Nanoparticles target intimal macrophages in atherosclerotic lesions.

Oxidized phosphatidylcholines (oxPCs) enriched on the oxidized LDL (oxLDL) surface are responsible ligands for binding oxLDL to the CD36 receptor of intimal macrophages in atherosclerotic lesions. We synthesized liposome-like nanoparticles (NPs) using soy phosphatidylcholine and incorporated 1-palmitoyl-2-(4-keto-dodec-3-enedioyl) phosphatidylcholine, a type of oxPCs, on their surface to make ligand-NP (L-NPs). The objectives of this study were to measure and compare their binding affinity to and uptake by primary mouse and THP-1 derived macrophages, and to determine their target specificity to intimal macrophages in aortic lesions in LDL receptor null (LDLr-/-) mice. All in vitro data demonstrate that L-NPs had a high binding affinity to macrophage CD36 receptor. L-NPs had 1.4-fold higher accumulation in aortic lesion areas than NPs. L-NPs co-localized with intimal macrophages and CD36 receptors in the aortic lesions. This target delivery approach may portend a breakthrough in molecular imaging and targeted treatment of atherosclerosis.

An appropriately sized soft polyester external stent prevents enlargement and neointimal hyperplasia of a saphenous vein graft in a canine model.

Although the efficacy of external stents for vein grafts in coronary artery bypass grafting has been recognized, the ideal diameter and material of the stent remain controversial. We created a new external stent made of soft polyester mesh and performed an animal experiment using canines. Bilateral saphenous vein grafts were interposed in the bilateral common carotid artery of 10 beagles. The grafts in the left carotid artery were designated as the control group, and those in the right rolled by a soft polyester mesh external stent were designated as mesh group. Two of the 10 animals were sacrificed due to severe wound infection. The other eight were observed by echography for 6 months, and then grafts were extracted and thickness of the neointima of the grafts was measured. The control group showed 146% ± 26% postoperative enlargement of the internal diameter of the vein grafts after 6 months, whereas the mesh group showed only 115% ± 15% after the same duration (P = 0.0003). The median thickness of the neointima in the mesh group (170 µm [range: 150-190]) was significantly thinner than that in the control group (260 µm [range: 220-310], P < 0.0001). Some degree of correlation between the thickness of neointima and proportion of enlargement was noted (r = 0.518, P = 0.0024). A soft polyester mesh external stent for vein grafts successfully suppressed the enlargement of the vein grafts and thickness of the neointima after 6 months.

Coating of intravascular balloon with paclitaxel prevents constrictive remodeling of the dilated porcine femoral artery due to inhibition of intimal and media fibrosis.

Here we investigated how a coating of intravascular balloon with paclitaxel (drug-coated balloon; DCB, Freeway™) impacted porcine peripheral artery vascular function and remodeling. Domestic swine (n = 54) underwent percutaneous overstretch balloon dilation of femoral and iliac arteries, controlled by angiography and optical coherence tomography (OCT). Paclitaxel tissue uptake was measured at 1 h and 1, 3, and 9 days post-dilation. At these time-points and at 32 ± 2 days, vascular function of the dilated arteries was assessed using the organ chamber model. Neointimal growth and remodeling indices were determined using OCT and histology at 32 ± 2 days. Intima and media fibrosis were quantified by picrosirius red staining. Post-inflation femoral artery tissue drug levels were 460 ± 214, 136 ± 123, 14 ± 6, and 0.1 ± 0.1 ng/mg at 1 h and 1, 3, and 9 days, respectively. Compared to plain balloon, Freeway™ resulted in a significantly smaller neointimal area (P < 0.05), less tunica intima (8.0 ± 5.4 vs 14.2 ± 4.7 %) and media fibrosis (15.6 ± 7.7 vs 24.5 ± 5.4 %), and less femoral artery constrictive remodeling (remodeling index: 1.08 ± 0.08 vs 0.94 ± 0.08). The DCB was associated with significantly increased vasoconstrictor tone and endothelium-dependent vasodilation impairment shortly after post-overstretch injury. Overall, DCB dilation of peripheral arteries resulted in high drug uptake into arterial tissue. Compared with the plain balloon, the DCB was associated with decreased vessel wall fibrosis after balloon overstretch injury, and reduced degrees of constrictive remodeling and neointimal hyperplasia.

