First human experience with the 17-beta-estradiol–eluting stent

Heparin-Tagged PLA-PEG Copolymer-Encapsulated Biochanin A-Loaded (Mg/Al) LDH Nanoparticles Recommended for Non-Thrombogenic and Anti-Proliferative Stent Coating

Drug-eluting stents have been widely implanted to prevent neointimal hyperplasia associated with bare metal stents. Conventional polymers and anti-proliferative drugs suffer from stent thrombosis due to the non-selective nature of the drugs and hypersensitivity to polymer degradation products. Alternatively, various herbal anti-proliferative agents are sought, of which biochanin A (an isoflavone phytoestrogen) was known to have anti-proliferative and vasculoprotective action. PLA-PEG diblock copolymer was tagged with heparin, whose degradation releases heparin locally and prevents thrombosis. To get a controlled drug release, biochanin A was loaded in layered double hydroxide nanoparticles (LDH), which are further encapsulated in a heparin-tagged PLA-PEG copolymer. LDH nanoparticles are synthesized by a co-precipitation process; in situ as well as ex situ loading of biochanin A were done. PLA-PEG-heparin copolymer was synthesized by esterification reaction, and the drug-loaded nanoparticles are coated. The formulation was characterized by FTIR, XRD, DSC, DLS, and TEM. In vitro drug release studies, protein adhesion, wettability, hemocompatibility, and degradation studies were performed. The drug release was modeled by mathematical models to further emphasize the mechanism of drug release. The developed drug-eluting stent coating is non-thrombogenic, and it offers close to zero-order release for 40 days, with complete polymer degradation in 14 weeks.

Cardiovascular stents: overview, evolution, and next generation

Compared to bare-metal stents (BMSs), drug-eluting stents (DESs) have been regarded as a revolutionary change in coronary artery diseases (CADs). Releasing pharmaceutical agents from the stent surface was a promising progress in the realm of cardiovascular stents. Despite supreme advantages over BMSs, in-stent restenosis (ISR) and long-term safety of DESs are still deemed ongoing concerns over clinically application of DESs. The failure of DESs for long-term clinical use is associated with following factors including permanent polymeric coating materials, metallic stent platforms, non-optimal drug releasing condition, and factors that have recently been supposed as contributory factors such as degradation products of polymers, metal ions due to erosion and degradation of metals and their alloys utilizing in some stents as metal frameworks. Discovering the direct relation between stent materials and associating adverse effects is a complicated process, and yet it has not been resolved. For clinical success it is of significant importance to optimize DES design and explore novel strategies to overcome all problems including inflammatory response, delay endothelialization, and sub-acute stent thrombosis (ST) simultaneously. In this work, scientific reports are reviewed particularly focusing on recent advancements in DES design which covers both potential improvements of existing and recently novel prototype stent fabrications. Covering a wide range of information from the BMSs to recent advancement, this study mostly sheds light on DES's concepts, namely stent composition, drug release mechanism, and coating techniques. This review further reports different forms of DES including fully biodegradable DESs, shape-memory ones, and polymer-free DESs.

Biodegradable polymer-based, argatroban-eluting, cobalt-chromium stent (JF-04) for treatment of native coronary lesions: final results of the first-in-man study and lessons learned

AIMS

The aim of the study was to investigate the six-month angiographic and nine-month clinical follow-up outcomes in a first-in-man study using the biodegradable polymer-based cobalt-chromium argatroban-eluting stent (JF-04) for treatment of native coronary atherosclerotic lesions.

METHODS AND RESULTS

A total of 31 patients with either stable or unstable angina, or silent myocardial ischaemia, exhibiting de novo coronary lesions were enrolled at seven Japanese sites. The lesions were treated with the JF-04 stent after predilatation. The primary endpoint was angiographic in-stent late loss six months after implantation. The secondary endpoints included angiographic restenosis and in-stent volume obstruction by intravascular ultrasound at six months and target vessel failure (TVF) at nine months. Procedural success was achieved in 100% of cases. At six months, angiographic in-stent late loss was 1.01±0.48 mm and binary restenosis was observed in nine cases (29.0%). Among these restenotic cases, most (n=8) demonstrated advanced angiographic restenosis patterns, including diffuse/proliferative restenosis and total occlusion. At nine months, TVF was observed in four cases (12.9%), exclusively attributed to target vessel revascularisation.

CONCLUSIONS

This argatroban-eluting stent failed to inhibit neointimal hyperplasia sufficiently, despite the theoretical benefits and promising clinical experience with local drug delivery.

Update on drug-eluting coronary stents

The introduction of drug-eluting stents (DES) to interventional cardiology practice has resulted in a significant improvement in the long-term efficacy of percutaneous coronary interventions. DES successfully combine mechanical benefits of bare-metal stents and stabilizing the lumen, with direct delivery and the controlled elution of a pharmacologic agent to the injured vessel wall to suppress further neointimal proliferation. The dramatic reduction in restenosis has resulted in the implementation of DES in clinical practice, and has rapidly expanded the whole spectrum of successfully treatable coronary conditions, particularly in high-risk patients and complex lesions. In this review the authors present current data on DES. Currently, two types of DES are available in the USA: sirolimus-eluting stents (SES) CYPHER (Cordis Corp., FL, USA) and paclitaxel-eluting stents (PES) TAXUS (Boston Scientific, MA, USA), and many more are on the way to approval. In addition to sirolimus and paclitaxel, several other drugs have been successfully used in DES. Everolimus and ABT-578 are both analogs of sirolimus that also have immunosuppressive and antiproliferative properties. Another approach in the development of DES is to use drugs that can accelerate re-endothelialization and restore normal endothelial function following vascular injury. Recent advances in vascular gene transfer have also demonstrated potential new treatment modalities for cardiovascular disease, particularly in the treatment of vascular restenosis.

