Drug-eluting stents: new era and new concerns

Validation and comparison of drug eluting stent to bare metal stent for restenosis rates following vertebral artery ostium stenting: A single-center real-world study

BACKGROUND AND PURPOSE

While drug-eluting stents (DES) have been widely applicated in coronary stenosis, uncertainty persists concerning the relative performance and clinical benefit in patients undergoing vertebral artery stenting when compared with a bare metal stent (BMS). We sought to compare in-stent restenosis (ISR) rates of DES and BMS in the treatment of vertebral artery ostium (VAO) stenosis.

MATERIALS AND METHODS

This study analyzed a single-center prospective cohort. Over 1.5-year period (January 2014-June 2015), 137 consecutive patients underwent VAO stenting involving deployment of 76 DES and 74 BMS. Patient demographics, comorbidities, stenosis severity, stent diameters and lengths, periprocedural complications, imaging and duplex ultrasonography follow-up and recurrent symptoms were assessed.

RESULTS

Technical success was achieved in all patients. Mean VAO stenosis at presentation were 82.4 ± 7.2% in the DES group and 83.3 ± 7.5% in the BMS group and were reduced to 12.5 ± 4.5% and 11.3 ± 4.0%. Mean stent diameter was 3.53 ± 0.40 mm in DES and 5.05 ± 0.40 mm in BMS (p < 0.0001). Mean follow-up was 12.3 months for DES and 11.7 months for BMS. The use of DES was associated with significant lower ISR rates compared with BMS (18.4% vs. 31.1%; OR = 2.628, p = 0.021). Recurrent symptoms rates were similar in DES vs. BMS (2.6% vs 2.7%, p = 0.680). Stent type and stent diameter were independent risk factors for ISR (P = 0.026).

CONCLUSION

Our results suggest superior efficacy of deploying DES for the treatment of VAO stenosis with lower ISR rates as compared to BMS, but do not support significant differences in periprocedural risk and recurrent symptoms rate.

Decreased PPAR-γ expression after internal carotid artery stenting is associated with vascular lesions induced by smooth muscle cell proliferation and systemic inflammation in a minipig model

Vascular restenosis after stenting is known to be largely mediated by proliferation of vascular smooth muscle cells. Recently, peroxisome proliferator-activated receptor gamma (PPAR-γ) has been implicated as a regulator of cellular inflammatory responses, and the PPAR-γ agonist rosiglitazone (ROSI) has been shown to attenuate atherosclerosis formation. However, whether ROSI can inhibit neointimal formation by regulating the inflammatory response and inhibiting vascular smooth muscle hyperplasia after stenting-induced injury remains to be clarified. Accordingly, in this study, 10 minipigs were randomly divided into two groups: the stenting group (n = 5) and the ROSI group (n = 5). Morphometric analysis was conducted for the stented arteries. The protein expressions of PPAR-γ and smooth muscle 22-alpha (SM22α) were analyzed by immunohistochemistry and western blotting, and the serum interferon-γ and interleukin-10 levels were measured by enzyme-linked immunosorbent assay. Three months after implantation, morphometric analysis revealed that administration of ROSI (0.5 mg/kg/d, continuous administration for 90 days) resulted in significant reductions of luminal stenosis, the neointimal area, and neointimal thickness, as compared to the stenting groups. The expression of PPAR-γ and the PPAR-γ/SM22α ratio in the ROSI group were higher than in the stenting group. Furthermore, the serum interferon-γ and interleukin-10 levels were found to be increased and to reach peak levels at 4 h and 7 days after stenting, respectively, after which both declined. However, ROSI treatment resulted in decreased interferon-γ and increased interleukin-10 levels after stenting. In both groups, the cytokine levels returned to the baseline levels on day 56 after stenting. Taken together, these results suggest that ROSI can reduce neointimal formation after stenting by inhibiting the local and systemic inflammatory responses as well as vascular smooth muscle hyperplasia.

The (PrS/HGF-pDNA) multilayer films for gene-eluting stent coating: Gene-protecting, anticoagulation, antibacterial properties, and in vivo antirestenosis evaluation

