Paclitaxel stent coating inhibits neointimal hyperplasia at 4 weeks in a porcine model of coronary restenosis

Drug delivery at the aortic valve tissues of healthy domestic pigs with a Paclitaxel-eluting valvuloplasty balloon

BACKGROUND

Restenosis occurs invariably within 1 year following balloon valvulopasty in aortic valve stenosis. The mechanism of restenosis seems to involve a dynamic cellular component that could be a target for drug inhibition. We investigated the feasibility of local drug delivery at the aortic valve tissues of healthy pigs with a paclitaxel-eluting balloon.

METHODS

Aortic valvuloplasty was performed in eight anesthetized domestic pigs using paclitaxel-eluting balloons (3 micro2) balloon surface area). They were assigned to two or four times 15-second balloon inflations and were sacrificed 30 minutes after final balloon inflation.

RESULTS

The aortic annulus to balloon diameter ratio was 1.15 +/- 0.07. The mean paclitaxel concentration in the aortic valve leaflets was 0.91 +/- 1.36 micro (0.34 +/- 0.05 micro in the two-inflation group, 1.48 +/- 1.86 micro in the four-inflation group, P = 0.23). The percentage of the total paclitaxel dose recovered in the aortic valve leaflets was 18 +/- 11(-6)% (13 +/- 6(-6)% and 25 +/- 14(-6)% in the two- and four-inflation group, P = 0.16).

CONCLUSION

Local drug delivery at the aortic valve leaflets of healthy pigs with a paclitaxel-eluting balloon is feasible and concentrations within the therapeutic window are detected 30 minutes after the procedure. The antirestenotic potential of this treatment should be studied.

Reduction of neointimal hyperplasia in porcine coronary arteries by 2-deoxy-D-glucose

BACKGROUND

The drug eluting stents have been shown to play a substantial role in preventing in-stent restenosis. This study was initiated to determine the efficacy of 2-deoxy-D-glucose (2-DG) in an in-stent restenosis model for reducing neointimal hyperplasia after coronary stent placement.

METHODS

In a porcine overstretch model, three kinds of stents were investigated (n = 12 per group): bare metal stents (BMS), rapamycin-eluted stents (RES), and BMS after intracoronary short-term application of 2-DG (DGS). After 42 days histomorphometric and histopathological analyses were performed.

RESULTS

Neointimal thickness (BMS: 0.38 +/- 0.08, RES: 0.24 +/- 0.11, DGS: 0.15 +/- 0.01), area stenosis (BMS: 47.39 +/- 2.76, RES: 32.2 +/- 2.08, DGS: 29.30 +/- 2.98) did not differ after 42 days between the RES and DGS but were significantly lower as compared to BMS only. Lumen area (BMS: 3.15 +/- 1.53, RES: 4.37 +/- 1.72, DGS: 4.77 +/- 2.14) was significantly higher in the DGS group in comparison to the BMS group. The calculated injury and inflammation scores were similar and re-endothelialization was confirmed in all groups.

CONCLUSIONS

This study could demonstrate that in porcine stent model neointimal hyperplasia and re-endothelialization after application of 2-DG are comparable to those seen in RES. Thus, 2-DG might be a promising clinical application for coronary stent coating.

Wall shear stress in intracranial self-expanding stents studied using ultra-high-resolution 3D reconstructions

BACKGROUND AND PURPOSE

Imaging of intracranial stents is constrained by resolution limits of current clinical imaging techniques providing insufficient visualization of deployment details and impeding its use for computational hemodynamic (CHD) simulations. The purpose of our study was to evaluate whether ultra-high-resolution MicroCT scans can illuminate detailed aspects of realistic in vitro stent deployment and serve as a reliable basis for CHD simulations of blood flow through self-expanding intracranial stents.

MATERIALS AND METHODS

A Neuroform Treo (NF) stent and an Enterprise (ENT) stent were deployed in identical straight polytetrafluoroethylene tubes filled with contrast agent. MicroCT scans were obtained at a spatial resolution of 14 mum and used for ultra-high-resolution 3D reconstructions. CHD simulations were performed, with particular emphasis on local flow behavior near the wall and struts. Flow differences between the geometrically different stents were studied.

RESULTS

MicroCT data revealed strut prolapse near the markers for the closed-cell design (ENT) stent and at some of the unconnected vertices of the open-cell design (NF) stent, which also showed some misalignments. CHD simulations showed that reverse wall shear stress occurred near some of the strut vertices and markers for the NF but only near the markers for the ENT.

CONCLUSIONS

This work demonstrates the feasibility of ultra-high-resolution MicroCT imaging in elucidating important details of intracranial stent deployment as a basis for accurate CHD simulations and in enabling a structural and hemodynamic study of realistically deployed stents with different geometry and design.

Comparison of changes in early inflammatory markers between sirolimus- and paclitaxel-eluting stent implantation

BACKGROUND

Systemic inflammation after coronary intervention identifies patients at increased risk of subsequent cardiac events. Cardiac events, especially in-stent restenosis, are less frequent after use of sirolimus-eluting stent (SES) compared with paclitaxel-eluting stent (PES). However, the underlying mechanism for this disparity is not well investigated. We hypothesize that an attenuated inflammatory response after SES implantation may be a contributor.

PURPOSE

In the present study, we sought to determine the early inflammatory response after SES implantation in patients with single-vessel disease compared with PES implantation, and evaluate the relationship between inflammatory response and late clinical outcomes in a randomized design.

METHODS

Thirty-two patients with stable angina were randomly enrolled into the two groups, SES or PSE group (n = 16 respectively). Peripheral blood samples were taken before PCI, 24 and 72 h after stenting. The plasma concentrations of C-reactive protein (CRP) and interleukin-6 (IL-6) were determined by enzyme-linked immunosorbent assay (ELISA). The clinical and angiographic follow-up was performed at 8 months after stenting.

RESULTS

The data showed that there was no significant difference in clinical and angiographic baseline characteristics between the two groups. The plasma CRP and IL-6 levels at 24 h after stenting were significant higher in both groups compared with baseline (p < 0.01 respectively). Likewise, the CRP levels at 72 h after stenting were also significant higher compared with baseline in both groups (p < 0.01 respectively). However, the plasma levels of IL-6 at 24 h and CRP at 72 h after stenting were higher in PES group compared with SES group (p < 0.05). At 8 months follow-up, the rates of major adverse cardiac events, target lesion revascularization, in-stent and in-segment restenosis were similar in both groups. However, the late loss in both in-stent and in-segment was significantly higher in the PES group than in SES group (p < 0.001 respectively).

CONCLUSIONS

Our findings suggest that a drug-eluting stent implantation could trigger a systemic inflammatory response as previously demonstrated. However, SES implantation results in a lower inflammatory response compared with PES implantation, which seems to be associated with greater late of in-stent and in-segment loss at 8-month follow-up with PES.