Advanced cardiovascular stent coated with nanofiber

Nanofiber was explored as a stent surface coating substance for the treatment of coronary artery diseases (CAD). Nanofibers loaded with nanoparticles containing β-estradiol were developed and exploited to prevent stent-induced restenosis through regulation of the reactive oxygen species (ROS). Eudragit S-100 (ES), a versatile polymer, was used as a nanoparticle (NP) base, and the mixtures of hexafluoro-2-propanol (HFIP), PLGA and PLA at varying ratios were used as a nanofiber base. β-Estradiol was used as a primary compound to alleviate the ROS activity at the subcellular level. Nile-Red was used as a visual marker. Stent was coated with nanofibers produced by electrospinning technique comprising the two-step process. Eudragit nanoparticles (ES-NP) as well as 4 modified types of NP-W (ES-NP were dispersed in H2O, which was mixed with HFIP (1:1 (v/v) and then subsequently added with 15% PLGA), NP-HW (ES-NP were dispersed in H2O, which was mixed with HFIP (1:1 (v/v)) already containing 15% PLGA), NP-CHA (ES-NP with a chitosan layer were added in H2O, which was mixed with HFIP (1:1 (v/v)) containing 15% PLGA), and NP-CHB (ES-NP with a chitosan layer were added in H2O, which was mixed with HFIP (1:1 (v/v)) containing the mixture of PLGA and PLA at a ratio of 4:1) were developed, and their properties, such as the loading capacity of β-estradiol, the release profiles of β-estradiol, cell cytotoxicity and antioxidant responses to ROS, were characterized and compared. Among composite nanofibers loaded with nanoparticles, NP-CHB had the maximal yield and drug-loading amount of 66.5 ± 3.7% and 147.9 ± 10.1 μg, respectively. The nanofibers of NP-CHB coated on metallic mandrel offered the most sustained release profile of β-estradiol. In the confocal microscopy study, NP-W exhibited a low fluorescent intensity of Nile-Red as compared with NP-HW, indicating that the stability of nanoparticles decreased, as the percentage volume of the organic solvent increased. Nanofibers incorporated with β-estradiol yielded a high endothelial proliferation rate, which was about 3-fold greater than the control (without β-estradiol). The cells treated with the enhanced level of H2O2 (>1 mM: as ROS source) were mostly nonviable (81.1 ± 12.4%, p < 0.01), indicating that ROS induce cell apoptosis and trigger the rupture of atheroma thin layer in a concentration dependent manner. Nanofibers containing β-estradiol (0.5 mM) lowered cellular cytotoxicity from 25.2 ± 4.9% to 8.1 ± 1.4% in the presence of 600 μM H2O2, and from 86.8 ± 8.4% to 59.4 ± 8.7% in the presence of 1.0 mM H2O2, suggesting that β-estradiol efficiently protected hPCECs from ROS induced cytotoxicity. The level of NO production in hPCECs in the presence of β-estradiol after 6 days of incubation was much greater than that of the control without β-estradiol. In summary, nanofibers loaded with nanoparticles containing β-estradiol could be used as a suitable platform for the surface coating of a cardiovascular stent, achieving enhanced endothelialization at the implanted sites of blood vessels.

Preventing restenosis in early drug-eluting stent era: recent developments and future perspectives

Restenosis is the major limitation of the successful therapy of percutaneous coronary intervention (PCI) for patients with coronary artery disease. The problem was appreciated in the late 1970s to early 1980s. Only in recent years, anti-restenotic therapy has achieved a breakthrough with the development of drug-eluting stents. Here, we provide an overview about pathological mechanisms of restenosis after PCI. Present therapeutic approaches to overcome restenosis and recent clinical results are revisited, and some major concerns in the post-drug-eluting stent era are discussed.

Estrogen-eluting stents

Coronary stenting is routinely utilized to treat symptomatic obstructive coronary artery disease. However, the efficacy of bare metal coronary stents has been historically limited by restenosis, which is primarily due to excessive neointima formation. Drug-eluting stents (DES) are composed of a stainless steel backbone encompassed by a polymer in which a variety of drugs that inhibit smooth muscle cell proliferation and excessive neointima formation are incorporated. DES have significantly reduced the incidence of restenosis but are also associated with a small (~0.5% per year) but significant risk of late stent thrombosis. In that regard, estrogen-eluting stents have also undergone clinical evaluation in reducing restenosis with the additional potential benefit of enhancing reendothelialization of the stent surface to reduce stent thrombosis. Estrogen directly promotes vasodilatation, enhances endothelial healing, and prevents smooth muscle cell migration and proliferation. Due to these mechanisms, estrogen has been postulated to reduce neointimal hyperplasia without delaying endothelial healing. In animal studies, estrogen treatment was effective in decreasing neointimal hyperplasia after both balloon angioplasty and stenting regardless of the method of drug delivery. The first uncontrolled human study using estrogen-coated stents demonstrated acceptable efficacy in reducing late lumen loss. However, subsequent randomized clinical trials did not show superiority of estrogen-eluting stents over bare metal stents or DES. Further studies are required to determine optimal dose and method of estrogen delivery with coronary stenting and whether this approach will be a viable alternative to the current DES armamentarium.

Vessel shrinkage as a sign of atherosclerosis progression in type 2 diabetes: a serial intravascular ultrasound analysis

OBJECTIVE

The aim of this study was to determine the natural history of vascular remodeling of atherosclerotic plaques in patients with type 2 diabetes and the predictors of vessel shrinkage.

RESEARCH DESIGN AND METHODS

In this serial intracoronary ultrasound (IVUS) study, 237 coronary segments from 45 patients enrolled in the DIABETES I, II, and III trials were included. Quantitative volumetric IVUS analyses (motorized pullbacks at 0.5 mm/s) were performed in the same coronary segment after the index procedure and at the 9-month follow-up. Nontreated mild lesions (angiographic stenosis <25%) with > or =0.5 mm plaque thickening and length of > or =5 mm assessed by IVUS were included. Vessel shrinkage was defined as a Deltaexternal elastic membrane area/Deltaplaque area < 0. Statistical adjustment by multiple segments and multiple lesions per patient was performed.

