Drug-eluting stents in preclinical studies: updated consensus recommendations for preclinical evaluation

Stent healing response following delivery of paclitaxel via durable polymeric matrix versus iopromide-based balloon coating in the familial hypercholesterolaemic swine model of coronary injury

AIMS

The routine use of paclitaxel-coated balloons (PCB) in combination with bare metal stents (BMS) in de novo coronary lesions has been questioned. In this study, we aimed to compare the vascular response of BMS implanted using a second-generation PCB (BMS+PCB) with the TAXUS stent (PES) and a BMS control (BMS) in the familial hypercholesterolaemic swine (FHS) model of coronary injury.

METHODS AND RESULTS

A total of 17 stents (PES=6, BMS+PCB=6, and BMS=5) were implanted in the coronary territory of 10 FHS using a 20% overstretch injury ratio. Imaging evaluation (QCA and IVUS) was conducted in all animals at baseline and 28 days following stent implantation. Following terminal imaging all animals were euthanised and stented coronary segments harvested for histological evaluation. At 28 days, the lowest degree of percentage diameter stenosis by QCA was achieved by the PES (2.9 ± 9%) followed by the BMS+PCB (9.5 ± 16.4%) and the BMS group (25.65 ± 18.7%, p<0.05). In histology, percentage area of stenosis (BMS+PCB=29.6 ± 6.4% vs. PES=21.5 ± 3.3% vs. BMS=55.2 ± 12.9%; p<0.01) and neointimal thickness (BMS+PCB=0.26 ± 0.1 mm vs. PES=0.21 ± 0.1 mm vs. BMS=0.59 ± 0.2 mm; p<0.01) were significantly reduced in both paclitaxel groups in comparison to BMS controls. Both BMS+PCB and BMS groups had higher endothelialisation scores (PES=1.50 ± 0.9 vs. BMS+PCB=2.73 ± 0.4 vs. BMS=3.00; p<0.05) and lower peri-strut inflammatory scores (PES=0.83 ± 0.4 vs. BMS+PCB=0.20 ± 0.2 vs. BMS=0.43 ± 0.6, p<0.05) when compared to PES. Neointima maturity (PCB+BMS: 2.00 [2-2.4] vs. PES: 1.00 [0.3-1] vs. BMS: 3.00, p<0.05) and fibrin deposition (PCB+BMS: 1.40 ± 0.3 vs. PES: 2.17 ± 0.7 vs. BMS: 0.27 ± 0.3, p<0.05) scores in PCB+BMS appeared to fall between the PES and the BMS ranges.

CONCLUSIONS

In the FHS coronary injury model, BMS implantation using a PCB yields a degree of neointimal inhibition comparable to the PES. The BMS+PCB combination presented lower degrees of inflammation and fibrin deposition; however, signs of delayed healing were still present.

Genetic experimental preparations for studying atherosclerosis

Atherosclerosis is a pathological process with several inputs (biological, chemical, physiological, and others) interacting slowly over a lifetime leading to coronary artery disease, significant morbidity, and a limited lifespan. Over the past two decades, biologists have used experimental preparations from cells, animals, and man to understand the biology of atherosclerosis. Much has been discovered but our use of the standard gene-targeted experimental preparations is now nearing its limit. Better preparations to answer the remaining questions in the field of atherosclerosis biology are needed.

Preclinical study of a biodegradable polymer-based stent with abluminal sirolimus release

Background

Bioabsorbable polymer stents with drug elution only on the abluminal surface may be safer than durable polymer drug-eluting stents.

Objective

To report the experimental findings with the Inspiron^TM stent - a bioabsorbable polymer-coated stent with sirolimus release from the abluminal surface only, recently approved for clinical use.

Methods

45 stents were implanted in the coronary arteries of 15 pigs. On day 28 after implantation, angiographic, intracoronary ultrasonographic and histomorphological data were collected. Five groups were analyzed: Group I (nine bare-metal stents); Group II (nine coated with bioabsorbable polymer on the luminal and abluminal surfaces); Group III (eight stents coated with bioabsorbable polymer on the abluminal surface); Group IV (nine stents with bioabsorbable polymer and sirolimus on the luminal and abluminal surfaces); and Group V (ten stents with bioabsorbable polymer and sirolimus only on the abluminal surface).

Results

The following results were observed for Groups I, II, III, IV and V, respectively: percentage stenosis of 29 ± 20; 36 ± 14; 33 ± 19; 22 ± 13 and 26 ± 15 (p = 0.443); late lumen loss (in mm) of 1.02 ± 0.60; 1.24 ± 0.48; 1.11 ± 0.54; 0.72 ± 0.44 and 0.78 ± 0.39 (p = 0.253); neointimal area (in mm²) of 2.60 ± 1.99; 2.74 ± 1.51; 2.74 ± 1.30; 1.30 ± 1.14 and 0.97 ± 0.84 (p = 0.001; Groups IV and V versus Groups I, II and III); and percentage neointimal area of 35 ± 25; 38 ± 18; 39 ± 19; 19 ± 18 and 15 ± 12 (p = 0.001; Groups IV and V versus Groups I, II and III). Injury and inflammation scores were low and with no differences between the groups.

Conclusion

The Inspiron^TM stent proved to be safe and was able to significantly inhibit the neointimal hyperplasia observed on day 28 after implantation in porcine coronary arteries.

Targeted disruption of LDLR causes hypercholesterolemia and atherosclerosis in Yucatan miniature pigs

Recent progress in engineering the genomes of large animals has spurred increased interest in developing better animal models for diseases where current options are inadequate. Here, we report the creation of Yucatan miniature pigs with targeted disruptions of the low-density lipoprotein receptor (LDLR) gene in an effort to provide an improved large animal model of familial hypercholesterolemia and atherosclerosis. Yucatan miniature pigs are well established as translational research models because of similarities to humans in physiology, anatomy, genetics, and size. Using recombinant adeno-associated virus-mediated gene targeting and somatic cell nuclear transfer, male and female LDLR+/− pigs were generated. Subsequent breeding of heterozygotes produced LDLR−/− pigs. When fed a standard swine diet (low fat, no cholesterol), LDLR+/− pigs exhibited a moderate, but consistent increase in total and LDL cholesterol, while LDLR−/− pigs had considerably elevated levels. This severe hypercholesterolemia in homozygote animals resulted in atherosclerotic lesions in the coronary arteries and abdominal aorta that resemble human atherosclerosis. These phenotypes were more severe and developed over a shorter time when fed a diet containing natural sources of fat and cholesterol. LDLR-targeted Yucatan miniature pigs offer several advantages over existing large animal models including size, consistency, availability, and versatility. This new model of cardiovascular disease could be an important resource for developing and testing novel detection and treatment strategies for coronary and aortic atherosclerosis and its complications.

