Vascular delivery of c-myc antisense from cationically modified phosphorylcholine coated stents

c-Myc is involved in the formation of neointimal hyperplasia. We investigated in vitro, ex vivo and in vivo release of antisense c-myc from cationically modified phosphorylcholine-coated stents, as well as the effects on c-Myc expression and neointima formation in a porcine coronary stent model. In vitro experiments were performed to determine optimal loading of stents with antisense. Stents loaded with labelled antisense were deployed in porcine arteries ex vivo and in vivo. Antisense was detected in the vessel wall directly surrounding the stent of pig carotid and coronary artery up to 48 h after stent deployment. Nuclear uptake was observed in endothelial and vascular smooth muscle cells. Labelled antisense within peripheral tissues in vivo was <1.0% of that within stented arterial segments. Control and antisense loaded stents implanted into 10 pig coronary arteries and analysed at 28 days post-stenting showed that lumen area within the antisense stents was significantly increased (i.e. 30.5% greater, P<0.01), whilst both neointimal area and neointimal thickness were significantly reduced (17.5% and 19.5%, respectively, P<0.01) compared to control stents. Cationically modified phosphorylcholine coated stent-based delivery of c-myc antisense is feasible with minimal systemic delivery and is associated with a reduction of in-stent neointimal hyperplasia in pig coronary arteries.     

A Novel Simulation Strategy for Stent Insertion and Deployment in Curved Coronary Bifurcations: Comparison of Three Drug-Eluting Stents

The introduction of drug-eluting stents (DES) has reduced the occurrence of restenosis in coronary arteries. However, restenosis remains a problem in stented coronary bifurcations. This study investigates and compares three different second generation DESs when being implanted in the curved main branch of a coronary bifurcation with the aim of providing better insights into the related changes of the mechanical environment. The 3D bifurcation model is based on patient-specific angiographic data that accurately reproduce the in vivo curvatures of the vessel segments. The layered structure of the arterial wall and its anisotropic mechanical behavior are taken into account by applying a novel algorithm to define the fiber orientations. An innovative simulation strategy considering the insertion of a folded balloon catheter over a guide wire is proposed in order to position the stents within the curved vessel. Straightening occurs after implantation of all stents investigated. The resulting distributions of the wall stresses are strongly dependent on the stent design. Using a parametric modeling approach, two design modifications, which reduce the predicted maximum values of the wall stress, are proposed and analyzed.     

Effectiveness of drug-eluting stents versus bare-metal stents in large coronary arteries in patients with acute myocardial infarction

This study compared clinical outcomes of drug-eluting stents (DES) versus bare-metal stents (BMS) in large coronary arteries in patients with acute myocardial infarction (MI). A total of 985 patients who underwent single-vessel percutaneous coronary intervention (PCI) in large coronary arteries (≥ 3.5 mm) in lesions < 25 mm were divided into DES group (n = 841) and BMS group (n = 144). Clinical outcomes during 12 months were compared. In-hospital outcome was similar between the groups. At six months, death/MI rate was not different. However, DES group had significantly lower rates of target-lesion revascularization (TLR) (1.7% vs 5.6%, P = 0.021), target-vessel revascularization (TVR) (2.2% vs 5.6%, P = 0.032), and total major adverse cardiac events (MACE) (3.4% vs 11.9%, P = 0.025). At 12 months, the rates of TLR and TVR remained lower in the DES group (2.5% vs 5.9%, P = 0.032 and 5.9% vs 3.1%, P = 0.041), but the rates of death/MI and total MACE were not statistically different. The use of DES in large vessels in the setting of acute MI is associated with lower need for repeat revascularization compared to BMS without compromising the overall safety over the course of one-year follow-up.     