Effects of 2-Deoxy-d-Glucose on Proliferation of Vascular Smooth Muscle Cells and Endothelial Cells

2-Deoxy-d-glucose (2-DG) is a glucose analogue that has been proposed for cancer therapy due to its cytostatic properties. Its effect on the proliferation of smooth muscle cells and endothelial cells has not been fully clarified. The aims of this study were to investigate the effects of 2-DG on the proliferation of porcine aortic endothelial cells (PAEC) and porcine smooth muscle cells (PSMC), to establish an overview of its dose-dependent inhibitory capacity and to examine whether the short-term incubation of cells with 2-DG has an impact on cell proliferation in culture. Our results showed a dose-dependent significant inhibitory effect on proliferation, which was more pronounced in PSMC than in PAEC. Even after short-term incubation of cells with 2-DG, relevant inhibition of proliferation was documented. The clinical application of 2-DG might be a promising concept by inhibiting cells that show a potentially rapid proliferation in response to non-malignant stimuli, such as smooth muscle cells after intracoronary stenting.

Synthesis and characterization of a new polysaccharide-graft-polymethacrylate copolymer for three-dimensional hybrid hydrogels

Hybrid materials constituted by hydrophobic and hydrophilic biocompatible macromolecules are useful for biomedical applications. In this context, a well-known acrylic monomer (methyl methacrylate) was polymerized and grafted onto the polysaccharide dextran by the use of ceric ammonium nitrate as a redox initiator in aqueous nitric acid medium. The effects of concentrations of dextran, acrylic monomer, and ceric ions on the copolymerization yields were investigated in detail. The obtained polymers were studied by solubility measurements, Fourier transform infrared spectrometry, (13)C nuclear magnetic resonance spectroscopy, and viscosimetric analysis. Interestingly, we found conditions to form transparent and homogeneous thin films or 3D structures with hybrid properties. Indeed, the copolymer, but not dextran or PMMA, could be dissolved in water/THF (20/80 v/v). The thermomechanical properties of the resulting copolymer analyzed by differential scanning calorimetry and dynamic mechanical analysis showed the occurrence of a single glass-transition temperature and a marked difference with the two homopolymers. The cytocompatibility of the copolymer with human endothelial cells was evidenced by the normal cell adhesion, proliferation, and morphology after 5 days in culture on these gels. In conclusion, this type of copolymer with hybrid properties of two biocompatible macromolecules could be of great interest as a 3D scaffold or for coating in biomedical applications.

Low-dose paclitaxel elution by novel bioerodible sol-gel coating on stents inhibits neointima with low toxicity in porcine coronary arteries

OBJECTIVES

The present study was designed to evaluate a novel bioerodible sol-gel film coated paclitaxel-eluting stent (sol-gel-PES, 3 microg per stent) in a porcine coronary artery model.

BACKGROUND

Although current polymer-based PES decrease restenosis, the permanent polymer and bound drug have raised concerns regarding delayed vessel healing and late stent thrombosis.

METHODS

Polymer-based PES (poly-PES, n = 8), sol-gel-PES (n = 15), bare metal (BMS, n = 14), and sol-gel film only (sham, n = 12), stents were implanted in 17 juvenile pigs. Animals were terminated 28 days post-implant for angiographic restudy and complete histopathologic and histomorphometric analyses.

RESULTS

Angiographic late loss was equally reduced for both poly-PES and sol-gel-PES (0.51 +/- 0.64 and 0.61 +/- 0.52 mm, respectively) compared to both BMS and sham (0.98 +/- 0.74 and 1.25 +/- 0.72 mm, p < 0.05). Similarly beneficial results were observed for histomorphometric parameters of neointimal thickness and area, yielding reductions of in-stent stenosis by 43% and 48% for poly-PES, as well as 31% and 37% for sol-gel-PES, vs. BMS and sham, respectively (p < 0.05). Re-endothelialization was complete in all groups. Although the inflammatory cell infiltration and intramural thrombus scores were no different between poly- and sol-gel-PES, medial necrosis was increased for poly-PES (p < 0.05 vs. all others).

CONCLUSIONS

A novel bioerodible sol-gel film coated with low-dose paclitaxel demonstrates less toxicity to the coronary tunica media, while retaining effective inhibition of neointimal formation at 28 days.

Approaches for prevention of restenosis

Coronary artery disease is characterized by a narrowing (stenosis) of the arteries that supply blood to the tissue of the heart. Continued restriction of blood flow manifests itself as angina and ultimately myocardial infarction (heart attack) for the patient. Heart bypass was once the only treatment for this condition, but over the years percutaneous coronary intervention (PCI) has become an increasingly attractive alternative to medical therapy and surgical revascularization for the treatment of coronary artery disease. A vascular stent is a medical device designed to serve as a temporary or permanent internal scaffold, to maintain or increase the lumen of a blood vessel. Metallic coronary stents were first introduced to prevent arterial dissections and to eliminate vessel recoil and intimal hyperplasia associated with PCI. Further advancement in the treatment of coronary artery disease is the development of drug-eluting stents that dramatically reduce the incidence of in-stent restenosis to less than 5%. Local drug delivery offers the advantages of allowing a relatively high local concentration of drug at the treatment site while minimizing systemic toxic effect. This review describes approaches for prevention of restenosis. It focuses on drugs for prevention of restenosis, bare metal stents, and drug-eluting stents. It also describes recent advances in bioresorbable stents. One of the chapters is dedicated to our novel composite bioresorbable drug-eluting fibers, designed to be used as basic elements in drug-eluting stents.

Update on drug-eluting stents for prevention of restenosis

Despite the success of coronary stent implantations in the last decade, in-stent restenosis due to neointimal hyperplasia remains a problem to overcome. Neointimal hyperplasia is a vascular response to stent injury and mainly consists of proliferation of smooth muscle cells and deposition of extracellular matrix. Recently, local drug delivery has been advocated as a potential strategy to prevent in-stent restenosis. Unprecedented results have been obtained in early clinical studies on sirolimus-eluting and paclitaxel-eluting stents. Trials using various pharmaceutical coatings on different coronary stents are ongoing. More types of drug-eluting stents are expected on the market in the near future. Meanwhile, the evaluation of drug-eluting stents is entering the second phase in which the safety and efficacy in more complex lesion subsets and different clinical presentations are being investigated. Results including cost-benefit analyses are expected to have a tremendous impact on the practice of interventional cardiology in the next decade.

Effectiveness of statin-eluting stent on early inflammatory response and neointimal thickness in a porcine coronary model

BACKGROUND

Drug-eluting stent (DES) implantation is routine during coronary revascularization because DES significantly reduce rates of restenosis and target lesion revascularization compared with bare metal stent (BMS). However, available DES have limitations, such as late thrombosis because of delayed healing with poorer endothelialization and persistent local inflammation. Statins can inhibit cell proliferation, inflammation, and restore endothelial function. The present study evaluated the ability of stent-based cerivastatin delivery to reduce stent-induced inflammatory responses and adverse effects on endothelial function, and to inhibit neointimal hyperplasia in a porcine coronary model.