Vascular gene-eluting stents (GES) is a promising strategy for treatment of cardiovascular disease. Very recently, we have proved that the (protamine sulfate/plasmid DNA encoding hepatocyte growth factor) (PrS/HGF-pDNA) multilayer can serve as a powerful tool for enhancing competitiveness of endothelial cell over smooth muscle cell, which opens perspectives for the regulation of intercellular competitiveness in the field of interventional therapy. However, before the gene multilayer films could be used in vascular stents for real clinical application, the preservation of gene bioactivity during the industrial sterilization and the hemocompatibility of film should be taken into account. Actually, both are long been ignored issues in the field of gene coating for GES. In this study, we demonstrate that the (PrS/HGF-pDNA) multilayer film exhibits the good gene-protecting abilities, which is confirmed by using the industrial sterilizations (gamma irradiation and ethylene oxide) and a routine storage condition (dry state at 4°C for 30 days). Furthermore, hemocompatible measurements (such as platelet adhesion and whole blood coagulation) and antibacterial assays (bacteria adhesion and growth inhibition) indicate the good anticoagulation and antibacterial properties of the (PrS/HGF-pDNA) multilayer film. The in vivo preliminary data of angiography and histological analysis suggest that the (PrS/HGF-pDNA) multilayer coated stent can reduce the in-stent restenosis. This work reveals that the (PrS/HGF-pDNA) multilayer film could be a promising candidate as coating for GES, which is of great potential in future clinic application.

Giant coronary artery aneurysm following implantation of Endeavour stent presenting with fever

Coronary artery aneurysms are a known but uncommon complication of percutaneous coronary intervention (PCI) probably related to effects of vessel wall trauma and possibly a combination of hypersensitivity and incomplete endothelisation associated with drug-eluting stents (DES). We present here a case of giant coronary artery aneurysm 3 months following implantation of a zotarolimus eluting endeavour stent presenting with fever.

Plasma treatment of polyurethane coating for improving endothelial cell growth and adhesion

The advantage of helium plasma treatment in enhancing endothelial cell growth and adhesion on polyurethane film coated on glass substrate is demonstrated with experimental data. Human coronary artery endothelial cell (HCAE) growth and attachment was studied on (1) bare glass substrate, used as control, (2) coated glass, with and without helium plasma treatment and (3) collagen-treated polyurethane-coated glass substrates. The untreated polyurethane film surface was rough (RMS = 690 nm) and highly hydrophobic (contact angle theta = 90 degrees). Cell growth on the untreated polyurethane surface was poor (cell concentration approximately 3750/cm2) compared to glass surface (cell concentration approximately 17 665/cm2). The atmospheric helium plasma treatment of the polyurethane film resulted in oxidation of the surface, a slight increase in roughness (RMS = 735 nm) and a significant drop in hydrophobicity (contact angle theta = 79 degrees). The critical surface tension (gamma c) of polyurethane film was also increased by 2 dynes/cm due to helium plasma treatment. These changes resulted in enhanced HCAE cell growth in polyurethane film (cell concentration approximately 16 230/cm2) compared to the untreated polyurethane film. The cell growth was also comparable to cell growth on a glass surface (17 665/cm2) and the collagen-treated polyurethane film surfaces (cell concentration approximately 21 645/cm2), respectively. Moreover, the strength of cell attachment on a plasma-treated surface (cell retention R = 89%) under laminar flow was significantly higher than that on a glass surface (R = 71%). While the collagen-treated polyurethane surface had the highest number of HCAE cells, the cell adhesion was found to be poor (R = 42%) compared to that of a plasma-treated surface. Thus, the overall performance of the plasma-treated polyurethane film surface on endothelial cell growth was better than other substrates studied here.

In vivo PEG modification of vascular surfaces for targeted delivery

OBJECTIVE

Thrombosis and restenosis remain problematic for many intravascular procedures. Previously, it has been demonstrated that modifying an injured vascular surface with a protein-reactive polymer could block undesirable platelet deposition. As an added benefit, it would be advantageous if one could target therapeutics to the injured site. This study investigates a site-specific delivery system to target microspheres to vascular surfaces modified with a reactive polyethylene glycol tagged with biotin.

METHODS

Rabbit femoral arteries were injured with a 2F embolectomy catheter. Modification of the vascular surface was achieved using a channeled balloon catheter or small-diameter tube. Microspheres were injected intravenously through catheterization of the ear vein. Polymer modification on the injured surface and delivery of microspheres was quantified using epifluorescence microscopy at 0, 24, 48, and 72 hours.

RESULTS

Polymer modification of the vascular surface could be achieved using a channeled drug delivery catheter or small-diameter tube with similar results. Maximum polymer coverage occurred at 0 hours and decreased to 85% maximal at 24 hours, 72% at 48 hours, and 67% at 72 hours. The initial number of microspheres per mm(2) binding to modified, injured arteries was 304 versus 141 for the unmodified, damaged control (P < .01). At subsequent times, the number of adherent microspheres to modified, injured arteries decreased by 50%, 70%, and 84% at 24, 48, and 72 hours, respectively; while nonspecific binding to unmodified, injured arteries quickly decreased by 93%. Initial microsphere binding to modified, healthy arteries was 153 microspheres/mm(2) as opposed to 26 microspheres/mm(2) for the unmodified, healthy controls (P < .01).