Safety and efficacy of different paclitaxel-eluting balloons in a porcine model

INTRODUCTION AND OBJECTIVES

Paclitaxel-eluting balloons have shown high antiproliferative efficacy in the treatment and prevention of restenosis. Nevertheless, not all available devices are equally effective, which makes it interesting to compare results in a preclinical model. Our objective was to assess the preclinical efficacy and safety of different devices.

METHODS

We implanted 51 metallic stents (Architect(®), iVascular) in 17 domestic swine (mean, 25 [3] kg), inserting 1 stent per major coronary artery. Stent postdilatation was performed with different control balloons (n=10) or paclitaxel-eluting balloons: paclitaxel-eluting balloon 1 (iVascular) (n=15); paclitaxel-eluting balloon 2 (iVascular) (n=16) and In.Pact Falcon(®) (Medtronic) (n=10). The restenosis rate (using angiography and histomorphometry) and vascular healing parameters (balloon-related vascular injury score, endothelialization rate, and fibrin and inflammation scores) were analyzed at 28 days.

RESULTS

The distinct paclitaxel-eluting balloons showed a similar degree of stenosis at follow-up, which was significantly lower than that in the control group: diameter stenosis was 9% (12%) vs 34% (18%) by angiography (P<.0001) and was 22% (8%) vs 51% (18%) by histomorphometry (P<.0001). Scores for vascular injury (mean, 0.6 [0.5]) and inflammation (mean, 0.8 [0.3]) were uniformly low across all groups. Drug effect markers differed significantly between the paclitaxel-eluting balloons and control groups, with lower endothelialization rates (87% [10%] vs 99% [2%]; P=.0007) and higher fibrin scores (2.1 [0.7] vs 0.4 [0.5]; P<.0001) in the paclitaxel-eluting balloons groups. There were no differences between the different paclitaxel-eluting balloons.

CONCLUSIONS

In this preclinical model, the paclitaxel-eluting balloons studied significantly reduced in-stent restenosis compared with the control balloons. Although there were no findings of persistent vascular injury or inflammation, delayed endothelialization and fibrin aggregate suggest a drug deposition response.

Quantitative analysis of high-resolution, contrast-enhanced, cone-beam CT for the detection of intracranial in-stent hyperplasia

BACKGROUND

Intracranial in-stent hyperplasia is a stroke-associated complication that requires routine surveillance.

OBJECTIVE

To compare the results of in vivo experiments to determine the accuracy and precision of in-stent hyperplasia measurements obtained with modified C-arm contrast-enhanced, cone-beam CT (CE-CBCT) imaging with those obtained by 'gold standard' histomorphometry. Additionally, to carry out clinical analyses comparing this CE-CBCT protocol with digital subtraction angiography (DSA).

METHODS

A non-binned CE-CBCT protocol (VasoCT) was used that acquires x-ray images with a small field-of-view and applies a full-scale reconstruction algorithm providing high-resolution three-dimensional (3D) imaging with 100 µm isotropic voxels. In an vivo porcine model, VasoCT cross-sectional area measurements were compared with gold standard vessel histology. VasoCT and DSA were used to calculate in-stent stenosis in 23 imaging studies.

RESULTS

Porcine VasoCT cross-sectional stent, lumen, and in-stent hyperplasia areas strongly correlated with histological measurements (r(2)=0.97, 0.93, 0.90; slope=1.14, 1.07, and 0.76, respectively; p<0.0001). Clinical VasoCT percentage stenosis correlated well with DSA percentage stenosis (r(2)=0.84; slope=0.76), and the two techniques were free of consistent bias (Bland-Altman, bias=3.29%; 95% CI -14.75% to 21.33%). An illustrative clinical case demonstrated the advantages of VasoCT, including 3D capability and non-invasive IV contrast administration, for detection of in-stent hyperplasia.

CONCLUSIONS

C-arm VasoCT is a high-resolution 3D capable imaging technique that has been validated in an animal model for measurement of in-stent tissue growth. Successful clinical implementation of the protocol was performed in a small case series.

Dynamic observation of artery endothelial cell layers in response to bare metal stent and paclitaxel-eluting stent in vitro

OBJECTIVES

We aimed to investigate the mechanism of paclitaxel-eluting stent (PES) induced thrombosis by real-time dynamic monitoring of live endothelial cells.

BACKGROUND

PES is widely used in clinics to inhibit restenosis effectively. However, late stent thrombosis is a major concern with the use of PES.

METHODS

We established an in vitro cell culture system to mimic the close contact of endothelial cells with PES struts. The dynamic response of porcine innominate artery endothelial cells (PIECs) to stents was observed using a bright field microscope and a high-resolution charge-coupled device

RESULTS

PES changed elongated PIECs to round PIECs within 24 hours. Paracellular gaps were readily observed in a PIEC monolayer exposed to PES. By contrast, paracellular gaps were almost undetectable in an endothelial monolayer incubated with bare metal stent (BMS). As incubation time was prolonged (days 5-9), round PIECs returned to their elongated shape, but paracellular gaps were retained at lower frequencies and smaller sizes than those on days 1 and 2. In addition, the PIEC monolayer in the PES group retained an uneven surface topology during incubation, whereas PIECs in the BMS group developed a smooth surface of epithelial cell sheets on days 5-7.

CONCLUSION

Our findings showed that the shift of cell shape causes impaired integrity of the monolayer characteristic with enlarged paracellular gaps and uneven surface topology in exposure to PES. The results might serve as structural information for understanding the mechanism of PES-induced early and late thrombosis.

Effect of atorvastatin-eluting stents in a rabbit iliac artery restenosis model

Statins have pleiotropic effects, which include the inhibition of neointima hyperplasia, the inhibition of vascular inflammation, and platelet inhibition. The aim of this study was to examine the effect of an atorvastatin-eluting stent (AES) in a rabbit iliac artery overstretch restenosis model. Ten rabbits were used in this study (10 rabbits, 10 iliac arteries for each stent). An AES and paclitaxel-eluting stent (PES) were implanted in the left and right iliac arteries in a rabbit (2 stents in each rabbit). The stents were deployed with oversizing (stent/artery ratio 1.3:1), and histopathologic analysis was assessed at 28 days after stenting. There were no significant differences in the injury score, lumen area, or inflammation score. There were significant differences in the neointimal area (0.7±0.18 mm² in the AES group vs. 0.4±0.25 mm² in the PES group, p<0.01), in the percentage stenosis area (14.8±5.06% in the AES group vs. 10.5±6.80% in the PES group, p<0.05), and in the fibrin score (0.4±0.51 in the AES group vs. 2.7±0.48 in the PES group, p<0.001). Although the AES did not suppress neointimal hyperplasia compared with the PES, it showed a superior arterial healing effect in a rabbit iliac artery overstretch restenosis model.