球囊过盈量与支架术后边缘效应的关系探讨

目的分析球囊过盈量与支架术后边缘效应的关系,为减少边缘效应、有效控制支架后再狭窄提供有益的参考。方法 24只雄性杂种犬随机分为两组,分别应用3mm×12mm及3mm×15mm两种规格的球囊于冠状动脉内置入3mm×12mm规格的不锈钢支架,利用冠状动脉造影及组织切片法分析不同球囊过盈量与支架术后边缘血管损伤及远期边缘效应的相关性。结果冠脉造影提示术后即刻两种过盈量的球囊对支架边缘部位血管内径的影响无显著差别,术后4周组织切片结果提示两组球囊过盈量对支架两端边缘部位血管壁的损伤程度及远期边缘效应的发生率明显不同,球囊过盈量与管壁损伤程度和远期边缘效应均呈显著正相关关系(r=0.668,P0.01)。结论球囊过盈量是导致支架术后边缘效应的原因之一。     

Medial collagen organization in human arteries of the heart and brain by polarized light microscopy.

The mechanical properties of collagen as a biopolymer ensures that collagen has a significant influence on the mechanical behavior of the host tissue. Structural organization is a key to that influence. We have assessed this relationship quantitatively in the tunica media of arteries from the heart and brain, using the polarizing light microscope and Universal stage. Arteries from 22 autopsies were isolated, cannulated and fixed with 10% buffered formalin, at a distending pressure spanning normal values in vivo. We prepared the tissue for light microscopy, with paraffin embedding, sectioning at 7 microns, and staining with picrosirius red to enhance the natural birefringence of medial collagen. Individual measurements, 30 to 50 per arterial section, referenced against the central axis of the vessel segment, revealed a coherent organization, with an average orientation which was within 1 to 2 degrees of being perfectly concentric for all artery segments. Analysis was done with Lambert projections and circular statistics. We calculated the circular standard deviation, which was 5.2 degrees for 27 brain arteries (S.D. 1.9 degrees) and 5.6 degrees (S.D. 2.1 degrees), for 5 coronary arteries sectioned at less than 15 degrees. Our interpretation is that medial collagen can be strained even though highly aligned, revealing a mechanical property which contrasts that of type I collagen.     

Long-term effect of stents eluting 6-mercaptopurine in porcine coronary arteries

Background

Drug-eluting stents (DES) have dramatically reduced restenosis rates compared to bare metal stents and are widely used in coronary artery angioplasty. The anti-proliferative nature of the drugs reduces smooth muscle cell (SMC) proliferation effectively, but unfortunately also negatively affects endothelialization of stent struts, necessitating prolonged dual anti-platelet therapy. Cell-type specific therapy may prevent this complication, giving rise to safer stents that do not require additional medication. 6-Mercaptopurine (6-MP) is a drug with demonstrated cell-type specific effects on vascular cells both in vitro and in vivo, inhibiting proliferation of SMCs while promoting survival of endothelial cells. In rabbits, we demonstrated that DES locally releasing 6-MP during 4 weeks reduced in-stent stenosis by inhibiting SMC proliferation and reducing inflammation, without negatively affecting endothelialization of the stent surface. The aim of the present study was to investigate whether 6-MP-eluting stents are similarly effective in preventing stenosis in porcine coronary arteries after 3 months, in order to assess the eligibility for human application.

Methods

6-MP-eluting and polymer-only control stents (both n?=?7) were implanted in porcine coronary arteries after local balloon injury to assess the effect of 6-MP on vascular lesion formation. Three months after implantation, stented coronary arteries were harvested and analyzed.

Results

Morphometric analyses revealed that stents were implanted reproducibly and with limited injury to the vessel wall. Unexpectedly, both in-stent stenosis (6-MP: 41.1?±?10.3 %; control: 29.6?±?5.9 %) and inflammation (6-MP: 2.14?±?0.51; control: 1.43?±?0.45) were similar between the groups after 3 months.

Conclusion

In conclusion, although 6-MP was previously found to potently inhibit SMC proliferation, reduce inflammation and promote endothelial cell survival, thereby effectively reducing in-stent restenosis in rabbits, stents containing 300 μg 6-MP did not reduce stenosis and inflammation in porcine coronary arteries.