RESULTS

Vessel shrinkage was identified in 37.1% of segments and was associated with a significant decrease in lumen area at 9 months (vessel shrinkage, 10 +/- 4 mm(2) vs. non-vessel shrinkage, 11 +/- 4 mm(2); P = 0.04). Independent predictors of vessel shrinkage were insulin requirements (odds ratio 4.6 [95% CI 1.40-15.10]; P = 0.01), glycated hemoglobin (1.5 [1.05-2.10]; P = 0.02), apolipoprotein B (0.96 [0.94-0.98]; P < 0.001), hypertension (3.7 [1.40-10.30]; P = 0.009), number of diseased vessels (5.6 [2.50-12.50]; P < 0.001), and prior revascularization (17.5 [6.50-46.90]; P < 0.001).

CONCLUSIONS

This serial IVUS study suggests that progression of coronary artery disease in patients with type 2 diabetes may be mainly attributed to vessel shrinkage. Besides, vessel shrinkage is influenced by insulin requirements and metabolic control and is associated with more advanced coronary atherosclerosis.

Inhibition of phosphodiesterase has an additive effect on estrogen's ability to inhibit collagen synthesis in vascular smooth muscle cells

Several studies have shown that estrogen has the ability to decrease collagen synthetic rates in vascular smooth muscle cells (VSMCs) by increasing cellular cyclic AMP (cAMP) levels. Phosphodiesterase inhibitors have also been shown to inhibit collagen synthesis in VSMCs presumably by preventing the degradation of cAMP. Since estrogens and phosphodiesterase inhibitors are used clinically, it is important to determine the potential for phosphodiesterase inhibitors to potentiate estrogen's ability to inhibit collagen synthesis in VSMCs. The results of the present study demonstrate that the phosphodiesterase inhibitors cilostamide and Ro-20-1724 had an additive effect on estrogen's ability to inhibit collagen synthesis in VSMC. Also, the data suggests that phosphodiesterase inhibitors mediated this additive effect by increasing cellular levels of cAMP.

The forgotten player of in-stent restenosis: Endothelial dysfunction

Reduced coronary endothelium-dependent vasodilation may play a role in the pathophysiology of in-stent restenosis. Moreover, endothelial dysfunction may cause to progression of athetrosclerosis in coronary arteries in patients undergoing percutaneous coronary intervention, especially stent deployment. We believe that the agents improving endothelial dysfunction and healing-enhanced stents, namely vascular endothelial growth factor (VEGF)-eluting stents, estradiol-eluting stents and stents attracting endothelial cells, might take an important role in the prevention of stent restenosis strategies in the near future.

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.

Estradiol accelerates endothelial healing through the retrograde commitment of uninjured endothelium

Although the accelerative effect of 17beta-estradiol (E2) on endothelial regrowth has been clearly demonstrated, the local cellular events accounting for this beneficial vascular action are still uncertain. In the present work, we compared the kinetics of endothelial healing of mouse carotid arteries after endovascular and perivascular injury. Both basal reendothelialization as well as the accelerative effect of E2 were similar in the two models. Three days after endothelial denudation, a regenerative area was observed in both models, characterized by similar changes in gene expression after injury, visualized by en face confocal microscopy (EFCM). A precise definition of the injury limits was only possible with the perivascular model, since it causes a complete and lasting decellularization of the media. Using this model, we demonstrated that the migration of uninjured endothelial cells precedes proliferation (bromodeoxyuridine incorporation) and that these events occur at earlier time points with E2 treatment. We have also identified an uninjured retrograde zone as an intimate component of the endothelial regeneration process. Thus, in the perivascular model, the regenerative area can be subdivided into a retrograde zone and a reendothelialized area. Importantly, both areas are significantly enlarged by E2. In conclusion, the combination of the electric perivascular injury model and EFCM is well adapted to the visualization of the endothelial monolayer and to investigate cellular events involved in reendothelialization. This process is accelerated by E2 as a consequence of the retrograde commitment of an uninjured endothelial zone to migrate and proliferate, contributing to an enlargement of the regenerative area.

Inhibition of plaque neovascularization and intimal hyperplasia by specific targeting vascular endothelial growth factor with bevacizumab-eluting stent: An experimental study

Neovascularization is associated with destabilization of atheromatic plaques. Increased expression of vascular endothelial growth factor (VEGF) is important in the process of neovascularization. We assessed the effect of bevacizumab, a monoclonal antibody specific for VEGF, on neovascularization. We used 12 New Zealand rabbits under atherogenic diet for 3 weeks. We immersed a phosphorycholine coated stent into a solution of 4 ml bevacizumab according to previous studies. Twelve eluting stents and 12 non-eluting stents were implanted in the middle segment of the rabbit's iliac arteries. Follow-up angiography was performed at 4 weeks and tissues were obtained for histological analysis. The procedure of stent loading with bevacizumab and stent implantation was successful. There was no difference in angiographic measurements before, after implantation and at follow-up between the two groups. mean neointimal thickness (0.09+/-0.02 versus 0.12+/-0.02 mm, p<0.01), and mean neointimal area (1.08+/-0.09 versus 1.20+/-0.12 mm(2), p<0.01) were less in the bevacizumab treated segments. bevacizumab-treated arterial segments demonstrated significantly decreased microvessel density compared with the control group (1.69+/-0.06 CI: 1.65-1.73 versus 15.68+/-0.56 CI: 15.32-16.04 vessels per mm(2), p<0.001) and vegf expression was decreased in the media and adventitia of bevacizumab group. Endothelialization, inflammation and injury scores were similar between the two groups. These results suggest that bevacizumab-eluting stent implantation in rabbit iliac arteries is safe, and inhibits neovascularization without affecting the endothelialization.