CONCLUSIONS

Chemical modification of injured vessels following intravascular procedures can be readily accomplished in vivo to create a substrate for targeted delivery systems. As a proof of concept, targeted microspheres preferentially adhered to polymer-modified surfaces as opposed to injured, unmodified, or healthy vascular surfaces.

Vascular inflammation and repair: implications for re-endothelialization, restenosis, and stent thrombosis

The cellular and molecular processes that control vascular injury responses after percutaneous coronary intervention involve a complex interplay among vascular cells and progenitor cells that control arterial remodeling, neointimal proliferation, and re-endothelialization. Drug-eluting stents (DES) improve the efficacy of percutaneous coronary intervention by modulating vascular inflammation and preventing neointimal proliferation and restenosis. Although positive effects of DES reduce inflammation and restenosis, negative effects delay re-endothelialization and impair endothelial function. Delayed re-endothelialization and impaired endothelial function are linked to stent thrombosis and adverse clinical outcomes after DES use. Compared with bare-metal stents, DES also differentially modulate mobilization, homing, and differentiation of vascular progenitor cells involved in re-endothelialization and neointimal proliferation. The effects of DES on vascular inflammation and repair directly impact clinical outcomes with these devices and dictate requirements for extended-duration dual antiplatelet therapy.

Regulator of calcineurin 1 mediates pathological vascular wall remodeling

Angiotensin-II–driven calcineurin activation and regulator of calcineurin-1 (Rcan-1) expression is required for pathological vascular remodeling in mice.

Artery wall remodeling, a major feature of diseases such as hypertension, restenosis, atherosclerosis, and aneurysm, involves changes in the tunica media mass that reduce or increase the vessel lumen. The identification of molecules involved in vessel remodeling could aid the development of improved treatments for these pathologies. Angiotensin II (AngII) is a key effector of aortic wall remodeling that contributes to aneurysm formation and restenosis through incompletely defined signaling pathways. We show that AngII induces vascular smooth muscle cell (VSMC) migration and vessel remodeling in mouse models of restenosis and aneurysm. These effects were prevented by pharmacological inhibition of calcineurin (CN) or lentiviral delivery of CN-inhibitory peptides. Whole-genome analysis revealed >1,500 AngII-regulated genes in VSMCs, with just 11 of them requiring CN activation. Of these, the most sensitive to CN activation was regulator of CN 1 (Rcan1). Rcan1 was strongly activated by AngII in vitro and in vivo and was required for AngII-induced VSMC migration. Remarkably, Rcan1^−/− mice were resistant to AngII-induced aneurysm and restenosis. Our results indicate that aneurysm formation and restenosis share mechanistic elements and identify Rcan1 as a potential therapeutic target for prevention of aneurysm and restenosis progression.

Effects of drug-eluting stents on systemic inflammatory response in patients with unstable angina pectoris undergoing percutaneous coronary intervention

Inflammatory markers are elevated in acute coronary syndromes, and are also known to play a crucial role in the pathogenesis of neointimal proliferation and stent restenosis. Drug-eluting stents (DESs) have been shown to decrease stent restenosis in different studies. In this study, we aimed to investigate the effect of treatment with DESs on systemic inflammatory response in patients with unstable angina pectoris who underwent percutaneous coronary intervention (PCI). We compared plasma high-sensitivity C-reactive protein (hsCRP), human tumor necrosis factor alpha (Hu TNF-alpha), and interleukin 6 (IL-6) levels after DES (dexamethasone-eluting stent [DEXES], and sirolimuseluting stent [SES]) implantation with levels after bare metal stent (BMS) implantation. We performed PCI with a single stent in 90 patients (62 men; 59 +/- 9 years of age; n = 30 in the BMS group, n = 30 in the DEXES group, n = 30 in the SES group) who had acute coronary syndrome. Plasma hsCRP, Hu TNF-alpha, and IL-6 levels were determined before intervention and at 24 h, 48 h, and 1 week after PCI. The results were as follows. Plasma hsCRP levels at 48 h (11.19 +/- 4.54, 6.43 +/- 1.63 vs 6.23 +/- 2.69 mg/l, P = 0.001) after stent implantation were significantly higher in the BMS group than in the DES group; this effect persisted for 7 days (P = 0.001). Plasma Hu TNF-alpha levels at each time point were higher in the SES group than in the BMS and DEXES groups (P < 0.05). The time course of Hu TNF-alpha values was similar in all groups. Although IL-6 levels at baseline and at 24 and 48 h showed no statistically significant difference between the study groups, postprocedural values at 7 days were slightly statistically significant in the SES group (P = 0.045). Drug-eluting stents showed significantly lower plasma hsCRP levels after PCI compared with BMSs. This may reflect the potent effects of DESs on acute inflammatory reactions induced by PCI.