Emerging technologies: polymer-free phospholipid encapsulated sirolimus nanocarriers for the controlled release of drug from a stent-plus-balloon or a stand-alone balloon catheter

Drug-eluting stents have proven to be effective in reducing the risk of late restenosis. In order to achieve a controlled and prolonged release of the antiproliferative agent, current drug-eluting stents utilise various biodegradable as well as non-erodible polymeric blends to coat the stent surface and to serve as drug carriers. The utilisation of polymeric compounds in current drug-eluting stents may eventually limit their performance as well as their clinical applicability due to the potential induction of undesirable local reactions. The development of alternative, polymer-free drug carriers has the potential to overcome some of the limitations of current drug-eluting stent formulations. Moreover, improvements in drug carriers may also result in an expansion of the technological possibilities for other intravascular drug delivery systems, such as metal-free or even implant-free solutions. This article describes the structure and the preclinical validation profile of a novel phospholipid encapsulated sirolimus nanocarrier, used as a coating in two formulations: a coronary stent-plus-balloon system and a stand-alone balloon catheter. The nanoparticles provided a stable, even and homogenous coating to the devices in both formulations. Dose-finding studies allowed the most appropriate identification of the best nanoparticle structure associated with an extremely efficient transfer of drug to all layers of the vessel wall, achieving high tissue concentrations that persisted days after the application, with low systemic drug leaks.

Bioresorbable drug-eluting magnesium-alloy scaffold: design and feasibility in a porcine coronary model

AIMS

Among three versions of bioresorbable magnesium scaffolds featuring different paclitaxel-elution kinetics, we determined the best-performing scaffold and compared it with established, paclitaxel-eluting, permanent stents TAXUS Liberté and eucaTAX.

METHODS AND RESULTS

Drug-elution kinetics in magnesium scaffolds were modulated by varying the composition of their bioresorbable poly(lactide-co-glycolide) coating loaded with paclitaxel. A 50:50 ratio of lactide to glycolide, or an 85:15 ratio and either high- or low-molecular-weight polymer was applied in the "50/50", "85/15H", and "85/15L" scaffolds, respectively. Seventy-three magnesium scaffolds (25 50/50, 24 85/15H, 24 85/15L) and 36 control stents (18 TAXUS Liberté, 18 eucaTAX) were implanted in coronary arteries of 50 Yucatan mini-pigs. Angiography, histomorphometry, and histopathology data were acquired at 28, 90 and 180 days. The best-performing magnesium scaffold, 85/15H, was equivalent to TAXUS Liberté and superior to eucaTAX regarding late luminal loss, intimal area, fibrin score, and endothelialisation. Intimal inflammation score was higher in 85/15H than in the control stents at 28 days, but this effect disappeared at later time points.

CONCLUSIONS

By selecting suitable paclitaxel-elution kinetics, it was feasible to develop a bioresorbable magnesium scaffold whose efficacy and healing characteristics in a porcine coronary model are comparable with those of established paclitaxel-eluting permanent metallic stents.

Histopathological Comparison among Biolimus, Zotarolimus and Everolimus-Eluting Stents in Porcine Coronary Restenosis Model

Background and Objectives

The aim of this study was to examine the histolopathogical effects among the biolimus, zotarolimus, and everolimus eluting stent (EES) in the porcine coronary restenosis model.

Subjects and Methods

Pigs were randomized into three groups in which the coronary arteries (15 pigs, 10 coronaries in each group) had either a biolimus A9 eluting stent (BES, n=10), zotarolimus eluting stent (ZES, n=10) or an EES (n=10). Histopathologic analysis was performed at 28 days after stenting.

Results

There were no significant differences in the injury score among the three groups. There was a significant difference in the internal elastic lamina, lumen area, neointima area, percent area stenosis, and the fibrin and inflammation score among the three groups (4.3±0.53 mm², 2.5±0.93 mm², 1.8±1.03 mm², 40.7±20.80%, 1.7±0.41, 1.4±0.72 in the BES group vs. 5.1±0.55 mm², 2.3±1.14 mm², 2.8±1.00 mm², 55.4±21.23%, 2.0±0.39, 1.6±0.76 in the ZES group vs. 4.4±0.53 mm², 1.7±1.22 mm², 2.8±1.23 mm², 64.0±26.00%, 1.8±0.76, 2.1±0.90 in the EES group, respectively). BES is more effective in inhibiting neointimal hyperplasia compared to ZES and EES (p<0.0001). According to the fibrin and inflammation score, BES and EES are more effective in decreasing the fibrin deposition compared to ZES (p<0.001). Moreover, BES and ZES are more effective in reducing the inflammatory reaction compared to EES (p<0.001).

Conclusion

The result demonstrates that BES shows better histopathological characteristics than ZES and EES at one month after stenting in the porcine coronary restenosis model.

Adventitial nab-rapamycin injection reduces porcine femoral artery luminal stenosis induced by balloon angioplasty via inhibition of medial proliferation and adventitial inflammation

BACKGROUND

Endovascular interventions on peripheral arteries are limited by high rates of restenosis. Our hypothesis was that adventitial injection of rapamycin nanoparticles would be safe and reduce luminal stenosis in a porcine femoral artery balloon angioplasty model.

METHODS AND RESULTS

Eighteen juvenile male crossbred swine were included. Single-injury (40%-60% femoral artery balloon overstretch injury; n=2) and double-injury models (endothelial denudation injury 2 weeks before a 20%-30% overstretch injury; n=2) were compared. The double-injury model produced significantly more luminal stenosis at 28 days, P=0.002, and no difference in medial fibrosis or inflammation. Four pigs were randomized to the double-injury model and adventitial injection of saline (n=2) or 500 μg of nanoparticle albumin-bound rapamycin (nab-rapamycin; n=2) with an endovascular microinfusion catheter. There was 100% procedural success and no difference in endothelial regeneration. At 28 days, nab-rapamycin led to significant reductions in luminal stenosis, 17% (interquartile range, 12%-35%) versus 10% (interquartile range, 8.3%-14%), P=0.001, medial cell proliferation, P<0.001, and fibrosis, P<0.001. There were significantly fewer adventitial leukocytes at 3 days, P<0.001, but no difference at 28 days. Pharmacokinetic analysis (single-injury model) found rapamycin concentrations 1500× higher in perivascular tissues than in blood at 1 hour. Perivascular rapamycin persisted ≥8 days and was not detectable at 28 days.