Effectiveness of Biodegradable Magnesium Alloy Stents in Coronary Artery and Femoral Artery.

OBJECTIVES: To access the biocompatibility, effectiveness, and safety of biodegradable magnesium (Mg) alloy stent (BMAS) in the coronary artery and femoral artery. BACKGROUND: Atherosclerosis is a lesion of cardiovascular system, including the diseases in heart and blood vessels. METHODS: The aluminum (Al) and zinc (Zn)-based BMAS was designed by cold drawing methods. Forty healthy immunized mongrel dogs were randomly divided into 8 groups. Five dogs who have not been treated with stent were included in control group. The other dogs were implanted with an absorbable magnesium (Mg) alloy in the coronary and/or femoral artery, and their artery angiography were observed at 7 time points (1, 3, 5, 7, 14, 21, and 28 days; n = 5) follow-up. Dogs from each cohort were sacrificed following angiography for pathology assessment. The histological response including inflammatory response, thrombosis, and intimal hyperplasia were analyzed by hematoxylin-eosin staining. Lumen area (La), intimal hyperplasia area (IHa), and the ratio of IHa were calculated by image analysis software. RESULTS: The thin-walled BMAS were designed and produced by cold-drawing technology. Fifty-one devices were implanted into coronary artery of 35 dogs successfully. During the follow-up days, the angiography of coronary artery and femoral artery had confirmed that the lumen was clear and there were no elastic recoil and thrombosis. The stents were completely disappeared at 7 days after implantation. Moderate intimal hyperplasia was found at 14 days after implantation. CONCLUSION: The BMAS stent proved to be of good biocompatibility, safety, and effectiveness. (J Interven Cardiol 2015;XXXX:XX-XX).

Muraglitazar-eluting bioabsorbable vascular stent inhibits neointimal hyperplasia in porcine iliac arteries.

PURPOSE: To evaluate the biocompatibility of a new muraglitazar-eluting polylactide copolymer stent and investigate its ability to prevent the formation of intimal hyperplasia. MATERIALS AND METHODS: Ten self-expandable muraglitazar-eluting poly-96 L/4D-lactic acid (PLA96) stents and 10 self-expandable control PLA96 stents were implanted into porcine common iliac arteries. After 28 days follow-up, all stent-implanted iliac arteries were harvested and prepared for quantitative histomorphometric analysis. RESULTS: Angiographic analysis revealed that one control PLA96 stent had occluded and one had migrated. Histomorphometric analysis demonstrated that, with the control PLA96 stent, the luminal diameter and area were decreased versus the muraglitazar-eluting PLA96 stents (means ± standard error of the mean, 3.58 mm ± 0.34 vs 4.16 mm ± 0.14 and 9.83 mm(2) ± 2.41 vs 13.75 mm(2) ± 0.93, respectively). The control PLA96 stent induced more intimal hyperplasia than the bioactive muraglitazar-eluting PLA96 stent (557 µm ± 122 vs 361 µm ± 32). Vascular injury scores demonstrated only mild vascular trauma for both stents (muraglitazar-eluting, 0.68 ± 0.07; control, 0.75 ± 0.08). Inflammation scores also showed mild inflammation for both stents (muraglitazar-eluting, 1.05 ± 0.17; control, 1.23 ± 0.19). CONCLUSIONS: This new muraglitazar-eluting PLA96 stent was shown to be biocompatible with a tendency for better patency and less intimal hyperplasia compared with the control PLA96 stents.

Effects of micro-amounts of Porphyromonas gingivalis lipopolysaccharide on rabbit inflammatory immune response and development of atherosclerosis.