     

Medial Collagen Organization in Human Arteries of the Heart and Brain by Polarized Light Microscopy

The mechanical properties of collagen as a biopolymer ensures that collagen has a significant influence on the mechanical behavior of the host tissue. Structural organization is a key to that influence. We have assessed this relationship quantitatively in the tunica media of arteries from the heart and brain, using the polarizing light microscope and Universal stage. Arteries from 22 autopsies were isolated, cannulated and fixed with 10% buffered formalin, at a distending pressure spanning normal values in vivo. We prepared the tissue for light microscopy, with paraffin embedding, sectioning at 7 μ, and staining with picrosirius red to enhance the natural birefringence of medial collagen. Individual measurements, 30 to 50 per arterial section, referenced against the central axis of the vessel segment, revealed a coherent organization, with an average orientation which was within 1 to 2° of being perfectly concentric for all artery segments. Analysis was done with Lambert projections and circular statistics. We calculated the circular standard deviation, which was 5.2° for 27 brain arteries (S.D. 1.9°) and 5.6° (S.D. 2.1°), for 5 coronary arteries sectioned at less than 15°. Our interpretation is that medial collagen can be strained even though highly aligned, revealing a mechanical property which contrasts that of type I collagen.     

Cellular breakdown within muscular arteries in hypercholesterolemic rats

Adult male rats were fed a high-fat cholesterol, thyroid-suppressive diet for three months, after which the structure of the muscular arteries (coronary and tarsal pedis) was examined by transmission electron microscopy. The plasma cholesterol concentration was elevated when the animals were killed and a distinct ultrastructural finding was the presence of necrotic cells in the media of both the coronary and the tarsal pedis arteries. Medial smooth muscle cells contained multivesicular membranous bodies, and membranous material accumulated in the intercellular space of the arterial media. It is proposed that the membrane changes and cellular death within muscular arteries may primarily be due to the increased membrane cholesterol concentration of smooth muscle cells during hypercholesterolemia. Dietary saturated fatty acids may have a contributing effect on smooth muscle cell injury in the hypercholesterolemic state.     

Recent developments in drug-eluting stents

Percutaneous coronary intervention (PCI) is an important treatment approach in the management of symptomatic coronary artery disease (CAD). A significant development in PCI in the mid 1970s was balloon angioplasty, followed by bare-metal stents a decade later, and now, the widespread use of drug-eluting stents (DES). While PCI has conferred remarkable benefit to millions of CAD patients, restenosis, and late stent thrombosis associated with DES remain problematic, and improvements are keenly sought. This article reviews recent developments in DES.     

Methodological Issues Related to Pathological Evaluation of Coronary Artery Stents

Abstract

Intravascular placement of metallic stents is a common treatment of stenosed coronary arteries; however, they are associated with risk of in-stent restenosis and late-stent thrombosis. Pathological evaluation of stented coronary arteries is needed to characterize stent-tissue interactions to improve the safety and efficacy of coronary stents. Thus, high-quality tissue sections are required with excellent preservation of the morphology of the stented artery, particularly at the stent-tissue interface. In this study, formalin-fixed and dehydrated stented coronary artery segments from cases of cardiac transplantation and routine autopsies were used. In a vacuum chamber, the specimens were immersed in infiltration solution (benzoylperoxide with hydroxyethyl methacrylate) from the JB-4 Plus Embedding Kit® (Polysciences, Inc.). The specimens were then transferred into the embedding medium (infiltration solution with polyethylene glycol) and allowed to polymerize under anaerobic conditions. Next, the specimens were cut into 5-mm-thick blocks with a rotary saw, sectioned with a JB-4 microtome, and stained with hematoxylin and eosin and Masson's trichrome. Morphology of all coronary artery segments, including the stent-tissue interface, was readily visible; however, to achieve adequate staining intensity, prolonged hematoxylin staining was required. Some stents were displaced from their original position during sectioning and staining. Attempts to use another plastic embedding medium (Technovit 9100 methyl methacrylate) have been unsuccessful so far. This was primarily related to failure of the block to adhere to the holder during sectioning. In conclusion, with the use of glycol methacrylate embedding technique the morphology of the stent-tissue interface of stented arteries can be readily observed by microscopy. Failure to maintain the stent in its original position is an important limitation, possibly related to the relative softness of the medium. Refining the methodology may lead to a more efficient protocol, enabling more specialized staining as well as the use of harder plastic media such as methyl methacrylate. (The J Histotechnol 32(4):151–154, 2009)     