CONCLUSIONS

Adventitial nab-rapamycin injection was safe and significantly reduced luminal stenosis in a porcine femoral artery balloon angioplasty model. Observed reductions in early adventitial leukocyte infiltration and late medial cell proliferation and fibrosis suggest an immunosuppressive and antiproliferative mechanism. An intraluminal microinfusion catheter for adventitial injection represents an alternative to stent- or balloon-based local drug delivery.

Mucin covalently bonded to microfibers improves the patency of vascular grafts

Due to high incidence of vascular bypass procedures, an unmet need for suitable vessel replacements exists, especially for small-diameter (<6 mm) vascular grafts. Here, we developed a novel, bilayered, synthetic vascular graft of 1-mm diameter that consisted of a microfibrous luminal layer and a nanofibrous outer layer, which was tailored to possess the same mechanical property as native arteries. We then chemically modified the scaffold with mucin, a glycoprotein lubricant on the surface of epithelial tissues, by either passive adsorption or covalent bonding using the di-amino-poly(ethylene glycol) linker to microfibers. Under static and physiological flow conditions, conjugated mucin was more stable than adsorbed mucin on the surfaces. Mucin could slightly inhibit blood clotting, and mucin coating suppressed platelet adhesion on microfibrous scaffolds. In the rat common carotid artery anastomosis model, grafts with conjugated mucin, but not adsorbed mucin, exhibited excellent patency and higher cell infiltration into the graft walls. Mucin, which can be easily obtained from autologous sources, offers a novel method for improving the hemocompatibility and surface lubrication of vascular grafts and many other implants.

Familial hypercholesterolemia and atherosclerosis in cloned minipigs created by DNA transposition of a human PCSK9 gain-of-function mutant

Lack of animal models with human-like size and pathology hampers translational research in atherosclerosis. Mouse models are missing central features of human atherosclerosis and are too small for intravascular procedures and imaging. Modeling the disease in minipigs may overcome these limitations, but it has proven difficult to induce rapid atherosclerosis in normal pigs by high-fat feeding alone, and genetically modified models similar to those created in mice are not available. D374Y gain-of-function mutations in the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene cause severe autosomal dominant hypercholesterolemia and accelerates atherosclerosis in humans. Using Sleeping Beauty DNA transposition and cloning by somatic cell nuclear transfer, we created Yucatan minipigs with liver-specific expression of human D374Y-PCSK9. D374Y-PCSK9 transgenic pigs displayed reduced hepatic low-density lipoprotein (LDL) receptor levels, impaired LDL clearance, severe hypercholesterolemia, and spontaneous development of progressive atherosclerotic lesions that could be visualized by noninvasive imaging. This model should prove useful for several types of translational research in atherosclerosis.

Mechanical and Histopathological Comparison between Commercialized and Newly Designed Coronary Bare Metal Stents in a Porcine Coronary Restenosis Model

The aim of this study was to compare the stent designed by Chonnam National University Hospital (designated as CNUH) with commercial cobalt-chromium coronary stent in a porcine coronary overstretch restenosis model. CNUH stent was subjected to mechanical performance tests. Pigs were randomized into two groups in which the coronary arteries (10 pigs, 10 coronaries in each group) had either CNUH stent or control commercial bare metal stent. Histopathologic analysis was assessed at 28 days after stenting. In mechanical performance tests, CNUH stent showed 2.65N, 35.1N, 0.52N, 1.94%, 4.29% in the flat plate radial compression, radial force, 3 point bending, Foreshortening and recoil test, respectively. There was no significant difference in the injury score, internal elastic lamina (IEL), lumen area, neointima area, percent area stenosis, inflammation score and fibrin score between the two groups (1.2±0.35, 4.1±0.41 mm², 2.7±0.56 mm², 1.6±0.47 mm², 36.7±11.2%, 1.2±0.62, 0.2±0.34 in CNUH stent group vs. 1.2±0.38, 3.7±0.64 mm², 2.5±0.49 mm², 1.5±0.61 mm², 36.3±12.17%, 1.1±0.12, 0.4±0.46 in commercial stent group, respectively). In the mechanical performance test, CNUH stent showed the moderated performance under the guideline of FDA. CNUH stent demonstrated similar histological reactions compared with commercial cobalt-chromium stent in a porcine coronary overstretch restenosis model.

Head-to-head comparison of sirolimus-eluting stent versus bare metal stent evaluation of the coronary endothelial dysfunction in the same patient presenting with multiple coronary artery lesions: the CREDENTIAL study

OBJECTIVES

To assess the endothelial dysfunction (ED) after bare metal stents (BMS) and sirolimus eluting stents (SES) implantation in the same patient, overcoming the confounding role of individual variables.

BACKGROUND

SES reduce restenosis rate compared to BMS but causes more ED. ED is a potentially unsafe phenomenon, since it is the first step in the cascade of atherosclerosis. Studies showing more pronounced ED with drug eluting stents than BMS involved different series of patients, making the comparison difficult because endothelial function (EF) is responsive to many risk factors.

METHODS

we designed a prospective comparison of 6 months post-deployment EF of SES versus BMS implanted in the same patient, but in different coronary segments. Forty-eight lesions were randomly assigned on a 1:1 allocation using block sizing of 4 according to a computer-generated sequence (SAS System, Version 9.1) basis to treatment with SES or BMS. The EF was evaluated by measuring vessel diameter variation in the stented segment, before and after selective intracoronary infusion of acetylcholine (iiAch).

RESULTS

In eligible patients, the relative magnitudes of major vasoconstriction were 2.6, 2.9, 4.6, and 3.1 at 5 mm proximal and 5, 10 and 20 mm distal to the stent edge. Overall, a 3.5-fold major distal vasoconstriction after iiAch of SES vs. BMS was calculated.

CONCLUSIONS

in the same patients, but treating different coronary segments, SES implantation induces a higher rate of vasoconstriction compared to BMS. The increased vasoconstriction after iiAch is an indicator of ED.

Threats to validity in the design and conduct of preclinical efficacy studies: a systematic review of guidelines for in vivo animal experiments

BACKGROUND

The vast majority of medical interventions introduced into clinical development prove unsafe or ineffective. One prominent explanation for the dismal success rate is flawed preclinical research. We conducted a systematic review of preclinical research guidelines and organized recommendations according to the type of validity threat (internal, construct, or external) or programmatic research activity they primarily address.