Therapeutic potential of VIVIT, a selective peptide inhibitor of nuclear factor of activated T cells, in cardiovascular disorders

Cardiovascular disease is the major cause of death in industrialized nations. Targeted intervention in calcineurin, a calmodulin-dependent, calcium-activated phosphatase and its substrate, nuclear factor of activated T cells (NFAT), was demonstrated to be effective in the treatment of cardiovascular diseases. Although effective in the disruption of calcineurin phosphatase activity, cyclosporin A (CsA) and FK506 also resulted in undesired side effects and toxicity, prompting the discovery of VIVIT, a novel peptide inhibitor. VIVIT selectively and potently inhibits calcineurin/NFAT interaction, but does not compromise calcineurin phosphatase activity and non-NFAT-mediated signaling. VIVIT displays a favorable therapeutic profile as a potential drug candidate and constitutes a useful tool in exploring calcineurin-NFAT functionality. This review describes the development of VIVIT peptide as a selective NFAT inhibitor and its application as a therapeutic agent in cardiovascular disorders including cardiac hypertrophy, restenosis, atherosclerosis, and angiogenesis.

Poly(ethylene carbonate): A thermoelastic and biodegradable biomaterial for drug eluting stent coatings?

A first feasibility study exploring the utility of poly(ethylene carbonate) (PEC) as coating material for drug eluting stents under in vitro conditions is reported. PEC (Mw 242 kDa, Mw/Mn=1.90) was found to be an amorphous polymer with thermoelastic properties. Tensile testing revealed a stress to strain failure of more than 600%. These properties are thought to be advantageous for expanding coated stents. In vitro cytotoxicity tests showed excellent cytocompatibility of PEC. Based on these findings, a new stenting concept was suggested, pre-coating a bare-metal stent with PPX-N as non-biodegradable basis and applying a secondary PEC coating using an airbrush method. After manual expansion, no delamination or destruction of the coating could be observed using scanning electron microscopy. The surface degradation-controlled release mechanism of PEC may provide the basis for "on demand" drug eluting stent coatings, releasing an incorporated drug predominantly at an inflamed implantation site upon direct contact with superoxide-releasing macrophages. As a release model, metal plates of a defined size and area were coated under the same conditions as the stents with PEC containing radiolabelled paclitaxel. An alkaline KO(2-) solution served as a superoxide source. Within 12 h, 100% of the incorporated paclitaxel was released, while only 20% of the drug was released in non-superoxide releasing control buffer within 3 weeks.

Physician factors as an indicator of technological device adoption

This paper analyzes a sample interventional cardiologist's demographic, academic, and professional characteristics to provide an understanding of their technological device adoption styles. The study sample consisted of 15 physicians from two large Midwestern hospitals, one an academic medical center and the other a medium-sized community hospital. Interventional cardiologists were identified through their online physician profile and respective departments. A questionnaire was developed to assess each physician's self-perceived adoption style, their awareness of the new technology, their participation in clinical trials, organizational support, and how various factors influence their adoption of new technology. Lastly, a database of bare metal and drug eluting stents was examined to document the number of stents used by each physician. Pragmatic and observational findings are presented from the questionnaire, physician profile, to database on stent use. The paper concludes with a discussion of the managerial and forecasting implications and methods to promote technology adoption.

Elevated Plasma Active Matrix Metalloproteinase-9 Level Is Associated With Coronary Artery In-Stent Restenosis

Objective— This study aimed to determine whether the plasma levels of matrix metalloproteinase-9 (MMP-9) or tissue inhibitor of metalloproteinases-1 (TIMP-1) were altered in patients with a history of symptomatic in-stent restenosis (ISR).

Methods and Results— A group of 158 patients with a history of ISR were compared with 128 symptom-free patients. Plasma samples and a detailed risk factor history were collected. Plasma samples were analyzed for pro–MMP-9 and latent MMP-9 and active MMP-9, latent MMP-3, and TIMP-1. Several variables were associated with ISR, including index coronary disease extent and severity (number of diseased vessels and American College of Cardiology/American Heart Association lesion classification), number, diameter, and total length of stent(s) inserted, and plasma high-density lipoprotein cholesterol. Plasma active MMP-9 (odds ratio, 1.96; 95% CI, 1.43 to 2.69) showed independent risk association with ISR. Patients with multiple sites of ISR had significantly higher levels of active MMP-9 compared with patients with only a single ISR lesion or no ISR.

Conclusion— Plasma active MMP-9 levels may be a useful independent predictor of bare metal stent ISR.