新型生物全降解药物支架置入小型猪冠状动脉的安全性

背景：目前冠状动脉支架的主要研究方向是高生物相容性的全降解生物材料及药物控释体系。 目的：评价2种新型生物全降解药物支架置入小型猪冠状动脉后的安全性。 方法：普通生物全降解支架为在聚左旋乳酸本体中融入抗增殖药物紫杉醇,新型生物全降解支架为在聚左旋乳酸及紫杉醇的基础上融入一种新型纳米材料无定形磷酸钙。①将普通生物全降解支架和新型生物全降解支架各5枚在冠状动脉造影下分别随机置入小型猪的冠状动脉,每种支架5头。于置入前和置入后28 d行血生化及C-反应蛋白水平检测;术后28 d冠状动脉造影观察支架置入段管腔通畅情况。②在微创显微镜辅助下于兔右髂外动脉分别置入普通生物全降解支架和新型生物全降解支架管状半成品(材料成分与上述支架一致),每种支架7只,在术前和术后28 d检测血尿素氮及肌酐水平。 结果与结论：置入后28 d两组猪谷丙转氨酶、谷草转氨酶、三酰甘油、总胆固醇、低密度脂蛋白及C-反应蛋白水平与置入前相比均无明显变化,但尿素氮、肌酐水平均明显高于置入前(P < 0.05);两组支架置入段血管均血流通畅、无血栓迹象和狭窄形成。支架置入前后两组兔肌酐和尿素氮水平无明显变化。表明新型生物全降解药物支架置入健康小型猪冠状动脉后是相对安全的,并且支架具有良好的组织相容性。     

Computational hemodynamics of an implanted coronary stent based on three-dimensional cine angiography reconstruction

Coronary stents are supportive wire meshes that keep narrow coronary arteries patent, reducing the risk of restenosis. Despite the common use of coronary stents, approximately 20-35% of them fail due to restenosis. Flow phenomena adjacent to the stent may contribute to restenosis. Three-dimensional computational fluid dynamics (CFD) and reconstruction based on biplane cine angiography were used to assess coronary geometry and volumetric blood flows. A patient-specific left anterior descending (LAD) artery was reconstructed from single-plane x-ray imaging. With corresponding electrocardiographic signals, images from the same time phase were selected from the angiograms for dynamic three-dimensional reconstruction. The resultant three-dimensional LAD artery at end-diastole was adopted for detailed analysis. Both the geometries and flow fields, based on a computational model from CAE software (ANSYS and CATIA) and full three-dimensional Navier-Stroke equations in the CFD-ACE+ software, respectively, changed dramatically after stent placement. Flow fields showed a complex three-dimensional spiral motion due to arterial tortuosity. The corresponding wall shear stresses, pressure gradient, and flow field all varied significantly after stent placement. Combined angiography and CFD techniques allow more detailed investigation of flow patterns in various segments. The implanted stent(s) may be quantitatively studied from the proposed hemodynamic modeling approach.     

国产可降解雷帕霉素药物洗脱支架置入的疗效评价：与金属裸支架比较

背景：药物洗脱支架明显降低了再狭窄率,但永久聚合物涂层在抑制血管平滑肌细胞增生的同时,阻碍血管完全内皮化进程,促使再狭窄发生,且永久聚合物涂层可引发晚期血栓等并发症。 目的：观察冠心病合并糖尿患者置入国产可降解药物洗脱支架后的远期疗效和安全性,并与置入金属裸支架患者进行比较。 方法：实验组选择冠心病合并2型糖尿病患者136例,首次经皮冠状动脉成形治疗,置入国产可降解药物洗脱支架(EXCELTM),并以同期行金属裸支架置入治疗的冠心病合并2型糖尿病患者87例为对照组,随访12个月以上,记录主要不良心血管事件发生情况,并复查冠状动脉造影。 结果与结论：实验组129例,对照组83例完成(13.5±3.5)个月随访,实验组及对照组分别有8例及12例患者发生不良心血管事件,两组间差异有显著性意义(P=0.045),对照组靶血管血运重建及再发心绞痛多于实验组(P < 0.05)。两组患者随访冠状动脉造影的定量分析提示实验组最终丢失指数小于对照组(P < 0.05),再狭窄率低于对照组(P < 0.05)。说明对于冠心病合并糖尿病患者,应用国产可降解药物洗脱支架可降低不良心血管事件发生率,减少再狭窄,改善患者远期预后,安全性能良好。     