BACKGROUND AND OBJECTIVE: Porphyromonas gingivalis (Pg) lipopolysaccharide is associated with the immune response and atherosclerosis. This study aimed to evaluate the effects of micro-amounts of Pg-lipopolysaccharide on rabbit inflammatory immune response and the development of atherosclerosis. MATERIAL AND METHODS: Twenty-four New Zealand white rabbits were randomly divided into four groups (n = 6). Group A was fed a regular diet and normal saline. Group B was supplied with a high-fat diet and normal saline. Group C was treated with a normal diet and Pg-lipopolysaccharide. Group D was given a high-fat diet and Pg-lipopolysaccharide. After 14 wk, the rabbits were killed to determine the changes in pathological indices. RESULTS: The serum lipid levels of groups B and D were significantly higher than that of group A (p < 0.01), and that of group C was higher (p < 0.05). Serum interleukin-6, monocyte chemoattractant protein-1 and tumor necrosis factor-α levels were significantly elevated by individual high-fat diets or Pg-lipopolysaccharide stimulation (p < 0.05). Groups A and C did not undergo evident aortic pathological damages, while foam cells appeared in the other two groups. Real-time polymerase chain reaction detection showed that toll-like receptor-2, interleukin-6, matrix metalloproteinase-9 and monocyte chemoattractant protein-1 were highly expressed in groups B and D (p < 0.05), and toll-like receptor-4, C-reactive protein and tumor necrosis factor-α levels were higher than those of group A (p < 0.05). Western blotting showed that transcription factor NF-κB p65 was expressed more highly in the three experimental groups than in group A (t = 9.26, p < 0.01). CONCLUSION: Micro-amounts of Pg-lipopolysaccharide induced the high expressions of inflammatory factors and mediated the inflammatory response. Pg-lipopolysaccharide elevated the blood lipid level less significantly than the high-fat diet did, but it may promote atherosclerosis.

Analysis of Microvascular Free Flap Failure Focusing on the Microscopic Findings of the Anastomosed Vessels.

Microvascular flap reconstruction is known as successful technique, although vascular thrombosis can cause free flap failure. To analyze the histologic characteristics and causes of free flap failure, this clinical study examined failed free flaps, including the microanastomosed sites. This study included a total of 5 failed flaps, including 3 radial forearm free flaps, 1 latissimus dorsi free flap, and 1 fibular free flap, all performed with microvascular reconstruction surgery from 2009 to 2011 at Seoul National University Dental Hospital. At the resection surgeries of the failed nonviable flaps, histologic specimens including the microanastomosed vessels were acquired. For light microscope observation, the slides were stained with hematoxylin and eosin (HE), and also with Masson trichrome. Selected portions of graft tissue were also observed under transmission electron microscope (TEM). It was found that the cause of flap failure was the occlusion of vessels because of thrombi formation. During the microanastomosis, damage to the vessel endothelium occurred, followed by intimal hyperplasia and medial necrosis at the anastomosed site. In the TEM findings, some smooth muscle cells beneath endothelium were atrophied and degenerated. The formation of thrombi and the degeneration of the smooth muscle cells were coincident with vascular dysfunction of graft vessel. The damaged endothelium and the exposed connective tissue elements might initiate the extrinsic pathway of thrombosis at the microanastomotic site. Therefore, it is suggested that accurate surgical planning, adequate postoperative monitoring, and skillful technique for minimizing vascular injury are required for successful microvascular transfer.

Inhibition of neo-intimal hyperplasia in porcine coronary arteries utilizing a novel paclitaxel-coated scoring balloon catheter.