Therapeutic Potential of a Synthetic Peptide Inhibitor of Nuclear Factor of Activated T Cells as Antirestenotic Agent

OBJECTIVE

The calcineurin/nuclear factor of activated T cells (NFAT) axis plays a pivotal role in the regulation of critical genes in vascular smooth muscle cell (vSMC) proliferation and inflammation, which makes NFAT inhibition an attractive modality in the prevention of restenosis.

METHODS AND RESULTS

Synthetic peptide VIVIT potently inhibited NFAT activation in RAW 264.7 macrophages, Ea.Hy.926 endothelial cells and vSMCs, and blocked ionomycin-elicited nuclear import of NFAT. VIVIT, as well as cyclosporine A (CsA) or FK506, completely blunted platelet-derived growth factor-BB (PDGF-BB) and thrombin-induced vSMC proliferation. Moreover, it significantly inhibited PDGF-BB and thrombin-induced interleukin-6, interleukin-8, transforming growth factor-beta1, stromal cell-derived factor-1alpha, and monocyte chemotactic protein-1 expression in vSMCs. Unlike FK506 or CsA, VIVIT did not affect nuclear factor kappaB reporter gene activation and did only marginally affect endothelial wound healing in vitro. VIVIT did not intervene in phorbol 12-myristate 13-acetate-stimulated extracellular signal-regulated kinase activation, confirming its specificity for NFAT. Furthermore, our data establish that NFAT is a regulator of PDGF-BB induced vSMC proliferation.

CONCLUSIONS

VIVIT appears to be a specific and potent inhibitor of NFAT activation and thus of NFAT-mediated proliferation and inflammation. Unlike FK506 or CsA, synthetic VIVIT therapy will not be accompanied by non-NFAT-mediated side effects on calcineurin signaling and constitutes a promising lead in antirestenotic therapy.

The paclitaxel-eluting stent in percutaneous coronary intervention: part I: background and clinical comparison to bare metal stents

The development of coronary artery stents that release (elute) a drug locally into the diseased vasculature has revolutionized the practice of interventional cardiology. These devices were designed to minimize the incidence of in-stent restenosis that may occur with bare metal stents. The paclitaxel-eluting stent is the most recent drug-eluting stent approved for use in the United States and is a bare metal stent coated with paclitaxel that is gradually released from the stent into the vessel wall with undetectable systemic concentrations of the drug. Paclitaxel functions to stabilize the assembly of microtubules, thereby interfering with cell division, motility, and shape, and ultimately inhibiting smooth muscle cell proliferation and migration, key processes in the development of neointimal hyperplasia during in-stent restenosis. Clinical trials have repeatedly demonstrated the superiority of the paclitaxel-eluting stent over the bare metal stent in terms of reducing restenosis rates and percent stenosis diameter as well as other angiographic end points. Although the rates of major adverse cardiac events are reduced with the paclitaxel-eluting stent compared with the bare metal stent, this is primarily the result of a reduction in the need for target vessel revascularization, whereas rates of myocardial infarction and death have not been shown to be significantly affected.

Drug-eluting stents: a multidisciplinary success story

Coronary stenting is the most common form of interventional treatment for symptomatic coronary artery disease. In-stent restenosis following bare metal stent (BMS) placement is the most common cause of procedural failure and occurs as a result of vessel wall trauma secondary to balloon angioplasty and stent deployment that results in an overly aggressive healing response (neointimal hyperplasia) that overgrows the stent lumen and causes vascular narrowing. Drug-eluting stents (DES) are specialized vascular stents capable of delivering drugs to the arterial wall in a controlled manner such that neointimal hyperplasia is reduced or prevented, luminal patency is preserved, coronary blood flow is maintained and the patient is spared a repeat procedure to re-open the vessel. The objectives of the review are to provide an overview of the major contributions that a broad range of disciplines have made to the design and development of drug-eluting stents and to summarize future directions of these fields of research. Engineers and biomaterials scientists have explored relationships between stent design and stent performance and work continues to optimize stent design and biocompatibility of stent biomaterials. Pharmaceutical scientists are continually expanding the range of candidate drugs for pharmacological intervention, and improving the technology using novel coatings to modulate drug release. Clinical scientists are investigating issues such as long-term safety and efficacy, new applications of drug-eluting stents and optimal deployment techniques.

Drug-Eluting Stents and the Future of Coronary Artery Bypass Surgery: Facts and Fiction

The treatment of patients with coronary artery disease continues to evolve. Recent, exciting data on the use of drug-eluting stents in diseased coronary vessels has generated immense enthusiasm within the interventional community leading to claims that "drug-eluting stents will put bypass surgeons out of business." However, despite promising short-term and midterm outcomes of this revolutionary new technology, valid concerns regarding long-term safety and efficacy of drug-eluting stents persist. This review article evaluates current status of drug-eluting stents with special emphasis on real and potential drawbacks of this emerging percutaneous coronary interventional modality and its impact on the practice of coronary artery bypass surgery.