Hemocompatibility of drug-eluting coronary stents coated with sulfonated poly (styrene-block-isobutylene-block-styrene)

The presence of polymer coating on a coronary stent is a major mediator of coronary inflammation reaction thereby affects re-endothelialization. Poly(styrene-block-isobutylene-block-styrene) (SIBS) is one of the most attractive alternatives to serve as stent coating, but has shown less than optimal biocompatibility. Increasing the sulfonic acid content in the polymer can result in increased strength and hydrophilicity. The present study was undertaken to determine the mechanism of action and in?vivo efficacy of sulfonated SIBS (S-SIBS) designed specifically as a stent polymer with reduced inflammatory potential and greater endothelialization preservation potential. The blood compatibility of S-SIBS in?vitro and its ability to support the attachment of human umbilical vein endothelial cells (HUVECs) were first assessed to get some insight into its potential use in?vivo. Baer metal stent (BMS), S-SIBS-coated stent without drug (BMS Plus S-SIBS), standard drug-eluting stent (DES) and S-SIBS-coated drug-eluting stent (DES Plus S-SIBS) were then implanted in the coronary arteries of a porcine model. Neointimal hyperplasia was evaluated at 28 and 180 days, and re-endothelialization was evaluated at 7 and 28 days post stents implantation. The results showed that DES Plus S-SIBS exhibited similar ability to reduce neointimal hyperplasia but preserved endothelialization compared with standard DES. These results suggest potentially promising performance of S-SIBS-coated stent in human clinical applications of coronary stenting.     

冠状动脉腔内超声显像的形态学研究

对１０段经生理压力固定的人冠状动脉进行血管内超声，然后血管组织片观察，对比二者结果发现：（１）血管内超声可准确测定冠状动腔面积，周长，直径，厚度，粥样斑块面积和最大厚度等重要参数，与组织学测值相关系数均在０．９２以上；     

Apolipoprotein B accumulation and development of foam cell lesions in coronary arteries of hypercholesterolemic swine

We wished to determine whether plasma low density lipoproteins (LDL) preferentially accumulate at specific anatomical sites in swine coronary arteries that are predisposed to atherosclerotic lesion development, and if so, to determine what alteration in wall structure may be responsible for this accumulation. Therefore, we measured the accumulation of apolipoprotein B (apo B), the major protein in LDL, by electroimmunoassay in seven separate segments of coronary arteries from swine fed a hypercholesterolemic or normolipemic control diet for periods of 4 to 15 weeks. Apo B accumulation was greater in segments from swine fed a hypercholesterolemic diet than in segments for corresponding time intervals from swine fed a normolipemic diet and was greater in proximal than in distal segments (nonbranch points) of coronary arteries. This accumulation of apo B generally increased with time on the hypercholesterolemic diet, already appearing elevated relative to controls at 4 weeks on the hypercholesterolemic diet, whereas the initial appearance of foam cells in these regions occurred at 6 weeks. Apo B was localized by immunofluorescence almost exclusively to areas of diffuse intimal thickening in the proximal portions of the coronary arteries and to focal areas of intimal thickening or cushions at branch points in more distal segments. In these regions, apo B was found primarily in edematous, cell-sparse zones close to the lumen surface, rather than the smooth muscle cell-rich areas making up most of the thickened intima. Apo B in these areas was associated with Alcian blue-positive areas suggested to contain sulfated glycosaminoglycans, which may be responsible for the preferential LDL accumulation. The diffuse and focal intimal thickening does not appear to have been induced by the hypercholesterolemia or the subsequent deposition of LDL, since such thickening was found at the same sites and to about the same degree in the normolipemic control animals. Thus, this study has shown that the areas of earliest and preferential accumulation of LDL are sites of intimal thickening containing deposits of sulfated glycosaminoglycan, and that these are the regions at which the first foam cell lesions eventually appear. These findings add additional strong circumstantial data linking LDL deposition in arteries to the atherosclerotic process.     