METHODS AND FINDINGS

We searched MEDLINE, Google Scholar, Google, and the EQUATOR Network website for all preclinical guideline documents published up to April 9, 2013 that addressed the design and conduct of in vivo animal experiments aimed at supporting clinical translation. To be eligible, documents had to provide guidance on the design or execution of preclinical animal experiments and represent the aggregated consensus of four or more investigators. Data from included guidelines were independently extracted by two individuals for discrete recommendations on the design and implementation of preclinical efficacy studies. These recommendations were then organized according to the type of validity threat they addressed. A total of 2,029 citations were identified through our search strategy. From these, we identified 26 guidelines that met our eligibility criteria--most of which were directed at neurological or cerebrovascular drug development. Together, these guidelines offered 55 different recommendations. Some of the most common recommendations included performance of a power calculation to determine sample size, randomized treatment allocation, and characterization of disease phenotype in the animal model prior to experimentation.

CONCLUSIONS

By identifying the most recurrent recommendations among preclinical guidelines, we provide a starting point for developing preclinical guidelines in other disease domains. We also provide a basis for the study and evaluation of preclinical research practice. Please see later in the article for the Editors' Summary.

Time course of endothelium-dependent and -independent coronary vasomotor response to coronary balloons and stents. Comparison of plain and drug-eluting balloons and stents

OBJECTIVES

This study sought to determine the time dependency of the endothelium-dependent and -independent vascular responses after percutaneous coronary intervention (PCI) with drug-eluting (DEB) or plain balloons, bare-metal (BMS), and drug-eluting (DES) stents, or controls.

BACKGROUND

Long-term endothelial dysfunction after DES implantation is associated with delayed healing and late thrombosis.

METHODS

Domestic pigs underwent PCI using DEB or plain balloon, BMS, or DES. The dilated and stented segments, and the proximal reference segments of stents and control arteries were explanted at 5-h, 24-h, 1-week, and 1-month follow-up (FUP). Endothelin-induced vasoconstriction and endothelium-dependent and -independent vasodilation of the arterial segments were determined in vitro and were related to histological results.

RESULTS

DES- and BMS-treated arteries showed proneness to vasoconstriction 5 h post-PCI. The endothelium-dependent vasodilation was profoundly (p < 0.05) impaired early after PCI (9.8 ± 3.7%, 13.4 ± 9.2%, 5.7 ± 5.3%, and 7.6 ± 4.7% using plain balloon, DEB, BMS, and DES, respectively), as compared with controls (49.6 ± 9.5%), with slow recovery. In contrast to DES, the endothelium-related vasodilation of vessels treated with plain balloon, DEB, and BMS was increased at 1 month, suggesting enhanced endogenous nitric oxide production of the neointima. The endothelium-independent (vascular smooth muscle-related) vasodilation decreased significantly at 1 day, with slow normalization during FUP. All PCI-treated vessels exhibited imbalance between vasoconstriction-vasodilation, which was more pronounced in DES- and BMS-treated vessels. No correlation between histological parameters and vasomotor function was found, indicating complex interactions between the healing neoendothelium and smooth muscle post-PCI.

CONCLUSIONS

Coronary arteries treated with plain balloon, DEB, BMS, and DES showed time-dependent loss of endothelial-dependent and -independent vasomotor function, with imbalanced contraction/dilation capacity.

Inhibition of neointimal hyperplasia with a novel zotarolimus coated balloon catheter

BACKGROUND

Non stent based delivery of antiproliferative agents using drug coated balloon catheters may offer additional flexibility and efficacy in a broad range of applications. The lipophilic antiproliferative drug zotarolimus makes it a potential candidate for balloon delivery. The aim of the present study was to evaluate the safety and efficacy of a prototype zotarolimus coated balloon (ZCB) catheter in comparison to a zotarolimus eluting stent (ZES) in the porcine coronary overstretch model.

METHODS

Eighty-four stents (diameters 3.0 and 3.5 mm; length 15 mm) were implanted in LAD and Cx of 42 domestic pigs: control (TriMaxx, Abbott, polymer coated stent without drug, implanted with uncoated PCI catheter, n = 56); ZES (ZoMaxx, Abbott, stent coated with zotarolimus in polymer, implanted with uncoated PCI catheter, n = 14); ZCB (TriMaxx, Abbott, polymer coated stent without drug, implanted with zotarolimus coated PCI catheter, n = 14). Drug content of the vessel wall (n = 9) was measured about 10-30 min post intervention with ZCB in additional pigs.

RESULTS

Immediately after ZCB treatment 101 ± 31 μg of zotarolimus was detected in the coronary arteries. After 28 days ZES led to a reduction of neointimal area from 4.32 ± 1.45 to 3.32 ± 1.11 mm2 (P = 0.019 vs. control). The effect of neointimal inhibition was more pronounced with the novel ZCB (2.79 ± 1.43 mm², P = 0.001 vs. control). Inflammation score was significantly reduced in vessels treated with the ZCB (0.75 ± 0.86 compared to control (1.45 ± 0.94, P = 0.013) and ZES (1.65 ± 0.90, P = 0.012).

CONCLUSION

Zotarolimus coated balloons and stents were found to effectively reduce neointimal proliferation in the porcine coronary model. Inflammation scores were significantly reduced after treatment with the coated balloon. Zotarolimus balloon coating might be a novel option in preventing and treating restenosis.

Comparative vascular responses three months after paclitaxel and everolimus-eluting stent implantation in streptozotocin-induced diabetic porcine coronary arteries

BACKGROUND

Diabetes remains a significant risk factor for restenosis/thrombosis following stenting. Although vascular healing responses following drug-eluting stent (DES) treatment have been characterized previously in healthy animals, comparative assessments of different DES in a large animal model with isolated features of diabetes remains limited. We aimed to comparatively assess the vascular response to paclitaxel-eluting (PES) and everolimus-eluting (EES) stents in a porcine coronary model of streptozotocin (STZ)-induced type I diabetes.

METHOD

Twelve Yucatan swine were induced hyperglycemic with a single STZ dose intravenously to ablate pancreatic β-cells. After two months, each animal received one XIENCE V® (EES) and one Taxus Liberte (PES) stent, respectively, in each coronary artery. After three months, vascular healing was assessed by angiography and histomorphometry. Comparative in vitro effects of everolimus and paclitaxel (10-5 M-10-12 M) after 24 hours on carotid endothelial (EC) and smooth muscle (SMC) cell viability under hyperglycemic (42 mM) conditions were assayed by ELISA. Caspase-3 fluorescent assay was used to quantify caspase-3 activity of EC treated with everolimus or paclitaxel (10-5 M, 10-7 M) for 24 hours.