Delivery of large biopharmaceuticals from cardiovascular stents: a review

This review focuses on new and emerging large-molecule bioactive agents delivered from stent surfaces in drug-eluting stents (DESs) to inhibit vascular restenosis in the context of interventional cardiology. New therapeutic agents representing proteins, nucleic acids (small interfering RNAs and large DNA plasmids), viral delivery vectors, and even engineered cell therapies require specific delivery designs distinct from traditional smaller-molecule approaches on DESs. While small molecules are currently the clinical standard for coronary stenting, extension of the DESs to other lesion types, peripheral vasculature, and nonvasculature therapies will seek to deliver an increasingly sophisticated armada of drug types. This review describes many of the larger-molecule and biopharmaceutical approaches reported recently for stent-based delivery with the challenges associated with formulating and delivering these drug classes compared to the current small-molecule drugs. It also includes perspectives on possible future applications that may improve safety and efficacy and facilitate diversification of the DESs to other clinical applications.

The cell cycle: a critical therapeutic target to prevent vascular proliferative disease

Percutaneous coronary intervention is the preferred revascularization approach for most patients with coronary artery disease. However, this strategy is limited by renarrowing of the vessel by neointimal hyperplasia within the stent lumen (in-stent restenosis). Vascular smooth muscle cell proliferation is a major component in this healing process. This process is mediated by multiple cytokines and growth factors, which share a common pathway in inducing cell proliferation: the cell cycle. The cell cycle is highly regulated by numerous mechanisms ensuring orderly and coordinated cell division. The present review discusses current concepts related to regulation of the cell cycle and new therapeutic options that target aspects of the cell cycle.

Angiographic and 3D intravascular ultrasound assessment of overlapping bare metal stent and three different formulations of drug-eluting stents in patients with diabetes mellitus

OBJECTIVES

The aim of this study was to examine the impact of overlapping bare-metal stent (BMS) and three different formulations of drug-eluting stent (DES) on intimal hyperplasia (IH) response of patients with diabetes mellitus (DM).

METHODS

Forty-nine DM patients treated with overlapping BMS (19 lesions), sirolimus-eluting stent (SES 12 lesions), paclitaxel-eluting stent (PES 8 lesions) or tacrolimus-eluting stent (TES 10 lesions) were studied. Baseline and 9-month follow-up volumetric intravascular vascular ultrasound (IVUS) and quantitative coronary angiography (QCA) analysis were performed in the entire stented segment and in the overlapped (OL) and non-overlapped (non-OL) subsegments. Clinical outcomes were evaluated at 1-year follow-up.

RESULTS

Post-procedure (PO-) QCA measurements were similar in all stent groups, and between OL and non-OL subsegments in each individual type of stents. Percent IH was lower in SES and PES vs. BMS (p < 0.05). Percent IH was significantly greater in OL subsegment compared with non-OL subsegment in BMS (p < 0.05), but not in all type of DES groups. SES showed significantly less %IH compared with PES and TES in OL and non-OL subsegments. Vessel area at the OL remained unchanged from PO to FU in all type of DES and BMS groups. There were no aneurysm formation and no stent thrombosis up to 1-year follow-up.

CONCLUSIONS

Overlapping BMS is associated with enhanced IH response in diabetic patients, whereas overlapping DES, particularly SES and PES, appear effective to inhibit IH without detectable late vascular adverse effects.

Unusual Cell Adhesion and Antithrombogenic Behavior of Citric Acid-Cross-Linked Collagen Matrices

We have developed a novel biodegradable matrix that has unusual cell adhesion and antithrombogenic properties. The prepared biodegradable matrix was alkali-treated collagen (AlCol) cross-linked with citric acid derivative (CAD), named as AlCol-CAD. The swelling ratio of AlCol-CAD decreased with increasing CAD concentration, but with a further increase of the CAD concentration, the swelling ratio of AlCol-CAD also began to increase; this behavior showed a point where the swelling ratio reached a minimum value before increasing. The highest shrinkage states of 7.5%, 15%, and 30% (w/v) in AlCol-CAD were observed at CAD concentrations of 10, 20, and 40 mM, respectively, and moreover, the residual amino groups in AlCol-CAD were found to decrease with increasing CAD concentration. On the other hand, increases in carboxyl groups of 7.5% and 15% (w/v) in AlCol-CAD were found at CAD concentrations higher than 10 and 20 mM, respectively, whereas, at CAD concentrations from 10 to 40 mM, no significant change of the carboxyl groups was observed in 30% (w/v) AlCol-CAD. Human umbilical vein endothelial cell (HUVEC) adhesion on 15% (w/v) AlCol-CAD increased with increasing CAD concentration up to 20 mM and then slightly decreased. In the case of 30% (w/v) AlCol-CAD, the number of adhered HUVECs on AlCol-CAD increased with increasing CAD concentration. Furthermore, it was observed that HUVECs had excellent cell proliferation on 15% (w/v) AlCol-CAD at CAD concentrations of 20 and 40 mM, after incubation for 7 days. No thrombus formation was observed on 15% (w/v) AlCol-CAD at CAD concentrations above 20 mM. These results suggested that the 15% (w/v) AlCol-CAD at CAD concentrations above 20 mM has both HUVEC adhesion and antithrombogenic properties.

Does Addition of Estradiol Improve the Efficacy of a Rapamycin-Eluting Stent?

OBJECTIVES

This study aimed to assess the efficacy of a rapamycin plus 17-beta-estradiol-eluting stent versus a rapamycin-eluting stent in patients with coronary artery disease.

BACKGROUND

Estradiol promotes rapid re-endothelialization of coronary stents in animal models, but it is not known whether combining this drug with rapamycin represents an improved drug-eluting stent technology in terms of reduced lumen renarrowing.

METHODS

In this randomized study, we enrolled 502 patients with de novo lesions in native coronary arteries who were randomly assigned to receive either a polymer-free, estradiol plus rapamycin-eluting stent (ERES) (n = 252) or a polymer-free, rapamycin-eluting stent (RES) (n = 250). The primary end point was in-stent late lumen loss in the follow-up angiography. Secondary end points were binary angiographic restenosis, target lesion revascularization, combined incidence of death and myocardial infarction, and incidence of stent thrombosis during 1 year after randomization. The study was designed to test for the superiority of the ERES compared with the RES with respect to in-stent late lumen loss.