OBJECTIVE: Scoring balloons are particularly useful in the acute treatment of fibro-calcific, bifurcation and in-stent restenosis lesions but have not been shown to affect the restenosis rate. Conventional balloons coated with paclitaxel have recently been shown to reduce restenosis rates in certain lesion subsets, but are associated with suboptimal acute results. A novel paclitaxel-coated scoring balloon was developed to overcome these limitations. DESIGN: AngioSculpt(®) scoring balloons (SB) were coated with paclitaxel admixed with a specific excipient. SETTING AND INTERVENTIONS: Four in vitro and in vivo studies were performed: (a) loss of the drug during passage to the lesion, (b) transfer of the drug to the vessel wall; (c) inhibition of neo-intimal proliferation in porcine coronary arteries as compared to uncoated SB and the Paccocath™, and (d) evaluation of the dose-response to 1.5-12 µg of paclitaxel/mm(2) . MAIN OUTCOME MEASURES AND RESULTS: Drug loss during delivery to the lesion was 17% ± 8%, and transfer to the vessel wall was 9% ± 4% of dose on unused balloons. The paclitaxel-coated SB resulted in a lower late lumen loss of 0.27 ± 0.24 mm compared to 1.4 ± 0.7 mm with the uncoated SB (P = 0.001). Histomorphometry revealed larger luminal areas of 6.8 ± 1.6 mm(2) (paclitaxel-coated SB) and 5.8 ± 1.7 mm(2) (Paccocath) as compared to the uncoated SB (2.3 ± 1.5 mm(2) ; P = 0.001). No coating related adverse effects were observed on follow-up angiography or histologic examination at the treatment site or downstream myocardium. CONCLUSION: A novel paclitaxel-coated SB leads to a significant inhibition of neointimal proliferation in the porcine coronary model.

Empty vein ablation (EVA) technique: an in-vivo animal model to assess the effects of sclerosing agent concentration and wall contact time on intima and media tunicae structure.

BACKGROUND: Sclerotherapy is a cornerstone of the treatment of chronic venous disease, despite some technical aspects (e.g., sclerosant liquid agent concentration [SLAC] and contact time between sclerosant agent and vein wall [ctSA/VW]) to maximize outcomes remain an unsolved problem and a source of debate. An innovative three-balloon catheter has been developed to allow sclerotherapy in empty vein conditions (Empty Vein Ablation technique, EVA), revolutionizing the definition of SLAC and ctSA/VW. Aim of this experimental study is to analyze EVA effects on intima and media vessel tunicae using different SLAC and ctSA/VW in an in-vivo animal model. METHODS: Two adult sheep were treated by EVA using jugular and common iliac vein axes (eight vein segments). Different SLAC (polidocanol 0.5% or 1%) and different ctSA/VW (3 or 5 minutes) were combined for testing residual circumferential intima percentage and media thickness after EVA. RESULTS: Intact circumferential residual intima after the treatment was 21.3±4.9%, 18.2±7.4%, 15.7±2.4% and 8.9±2.0% using 0.5% (3 min), 0.5% (5 min), 1% (3 min) and 1% (5 min), respectively (R2=0.945; control sample: 97.6%). Media thickness after the treatment was 121.6±35.3 µm, 110.9±7.8 µm, 96.1±30.4 µm and 79.1±34.1 µm using 0.5% (3 min), 0.5% (5 min), 1% (3 min) and 1% (5 min), respectively (R2=0.990; control sample 125.7 µm). No significant modifications were detected analyzing the adventitia in all samples. CONCLUSIONS: EVA proved to be effective in venous wall destruction even with a very low SLAC and ctSA/VW (0.5% in 3 minutes), in quite large caliber veins. Direct comparisons with foam/liquid sclerotherapy should be done to confirm therapeutic effectiveness of these results, despite EVA has provided a maximized and controlled SA/VW contact time and ratio.

[Biomaterials and technologies for vascular grafts: from bench to bedside]. / Biomateriali e graft technology per protesi vascolari: dal laboratorio alla clinica.

Peripheral artery disease and related revascularization procedures are increasing, due to the aging population and growing incidence of diabetes mellitus. Up to now, autologous saphenous vein is the conduit of choice for peripheral by-pass. Synthetic vascular graft in polyethylene terephthalate (Dacron®) and expanded polytetrafluoroethylene (ePTFE) are used if vein access cannot be obtained. These synthetic grafts are successfully used to replace large diameter vessels, but they fail in small diameters (<6 mm) such as for infragenicular by-pass. Reasons for failure are early thrombosis and late intimal hyperplasia. Novel small-diameter vascular grafts with an acceptable clinical outcome are therefore needed. Here, the main materials and technologies for the manufacturing of vascular grafts and the pathway from bench to bedside are discussed .