METHODS AND RESULTS

Pigs were randomized into groups in which the coronary arteries (9 pigs, 18 coronaries in each group) had either a cerivastatin-eluting stent (CES) or a BMS. All animals survived without any adverse effects. Inflammatory cell infiltration evaluated using scanning electron microscopy on day 3 after stenting was significantly decreased in the treated vessels (inflammation score: 1.15+/-0.12 vs 2.43+/-0.34, p<0.0001). At day 28, endothelial function with intracoronary infusion of bradykinin was preserved in both the CES and BMS groups. Volumetric intravascular ultrasound images revealed decreased intimal volume in the CES group (28.3+/-5.4 vs 75.9+/-4.2 mm3, p<0.0001). Histomorphometric analysis showed reduced neointimal area (1.74+/-0.45 vs 3.83+/-0.51 mm2, p<0.0001) in the CES group despite similar injury scores (1.77+/-0.30 vs 1.77+/-0.22, p=0.97).

CONCLUSION

In porcine coronary arteries CES significantly decreased neointimal hyperplasia with a decreased early inflammatory response and without endothelial dysfunction.

Endothelial progenitor cells, late stent thrombosis and delayed re-endothelialisation

A decade ago, the description of a primitive novel cell type capable of differentiating into cells expressing a mature endothelial cell -phenotype and their capacity to incorporate into regions of active angiogenesis, witnessed the emergence of endothelial progenitor cell (EPC) biology1. The development and maturation of this new concept in vascular biology has resulted in numerous studies describing the role of EPCs in a myriad of disease states where abnormalities of the vasculature have been implicated. Thus, from pre-eclampsia to pulmonary hypertension, erythropoietin administration to erectile dysfunction and cancer to coronary disease the discovery of EPCs has added greatly to the understanding of basic pathophysiology. However, it is in the study of coronary artery -disease where this paradigm shift has had greatest impact, not only regarding basic disease mechanisms, but in the rapid translation of these findings into a clinical context. The purpose of this review is to outline the current understanding of the EPC phenotypes and their relationship with risk factors for coronary disease. In addition, the potential problems of EPC dysfunction and its impact on percutaneous intervention will be appraised together with both pharmacological and stent based strategies to augment EPC -number and function.

Short- and long-term effects of a novel paclitaxel coated stent in the porcine coronary model

BACKGROUND

Drug eluting stents (DES) are unique in allowing sustained release for weeks after a single short intervention. The challenge with DES still remaining is the combination of a biocompatible drug-eluting matrix including an antiproliferative drug showing efficacy and safety in restenosis prevention. The aim of the present animal studies was to evaluate the novel paclitaxel coated Coroflex. Please stent in the porcine coronary model.

METHODS AND RESULTS

Stents were implanted into LAD and CX arteries of 49 domestic pigs. After 5 days, 4 weeks, 3 months, or 6 months, the animals underwent control angiography including dissection of the stented coronary arteries for histology. After 5 days, 3 and 6 months the Coroflex. Please stent was compared with its uncoated counterpart and a paclitaxel free but polymer coated version. After 28 days, an additional group received the Taxus Express(2) stent. After 5 days, healing with the paclitaxel coated stent was comparable to the uncoated bare metal stent as reflected in a similar neointimal proliferation. Compared to the Taxus stent, the new Coroflex. Please stent showed a similar neointimal proliferation after 4 weeks. Inflammatory reaction was comparable among the bare stent and polymer coated stent groups. Paclitaxel coating was associated with a slightly increased inflammatory reaction with both DES. After 3 and 6 months, all groups showed a similar neointimal proliferation and inflammatory reaction.

CONCLUSION

The present porcine studies demonstrate excellent safety of the new paclitaxel coated Coroflex stent in the porcine coronary stent model.

Angiographic and clinical outcome following paclitaxel-eluting stent (taxus) implantation: a single center experience

Coronary stents dramatically improve acute outcomes of percutaneous coronary interventions but also induce abundant intraluminal neointimal growth. Drug-eluting stents reduce intimal hyperplasia, the main cause of in-stent restenosis. The safety and beneficial effects of paclitaxel-eluting stents (Taxus) in patients treated in daily practice remains to be defined. The aim of this study was to report the late outcomes of Taxus implantation in patients with coronary artery disease. The study population consisted of 151 patients (202 stents) who had undergone coronary Taxus stent implantation between March 2003 and May 2005. Patients were eligible for enrollment if there was symptomatic coronary artery disease or positive functional testing, and angiographic evidence of single or multivessel disease with a target lesion stenosis of 70% in a 2.0 mm vessel. The control coronary angiographies were performed after stent deployment at 12 +/- 2.8 months, and approximately 2 years of follow-up was completed. The polymer-based paclitaxel-eluting stent has been shown to be effective in reducing restenosis. Patients were followed-up for 16.7 +/- 7.4 months. All patients survived after stent implantation, but 2 (1.3%) patients experienced acute myocardial infarction after 3 and 9 months following angioplasty. Recurrent angina pectoris was observed in 3 patients. Angiographic evidence of restenosis was observed in these 5 patients. Three patients underwent angioplasty because of re- stenosis, and coronary artery bypass grafting was conducted in the other 2 patients. The results indicate that Taxus stents can be implanted with a very high success rate and have encouraging long-term angiographic and clinical results.

Application of paclitaxel-eluting metal stents in renal artery of pig model

BACKGROUND AND PURPOSE

Recent reports concerning coronary, carotid, and femoral vasculature have proposed the use of drug-eluting metal stents (MS) to improve clinical and angiographic outcomes. Based on these reports, we used paclitaxel-eluting MS within an animal renal artery lumen and compared the results with those using a bare-metal stent.

MATERIALS AND METHODS

The experimental model in this study was the female pig renal artery. Ten pigs with weights ranging from 25 to 30 kg were used. Twenty stents were placed, two in each animal. The MS placement was randomly performed in either the right or left renal artery of each animal. In 10 arteries, a 3.5 x 18 mm R-stent (group A) was placed; in the remaining 10 arteries, a 3 x 32 mm paclitaxel-eluting coronary stent (T-stent, group B) was inserted. Patency was estimated with the use of digital subtraction angiography, CT angiography, and virtual endoscopy at 24 hours and 1 month poststent placement.

RESULTS

The positioning of the MS was successful in all cases. The initial angiographic result was maintained 24 hours after the intervention. No stent migration was seen, except for one paclitaxel stent that was acutely occluded. The one-month patency rate, as demonstrated by angiography, CT angiography, and virtual endoscopy, was 70% (8 arteries) in group A and 90% (9 arteries) in group B. The thickness of the endothelium and of the muscular coat was statistically significantly less in group B compared with group A (P = 0.0352 and P = 0.0046, respectively).

CONCLUSION

These preliminary experimental study results suggest that the paclitaxel-eluting MS is more efficient than the bare-metal stent when used within the pig renal artery. Further experimental and clinical studies are necessary to validate our preliminary encouraging results.