RESULTS

After 3 months, EES reduced neointimal area (1.60 ± 0.41 mm, p < 0.001) with trends toward reduced % diameter stenosis (11.2 ± 9.8%, p = 0.12) and angiographic late-loss (0.28 ± 0.30 mm, p = 0.058) compared to PES (neointimal area: 2.74 ± 0.58 mm, % diameter stenosis: 19.3 ± 14.7%, late loss: 0.55 ± 0.53 mm). Histopathology revealed increased inflammation scores (0.54 ± 0.21 vs. 0.08 ± 0.05), greater medial necrosis grade (0.52 ± 0.26 vs. 0.0 ± 0.0), and persistently elevated fibrin scores (1.60 ± 0.60 vs. 0.63 ± 0.41) with PES compared to EES (p < 0.05). In vitro, paclitaxel significantly increased (p < 0.05) EC/SMC apoptosis/necrosis at high concentrations (≥ 10-7 M), while everolimus did not affect EC/SMC apoptosis/necrosis within the dose range tested. In ECs, paclitaxel (10-5 M) significantly increased caspase-3 activity (p < 0.05) while everolimus had no effect.

CONCLUSION

After 3 months, both DES exhibited signs of delayed healing in a STZ-induced diabetic swine model. PES exhibited greater neointimal area, increased inflammation, greater medial necrosis, and persistent fibrin compared to EES. Differential effects of everolimus and paclitaxel on vascular cell viability may potentially be a factor in regulating delayed healing observed with PES. Further investigation of molecular mechanisms may aid future development of stent-based therapies in treating coronary artery disease in diabetic patients.

Do pharmacokinetics explain persistent restenosis inhibition by a single dose of paclitaxel?

BACKGROUND

The purpose of this study was to investigate the elimination of paclitaxel from the arterial wall after a single short administration with a coated balloon.

METHODS AND RESULTS

Slightly oversized paclitaxel-coated balloons (dose 3 or 9 μg/mm(2)) without or with premounted stents were inflated in nonatherosclerotic coronary arteries of either young domestic pigs or adult Goettingen minipigs. The paclitaxel content of plasma, arterial segments, and residual hearts (without treated arteries) was measured for up to 180 days using high-performance liquid chromatography/ultraviolet detection or mass spectrometry. Angiograms were evaluated for lumen narrowing. The paclitaxel concentration in plasma remained <10 ng/mL. In arteries of domestic pigs and minipigs treated with paclitaxel-coated balloons with premounted stents, 10%±5% or 21%±8% of dose, respectively, was initially detected and decreased to 3.5%±3.1% of dose (domestic pig) by Day 7. Within 6 months it fell with a half-life of 1.9 months to 0.40%±0.35%. After 3 months the concentration in the arterial wall was 17±11 μmol/L. Without a stent, drug transfer to the vessel wall was somewhat reduced and elimination faster. Immediately after treatment up to 26%±4% of dose was detected in the residual whole hearts. It dropped with a half-life of 45 days to 1.5%±0.6% of dose (0.3 μmol/L) within 6 months.

CONCLUSIONS

After a single local administration with coated balloons, paclitaxel stays in the vessel wall of pigs long enough to explain persistent inhibition of neointimal proliferation. The pharmacokinetics of paclitaxel does, however, not exclude other reasons for sustained efficacy such as early blocking of processes initiating excessive and prolonged neointimal proliferation.

Thromboresistant and endothelialization effects of dopamine-mediated heparin coating on a stent material surface

Heparinization of surfaces has proven a successful strategy to prevent thrombus formation. Inspired by the composition of adhesive proteins in mussels, the authors used dopamine to immobilize heparin on a stent surface. This study aimed to assess the thromboresistant and endothelialization effects of dopamine-mediated heparin (HPM) coating on a stent material surface. The HPM was synthesized by bonding dopamine and heparin chemically. Cobalt-chromium (Co-Cr) alloy disks were first placed in the HPM solution and applied to surface stability then underwent thromboresistant tests and human umbilical vein endothelial cells (HUVEC) cytotoxicity assays. The results showed not only thromboresistant activity and a stable state of heparin on the surfaces after investigation with toluidine blue and thrombin activation assay but also proliferation of HUVEC in vitro. Studies on animals showed that the HPM-coated stent has no obvious inflammation response and increasing of restenosis rate compared to the bare metal stent (BMS) indicating good biocompatibility as well as safety in its in vivo application. Moreover, improving the endothelial cell (EC) proliferation resulted in a higher strut-covering rate (i.e., endothelialization) with shuttle-shaped EC in the HPM-coated stent group compared to that of the BMS group. These results suggest that this facile coating approach could significantly promote endothelialization and offer greater safety than the BMS for its much improved thromboresistant property. Moreover, it may offer a platform for conjugating secondary drugs such as anti-proliferative drugs.

PolarCath cryoplasty enhances smooth muscle cell apoptosis in a rabbit iliac artery model: an experimental in vivo controlled study

PURPOSE

To in vivo investigate the histological response after single and double cryoplasty therapy in a rabbit iliac artery model.

MATERIALS AND METHODS

In total, 40 New Zealand White rabbits underwent percutaneous transluminal angioplasty of the iliac artery using either PolarCath balloon or a conventional angioplasty balloon of equal diameter. Arterial injury, inflammatory response and smooth muscle cells (SMC) apoptosis with the TUNEL (Terminal deoxynucleotidyl transferase dUTP Nick End Labeling) immunohistochemical assay were analyzed. Rabbits were divided between single or double balloon inflation and histological results were compared between cryoplasty and control angioplasty both at 30 min and 72 h.

RESULTS

Arterial injury and wall inflammation scores were low and similar between cryoplasty and control groups after single and double balloon inflation. Compared to conventional balloon angioplasty, Polarcath cryoplasty demonstrated superior SMC apoptosis after single inflation at 30 min [12.0±1.2 cells/(0.025 mm)2 vs 7.0±1.5 cells/(0.025 mm)(2), p=0.002], single inflation at 72 h [9.0±1.0 cells/(0.025 mm)(2) vs 5.4±1.4 cells/(0.025 mm)(2), p=0.001], double inflation at 30 min [11.6±1.5 cells/(0.025 mm)(2) vs 6.8±1.4 cells/(0.025 mm)(2), p=0.001] and double inflation at 72h [9.2±0.8 cells/(0.025 mm)(2) vs 5.0±0.7 cells/(0.025 mm)(2), p=0.001]. There were no significant differences in apoptosis between single and double cryoplasty application at 30 min and 72 h.

