Drug-eluting stent restenosis: effect of drug type, release kinetics, hemodynamics and coating strategy

Comparison of drug-coated balloon with bare-metal stent in patients with symptomatic intracranial atherosclerotic stenosis: the AcoArt sICAS randomized clinical trial

BACKGROUND

Restenosis after stenting with a standard bare-metal stent (BMS) is the main cause of stroke recurrence for symptomatic intracranial atherosclerotic stenosis (sICAS). Whether a drug-coated balloon (DCB) could reduce the risk of restenosis for such patients is unknown. We aimed to investigate the efficacy and safety of DCB in reducing 6 month restenosis in patients with sICAS.

METHODS

A prospective, multicenter, randomized, open-label, blinded endpoint clinical trial was conducted at 13 stroke centers across China. Eligible patients aged 18-80 years with sICAS defined as a recent transient ischemic attack (<180 days) or ischemic stroke (14-180 days) before enrollment attributed to a 70-99% atherosclerotic stenosis of a major intracranial artery were recruited between June 4, 2021 and September 15, 2022 (final follow-up: April 13, 2023). Patients were randomly assigned to receive a DCB (n=90) or BMS at a 1:1 ratio. The primary outcome was the post-procedure incidence of restenosis in the target lesion at 6 months (165-225 days). The safety outcome was post-procedure target vessel-related stroke (hemorrhage or ischemia) or death at 30 days.

RESULTS

Among 201 randomized patients, 180 were confirmed eligible (mean age 58 years) and completed the trial. Compared with BMS, DCB was associated with a lower rate of post-procedure incidence of restenosis in the target lesion at 6 months (6.9% vs 32.9%, OR 0.15, 95% CI 0.05 to 0.42, P=0.0003). Regarding the safety outcome, post-procedure target vessel-related stroke (hemorrhage or ischemia) or death at 30 days did not differ between the two groups (4.4% vs 5.6%, OR 0.79, 95%CI 0.21 to 3.05, P=0.73).

CONCLUSION

DCB was superior to BMS in reducing the incidence of restenosis without increasing the risk of target vessel-related stroke or death within 6 months. Further trials comparing the outcomes of DCB with medical management for sICAS are warranted.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT04631055.

Risk Factors and Incidence for In-Stent Restenosis with Drug-Eluting Stent: A Systematic Review and Meta-Analysis

Background

Despite significant reductions in in-stent restenosis (ISR) incidence with the adoption of drug-eluting stents (DES) over bare metal stents (BMS), ISR remains an unresolved issue in the DES era. The risk factors associated with DES-ISR have not been thoroughly analyzed. This meta-analysis aims to identify the key factors and quantify their impact on DES-ISR.

Methods

We conducted comprehensive literature searches in PubMed, EMBASE, Cochrane, and Web of Science up to 28 February 2023, to identify studies reporting risk factors for DES-ISR. Meta-analysis was performed on risk factors reported in two or more studies to determine their overall effect sizes.

Results

From 4357 articles screened, 17 studies were included in our analysis, evaluating twenty-four risk factors for DES-ISR through meta-analysis. The pooled incidence of DES-ISR was approximately 13%, and significant associations were found with seven risk factors. Ranked risk factors included diabetes mellitus (odds ratio [OR]: 1.46; 95% confidence interval [CI]: 1.14-1.87), stent length (OR: 1.026; 95% CI: 1.003-1.050), number of stents (OR: 1.62; 95% CI: 1.11-2.37), involvement of the left anterior descending artery (OR: 1.56; 95% CI: 1.25-1.94), lesion length (OR: 1.016; 95% CI: 1.008-1.024), medical history of myocardial infarction (OR: 1.79; 95% CI: 1.12-2.86) and previous percutaneous coronary intervention (OR: 1.97; 95% CI: 1.53-2.55). Conversely, a higher left ventricular ejection fraction was identified as a protective factor (OR: 0.985; 95% CI: 0.972-0.997).