药物洗脱冠状动脉支架系统动物实验研究

目的通过观察在猪动脉中置人心畅可降解聚合物涂层药物洗脱冠状动脉支架（天津百畅公司开发）及对照组支架后的植入后管腔丢失、内皮化、炎症反应、损伤及血栓形成情况来评价国产可降解聚合物涂层药物洗脱支架临床应用的可行性。方法将2种共60枚支架分别置入30头猪冠状动脉的前降支、回旋支以及右冠状动脉。支架植入后的2,5,12,25周,将不同数量的猪处死行组织形态学检查,观察炎症、血栓形成情况和内皮化评价。结果支架置入术后的冠脉通畅,无明显狭窄;支架贴血管内壁良好,血管内腔表面光滑;2种支架均无血栓形成,心畅可降解聚合物涂层药物洗脱支架炎症反应及内皮化与对照组无明显差异,其管腔丢失较对照组轻或无明显差异。结论实验提示心畅可降解聚合物涂层药物洗脱支架置入后有良好的血液相容性,生物性能稳定,支架内表面迅速内皮化,血管有良好的开通率。说明可降解聚合物涂层药物洗脱支架是安全、有效的。     

载药复合支架的抗血管组织增生的研究

在氧化钛表面改性的国产不锈钢支架上涂覆一定量药物,制备出新型复合的抗增生载药支架.观察支架植入猪冠状动脉3个月后血管的开通情况及血管的内膜反应.将7枚国产的普通不锈钢支架和7枚制备的新型载药支架植入14头小型猪冠状动脉内,3个月后对支架植入段血管进行血管造影、光镜及电镜检查并进行免疫组织化学分析.冠状动脉造影显示动物处死前支架段血管开通率100%,支架X光下清晰可见,未经特殊抗血栓治疗,支架段血管内无血栓形成.扫描电镜显示两组支架表面都完全被血管内膜覆盖,表面光滑,无血栓形成.覆盖的血管内膜中内皮细胞沿血流方向成典型的铺路石状排列.组织学形态分析显示植入支架3个月后,所有支架植入段血管内膜都有明显的增生,增生内膜主要由细胞外基质和平滑肌细胞构成.结论:含有新型载药支架的冠状动脉血管段内膜增生厚度比普通不锈钢支架的冠状动脉血管段内膜增生厚度小,这种载药复合支架具有良好的应用前景,需扩大样本进行深入研究.     

The consequences of the mechanical environment of peripheral arteries for nitinol stenting

The use of stents in peripheral arteries has not been as successful as in coronary arteries, with high rates of restenosis and stent fracture common. Normal joint flexion induces a range of forces on the arteries, which has an unknown effect on the outcomes of stenting. The objective of this study is to determine how physiological levels of vessel bending and compression following stent implantation will influence the magnitude of stent stresses and hence the risks of fatigue fracture. A further objective is to compare how this mechanical environment will influence arterial stresses following implantation of either stainless steel or nitinol stents. To this end, models of both nitinol and stainless steel stents deployed in peripheral arteries were created, with appropriate loading conditions applied. At high levels of bending and compression, the strain amplitude threshold value for fatigue failure is exceeded for nitinol stents. Bending was predicted to induce high stresses in the artery following stenting, with higher arterial stresses predicted following implantation of a stainless steel stent compared to a nitinol stent. Both bending and compression may contribute to stent fracture by increasing the strain amplitude within the stent, with the dominant factor dependant on location within the arterial tree. For the specific stent types investigated in this study, the model predictions suggest that compression is the dominant mechanical factor in terms of stent fatigue in the femoral arteries, whereas bending is the most significant factor in the popliteal artery. To increase fatigue life and reduce arterial injury, location specific stent designs are required for peripheral arteries.