CONCLUSION

Cryoplasty demonstrated superior rates of SMC apoptosis at 30 min and 72 h and was associated to relatively low arterial injury and inflammation scores. An immediate second PolarCath inflation did not achieve superior apoptosis.

A histopathological comparison of different definitions for quantifying in-stent neointimal tissue: implications for the validity of intracoronary ultrasound and optical coherence tomography measurements

PURPOSE

Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) define neointima as the tissue encompassed between the stent and the lumen boundaries. This approach differs from the gold-standard histopathology, where neointima is traditionally calculated as the tissue between the internal elastic lamina (IEL) and the lumen. We aimed to investigate whether the neointimal assessment using IVUS and OCT-like definitions would correlate with the traditional histopathological quantification of neointima.

METHODS

Histopathological analysis was obtained from a porcine model of 28-day coronary in-stent neointimal proliferation (n=13 bare stents). Traditional histopathology neointimal area (NIHPATH area) was calculated as the lumen area minus the IEL area, while the percent neointimal obstruction was defined as NIHPATH area divided by the IEL area. The IVUS/OCT-like neointima area (NIHIVUS/OCT area) was defined as the lumen area minus the stent area, while the percent neointimal obstruction was defined as NIHIVUS/OCT area divided by the stent area.

RESULTS

The neointimal area as well as the percent obstruction were significantly correlated between histopathology and IVUS/OCT-like definitions (R(2)=0.89 and 0.95 respectively; P<0.01 for both). The average absolute difference between the IVUS/OCT-like and the pathology-like measurements was close to zero, however with a relatively wide dispersion (difference for neointimal area: 0.41 mm(2) [95% CI 1.72 to (-)0.90 mm(2)]; difference for percent neointimal obstruction: 2.5% [95% CI 11.5% to (-)6.5%]).

CONCLUSIONS

The present findings support the use of stent area in replacement to IEL area, as in IVUS & OCT imaging protocols, for the calculation of neointimal parameters in experimental model of restenosis.

Vascular response to zotarolimus-coated balloons in injured superficial femoral arteries of the familial hypercholesterolemic Swine

BACKGROUND

Drug-coated balloons are rapidly emerging as a therapeutic alternative for the interventional treatment of peripheral vascular disease. The purpose of this study was to test the hypothesis that an angioplasty balloon coated with the mTOR inhibitor zotarolimus (ZCB) would inhibit neointimal hyperplasia in a novel injury-based superficial femoral artery model in the familial hypercholesterolemic swine.

METHODS AND RESULTS

A total of 44 familial hypercholesterolemic swine were included (12 designated to study tissue pharmacokinetics and 32 to study safety and efficacy). Fogarty balloon denudation was performed in all superficial femoral artery segments, followed by balloon angioplasty. In the pharmacokinetic study, a total of 24 ZCBs (300 μg/cm(2)) were used. Zotarolimus was detected in arterial tissue at 5 minutes (162 ng/mg of tissue), 24 hours (5.9 ng/mg of tissue), and 28 days (0.007 ng/mg of tissue) after ZCB inflation. In the safety and efficacy study, superficial femoral artery segments were randomized to either high-dose (600 μg/cm(2), n=16), low-dose (300 μg/cm(2), n=16), or paired uncoated balloons (high-dose ZCB control, n=16; low-dose ZCB control, n=16). At 28 days, the percentage of angiographic stenosis was similar among all tested groups. Histological analysis demonstrated a reduction in neointimal formation in both ZCB groups compared with controls (high-dose ZCB 44% reduction, P=0.007; low-dose ZCB 22% reduction, P=0.08). There was no evidence of delayed arterial healing or vascular toxicity in any of the ZCB groups.

CONCLUSIONS

The single delivery of zotarolimus via coated balloon is feasible, and therapeutic levels are maintained up to 28 days. The ZCB technology appears to be effective in the reduction of neointimal proliferation in the superficial femoral artery of the familial hypercholesterolemic swine.

Effect of a dual drug-coated stent with abciximab and alpha-lipoic Acid in a porcine coronary restenosis model

Background and Objectives

The aim of this study was to examine the anti-proliferative and anti-inflammatory effects of a stent coated with abciximab and alpha-lipoic acid (ALA) in a porcine coronary overstretch restenosis model.

Materials and Methods

A total of 10 pigs were randomized into two groups (10 pigs, 10 coronaries in each group) in which the coronary arteries were stented with a dual-coated stent and a bare metal stent (control) by randomization. Stents were deployed with oversizing (stent/artery ratio 1.3 : 1) in the porcine coronary arteries, and histopathology was assessed 28 days after stenting.

Results

There was no significant difference in the injury score between the two groups. In the neointima, the lymphohistiocyte count was significantly lower in dual-coat stent group compared with the control stent group (120±85 cells vs. 159±80 cells, p=0.048). There was no significant difference in the fibrin score between the two groups (0.16±0.34 in the dual-coated stent group vs. 0.25±0.48 in the control stent group, p=0.446). The neointima area was not significantly different between both groups (1.55±0.8 mm² in dual-coated stent group vs. 1.40±0.86 mm² in the control stent group, p=0.447).

Conclusion

Although the dual-coated stent with abciximab and ALA showed no significant difference in inhibition of neointimal hyperplasia when compared with the bare metal stent, it was associated with a reduced inflammatory reaction when compared with the control stent in a porcine coronary restenosis model.

Time course of reendothelialization of stents in a normal coronary swine model: characterization and quantification

Late thrombosis of coronary drug-eluting stents is an infrequent but serious complication of percutaneous transluminal coronary angioplasty. The best predictor of this event is the lack of endothelialization of stent struts. The objective of this study is to characterize and quantify the time course of endothelialization of different stents implanted in nonatherosclerotic swine coronary arteries. Thirty-three Carbofilm-coated stents were implanted percutaneously in 11 anesthetized domestic, crossbred pigs (weight 25 ± 3 kg, 2 months old). Each animal received 1 stainless steel stent (SS), 1 cobalt-chromium stent (CCS), and 1 tacrolimus-eluting stent (TES) in each coronary artery. Follow-up periods were 1 day (n = 9 stents), 3 days (n = 9 stents), and 7 days (n = 15 stents). Longitudinal sections of the stented vessels were examined using scanning electron microscopy. At 1 day, there was scarce, patchy endothelialization with areas of fibrin; the endothelialization rate was similar for all the stents (SS, 29% ± 23%; CCS, 29% ± 24%; TES, 31% ± 25%; P = .9). At 3 days, there were more endothelial cells but with immature features and giant cells over fibrin; the endothelialization was greater in SS and CCS than in TES (SS, 79% ± 14%; CCS, 81% ± 17%; TES, 46% ± 9%; P = .007). At 7 days, arteries showed better endothelialization with few giant cells; the endothelialization was greater in SS and CCS than in TES (SS, 95% ± 4%; CCS, 98% ± 4%; TES, 79% ± 9%; P = .01). In conclusion, the described model is useful for the analysis of endothelialization of coronary stents and facilitates measurement of its rate of formation and characterization of the involved cell types.