Inhibition of pseudointimal hyperplasia in swine TIPS models: the efficacy of local delivery of paclitaxel using a perforated balloon catheter

The aim of this study was to investigate the efficacy and feasibility of local delivery of paclitaxel to inhibit pseudointimal hyperplasia/intimal hyperplasia in swine transjugular intrahepatic portosystemic shunt (TIPS) models TIPS were created in seven healthy domestic swine (15-20 kg). Before TIPS stent insertion, we performed a short-term infusion of paclitaxel (treatment group: n = 4) and saline (control group: n = 3) into the TIPS tract using a balloon catheter in which two 0.010 inch holes were created on opposite sides of the balloon. Paclitaxel or saline was given to all animals via the hepatic parenchymal and venous outflow tract. The animals were followed for up to two weeks and then killed. Gross and histological evaluations of the shunts were performed, and the maximum pseudointimal/intimal hyperplasia thicknesses were calculated for each animal The average infusion time of paclitaxel or saline was 7.6 min (6-9 min). At gross and histological evaluation, considerable pseudointimal hyperplasia had formed in the control group and statistically significant differences were found upon microscopic evaluation in the maximum pseudointimal hyperplasia thickness between the control (2.41 mm, range 1.7-3.16 mm) and animals receiving paclitaxel (0.63 mm, range 0.42-0.98 mm, p<0.05) Local delivery of paclitaxel at the time of TIPS creation may have been effective in reducing pseudointimal/intimal hyperplasia in swine TIPS models.

Anti-inflammatory effect of abciximab-coated stent in a porcine coronary restenosis model

The aim of this study was to examine the anti-inflammatory effect of abciximab-coated stent in a porcine coronary overstretch restenosis model. Ten abciximab-coated stents, ten sirolimus-eluting stents (SES), and ten paclitaxel-eluting stents (PES) were deployed with oversizing (stent/artery ratio 1.3:1) in porcine coronary arteries, and histopathologic analysis was done at 28 days after stenting. There were no significant differences in the neointima area normalized to injury score and inflammation score among the three stent groups (1.58 +/- 0.43 mm(2), 1.57 +/-0.39 mm(2) in abciximab-coated stent group vs. 1.69 +/- 0.57 mm(2), 1.72 +/- 0.49 mm(2) in the SES group vs. 1.92 +/- 0.86 mm(2), 1.79 +/- 0.87 mm(2) in the PES group, respectively). In the neointima, most inflammatory cells were lymphohistiocytes. Significant positive correlations were found between the extent of inflammatory reaction and the neointima area (r=0.567, p<0.001) and percent area stenosis (r=0.587, p<0.001). Significant correlations were found between the injury score and neointimal area (r=0.645, p<0.001), between the injury score and the inflammation score (r=0.837, p<0.001), and between the inflammation score and neointimal area (r=0.536, p=0.001). There was no significant difference in the inflammatory cell counts normalized to injury score among the three stent groups (75.5 +/- 23.1/microL in abciximabcoated stent group vs. 78.8 +/- 33.2/microL in the SES group vs. 130.3 +/- 46.9/microL in the PES group). Abciximab-coated stent showed comparable inhibition of inflammatory cell infiltration and neointimal hyperplasia with other drug-eluting stents in a porcine coronary restenosis model.

Antirestenotic effects of a novel polymer-coated d-24851 eluting stent. Experimental data in a rabbit iliac artery model

Experimental and clinical data suggest that stents eluting antiproliferative agents can be used for the prevention of in-stent restenosis. Here we investigate in vitro the antiproliferative and apoptotic effect of D-24851 and evaluate the safety and efficacy of D-24851-eluting polymer-coated stents in a rabbit restenosis model (n = 53). Uncoated stents (n = 6), poly (DL: -lactide-co-glycolide) (PLGA)-coated stents (n = 7), and PLGA-coated stents loaded with 0.08 +/- 0.0025 microM (31 +/- 1 mug; low dose; n = 7), 0.55 +/- 0.02 microM (216 +/- 8 mug; high dose; n = 6), and 4.55 +/- 0.1 microM (1774 +/- 39 mug; extreme dose; n = 5) of D-24851 were randomly implanted in New Zealand rabbit right iliac arteries and the animals were sacrificed after 28 days for histomorphometric analysis. For the assessment of endothelial regrowth in 90 days, 12 rabbits were subjected to PLGA-coated (n = 3), low-dose (n = 3), high-dose (n = 3), and extreme-dose (n = 3) stent implantation. In vitro studies revealed that D-24851 exerts its growth inhibitory effects via inhibition of proliferation and induction of apoptosis without increasing the expression of heat shock protein-70, a cytoprotective and antiapoptotic protein. Treatment with low-dose D-24851 stents was associated with a significant reduction in neointimal area and percentage stenosis only compared with bare metal stents (38% [P = 0.029] and 35% [P = 0.003] reduction, respectively). Suboptimal healing, however, was observed in all groups of D-24851-loaded stents in 90 days in comparison with PLGA-coated stents. We conclude that low-dose D-24851-eluting polymer-coated stents significantly inhibit neointimal hyperplasia at 28 days through inhibition of proliferation and enhancement of apoptosis. In view of the suboptimal re-endothelialization, longer-term studies are needed in order to establish whether the inhibition of intimal growth is maintained.

Is there delayed restenosis in patients with coronary artery disease treated with sirolimus-eluting stent?

BACKGROUND

Although long-term follow-up after sirolimus-eluting stent implantation shows a sustained clinical benefit in several randomized and registered trials, little is known about the pattern of neointimal growth beyond the first 6 to 9 months. In this study, we therefore evaluated the possible delayed restenosis in patients with coronary artery disease treated with sirolimus-eluting stent.

METHODS

A total of consecutive 333 patients with 453 lesions were enrolled in this study (among 782 consecutive patients with 1023 lesions). Lesions were subjected to follow-up by quantitative coronary angiography, and patients were divided into two groups according to the time of follow-up by quantitative coronary angiography: early group (< or =270 days, n=270 with 369 lesions) and late group (>270 days, n=63 with 84 lesions). Binary restenosis was defined as stenosis of more than 50% of the lumen diameter in the target lesion.

RESULTS

Baseline clinical, demographic or angiographic characteristics were well balanced between the two groups. The in-stent restenosis rate was not significant between the early group and the late group (3.5 vs. 6.0%; P>0.05). The late loss and target lesion revascularization appeared higher in late group but there were no significant differences (0.15+/-0.38 mm vs. 0.24+/-0.44 mm; and 4.9 vs. 9.5%, P>0.05, respectively). Similarly, overall thrombosis rate was also same in both groups. In-segment restenosis was, however, higher in late group compared with that in early group (7.9 vs. 16.7%, P=0.013).

CONCLUSION

In this unrestricted population, the beneficial effects of sirolimus-eluting stent implantation extend out more than 1 year in real world practice, that has been confirmed by the results of the large randomized clinical trials. The late in-segment restenosis could, however, be found, suggesting that a prolonged clinical and angiographic surveillance in this subset of patients seems to be warranted.

Reduction of Stenosis Due to Intimal Hyperplasia After Stent Supported Angioplasty of Peripheral Arteries by Local Administration of Paclitaxel in Swine

PURPOSE

To assess if local intra-arterial administration of paclitaxel using drug-coated balloons or an admixture of paclitaxel to contrast medium inhibits stenosis after percutanous transluminal angioplasty (PTA) of peripheral arteries in a porcine overstretch model.

METHODS

Neointimal proliferation and stenosis were induced by overstretch and stenting of 40 peripheral arteries in 20 pigs. Paclitaxel was administered locally during PTA using coated balloons (n = 20) or dissolved in contrast medium (n = 10). Conventional balloons and contrast medium were used in a control group (n = 10). Reangiography with quantitative analysis was performed after 5 weeks.