RESULTS

Late lumen loss (0.52 +/- 0.58 mm vs. 0.51 +/- 0.58 mm, p = 0.83), the incidence of binary angiographic restenosis (17.6% vs. 16.9%, p = 0.85), the incidence of target lesion revascularization (14.3% vs. 13.2%, p = 0.72), the combined incidence of death and myocardial infarction (7.9% vs. 8.0%, p = 0.98), and the incidence of stent thrombosis (0.8% vs. 1.2%, p = 0.99) were not significantly different between the ERES group and the RES group.

CONCLUSIONS

No apparent beneficial effect is obtained by adding estradiol to a polymer-free rapamycin-eluting stent during the first year after the procedure. (The ISAR-PEACE trial; http://clinicaltrials.gov/ct/show/NCT00402636?order=1; NCT00402636).

Estrogen-eluting stent implantation inhibits neointimal formation and extracellular signal-regulated kinase activation

OBJECTIVES

The goal of this study was to evaluate the efficacy and the mechanism of 17beta-estradiol-eluting stents on inhibiting neointimal formation of abdominal aortas in rabbits fed with high fat diet.

BACKGROUND

Animal experiments have shown that local delivery of estrogen reduced neointimal formation after coronary angioplasty. Preliminary trial of estrogen-eluting stent implantation in patients with coronary disease also suggests a reduction in restenosis.

METHODS

We implanted 17beta-estradiol-eluting stents, or control phosphorylcholine- coated stents, or bare metal stents of abdominal aortas in rabbits fed with high fat diet. Histology, immunohistochemistry, and Western blot analysis were used to assess the efficacy and mechanism of inhibiting neointimal formation of 17beta-estradiol-eluting stents.

RESULTS

Western blot analysis revealed marked increase in ERK phosphorylation in 30 min after deployment of phosphorylcholine-coated or bare metal stents, indicating activation of MAP kinase pathway. Immunohistochemistry showed intense staining of phospho-ERK in the medial smooth muscle cells in stent-implanted region. Extensive neointimal hyperplasia developed 12 weeks after stenting. In contrast, we observed significant inhibition of ERK phosphorylation and neointimal thickening in estrogen-eluting stent-implanted animals. Immunohistochemistry of factor VIII-related antigen demonstrated an accelerated reendothelialization as compared with the bare metal stent or phosphorylcholine-coated stent-implanted controls.

CONCLUSIONS

Current study suggests that estrogen-eluting stents reduce neointimal formation and hence prevent restenosis after angioplasty possibly by inhibiting ERK activation in smooth muscle cells and promoting reendothelialization.

Relocation of minimal luminal diameter after bare metal and drug-eluting stent implantation: Incidence and impact on angiographic late loss

Late loss (LL) has been a fundamental angiographic end-point in drug-eluting stents (DES) clinical trials. However, calculation of LL may be affected by a mismatch between post-procedure (PO) and follow-up (FU) sites of the minimal lumen diameter (MLD). Our aims were to investigate the incidence and methodological implications of the relocation of MLD after bare metal (BMS), sirolimus-eluting (SES), and paclitaxel-eluting (PES) stent implantation. Data from DIABETES I and II trials, which involved diabetic patients treated with BMS, SES, and PES, were analyzed. Angiographic data with matched projections between PO and 9-month angiographic FU were included. In-stent, in-lesion, and in-segment analyses included conventional and customized sub-segmental (5-mm/subsegment) methodology. MLD relocation was considered when the sites of MLD shifted a distance >> the intrinsic variability of the method. Conventional LL, site matched LL, maximal LL (MaxLL), and average LL (AvgLL) were calculated. Relationships between various LL and 1-year target lesion revascularization (TLR) were investigated. Post MLD was located distally, outside the stent, in > or =65% of the analyses. At FU, MLD relocation occurred in 70.5% (BMS), 40% (SES), and 35% (PES). MLD shifted > or =11 mm on average, mainly towards the stented segment. MLD relocation still occurred in 42.8% (BMS), 33.7% (SES), and 36.4% (PES), when analysis was restricted to in-stent segment. Among LL measurements, MaxLL showed the best association with TLR rates. Relocation of the MLD is a frequent phenomenon after both BMS and DES, and should be taken into account when calculating LL. Comprehensive LL analyses, including MaxLL and AvgLL, provides a better appraisal of the biological and clinical effectiveness of DES.

17Beta-estradiol effects on human coronaries and grafts employed in myocardial revascularization: a preliminary study

Background

This study was undertaken to compare the in vitro effects of 17β-estradiol on human epicardial coronary arteries, resistance coronary arteries and on arterial vessels usually employed as grafts in surgical myocardial revascularization.

Methods

Coronary artery rings (descending coronary artery, right coronary artery, circumflex coronary artery, first septal branch) and arterial graft rings (internal thoracic artery, gastro-epiploic artery) obtained from human heart donors with heart not suitable to cardiac transplantation were connected to force transducer for isometric force recording. Precontracted specimens with and without endothelium were exposed to increasing concentration of 17β-estradiol (3–30–300–3000 nmol/l) and to vehicle (0.1% v/v ethanol). We also evaluated the effects of 17β-estradiol on vessels before and 20 minutes after exposure to L-monomethyl-arginine and indomethacin.

Results

17β-estradiol induced a significant relaxation in all precontracted vessels (mean maximum effect: 78,6% ± 8,5). This effect was not different among the different rings and was not related to the presence of endothelium. N-monomethyl-L-arginine and indomethacin did not modify 17β-estradiol relaxant effect.

Conclusion

The vasodilator action of the 17β-estradiol is similar on coronary arteries, resistance coronary arteries and arterial vessels usually employed as grafts in myocardial revascularization.

Estrogen decreases neointimal hyperplasia and improves re-endothelialization in pigs

BACKGROUND

17-Beta-estradiol inhibits smooth muscle cell proliferation and migration and accelerates endothelial cell repair in response to balloon injury. The aim of this study was to determine whether administration of estrogen is associated with decreased neointimal hyperplasia after stenting in the porcine model.