Porphyromonas gingivalis accelerates neointimal formation after arterial injury.

BACKGROUND: Inflammation plays a key role in neointimal hyperplasia after an arterial injury. Chronic infectious disorders, such as periodontitis, are associated with an increased risk of cardiovascular diseases. However, the effects of a periodontal infection on vascular remodeling have not been examined. We assess the hypothesis that periodontal infection could promote neointimal formation after an arterial injury. METHODS: Mice were implanted with subcutaneous chambers (n = 41). Two weeks after implantation, the femoral arteries were injured, and Porphyromonas gingivalis (n = 21) or phosphate-buffered saline (n = 20) was injected into the chamber. The murine femoral arteries were obtained for the histopathological analysis. The expression level of mRNA in the femoral arteries was analyzed using quantitative reverse transcriptase polymerase chain reaction (n = 19-20). RESULTS: The intima/media thickness ratio in the P. gingivalis infected group was found to be significantly increased in comparison to the non-infected group. The expression of matrix metalloproteinase-2 mRNA was significantly increased in the P. gingivalis infected group compared to the non-infected group. CONCLUSION: These findings demonstrate that P. gingivalis injection can promote neointimal formation after an arterial injury. Periodontitis may be a critical factor in the development of restenosis after arterial intervention.

Prevention of neointimal hyperplasia associated with modified stretch expanded polytetrafluoroethylene hemodialysis grafts (Gore) in an experimental preclinical study in swine.

OBJECTIVE: Stenosis is the main cause of hemodialysis vascular graft failure and it is primarily caused by neointimal hyperplasia (NH) development at the vein-graft anastomosis. Even though NH development factors are well known, their activation pathway still remains disputed and the real role of the mismatch compliance between the vein and the graft wall has not yet been resolved. The purpose of this experimental study in swine was to verify the possibility of preventing the development of NH at the vein-graft anastomosis using a modified commercially available longitudinal stretch expanded polytetrafluoroethylene (ePTFE) Gore (W. L. Gore & Associates, Flagstaff, Ariz) graft (either standard or heparin-bonded) with an added handmade ePTFE radial stretch cuff at one end to reduce the compliance between the graft and the vein wall. METHODS: Twelve ePTFE stretch grafts (6 modified and 6 unmodified) were surgically placed as arterovenous grafts (AVGs) between the carotid artery and the external jugular vein in 6 pigs. In each pig, one modified graft was placed on one side and one corresponding unmodified graft on the other side as a control. In 4 pigs, standard stretch ePTFE Gore grafts were used, and in 2 pigs, heparin-bonded stretch Gore grafts were used; 2 pigs were also treated with antiplatelet drugs. All the implanted grafts had a total length of 8 cm and a diameter of 6 mm. The modified graft was realized by cutting a short segment of the commercially available graft lengthwise which was then sewn crosswise (rotated 90°) with the same diameter as the original graft and was then added to it. A Doppler ultrasound scan was used for monitoring the graft patency immediately, weekly, and before death. At death (21-28 days after implantation), artery, vein, and graft specimens were collected "en bloc" for histopathology. RESULTS: The modified grafts in the antiplatelet-treated animals were able to completely prevent NH development on vein wall (100% in 2 subjects) which was also reduced in antiplatelet untreated animals (66.5%, 96.4%, and 100% in 3 subjects, respectively). The modified standard stretch grafts and similarly modified heparin-bonded stretch grafts obtained the same good results in NH prevention. CONCLUSION: Data provide evidence of the efficacy of modified stretch ePTFE grafts with an added radial stretch cuff for the prevention of NH in swine models and support the hypothesis of the pivotal role of mismatch compliance between the graft and the vein wall in NH development.