RESULTS

On reangiography diameter stenosis and late lumen loss were significantly reduced by both methods of local drug delivery compared with control group; minimal luminal diameter was significantly larger in the treatment groups.

CONCLUSIONS

Local short-term administration of paclitaxel during PTA of peripheral arteries using balloons or contrast medium as drug carriers reduced stenosis due to intimal hyperplasia.

Coating with paclitaxel improves graft survival in a porcine model of haemodialysis graft stenosis

BACKGROUND

Most commonly resulting from intimal hyperplasia at the venous anastomosis, stenosis leading to thrombosis is a major cause of failure of polytetrafluoroethylene (PTFE) dialysis grafts. We recently reported that coating haemodialysis grafts with paclitaxel could reduce neointimal hyperplasia. This study tested whether paclitaxel-coating could prolong graft survival in a porcine model.

METHODS

PTFE grafts were double-coated with paclitaxel. Bilateral grafts were created between the carotid arteries and the external jugular veins, and we evaluated graft survival by weekly measurements of blood flow for 12 weeks.

RESULTS

We successfully implanted four pairs of paclitaxel-coated grafts and four pairs of control grafts in eight Landrace pigs. One control pig had to be euthanized at 4 weeks after graft placement. The grafts in the other three controls and four paclitaxel pigs survived until harvesting of the grafts. All paclitaxel-coated grafts remained patent for 12 weeks without decrease of blood flow. Median blood flow was 702 ml/min at three weeks and 818 ml/min at 12 weeks after placement. In contrast, the four control grafts lost luminal patency at 5, 6, 6 and 8 weeks, respectively. In Kaplan-Meier analysis, paclitaxel-coated grafts showed better survival than uncoated grafts (P = 0.011).

CONCLUSIONS

Double-coating with paclitaxel improved graft survival. Coated PTFE grafts may be effective for the prevention of graft failure in patients on haemodialysis.

Epothilone D, a microtubule-stabilizing compound, inhibits neointimal hyperplasia after rat carotid artery injury by cell cycle arrest via regulation of G1-checkpoint proteins

Epothilone D (Epo-D) is a paclitaxel-like microtubule-stabilizing agent that was isolated from the myxobacterium Sorangium cellulosum. Although Epo-D can inhibit proliferation in multiple tumor cell lines, the effect of Epo-D on neointimal hyperplasia after angioplasty has not been reported. The aim of the present study was to investigate the effects of Epo-D on neointimal hyperplasia using an in vivo rat carotid artery injury model. We demonstrated that local Epo-D treatment significantly reduced neointimal hyperplasia after in vivo rat carotid artery injury, and Epo-D potently inhibited DNA synthesis, cell cycle progression and cell proliferation after FBS- and PDGF-BB-stimulation; PDGF-BB has been identified as the most potent growth factor for stimulating the proliferation of activated rat aortic smooth muscle cells (RASMCs). To clarify the specific effects of Epo-D on cell cycle machinery, we examined its effects on cyclin-dependent kinase (CDK)2, CDK4, cyclin E, p27, and retinoblastoma (Rb) proteins as cell cycle-related proteins in cellular lysates from PDGF-BB-stimulated RASMCs. Epo-D treatment significantly decreased the level of CDK2 protein, but did not change the levels of CDK4 and cyclin E proteins. Furthermore, Epo-D inhibited the phosphorylation of Rb, a key regulator of the G1 to S phase transition in the cell cycle. These findings suggest that Epo-D may regulate the cell cycle G1-checkpoint proteins as its major molecular mechanism for inhibiting neointimal hyperplasia after in vivo rat carotid artery injury.

The efficacy of nanoscale poly[bis(trifluoroethoxy) phosphazene] (PTFEP) coatings in reducing thrombogenicity and late in-stent stenosis in a porcine coronary artery model

OBJECTIVES

Previous experimental studies have demonstrated that poly[bis(trifluoroethoxy)phosphazene] (PTFEP) nanocoated stents have antithrombotic characteristics, reduce in-stent stenosis, prevent wall inflammation, and do not hamper endothelialization. This study was designed to validate these findings in a porcine coronary artery model.

MATERIALS AND METHODS

PTFEP-coated (n = 15) and bare stents (n= 13) were implanted in coronary arteries of 18 mini-pigs (4- and 12-week follow-up). Primary study endpoints were thrombogenicity and in-stent stenosis, secondary study endpoints were inflammatory response and re-endothelialization evaluated by quantitative angiography and light microscopy.

RESULTS

No thrombus deposition occurred on any stent. At 4 weeks follow-up, the bare stents (n = 4) had a significantly smaller neointimal area (1.93 vs. 3.20 mm(2), P = 0.009). At 12 weeks, PTFEP-coated stents (n = 11) had significantly superior results in almost all parameters: neointimal area (2.25 vs. 2.65 mm(2), P = 0.034), neointimal height (204.46 vs. 299.41 microm, P = 0.048), percentage stenosis (38.25 vs. 50.42%, P = 0.019), and inflammation score (0.12 vs. 0.30, P = 0.029). Complete re-endothelialization was seen in both stent types at both intervals.

CONCLUSION

At long-term follow-up, the superior results of PTFEP-coated stents were characterized by a noteworthy reduction of neointimal growth and inflammatory response.

Prevention of restenosis: is angioplasty the answer?

"The drug-coated balloon has the potential to improve the limited results of drug-eluting stents"

Sirolimus and paclitaxel provoke different vascular pathological responses after local delivery in a murine model for restenosis on underlying atherosclerotic arteries

BACKGROUND

Drug-eluting stents (DES) have been introduced successfully in clinical practice to prevent post-angioplasty restenosis. Nevertheless, concerns about the safety of DES still exist.

OBJECTIVE

To investigate the vascular pathology and transcriptional responses to sirolimus and paclitaxel in a murine model for restenosis on underlying diseased atherosclerotic arteries.

METHODS

Atherosclerotic lesions were induced by placement of a perivascular cuff around the femoral artery of hypercholesterolaemic ApoE*3-Leiden transgenic mice. Two weeks later these cuffs were replaced either by sirolimus- or paclitaxel-eluting cuffs. The vascular pathological effects were evaluated after two additional weeks.

RESULTS

Both anti-restenotic compounds significantly inhibited restenotic lesion progression on the atherosclerotic plaques. Vascular histopathological analyses showed that local delivery of sirolimus has no significant adverse effects on vascular disease. Conversely, high dosages of paclitaxel significantly increased apoptosis, internal elastic lamina disruption, and decreased medial and intimal smooth muscle cells and collagen content. Moreover, transcriptional analysis by real-time RT-PCR showed an increased level of pro-apoptotic mRNA transcripts (FAS, BAX, caspase 3) in paclitaxel-treated arteries.

CONCLUSIONS

Sirolimus and paclitaxel are effective in preventing restenosis. Sirolimus has no significant effect on arterial disease. In contrast, paclitaxel at high concentration demonstrated adverse vascular pathology and transcriptional responses, suggesting a narrower therapeutic range of this potent drug. Since the use of overlapping stents is becoming more common in DES technology, this factor is important, given that higher dosages of paclitaxel may lead to increased apoptosis in the vessel wall and, consequently, to a more unstable phenotype of the pre-existing atherosclerotic lesion.