Synergistic suppression of rat neointimal hyperplasia by rapamycin and imatinib mesylate: implications for the prevention of accelerated arteriosclerosis

BACKGROUND

Accelerated arteriosclerosis remains a major limitation to therapeutic interventions such as angioplasty, stent deployment, and solid organ transplantation. Rapamycin, a powerful new immunosuppressant set to replace calcineurin inhibitors in the transplant setting, and imatinib mesylate, a receptor tyrosine kinase inhibitor, are both angioprotective. Here, we explored the pharmacological and therapeutic interactions of these two agents in a rat model of neointimal hyperplasia.

METHODS

Wistar rats, subjected to balloon catheter-induced aortic injury, received daily drug treatment until postoperative day 14 and were subsequently sacrificed or followed up to day 40 without further treatment. Development of neointimal lesions was assessed histologically and immunohistochemically. Steady-state rapamycin levels in whole blood were determined by HPLC-UV.

RESULTS

Rapamycin and imatinib, administered individually or in combination, produced no signs of overt toxicity. Continuous postoperative therapy with either rapamycin (0.5-1.5 mg/kg/day) or imatinib (2- 50 mg/kg/day) dose-dependently suppressed neointimal hyperplasia on day 14. Combined treatment (0.5 or 1 + 10 mg/kg/day, respectively) showed a trend towards synergistic action on day 14. Withdrawal of medication on day 14 nullified the early therapeutic effect of either agent by day 40. In contrast, early combination therapy (1 + 10 mg/kg/day) achieved long-term suppression of neointimal hyperplasia by approximately 81%. Notably, coadministration of imatinib appeared to reduce exposure to rapamycin, although this finding did not reach statistical significance.

CONCLUSIONS

Short-term combination therapy with rapamycin and imatinib is well tolerated and produces synergistic, sustained suppression of neointimal hyperplasia in rats. Subject to clinical evaluation, this new drug regimen may afford definitive prophylaxis against accelerated arteriosclerosis.

Comparison of effects of drug-eluting stents versus bare metal stents on plasma C-reactive protein levels

After coronary stenting, inflammatory mechanisms play a crucial role in the pathogenesis of neointimal proliferation and in-stent restenosis. Drug-eluting stents (DESs) have been shown to decrease in-stent restenosis in different studies. We compared plasma C-reactive protein (CRP) levels after DES implantation with levels after bare metal stent (BMS) implantation. We performed percutaneous coronary intervention with a single stent in 67 patients (54 men; 59 +/- 9 years of age; n = 21 in the BMS group, n = 46 in the DES group) who had stable angina. Plasma CRP levels were determined before intervention and at 48 hours, 72 hours, and 2 weeks after coronary stenting. There was no difference in clinical and angiographic baseline characteristics except that the DES group had more patients with diabetes (34.8% vs 9.5%, p = 0.04), smaller reference vessels (2.95 +/- 0.53 vs 3.29 +/- 0.53 mm, p = 0.02), and smaller stent diameters (3.0 +/- 0.4 mm vs 3.4 +/- 0.5 mm, p <0.01). Plasma CRP levels at 48 hours (13.4 +/- 14.7 vs 5.9 +/- 4.9 mg/L, p <0.01) and 72 hours (16.7 +/- 19.8 vs 5.4 +/- 3.9 mg/L, p <0.01) after stent implantation were significantly higher in the BMS than in the DES group. In conclusion, DESs showed significantly lower plasma CRP levels after coronary stenting compared with BMSs. This may reflect the potent effects of DESs on acute inflammatory reactions induced by coronary intervention.

Localized delivery of nitric oxide from hydrogels inhibits neointima formation in a rat carotid balloon injury model