Paclitaxel coating of the luminal surface of hemodialysis grafts with effective suppression of neointimal hyperplasia.

OBJECTIVES: Paclitaxel coating of hemodialysis grafts is effective in suppressing neointimal hyperplasia in the graft and vascular anastomosis sites. However, paclitaxel can have unwanted effects on the surrounding tissues. To reduce such problems, we developed a method to coat the drug only on the luminal surface of the graft, with little loading on the outer surface. METHODS: A peristaltic pump and a double-solvent (water and acetone) system were used to achieve an inner coating of paclitaxel. At the ratio of 90% acetone, paclitaxel was homogeneously coated only on the luminal surface of the graft without changing the physical properties. To determine its effect, grafts were implanted between the common carotid artery and the external jugular vein in pigs using uncoated control grafts (n = 6) and low-dose (n = 6, 0.22 µg/mm(2)) and high-dose (n = 6, 0.69 µg/mm(2)) paclitaxel inner-coated grafts. Cross-sections of graft-venous anastomoses were analyzed histomorphometrically 6 weeks after placement to measure the patency rate, percentage of luminal stenosis, and neointimal area. RESULTS: No signs of infection or bacterial contamination were observed in the paclitaxel inner-coated groups. Only one of the six control grafts was patent, but all of the paclitaxel-coated grafts were patent, with little neointima. The mean ± standard error values of percentage luminal stenosis were 75.7% ± 12.7% (control), 17.5% ± 3.1% (low dose), and 19.7% ± 3.0% (high dose). The values for the neointimal area (in mm(2)) were 8.77 ± 1.66 (control), 3.53 ± 0.73 (lose dose), and 4.24 ± 0.99 (high dose). Compared with the control group, paclitaxel inner-coated vascular grafts significantly suppressed neointimal hyperplasia (low dose, P = .001; high dose, P = .002). Myofibroblast proliferation and migration into the graft interstices confirmed the firm attachment of the implanted graft to the surrounding tissue. CONCLUSIONS: Paclitaxel coating on the inner luminal surface of vascular grafts was effective in suppressing neointimal hyperplasia, with little inhibition of myofibroblast infiltration within the graft wall.

An arteriovenous fistula model of intimal hyperplasia for evaluation of a nitinol U-Clip anastomosis.

OBJECTIVES: The aim of this study was to create an ovine arteriovenous fistula (AVF) model which would closely replicate a human forearm fistula and use this to quantify the degree of intimal hyperplasia in those created with the U-Clip compared to a conventional sutured anastomosis. MATERIALS AND METHODS: Twenty AVFs were created in 10 Border Leicester-Merino sheep between the superficial femoral artery and vein of each hind limb. On one side the U-Clip and on the other a continuous polypropylene suture was used to perform the anastomosis. The animals were sacrificed at 2 (n = 3), 4 (n = 4), 6 (n = 3) weeks and histological slices were taken of each AVF in cross section to determine the intimal media area per unit length (IMA/L). RESULTS: Intimal hyperplasia (IH) was observed at all time points with one AVF found occluded with thrombus at the time of harvest. The IMA/L was significantly lower in the U-Clip groups by 24% at 2 weeks, 32% at 4 weeks and 23% at 6 weeks (Two-way ANOVA, p = 0.019, observed power = 0.825, time or side p ≥ 0.766, type p = 0.001; Paired t-test, p < 0.001 between matched anastomotic types). Time taken to perform the anastomosis was similar between the two anastomotic techniques (Polypropylene 14(8-18) vs. U-Clip 15.3(11-23) min; p = 0.47). CONCLUSION: This ovine AVF model results in IH similar to that seen in a human AVF. The IH that occurs with the U-Clip is less than that of continuous polypropylene suture.

Radiation therapy for dialysis access stenosis: unfulfilled promise or false expectations.

