of edaravone on the development of postoperative intimal hyperplasia in a rat model. In ten male rats (498 ± 53 g) we interposed the right epigastric vein graft into the common femoral artery. The ten rats were divided into two groups: edaravone group (n = 5) in which there was the preoperaiive administration of edaravone (3.0 mg/kg) into peritoneal cavity, and the control (n = 5) in which the same dose of saline was used. After 4 weeks three sections were taken from the vein grafts and stained with Verhoeff's and van Gieson's stains. The intimal areas of the vein graft were measured using computerized planimetry. The averages of the intimal area and serum monocyte chemoattractant protein 1 (MCP-1) level were compared between the two groups. The mean ischemic time was 68 ± 6 min. The average of the intimal area in the edaravone group was significantly lower than the control group (0.05 ± 0.02 mm2 vs. 0.43 ± 0.05 mm2, p < 0.001). The average of serum MCP-1 in the edaravone group was also significantly lower than that of the control group (116 ± 11 pg/mL. vs. 169 ± 10 pg/mL, p < 0.01). Our results suggested that edaravone could suppress postoperative intimal hyperplasia of the vein graft in a rat model.

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

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. 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. 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. 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.