Evaluation of polymer-based comparator drug-eluting stents using a rabbit model of iliac artery atherosclerosis

BACKGROUND

Although atherosclerotic models, especially in the rabbit, have existed for a long time, a comparative study of various drug-eluting stent (DES) implantations in atherosclerotic arteries have not been systematically studied.

METHODS AND RESULTS

New Zealand White rabbits (n=44) with induced atheroma received bilateral iliac artery stents: bare metal stent (BMS) (Driver) or a stent eluting zotarolimus (ZES) (Endeavor), sirolimus (SES) (Cypher), or everolimus (EES) (Xience V). After 28 days, tissues were harvested for histomorphometric analyses, en face analysis of endothelial coverage, and expression of endothelial nitric oxide synthase (eNOS). Area measurements of external elastic lamina and stent area were similar. Neointimal area was significantly less in all DES versus BMS, which was least in SES and EES; similar trends were noted for cell proliferation. Uncovered struts were greater for SES and EES and least in BMS, whereas ZES were in between and associated with the least fibrin. Macrophages of the neointima were significantly less for all DES relative to BMS. Plaque calcification underneath stents, however, was significantly greater in SES and ZES than in BMS. Although endothelial coverage in between struts was comparable between BMS and DES, there was significantly greater expression of eNOS in BMS and ZES relative to EES and SES.

CONCLUSIONS

The rabbit atherosclerotic model of stenting showed delayed healing and significantly greater reduction of neointima following implantation of SES and EES; however, delayed healing was less in ZES with greater neointima (but less than BMS), endothelial regrowth, and eNOS expression.

The representative porcine model for human cardiovascular disease

To improve human health, scientific discoveries must be translated into practical applications. Inherent in the development of these technologies is the role of preclinical testing using animal models. Although significant insight into the molecular and cellular basis has come from small animal models, significant differences exist with regard to cardiovascular characteristics between these models and humans. Therefore, large animal models are essential to develop the discoveries from murine models into clinical therapies and interventions. This paper will provide an overview of the more frequently used large animal models, especially porcine models for preclinical studies.

Effects of an alpha-4 integrin inhibitor on restenosis in a new porcine model combining endothelial denudation and stent placement

Restenosis remains the main complication of balloon angioplasty and/or stent implantation. Preclinical testing of new pharmacologic agents preventing restenosis largely rely on porcine models, where restenosis is assessed after endothelial abrasion of the arterial wall or stent implantation. We combined endothelial cell denudation and implantation of stents to develop a new clinically relevant porcine model of restenosis, and used this model to determine the effects of an α4 integrin inhibitor, ELN 457946, on restenosis. Balloon-angioplasty endothelial cell denudation and subsequent implantation of bare metal stents in the left anterior descending coronary, iliac, and left common carotid arteries was performed in domestic pigs, treated with vehicle or ELN 457946, once weekly via subcutaneous injections, for four weeks. After 1 month, histopathology and morphometric analyses of the arteries showed complete healing and robust, consistent restenotic response in stented arteries. Treatment with ELN 457946 resulted in a reduction in the neointimal response, with decreases in area percent stenosis between 12% in coronary arteries and 30% in peripheral vessels. This is the first description of a successful pig model combining endothelial cell denudation and bare metal stent implantation. This new double injury model may prove particularly useful to assess pharmacological effects of drug candidates on restenosis, in coronary and/or peripheral arteries. Furthermore, the ELN 457946 α4 integrin inhibitor, administered subcutaneously, reduced inflammation and restenosis in stented coronary and peripheral arteries in pigs, therefore representing a promising systemic therapeutic approach in reducing restenosis in patients undergoing angioplasty and/or stent implantation.

The impact of vascular endothelial growth factor-transfected human endothelial cells on endothelialization and restenosis of stainless steel stents

OBJECTIVES

The purpose of this study was to investigate the effects of gene transfection of endothelial cells with vascular endothelial growth factor (VEGF) on re-endothelialization and inhibiting in-stent restenosis.

METHODS

Stents coated with human umbilical vein endothelial cells (HUVECs) transfected with VEGF(121) were studied both in vitro and in vivo. In vitro studies were performed using a homemade extracorporeal circulation system. In vivo studies were performed using the rabbit abdominal aorta model.

RESULTS

In vitro studies confirmed that VEGF(121)-transfected cells adhered on the surface of stainless steel stents with over 90% of the surface covered within 24 hours of seeding. In vivo results showed that VEGF(121)-transfected HUVECs-coated stents were covered with seeding cells after implanting, and almost completely covered with cells after stent implantation for 1 week. In contrast, the non-endothelialized areas of bare metal stents and glutin/poly-L-lysine-coated stents were covered at 4 weeks, and the monolayers of cells were not observed, but fragile neointima was found on the surface. After 12 weeks, VEGF(121)-transfected HUVECs-coated stents significantly reduced the neointima area (0.78 ± 0.03 mm(2)) and stenosis (15.69 ± 2.61%) as compared with those for bare metal stents (neointima area = 2.26 ± 0.67 mm(2); the percentage of stenosis = 47.55 ± 7.10%;P < .01) and glutin/poly-L-lysine-coated stents (neointima area = 1.40 ± 0.37 mm(2); the percentage of stenosis = 31.37 ± 8.18%;P < .01).

CONCLUSION

In this small animal study, VEGF transfected human endothelial cells, when coated on stainless steel stents, reduce neointimal hyperplasia, promote endothelialization, and reduce in-stent restenosis. Additional studies with this technology are necessary to determine its ultimate utility in improving stents performance.

The pre-clinical animal model in the translational research of interventional cardiology

Scientific discoveries for improvement of human health must be translated into practical applications. Such discoveries typically begin at "the bench" with basic research, then progress to the clinical level. In particular, in the field of interventional cardiology, percutaneous cardiovascular intervention has rapidly evolved from an experimental procedure to a therapeutic clinical setting. Pre-clinical studies using animal models play a very important role in the evaluation of efficacy and safety of new medical devices before their use in human clinical studies. This review provides an overview of the emerging role, results of pre-clinical studies and development, and evaluation of animal models for percutaneous cardiovascular intervention technologies for patients with symptomatic cardiovascular disease.