Epothilone B Inhibits Neointimal Formation after Rat Carotid Injury through the Regulation of Cell Cycle-Related Proteins

The abnormal proliferation of vascular smooth muscle cells (VSMCs) in arterial walls is an important pathogenetic factor of vascular disorders such as atherosclerosis and restenosis after angioplasty. Epothilone B, a novel potential antitumor compound, has a potent effect on preventing postangioplasty restenosis. Therefore, we established an in vivo rat carotid injury model and examined the potential effects of epothilone B on cardiovascular disease. We found that epothilone B potently prevented neointimal formation and in vivo VSMCs proliferation. In addition, we also showed that epothilone B significantly inhibited 5% fetal bovine serum (FBS)- and 50 ng/ml platelet-derived growth factor (PDGF)-BB-induced proliferation and cell cycle progression in rat aortic VSMCs. Furthermore, FBS and PDGF-BB induced the activations of extracellular signal-regulated kinases 1 and 2, Akt, phospholipase C gamma 1, and PDGF-receptor beta chain tyrosine kinase were not changed by epothilone B. However, epothilone B treatment caused a significant decrease in the level of cyclin-dependent protein kinase (CDK) 2, whereas it caused no change in the levels of cyclin E and down-regulated the phosphorylation of retinoblastoma, which plays a critical role in cell cycle regulation. Furthermore, levels of p27, an inhibitor of cyclin E/CDK2 complex, were significantly increased in VSMCs treated with epothilone B, indicating that this might be a major molecular mechanism for the inhibitory effects of epothilone B on the proliferation and cell cycle of VSMCs. These findings suggest that epothilone B can inhibit neointimal formation via the cell cycle arrest by the regulation of the cell cycle-related proteins in VSMCs.

Drug-Eluting Stents

The introduction of percutaneous transluminal coronary angioplasty has revolutionized the field of cardiology by providing patients with coronary artery disease immediate and effective therapy. Overshadowing the early success of angioplasty was the high rate of angiographic restenosis and recurrent symptoms at 6 months. The use of stents reduced the incidence of restenosis; however, the rise in the number of patients undergoing percutaneous interventions produced a new problem of restenosis occurring within the stent: in-stent restenosis (ISR). Mechanical approaches, including directional and rotational atherectomy and systemic pharmacotherapy, have failed to demonstrate a reduction in ISR in randomized clinical trials. Intravascular brachytherapy is currently the only approved therapy for ISR, although this treatment has numerous unresolved questions and is not effective in a large percent of patients. Drug-eluting stents have reduced the incidence of restenosis by providing localized therapy to the targeted lesion without systemic toxicity. The purpose of this review is to synthesize data from major clinical trials involving the 2 most successful agents used in the prevention of restenosis: sirolimus and paclitaxel. The cellular and molecular mechanisms of both ISR and restenosis postangioplasty derived from animal models will be introduced. Second, an overview of 3 alternate interventions that attempt to reduce the rates of restenosis is presented. Finally, the major randomized, controlled trials involving sirolimus and paclitaxel are described, and their clinical implications and use as a possible solution in the prevention of restenosis is discussed.

Coronary stents: a materials perspective

The objective of this review is to describe the suitability of different biomaterials as coronary stents. This review focuses on the following topics: (1) different materials used for stents, (2) surface characteristics that influence stent-biology interactions, (3) the use of polymers in stents, and (4) drug-eluting stents, especially those that are commercially available.

Recanalização da artéria femoral superficial com stents Zilver: técnica padronizada e análise retrospectiva de 3 anos

OBJETIVOS: Descrever a técnica de recanalização endovascular da artéria femoral superficial e fazer uma análise retrospectiva dos 3 primeiros anos da técnica. MÉTODOS: Análise retrospectiva dos pacientes tratados entre 2001 e 2004, visando obter as taxas de perviedade das recanalizações. A amostra considerada neste estudo consta de 79 artérias femorais superficiais recanalizadas em 61 pacientes, nos quais foram utilizados exclusivamente a técnica descrita e o mesmo modelo de stent de nitinol auto-expansível (Zilver, COOK). RESULTADOS: Dos 61 pacientes, 8% possuíam isquemia crítica de membro inferior e 92% apresentavam claudicação incapacitante refratária ao tratamento clínico. A melhora clínica foi observada e referida pelos pacientes numa relação direta à perviedade das recanalizações. A análise estatística demonstrou taxas acumuladas de perviedade primária assistida de 98, 91 e 84% em 12, 24 e 37 meses, respectivamente. As taxas de perviedade, entendida como fluxo continuado nas recanalizações, foram de 96, 93 e 93% em 12, 24 e 37 meses, respectivamente. CONCLUSÕES: Consideramos a técnica da recanalização da artéria femoral superficial um método ao mesmo tempo pouco invasivo, com reduzidas complicações e de consideráveis taxas de sucesso anatômico e perviedade, que, em conjunto, são capazes de proporcionar satisfação e qualidade de vida aos pacientes portadores de doença arterial obstrutiva periférica.

Polymer-based paclitaxel-eluting stents are superior to nonpolymer-based paclitaxel-eluting stents in the treatment of de novo coronary lesions

Although polymer coating of coronary stents enables sufficient loading and release of incorporated drugs, it has also been associated with potentially negative effects. This study compared the clinical, angiographic, and intravascular ultrasound (IVUS) outcomes of patients treated with polymer- versus nonpolymer-based paclitaxel-eluting stents (PESs). Sixty-five consecutive patients (70 de novo lesions) treated with polymer-based PESs (TAXUS, 1 microg/mm2 of paclitaxel; Boston Scientific Corp.) and 65 consecutive patients (65 de novo lesions) treated with nonpolymer-based PESs (V-Flex Plus, 2.7 microg/mm2 of paclitaxel; Cook, Inc.) were enrolled in the study. Six-month angiographic follow-up was performed on 54 lesions of the polymer-based PES group and 51 lesions of the nonpolymer-based PES group. IVUS at angiographic follow-up was performed in 61 of the first 70 included lesions. At 6-month IVUS follow-up, mean intimal hyperplasia cross-sectional area was 2.36 +/- 1.60 mm2 in the nonpolymer-based PES group versus 0.62 +/- 0.41 mm2 in the polymer-based PES group (p = 0.003). Implantation of polymer-based PESs resulted in significantly lower in-stent late lumen loss (0.22 +/- 0.27 vs 0.74 +/- 0.61 mm, respectively, p <0.001). In-stent binary restenosis rate was 5% versus 20%, respectively (p <0.001). Target lesion revascularization rate was 9% after implantation of polymer-based PES versus 18% (p = 0.128) after implantation of nonpolymer-based PES, and the major adverse cardiac event rate was 9% versus 23%, respectively (p = 0.032). In conclusion, polymer-based PESs result in superior angiographic and IVUS follow-up findings compared with nonpolymer-based PESs.

Paclitaxel Delivered to Adventitia Attenuates Neointima Formation Without Compromising Re-Endothelialization After Angioplasty in a Porcine Restenosis Model

PURPOSE

To investigate the effect of paclitaxel delivered into the adventitia of pig femoral arteries on neointima formation and hyperplasia as well as re-endothelialization.