METHODS AND RESULTS

Twenty-two farm female pigs 7 months old were oophorectomized and at the third day normal saline (11 pigs) or 20 mg of estradiol valerate (11 pigs), modified release, were administered intramuscularly. At the 10th day after oophorerectomy, 1 or 2 stainless steel stents were implanted in the right coronary artery in each pig, and at the 17th day, normal saline or 10 mg estradiol valerate, modified release, were administered intramuscularly in the two groups. Pigs were sacrificed 28 days after stent implantation and histomorphometric analysis of the coronary arteries was performed (20 stents from the estrogen and 18 stents from the control groups). In the estrogen group, neointimal proliferation area was 1.42+/-0.55 mm(2), whereas in the control group, 1.96+/-0.89 mm(2) (p=0.02). Area stenosis was 39+/-13% and 49+/-16% in the two groups, respectively (p=0.07). Re-endothelialization was 2.67+/-0.34 and 2.22+/-0.46 in the two groups, respectively (p<0.010). The injury score was similar between the two groups.

CONCLUSIONS

These data suggest that intramuscular administration of estrogen accelerates the endothelial cell repair in response to injury and reduces intimal hyperplasia in the porcine model.

Characterization of plaque prolapse after drug-eluting stent implantation in diabetic patients: a three-dimensional volumetric intravascular ultrasound outcome study

OBJECTIVES

The aim of this research was to evaluate the plaque prolapse (PP) phenomenon after bare-metal (BMS) and drug-eluting stent (DES) implantation in patients with diabetes mellitus using 3-dimensional volumetric intravascular ultrasound (IVUS).

BACKGROUND

Plaque prolapse has been observed in up to 22% of patients treated with BMS. Diabetic patients have a larger atherothrombotic burden and may be more prone to have PP. However, the incidence of PP and its clinical impact after DES implantation is unknown.

METHODS

Three-dimensional IVUS was performed after intervention and at 9-month follow-up in 168 patients with diabetes (205 lesions) treated with bare BX Velocity stents ((BX Velocity/Sonic, Cordis, Johnson & Johnson) (BMS, n = 65), sirolimus-eluting stents (Cypher, Cordis) (SES, n = 69), and paclitaxel-eluting stents (Taxus, Boston Scientific, Natick, Massachusetts) (PES, n = 71). Intravascular ultrasound data at the sites of PP were compared with stented segments without PP in each lesion. Outcomes were evaluated at 9- and 12-month follow-up.

RESULTS

There were 42 sites of PP (BMS = 11, SES = 11, PES = 20, p = NS) in 34 stented segments of 205 (16.6%) lesions. Plaque prolapse was more frequent in the right coronary artery and in chronic total occlusion lesions. Post-procedure PP volume was 1.95 mm3 in BMS, 2.96 mm3 in SES, and 4.53 mm3 in PES. At follow-up, tissue volume increased at PP sites in both BMS and PES, but not after SES. Neointimal proliferation was similar between PP and non-PP sites. Stent thrombosis and restenosis rates were similar between PP and non-PP lesions.

CONCLUSIONS

The incidence of PP after implantation of new generation tubular stents in patients with diabetes remains high. Drug-eluting stent implantation was not associated with increased risk of PP. Plaque prolapse was not associated with stent thrombosis or increased neointimal proliferation.

Vascular Effects of Sirolimus-Eluting Versus Bare-Metal Stents in Diabetic Patients

OBJECTIVES

A predefined intravascular ultrasound (IVUS) substudy was performed to evaluate the vascular effects of sirolimus-eluting stent (SES) versus bare-metal stent (BMS).

BACKGROUND

The Diabetes and Sirolimus-Eluting Stent (DIABETES) trial is a prospective, multicenter, randomized, controlled trial aimed at demonstrating the efficacy of the SES compared with BMS in diabetic patients.

METHODS

Serial intravascular ultrasound analyses were performed in 140 lesions (SES = 75; BMS = 65) immediately after stent implantation and at nine-month follow-up. Vessel, luminal, and stent mean areas and volumes were evaluated at both edges and within the stented segment. Qualitative assessment of residual dissections and stent apposition were also performed.

RESULTS

Baseline clinical and angiographic characteristics were similar between groups. At 9 months, in-stent neointimal hyperplasia (NIH) mean area and volume were significantly reduced in the SES group (median NIH area 0.01 mm2 [0.0 to 0.1] vs. 2.0 mm2 [1.0 to 2.9] and median NIH volume 0.11 mm3 [0 to 2.1] vs. 35.3 mm3 [16.6 to 62.6]; both p < 0.0001). In the SES group, stent edges evidenced significant increase in lumen dimensions mainly due to significant increase in vessel volume, whereas those of the BMS group presented vessel shrinkage leading to significant lumen reduction. Late acquired incomplete stent apposition was observed in 11 lesions (14.7%) in the SES group and 0 in the BMS group (p = 0.001). At one year, no stent thromboses occurred in malapposed stents.

CONCLUSIONS

The SES implantation effectively inhibits NIH in diabetic patients. The antirestenotic effect of SES is also appreciated at the stent edges. Late acquired stent malapposition is a frequent phenomenon in diabetic patients treated with SES.