Hemodialysis vascular access dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population at a cost of well over $1 billion per annum. Venous stenosis (due to venous neointimal hyperplasia [VNH]) is the most common cause of polytetrafluroethylene PTFE) dialysis access graft and arteriovenous fistula (AVF) failure. Despite the magnitude of the clinical problem, however, there are currently no effective therapies for this condition. We and others have previously demonstrated that VNH in PTFE dialysis grafts and AVF is composed of smooth muscle cells/myofibroblasts, endothelial cells within neointimal microvessels, and peri-graft macrophages. Radiation therapy blocks the proliferation and activation of all these cell types. The current review will dissect out the available in vitro, experimental, and clinical data on the use of radiation therapy for vascular stenosis in general, and for dialysis access dysfunction in particular. It is important to try and identify whether there is still a role for radiation therapy in this specific clinical setting. We believe that this is a critically important question to answer in view of the huge unmet clinical need that is currently associated with hemodialysis vascular access dysfunction.

Thermal sensitivity of endothelial cells on synthetic vascular graft material.

PURPOSE: The goal is to identify thermal exposures capable of reducing or eliminating cell survival on expanded polytetrafluoroethylene (ePTFE), in an effort to develop a mild hyperthermia treatment of neointimal hyperplasia in ePTFE vascular grafts. MATERIALS AND METHODS: Viable and dead bovine aortic endothelial cells were quantified following different thermal exposure conditions: cells on collagen-coated ePTFE sheets or tissue culture polystyrene dishes were heated at 42° and 45°C to determine their thermal sensitivity on different surfaces, and cells cultured on collagen-coated ePTFE sheets were heated at 43-50°C for various durations, followed by incubation at 37°C for 0 and 20 h, respectively. Significant cell death was set to be 50%. Two types of cell death, apoptosis and necrosis, were distinguished by cell morphology and membrane integrity assessments. RESULTS: The attachment and survival of cells on ePTFE sheets were more sensitive to inhibition by mild heating than those on tissue culture dishes. Exposure to 45°C for 90 min and 50°C for 30 min caused significant necrotic cell death on ePTFE (65% and 75%, respectively). A 37°C/20-h incubation following 30-min exposures at 47° and 50°C increased total cell death (necrosis + apoptosis) from 20% to 50% and 75% to 100%, respectively. CONCLUSION: Cells grown on ePTFE were more susceptible to mild hyperthermia-induced death, compared to those on tissue culture dishes. Significant cell death on ePTFE mainly via apoptosis can be achieved by optimising temperature and duration of exposure.

[Histological character of intimal hyperplasia post jugular vein grafts and the protective effect of lovastatin].

OBJECTIVE: To investigate the characteristics of intimal hyperplasia and lovastatin's effects on canine jugular venous prosthesis bypass grafting. METHODS: In the study, 12 adult mistus dogs were randomly divided into 2 groups: lovastatin group and control group. All the dogs were performed with jugular venous prosthesis bypass grafting (ePTFE, 6 mm in diameter, and 5 cm in length). Four weeks later, all the 12 specimens were harvested. The patency and mural thrombus of grafts were evaluated. The characteristics of intimal hyperplasia were described and measured by HE staining and endothelial nitric oxide synthase (eNOs) immunohistochemical method. The differences between the two groups were compared. RESULTS: Four weeks later, 3 grafts with complete occlusion were found in the two groups separately. Apparent intimal hyperplasia was observed in all the grafts. The neointima of proximal and distal part in lovastatin group were thinner than in control group respectively (proximal P=0.045, distal P=0.040). The endothelial cells were found in the surface of neointima. Newly born vessels could be found in the neointima and the new vessels were more in lovastatin group than in control group (proximal P=0.041, distal P=0.031). CONCLUSION: At the end of 4 weeks, the intimal hyperplasia with neovascularization was obviously near the anastomosis. Lovastatin showed the ability to inhibit the intimal hyperplasia and promote the neovascularization.

Mechanisms of smooth muscle cell proliferation and endothelial regeneration after vascular injury and stenting: approach to therapy.