METHODS

Paclitaxel or vehicle was delivered into the adventitia of pig femoral arteries using a needle injection catheter following balloon overstretch. Arteries were then serially examined by angiography, Evan's blue staining, morphometry, and immunohistochemistry for up to 12 weeks.

RESULTS

Local adventitial delivery of paclitaxel significantly attenuated neointima formation. The area of neointima (0.41+/-0.17 versus 2.75+/-0.81 mm(2), p<0.01), the ratio of intima to media (0.12+/-0.05 versus 0.86+/-0.35, p<0.05), and the degree of stenosis (12.80%+/-3.13% versus 47.06%+/-7.25%, p<0.01) were significantly lower in the paclitaxel-treated group compared to controls. Furthermore, cell proliferation was significantly diminished following adventitial delivery of paclitaxel from day 3 to 21 compared to controls. Complete re-endothelialization was observed 3 weeks after intervention in both groups of arteries treated with paclitaxel or vehicle alone.

CONCLUSION

Paclitaxel delivered into the adventitia of pig femoral arteries effectively attenuates neointima formation after angioplasty without compromising re-endothelialization. Adventitial drug delivery may therefore be an alternative to drug-eluting stents for the prevention of restenosis.

Hemodialysis vascular access dysfunction: a cellular and molecular viewpoint

Hemodialysis vascular access dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population. The major cause of hemodialysis vascular access dysfunction is venous stenosis as a result of neointimal hyperplasia. Despite the magnitude of the clinical problem, however, there has been a paucity of novel therapeutic interventions in this field. This is in marked contrast to a recent plethora of targeted interventions for the treatment of arterial neointimal hyperplasia after coronary angioplasty. The reasons for this are two-fold. First there has been a relative lack of cellular and molecular research that focuses on venous neointimal hyperplasia in the specific setting of hemodialysis vascular access. Second, there have been inadequate efforts by the nephrology community to translate the recent advances in molecular and interventional cardiology into therapies for hemodialysis vascular access. This review therefore (1) briefly examines the different forms of hemodialysis vascular access that are available, (2) describes the pathology and pathogenesis of hemodialysis vascular access dysfunction in both polytetrafluoroethylene grafts and native arteriovenous fistulae, (3) reviews recent concepts about the pathogenesis of vascular stenosis that could potentially be applied in the setting of hemodialysis vascular access dysfunction, (4) summarizes novel experimental and clinical therapies that could potentially be used in the setting of hemodialysis vascular access dysfunction, and, finally, (5) offers some broad guidelines for future innovative translational and clinical research in this area that hopefully will reduce the huge clinical morbidity and economic costs that are associated with this condition.

Control of drug accessibility on functional polyelectrolyte multilayer films

A surface coating based on polylysine/hyaluronic acid multilayers was designed and acted as a reservoir for an antiproliferative agent, paclitaxel (Taxol). Absolutely no chemical modification of polyelectrolytes or of the drug was needed and the final architecture was obtained in an extremely simple way using the layer-by-layer method. The paclitaxel dose available for human colonic adenocarcinoma cells HT29 seeded on the films could be finely tuned. Moreover, the accessibility of the drugs was controlled by adding on the top of the drug reservoir a capping made of synthetic polyelectrolyte multilayers. This capping was also required to allow adhesion of HT29 cells. Paclitaxel activity was maintained after embedding in the polyelectrolyte multilayers and cellular viability could be reduced by about 80% 96 h after seeding. The strategy described in this paper could be valuable for various other drug/cell systems.

Mechanisms of controlled drug release from drug-eluting stents

The clinical importance of drug-eluting stents (DESs) has been demonstrated by their unparalleled success in preventing restenosis after stenting procedures. The magnitude of success is historic despite their short history. The current DESs deliver a single drug aiming to prevent or minimize proliferation of smooth muscle cells. Since the restenosis process involves several different biological responses, the ability to deliver the right drugs at the right times is critical for further development of the second generation of DESs. As the type of drugs that can be delivered from DESs varies, it is imperative to understand the drug delivery mechanisms and the approaches available for drug coating on the stents. The drug delivery mechanisms of current DESs that have been used clinically and under clinical trials are explained.

The Taxus drug-eluting stent: a new paradigm in controlled drug delivery

The advent of drug-eluting stents (DES) has provided the medical community with a technology that is transforming the treatment of coronary artery disease. As the newest treatment modality available to the interventional cardiologist, drug-eluting stents have not only significantly reduced the risk of restenosis, but they are also allowing the interventionalists to treat more complex lesions in patients that would otherwise require more invasive bypass surgery. Development of these drug-device combination products has presented considerable challenges to the device industry because it involves a multi-disciplinary approach that combines conventional device design and manufacturing with the principles of controlled local drug delivery. This review article provides an in-depth discussion of the key elements of drug-eluting stents, focusing on the TAXUS paclitaxel-eluting stent as an example of this new class of product. Specific sections will review the drug and polymer matrix components, formulation development and evaluation, pre-clinical studies and clinical trial results.

Paclitaxel-eluting stents in coronary artery disease

PURPOSE

Clinical information regarding paclitaxel-eluting coronary artery stents is reviewed.

SUMMARY

Restenosis is a significant complication of percutaneous coronary intervention. Coronary artery stenting has reduced restenosis compared with traditional balloon angioplasty, although restenosis still occurs with bare-metal coronary artery stents. The pathogenesis of in-stent restenosis is believed to involve smooth-muscle-cell proliferation and migration in response to vessel injury. A neointimal layer of extracellular matrix and collagen forms, which may impinge on the vessel lumen. Paclitaxel inhibits vascular smooth-muscle-cell proliferation and reduces neointimal mass. Local delivery of paclitaxel through a coronary stent has been shown to reduce restenosis rates and percent diameter stenosis and to produce other angiographic benefits compared with bare-metal stents. Fewer major adverse coronary events are seen with paclitaxel-eluting stents, predominantly because of a reduction in the need for target-vessel revascularization with minimal impact on rates of mortality and myocardial infarction (MI). The Taxus Express(2) stent, the only approved paclitaxel-eluting stent in the United States, costs about three times as much as a bare-metal stent. Cost-effectiveness analyses are needed to determine if the Taxus stent is cost-effective in clinical practice.

CONCLUSION

Paclitaxel-eluting stents reduce the rates of restenosis and target-vessel revascularization compared with bare-metal stents and have comparable effects on mortality and MI rates.

Zotarolimus-eluting stents reduce experimental coronary artery neointimal hyperplasia after 4 weeks

AIMS

The addition of drug elution to coronary stents plays an integral role in coronary restenosis prevention. The present study was undertaken to determine the mechanism of action and the in vitro and in vivo efficacy of zotarolimus, a new chemical entity designed specifically for elution from phosphorylcholine (PC)-coated stents, for the reduction of neointimal hyperplasia in porcine coronary arteries.