The effect of medroxyprogesterone acetate on estrogen-dependent risks and benefits--an attempt to interpret the Women's Health Initiative results

The results of the two arms of the Women's Health Initiative (WHI) study allow a comparative assessment of the contribution of the progestogen component to the changes in risk of cardiovascular disease and cancer during treatment of postmenopausal women with conjugated equine estrogens and medroxyprogesterone acetate (CEE/MPA). However, the high proportion of older and overweight or obese women compromises any conclusions, since we estimate that 50% of the women would have the metabolic syndrome. In overweight postmenopausal women with hyperinsulinemia, the risk of breast cancer is elevated and cannot be increased further by hormone replacement therapy (HRT). Therefore, the non-significant, but consistent reduction in breast cancer risk during treatment with CEE alone might be based on an improvement of hyperinsulinemia. The 24% increase in breast cancer risk in the CEE/MPA group can be regarded as an artifact due to very low numbers of breast cancer diagnoses in the placebo group of women who had received HRT prior to the WHI study. The elevated risk of venous thromboembolism and the transient increase in the risk of coronary heart disease (CHD) during treatment with CEE/MPA but not CEE alone suggests a direct effect of MPA on the vessel wall. MPA has been demonstrated to upregulate the thrombin receptor, the thrombin-induced production of tissue factor and procoagulatory activity in the vessel wall owing to its glucocorticoid activity. In contrast, CEE alone reduced non-significantly the risk of CHD in women aged 50-59 years, suggesting that primary prevention is possible if estrogen replacement therapy is initiated early. As clinical studies on the effect of different progestogens combined with estrogens are scarce, a possible superiority of progestogens other than MPA remains to be proven.

Intravascular ultrasound characterization of the "black hole" phenomenon after drug-eluting stent implantation

An intraluminal echolucent tissue, dubbed "black hole," has been identified by intravascular ultrasonography after intracoronary brachytherapy. This study reports the characteristics and incidence of the black hole in patients treated with drug-eluting stent implantation using a sirolimus-eluting stent (SES). We included intravascular ultrasound data from the Compassionate Use of Sirolimus-Eluting Stent (SECURE, n = 61 lesions) registry, a study involving patients in whom previous brachytherapy had failed, and the DIABETES trial (n = 165 lesions), a multicenter, randomized study comparing SES versus bare metal stents in diabetic patients. Intravascular ultrasound follow-up was scheduled at 8 months (SECURE trial, post-brachytherapy population) and 9 months (DIABETES trial). In the SECURE population, a black hole was observed in 10 patients (19.6%). Seven black hole segments had significant intimal hyperplasia (> 10%). A black hole accounted for 27% of total intraluminal tissue. In the DIABETES trial, 2 patients (2.5%) in the SES group and none in the bare metal stent group showed echolucent intimal hyperplasia. In conclusion, a black hole occurred frequently after implantation of a SES in patients in whom intracoronary brachytherapy had previously failed. Black holes were also identified in a nonirradiated population, although the incidence was lower than in the post-brachytherapy patients. Bare metal stents were not associated with this phenomenon.

Technology Insight: an overview of research in drug-eluting stents

Drug-eluting stents (DESs) have revolutionized interventional cardiology over the past few years to the extent that balloon angioplasty and bare stents did in the 1980s and 1990s. The first DESs became commercially available in Europe in 2002 and in the US in 2003, and it is estimated that up to 80% of patients who undergo stent implantation in the US now receive a DES. Two devices, Cypher sirolimus-eluting stents (Cordis Corporation, Miami Lakes, FL) and Taxus paclitaxel-eluting stents (Boston Scientific Corporation, Natick, MN), are currently licensed for sale in both regions. Multiple new devices using different drugs, carriers and stents are currently undergoing clinical trials to establish their efficacy and obtain approval for commercialization. While the remarkable reduction of restenosis has accounted for the success of DESs, concerns remain regarding long-term follow-up; published 3-year follow-up results are available for fewer than 200 patients overall. Reports of late stent thrombosis have emerged, particularly in relation to discontinuation of antiplatelet therapy. In patients treated with DESs, long-term administration of at least one antiplatelet agent must be continued following completion of the mandatory dual antiplatelet regimen. In this review, we summarize the findings available for DESs so far, discuss emerging safety and efficacy data, and look at the future directions for these devices.

17-beta-estradiol eluting stent versus phosphorylcholine-coated stent for the treatment of native coronary artery disease

In this study we randomly compared the estradiol eluting stent (17-beta-E) with phosphorylcholine (PC)-coated stents in native coronary arteries. The incidence of angiographic restenosis was 23% in the 17-beta-E group and 31% in the PC group (p = 0.34). The major adverse cardiovascular event rates were also similar in the 2 groups (17% in the 17-beta-E group vs 22% in the PC group, p = 0.47). The mid-term clinical and angiographic outcomes did not indicate superiority of the 17-beta-E eluting stent over the control PC stent.

[Drug eluting stents: from evidence based medicine to clinical practice]

Drug eluting stents have been developed in order to reduce in-stent restenosis observed with a 20 to 40% rate in bare-stents. Neoinitimal smooth muscular cells proliferation have been characterized as the corner stone of in-stent restenosis. Consequently, many anti-mitotic and anti-inflammatory drugs have been evaluated in a new stent generation, so called coated stents or drug eluting stents. Three major components must be considered to evaluate the beneficial effects: the bare-stent, the drug, and the deliverance system, most usually a polymer. For the present, sirolimus eluting stent and paclitaxel eluting stent are available in the market with the european conformity label considering evidence based medicine established in randomized trials. Both stents have been shown to reduce in-stent restenosis incidence to less than 7%. Long-term follow-up still remain expected and would give answers to two safety queries: what is about the incidence of late stent thrombosis, what is about mal-apposition consequences in clinical feature. Utilization of drug eluting stent in clinical practice must considered materials with european conformity and must applied French society of cardiology guidelines restricting implantation to patients who meet high-risk restenosis criteria. Medicoeconomic approach must be considered beneficial at the present only in patients with high restenosis risk. Long-term antiplatelet regimen of aspirin and clopidogrel must be considered to avoid late stent thrombosis.

Four-Year Angiographic and Intravascular Ultrasound Follow-Up of Patients Treated With Sirolimus-Eluting Stents

Background— Despite the proven superiority of sirolimus-eluting stents (SESs) compared with bare stents in the first year after implantation, long-term outcomes of patients treated with these novel devices remain unknown. Our goal was to evaluate the clinical, angiographic, and intravascular ultrasound (IVUS) outcomes of patients treated with SESs 4 years after implantation.