Using novel nitric oxide (NO)-generating polymeric hydrogels that can be rapidly photopolymerized in situ, we can deliver NO locally at the site of vascular injury. Depending on material design, these poly(ethylene glycol) (PEG)-based hydrogels can generate NO for up to 50 d. This study demonstrates the ability of nitric oxide-generating hydrogels (PEG-Cys-NO) to influence key components of the restenosis cascade both in vitro and in vivo. PEG-Cys-NO hydrogels inhibited smooth muscle cell proliferation, increased endothelial cell proliferation, and inhibited platelet adhesion in vitro. Moreover, in vivo, PEG-Cys-NO hydrogels inhibited intimal thickening in a rat carotid balloon injury model. The perivascular application of NO-generating polymers post-injury reduced neointima formation at 14 d by approximately 80% compared to controls (intimal area/medial area (I/M): PEG-Cys-NO=0.20+/-0.17, control=0.84+/-0.19, p<0.00002; intimal thickness: PEG-Cys-NO=12+/-10 microm, control=60+/-18 microm, p<0.00002). Treatment with the PEG-Cys-NO hydrogels caused a significant decrease in the per cent of proliferating cell nuclear antigen positive medial cells (29+/-5%) at 4 d as compared to treatment with the control hydrogels (51+/-1%, p<0.02). Additionally, vessel re-endothelialization at 14 d was slightly enhanced in the presence of the NO-generating hydrogels. These data indicate that localized delivery of NO from these hydrogels can significantly inhibit neointima formation in a rat carotid balloon injury model and suggest that these materials may be useful in preventing restenosis.

Early elevation of interleukin-1beta and interleukin-6 levels after bare or drug-eluting stent implantation in patients with stable angina

INTRODUCTION

Drug-eluting stent (DES) implantation represents an important innovation in the treatment of coronary artery disease. However, inflammatory-related complications, including subacute thrombosis and in-stent restenosis, are still important limitations to percutaneous coronary intervention (PCI). The aim of this study was to compare early local release of interleukin 1beta (IL-1beta) and IL-6 proinflammatory cytokines after elective placement of either bare metal stents or DES.

MATERIALS AND METHODS

IL-1beta and IL-6 levels were assayed in plasma obtained from the coronary sinus both before and 20 min after stent implantation in 59 patients with stable angina, who were randomly assigned to receive bare, paclitaxel-, or sirolimus-eluting stents during elective PCI.

RESULTS

We found that IL-1beta and IL-6 levels were significantly increased in the coronary sinus of patients receiving either bare, paclitaxel- or sirolimus-eluting stents 20 min after stent implantation as compared with basal concentrations. The variation in the level of both cytokines was comparable among the three study groups.

CONCLUSIONS

A local release of proinflammatory cytokines occurs shortly after coronary stent placement, including DES, which is possibly related to plaque rupture and/or endothelium traumatism following the stenting procedure. This suggests that precocious anti-inflammatory treatment could be of benefit to further improve the PCI clinical outcome.

Effects of mycophenolate mofetil on key pattern of coronary restenosis: a cascade of in vitro and ex vivo models

Background

Mycophenolate mofetil (MMF), the prodrug of mycophenolic acid (MPA), is a rationally designed immunosuppressive drug. The current study investigates the effect of MMF on key pattern of restenosis in a cascade of in vitro and ex vivo models.

Methods

Part I of the study investigated in northern blot and cytoflow studies the effect of MMF (50, 100, 150, 200, 250, and 300 μg/mL) on TNF-α induced expression of intercellular adhesion molecule 1 (ICAM-1) in human coronary endothelial cells (HCAEC) and human coronary medial smooth muscle cells (HCMSMC). Part II of the study applied a human coronary 3D model of leukocyte attack, the 3DLA-model. HCAEC and HCMSMC were cultured on both sides of a polycarbonate filters, mimicking the internal elastic membrane. Leukocyte attack (LA) was carried out by adding human monocytes (MC) on the endothelial side. The effect of MMF (50 μg/mL) on adhesion and chemotaxis (0.5, 1, 2, 3, 4, 6, and 24 h after LA) and the effect on proliferation of co-cultured HCMSMC (24 h after LA) was studied. In part III of the study a porcine coronary organ culture model of restenosis (POC-model) was used. After ex vivo ballooning MMF (50 μg/mL) was added to the cultures for a period of 1, 2, 3, 4, 5, 6, and 7 days. The effect on reactive cell proliferation and neointimal thickening was studied at day 7 and day 28 after ballooning.

Results

Expression of ICAM-1 in northern blot and cytoflow studies was neither clearly inhibited nor stimulated after administration of MMF in the clinical relevant concentration of 50 μg/mL. In the 3DLA-model 50 μg/mL of MMF caused a significant antiproliferative effect (p < 0.001) in co-cultured HCMSMC but had no effect on MC-adhesion and MC-chemotaxis. In the ex vivo POC-model neighter reactive cell proliferation at day 7 nor neointimal hyperplasia at day 28 were significantly inhibited by MMF (50 μg/mL).

Conclusion

Thus, the data demonstrate a significant antiproliferative effect of clinical relevant levels of MMF (50 μg/mL) in the 3DLA-model. The antiproliferative effect was a direct antiproliferative effect that was not triggered via reduced expression of ICAM-1 or via an inhibition of MC-adhesion and chemotaxis. Probably due to technical limitations (as e.g. the missing of perfusion) the antiproliferative effect of MMF (50 μg/mL) could not be reproduced in the coronary organ culture model. A cascade of focused in vitro and ex vivo models may help to gather informations on drug effects before large experimental studies are initiated.