METHODS AND RESULTS

In vitro studies of Zotarolimus bound to FKBP-12 potently inhibited smooth muscle cells (SMCs) and endothelial cell (EC) proliferation. Twenty PC-only and 20 stents eluting zotarolimus 10 microg/mm were implanted in the coronary arteries of 20 domestic juvenile swine. After 28 days, zotarolimus stents exhibited less area stenosis (22.4+/-8.6 vs. 35.7+/-13%, P = 0.01), less neointimal area (1.69+/-0.55 vs. 2.78+/-1.07 mm(2), P = 0.01), less neointimal thickness (0.25+/-0.07 vs. 0.38+/-0.13 mm, P = 0.01), and greater lumen area (6.07+/-1.39 vs. 5.02+/-1.3 mm2, P = 0.01). All arteries in both the polymer-only and polymer/drug stent showed near-complete healing and minimal toxicity. Zotarolimus did not affect the extrastent segments nor alter the overall artery size (external elastic lamina cross-sectional area 9.18+/-1.19 vs. 9.06+/-1.28 mm2, P = 0.7).

CONCLUSION

Zotarolimus binds to FKBP-12 and in vitro inhibits SMC and EC proliferation. Zotarolimus applied to PC-coated stents reduces neointima in the swine coronary model after 28 days. These results suggest potentially promising human clinical application for coronary stenting with this polymer/drug combination.

Irinotecan-eluting stents inhibited neointimal proliferation in hypercholesterolemic rabbit aortas

OBJECTIVE

To assess the effect of irinotecan-eluting stents (IS) on neointimal growth in the aortas of hypercholesterolemic rabbits and to determine other local histopathological effects such as necrosis, fibrin, and inflammatory reaction.

METHODS

Phosphorylcholine-coated stents were deployed in the aortas of hypercholesterolemic rabbits. Group 1 (control; n = 8) received unloaded stents, group 2 (n = 7) and group 3 (n = 9) received IS with 0.046 mg and 1.29 mg of irinotecan, respectively. Eight weeks after implantation the rabbits were killed. Neointimal thickness (NT) was assessed by morphometry. Semiquantitative injury score (from 0 to 3+) was used to analyze inflammatory infiltrate, fibrin deposits, and necrosis in the stented segments.

RESULTS

NT was reduced only in high-doses IS (G1, 167.4 +/- 20.8 mu; G2, 170.24 +/- 21.2 mu; G3, 111.56 +/- 12.7 mu; P < 0.05, G3 vs G1 and G2). Necrosis decreased significantly with IS [1.00 +/- 0.10 in G1 to 0.33 +/- 0.07 and 0.02 +/- 0.01 in G2 and G3, respectively] only in the media layer. The inflammatory infiltrate was present in the three layers of aortas from G1, but only decreased significantly in the intimae layer of the high-dose group [1.50 +/- 0.15 in G1 vs 1.00 +/- 0.18 in G3, P < 0.05].

CONCLUSION

Stents loaded with high-dose irinotecan inhibit NT in the aortas of hypercholesterolemic rabbits. This effect was accompanied by decreased inflammatory infiltrate and media necrosis.

The paclitaxel-eluting Coroflex™ please stent pilot study (PECOPS I): Acute and 6-month clinical and angiographic follow-up

BACKGROUND AND OBJECTIVES

Various active stent coatings significantly reduce restenosis rates and target lesion revascularization compared to bare metal stents. Therefore, the procedural and 6-month performance of the new paclitaxel-eluting Coroflex. Please stent was investigated.

METHODS

Ninety-seven patients (66 +/- 7.6 years, 34/97(35.1%) diabetics, 11/97(11.3%) unstable angina) were enrolled per protocol for elective single stent deployment into native coronary de-novo or post-PTCA restenotic lesions (stenosis: >or= 70%, < 100%; reference diameter >or= 2.25 mm and <3.3 mm; lesion length <or= 16 mm) with 13/97(13.4%) lesion type A, 64/97(66%) type B1, 20/97(20.6%) type B2). The mean reference diameter was 2.88 +/- 0.42 mm, the lesion length 10.03 +/- 2.93 mm, and the minimal lumen diameter 0.64 +/- 0.22 mm.

RESULTS

The success rates of procedure and study stent deployment were 100% and 94.8%, respectively. In 5/97(5.2%) two stents were implanted. Follow-up was performed clinically in 86/87(98.9%) and angiographically in 77/87(88.5%) patients after 6.1 +/- 0.7 months. Major adverse cardiac events occurred in 7/87(8%) 1/87(1.2%) subacute thrombosis 10.3hrs post procedure, 1/87(1.2%) myocardial infarction, 5/87(5.7%) target lesion revascularizations. The in-segment stenosis declined from 78 +/- 7.2% to 9.4 +/- 6.2% after stenting increasing to 31.9 +/- 18.6% at follow-up. The in-segment late loss and the late loss index were 0.47 +/- 0.6 mm and 0.23 +/- 0.29 resulting in 6/77(7.8%) in-segment restenoses three each of which were located either within or beyond the stent structure. The outcome was neither influenced by the prevalence of diabetes ( p = 0.4), hypercholesterolemia ( p = 1), hypertension ( p = 1), overweight ( p = 1), nor by the family history of coronary artery disease ( p = 0.7).

CONCLUSION

The data of the paclitaxel-eluting Coroflex. Please stent tested in PECOPS I are within the range other available paclitaxel-eluting stent.

In vitro study of drug loading on polymer-free oxide films of metallic implants

Traditionally, a drug that is loaded onto a metallic surface has to use various polymer bondings as its platform. Unfortunately, polymer coatings on a metallic surface cause numerous problems after implantation, such as late thrombosis, inflammation, and restenosis. This research was conducted to investigate whether an oxide layer can be used as a polymer-free platform for drug loading, especially for cardiovascular stents. The interaction and loading of heparin onto different oxide films on 316LVM stainless steel wire was confirmed in vitro by experimental studies using linear voltammetry, electrochemical impedance spectroscopy, and electron spectroscopy for chemical analysis. The eluting of heparin from heparinized surface was studied by using high-performance liquid chromatography, and activated clotting time in addition to linear voltammetry and electron spectroscopy for chemical analysis analyses. Experimental results show that amorphous oxide could be a potential substitute for the polymer coating of drug-loaded stents for minimizing metallic corrosion, inflammation, late thrombosis, and restenosis.

Drug-eluting stents: Sirolimus and paclitaxel differentially affect cultured cells and injured arteries

Sirolimus and paclitaxel eluted from stents inhibit cell proliferation and other cellular processes by dramatically different mechanisms. In this study, the effects of sirolimus and paclitaxel on cultured human coronary artery smooth muscle and endothelial cell function or cell cycle changes in balloon-injured arteries were directly compared. Both sirolimus and paclitaxel inhibited smooth muscle and endothelial cell proliferation. However, only paclitaxel inhibited smooth muscle and endothelial cell migration at low (nM) concentrations. Sirolimus arrested smooth muscle and endothelial cells in the G0/G1 phase of the cell cycle without inducing apoptosis while paclitaxel produced apoptosis in both cell types at low nanomolar concentrations. Although both agents blocked neointimal formation, sirolimus applied locally to injured rat carotid arteries increased the percentage of cycling vascular cells in G0/G1 without inducing apoptosis while paclitaxel increased the percentage of cycling cells in S and G2/M phases while inducing apoptosis. These results suggest that sirolimus reduces neointimal hyperplasia through a cytostatic mechanism while paclitaxel produces apoptotic cell death.