Methods and Results— The study included 30 patients treated with sirolimus-eluting Bx Velocity stenting (slow release [SR; n=15] and fast release [FR; n=15]). Twenty-six patients underwent 4-year angiographic and IVUS follow-up and had matched assessments at all time points (index and 4-, 12-, 24-, and 48-month follow-up). One death occurred during the study period in a patient with a patent SES. There were no target-vessel revascularizations or thromboses between 2- and 4-year follow-up examinations. There was no stent thrombosis, target-lesion revascularization, death, or myocardial infarction in the SR group up to 4 years. Cumulative event-free survival rate was 87% for the total population (80% in the FR group and 93% in the SR group). In-stent late loss was slightly greater in the FR group (0.41±0.49 mm) than the SR group (0.09±0.23) after 4 years. One patient in the FR group had a 52% in-stent restenosis lesion. Percent neointimal hyperplasia volume, as detected by IVUS, remained minimal after 4 years (FR=9.1% and SR=5.7%).

Conclusions— This study confirms the longevity of the optimal outcomes observed in patients treated with sirolimus-eluting Bx Velocity stents 4 years after implantation. In-stent lumen dimensions remained essentially unchanged at 4-year follow-up, particularly in the population treated with the currently available SES (SR formulation).

The drug-based pipeline against restenosis

More than 1 million percutaneous coronary interventions (PCIs) are performed yearly worldwide. Restenosis is the recurrent narrowing that can occur within 6 months following an initially successful PCI. Although drug-eluting stents have accomplished remarkable success, restenosis has not been eliminated and optimisation of both the polymers and drugs associated with them is desirable. This article reviews the presently available and potential preventive approaches against restenosis, including the sirolimus and paclitaxel drug-eluting stents.

Angiotensin Antagonism in Coronary Artery Disease

The renin-angiotensin system (RAS) is an ancient and complex cascade of homeostatic reactions aimed at regulating primordial functions that ensure organ perfusion through the control of blood pressure and the regulation of renal-cardiac activity. However, the over-expression or lack of compensatory mechanisms of any of its components may initiate detrimental effects that potentially lead to disease, a balance that makes the RAS a sequence with a labile physiological equilibrium and with a strong harm potential. These characteristics of the RAS in general, and of the angiotensin converting enzyme (ACE) in particular, make it not only an important complex for the regulation of blood pressure and neuropeptide metabolism, but also a fascinating subject of study from a biochemical, evolutionary and genetic point of view. Pharmacological interventions that influence the RAS by inhibiting the ACE or the angiotensin II type 1 receptor (AT1R) have demonstrated sustained efficacy in reducing the incidence of cardiovascular events and, consequently, vascular mortality in several clinical situations. ACE inhibitors and angiotensin II receptor antagonists (ARAs) reduce blood pressure and have cardio- and vasculoprotective effects. Anti-atherosclerotic effects have also been attributed to these drugs. For these reasons, it has been hypothesised that RAS inhibitors could also reduce the recurrence of ischaemic events after myocardial revascularisation procedures, namely coronary artery by-pass graft surgery (CABG) or percutaneous coronary interventions (PCI). Information available on the effect of ACE inhibitors and ARAs in patients with coronary artery disease (CAD) previously treated with revascularisation techniques indicates a substantial reduction of mortality and infarction in these patients. However, data regarding the progression of CAD, restenosis or reocclusion of vascular conduits of the coronary circulation after myocardial revascularisation are inconsistent. In most studies, the administration of ACE inhibitors neither improved the ischaemic threshold nor reduced the need for new revascularisation procedures. On the contrary, ACE inhibitors have been associated with higher restenosis rates after PCI in some retrospective series. Conversely, a single, exploratory randomised trial demonstrated that the selective AT1R antagonist valsartan significantly reduced stent restenosis after PCI. In patients undergoing CABG, ACE inhibitors did not reduce the risk of graft degeneration or occlusion. Studies that evaluated a possible anti-atherosclerotic effect of ACE inhibitors (including some large randomised trials) have generally been negative.

Which Parameter Should Be Chosen as Primary Endpoint for Randomized Drug-Eluting Stent Studies?

In Europe, 1,108 percutaneous coronary interventions (PCIs) per one Mio inhabitants are currently annually performed, most of them with stent implantation. Drug-eluting stents have been the focus of attention of interventional coronary therapy since the RAVEL study was first presented in September 2001 at the European Society of Cardiology Meeting. Ever since, numerous studies have assessed the effects of various antiproliferative and anti-inflammatory substances and a variety of different stents was used as platform, either covered with polymer carriers of different chemical and physical properties or without a polymer carrier. CE- or FDA-certified drug-eluting stents are increasingly replacing the use of bare metal stents to reduce in-stent restenosis. Today, physicians have a choice of several approved drug-eluting stents and, therefore, need some evidence-based guidance through the "jungle of information" to make the right decisions. Even when focusing on randomized trials, differences between the studies regarding primary endpoints and sample sizes exist, making it difficult to compare the various drug-eluting stent studies. Randomized studies use either nonclinical (i.e., angiographic diameter stenosis, in-stent MLD, or in-stent late lumen loss) or clinical (i.e., TVF, TVR, and MACE) parameters as primary endpoints. Choosing an angiographic parameter as primary endpoint results in two major limitations: first, a significant improvement of an angiographic "surrogate" parameter does not necessarily translate into a better clinical outcome (DELIVER-I); second, conclusions regarding possible improvements of clinical outcome are underpowered, because the sample size calculation is based on the primary endpoint. Usually the number of patients needed is lower for angiographic than for clinical endpoints. Until today, only three trials with a primary clinical endpoint have shown a significantly positive impact on patients' outcome: the SIRIUS trial (Cypher stent) with its reduction of primary endpoint TVF (21.0% vs 8.6%), the TAXUS-IV trial (Taxus stent) with its reduction of primary endpoint TVR (12.0% vs 4.7%) and TAXUS-VI in long lesions with its reduction of primary endpoint TVR (19.4% vs 9.1%). Although the angiographic results of other drug-eluting stents are encouraging, they will have to prove their clinical impact based on adequately powered randomized trials with a primary clinical endpoint at an adequate time interval.