Bare metal stents (BMS) successfully prevented abrupt artery closure and reduced the restenosis rate compared with balloon angioplasty. This review summarizes laboratory and recent clinical investigations concerning neointimal formation and endothelial regeneration after vascular injury. BMS efficacy was severely hampered by proliferating vascular smooth muscle cells (VSMCs), and the resultant neointimal hyperplasia, which is the only mechanism responsible for restenosis after metal stent placement. The advent of drug-eluting stents (DES) in 2002 have since then revolutionized interventional cardiology. By using the stent struts as a platform coated with polymers to elute drugs targeting VSMC proliferation, a substantial attenuation of in-stent restenosis is feasible. As with any medical innovation this technology still has restrictive factors, and novel approaches are promoted to improve the safety and efficacy of DES. Indeed, the antiproliferative properties of DES impair and/or delay endothelialization, hence leading to late stent thrombosis. Improvements in percutaneous coronary intervention procedures include the use of the so-called "second-generation DES", together with new coating technologies, bioabsorbable stents, and non-drug-based stent coatings. Particular emphasis will be placed on the concept that endothelial regeneration might be pursued as well as reduction of VSMC proliferation to allow stable successful revascularization after DES deployment.

Rapamycin-loaded nanoparticles for inhibition of neointimal hyperplasia in experimental vein grafts.

BACKGROUND: Nanoparticles (NPs) possess several advantages as a carrier system for intracellular delivery of therapeutic agents. Rapamycin is an immunosuppressive agent which also exhibits marked antiproliferative properties. We investigated whether rapamycin-loaded NPs can reduce neointima formation of vein graft disease in a rat model. METHODS: Poly(lactic-co-glycolic acid) (PLGA) NPs-containing rapamycin was prepared using an oil/water solvent evaporation technique. The size and morphology of the NP were determined by dynamic light scattering methodology and electron microscopy. In vitro cytotoxicity of blank, rapamycin-loaded PLGA NPs was studied using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Excised rat jugular vein was treated ex vivo with blank NPs, or rapamycin-loaded NPs, and then interposed back into the carotid artery position using a cuff technique. Grafts were harvested for 21 days and subjected to morphometric analysis as well as immunohistochemical analysis and Western blotting. RESULTS: Rapamycin was efficiently loaded in PLGA NPs with an encapsulation efficiency of 87.6%. The average diameter of NPs was 180.3 nm. The NPs-containing rapamycin at 1 ng/mL significantly inhibited vascular smooth muscular cells proliferation. Measurement of rapamycin levels in vein grafts showed that the concentration of rapamycin in vein grafts at 3 weeks after grafting was 0.9 ± 0.1 µg/g. In grafted veins without treatment, intima-media thickness was 300.4 ± 181.5 µm at 21 days after grafting, whereas veins treated with rapamycin-loaded NPs showed a reduction of intimal-media thickness of 150.2 ± 62.5 µm (p = 0.001). Cell proliferation was measured by proliferating cell nuclear antigen immunohistochemistry staining. As expected, proliferating cell nuclear antigen index declined from 83.4% ± 7.4% to 66.2% ± 4.5% in vein grafts after 3 weeks (p = 0.002). Platelet endothelial cell adhesion molecule (PECAM-1/CD31) staining was used to measure luminal endothelial coverage in grafts and indicated a high level of endothelialization at 21 days after grafting, with no significant effect of blank or rapamycin-loaded NPs group. Western blot analysis showed that treatment with rapamycin-loaded PLGA NPs markedly attenuated phosphorylation and activation of S6 kinase 1 phosphorylation and inactivation of 4E (eIF4E)-binding protein 1, both in vascular smooth muscular cells and vein grafts at 7 and 21 days after grafting. CONCLUSIONS: We conclude that sustained-release rapamycin from rapamycin-loaded NPs inhibits vein graft thickening without affecting the endothelial cells in rat carotid vein-to-artery interposition grafts; thus, this may be a promising therapy for the treatment of vein graft disease.