Targets for immunomodulation in cardiovascular disease – where are we now?

The recognition that inflammation plays an important role in most cardiovascular pathologies offers the potential for the development of new therapeutic targets. Heart failure and in-stent restenosis are two areas in which there have been very recent developments in identifying and targeting potential inflammatory mediators. The development of both broad anti-inflammatory strategies and more targeted approaches have confirmed that immunomodulation may have a beneficial effect on disease progression of restenosis and heart failure in experimental animals, while the results from clinical studies highlight the need to consider the inflammatory processes as a whole, rather than some aspects in isolation. This review briefly summarizes the key stimuli for initiating inflammation in cardiovascular disease, recent clinical and experimental developments in the search for appropriate anti-inflammatory strategies and considers the possible pitfalls and future challenges for developing this area.

Styrenic block copolymers for biomaterial and drug delivery applications

The use of styrenic block copolymers has undergone a renaissance as a biomaterial and drug delivery matrix. The early promise posed by the physical and biological properties of these block copolymers for implantable medical devices was not met. However, there has been an increased understanding of the role of microphase separation on the mediation of the biological response. Poly (styrene-b-isobutylene-b-styrene) (SIBS) block copolymer has critical enabling properties related to processing, vascular compatibility and bio-stability that has resulted in its use as the matrix for paclitaxel delivery from Boston Scientific's TAXUS coronary stent. These enabling properties will allow the continuing development of medical devices based on SIBS that meet demanding physical and biological requirements.

Hammerhead ribozymes targeted against cyclin E and E2F1 cooperate to down-regulate coronary smooth muscle cell proliferation

BACKGROUND

Anti-proliferative drugs released from endo-vascular stents have substantially contributed to reduce in-stent restenosis rates in coronary arteries bearing single primary lesions by down-regulating coronary smooth muscle cell (CSMC) growth. However, the considerably lower drug efficacy shown in treatment of more complex coronary lesions suggests that alternative anti-proliferative approaches can be beneficial. Thus, we explored the use of hammerhead ribozymes as tools to knock down cyclin E and E2F1, two potent activators of cell proliferation which cooperate to promote the G1 to S phase transition.

METHODS

Two ribozymes, one directed against cyclin E and the other against E2F1 mRNAs, were delivered by liposomes to cultured human CSMCs. The influences on cell proliferation were measured evaluating BrdU incorporation into newly synthesised DNA. The effects on cell cycle phase distribution were determined by BrdU and 7-aminoactinomycin D incorporation into DNA.

RESULTS

Both ribozymes exhibited a sequence-specific and dose-dependent reduction in BrdU incorporation, which, at a concentration of 280 nM, persisted up to 4 days after transfection of CSMCs. A combined administration of the two ribozymes (210+210 nM) resulted in a more pronounced decrease in BrdU incorporation compared to the administration of an equimolar amount (420 nM) of each of them. Finally, both ribozymes induced a significant (P<0.05) reduction in S phase cells with a concomitant increase of G1/G0 and G2-M phase cells, compared to controls.

CONCLUSIONS

The ribozymes selected represent potent tools to prevent CSMC proliferation, especially when administered together, and thus are ideal candidates for in vivo application.

Physical characterization of controlled release of paclitaxel from the TAXUS? Express2? drug-eluting stent

The polymer carrier technology in the TAXUS drug-eluting stent consists of a thermoplastic elastomer poly(styrene-b-isobutylene-b-styrene) (SIBS) with microphase-separated morphology resulting in optimal properties for a drug-delivery stent coating. Comprehensive physical characterization of the stent coatings and cast film formulations showed that paclitaxel (PTx) exists primarily as discrete nanoparticles embedded in the SIBS matrix. Thermal and chemical analysis did not show any evidence of solubility of PTx in SIBS or of any molecular miscibility between PTx and SIBS. Atomic force microscope data images revealed for the first time three-dimensional stent coating surfaces at high spatial resolutions in air and in situ under phosphate-buffered saline as drug was released. PTx release involves the initial dissolution of drug particles from the PTx/SIBS coating surface. Morphological examination of the stent coatings in vitro supported an early burst release in most formulations because of surface PTx followed by a sustained slower release of PTx from the bulk coating. The in vitro PTx release kinetics were dependent on the formulation and correlated to the drug-to-polymer ratio. Atomic force microscopy analysis confirmed this correlation and further supported the concept of a matrix-based drug-release coating.