Conclusions

Despite advancements in stent technology, the incidence of ISR remains a significant clinical challenge. Our findings indicate that patient characteristics, lesion specifics, stent types, and procedural factors all contribute to DES-ISR development. Proactive strategies for early identification and management of these risk factors are essential to minimize the risk of ISR following DES interventions.

The PROSPERO Registration

CRD42023427398, https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=427398.

Comparative Efficacy and Safety of Different Balloon Angioplasty Procedures for Infrapopliteal Artery Lesions in Chronic Limb-Threatening Ischemia Patients: A Systematic Review and Network Meta-Analysis

BACKGROUND

The optimal endovascular method to treat infrapopliteal chronic limb-threatening ischemia (CLTI) remains to be determined, given the limitations of stent use in infrapopliteal artery disease. We performed a network meta-analysis (NWM) of randomized controlled trials (RCTs) to simultaneously compare the outcomes of different balloon angioplasty procedures for infrapopliteal artery lesions in CLTI patients.

METHODS

We searched the Cochrane Central Register of Controlled Trials, Embase, and PubMed. 8 eligible RCTs involving 3 endovascular modalities or combinations (plain old balloon angioplasty [POBA], drug-coated balloon [DCB], orbital atherectomy plus plain old balloon angioplasty [OA+POBA]) were included. Primary outcomes were efficacy (12-month clinically driven target lesion revascularization [CDTLR]) and safety (12-month major amputation and all-cause mortality). We used random-effects models based on the frequentist framework.

RESULTS

Plain old balloon angioplasty had a higher 12-month CDTLR rate than DCB (relative risk [RR]: 2.11, confidence interval [CI]: 1.33, 3.34) in the NWM and this result was still statistically significant (RR: 0.47, CI: 0.30, 0.75) in subgroup analyses. According to the SUCRA value, in terms of 12-month CDTLR, OA+POBA was considered the best treatment (SUCRA=72.2), while POBA was considered the worst treatment (SUCRA=8.9). In terms of 12-month all-cause mortality, OA+POBA was considered the best treatment (SUCRA=95.0), while DCB was considered the worst treatment (SUCRA=12.8). In terms of 12-month major amputation, POBA was considered the best treatment (SUCRA=72.0), while DCB was considered the worst treatment (SUCRA=23.0).

CONCLUSIONS

In infrapopliteal CLTI disease, DCB showed a significantly lower 12-month CDTLR in comparison to POBA. There is no statistically significant evidence to suggest that DCB raises safety concerns. The SUCRA values of OA+POBA indicate that it might offer a superior treatment option compared to DCB or POBA in terms of CDTLR and mortality. This advantage, however, was not sustained when major-amputation rates were analyzed. Consequently, further RCTs are required to examine the potential benefits of OA and other forms of atherectomy for managing infrapopliteal CLTI disease.

CLINICAL IMPACT

The findings of this study provide further evidence for the safety of DCB in the application of infrapopliteal CLTI disease and suggest preliminary benefits of atherectomy. These results are likely to encourage further research and application of these treatment modalities in managing infrapopliteal CLTI.POBA has been a traditional approach for treating infrapopliteal artery disease. The current evidence supports clinicians in exploring and utilizing DCB and atherectomy as better treatments.We focused on the performance of different balloon angioplasty procedures in infrapopliteal CLTI, considering the characteristics of infrapopliteal CLTI.

NONRATT000538.2 promotes vascular smooth muscle cell phenotypic switch and in-stent restenosis

Vascular smooth muscle cell (VSMC) excessive proliferation and migration are considered the main pathological process in in-stent restenosis (ISR) following vascular intervention. Certain long noncoding RNAs play vital roles in this process. Therefore, this study aimed to explore novel regulators for ISR and further uncover the mechanism. Using a rat abdominal aorta stent implantation model, we observed that NONRATT000538.2 (NR538.2) served as a positive regulator for VSMC proliferation and migration. By manipulating NR538.2 expression via adenoviral overexpression or siRNA knockdown, we noted that NR538.2 promoted VSMC phenotypic switching, thereby inducing proliferation and migration. Significantly, the local delivery of siRNA of NR538.2 via adeno-associated virus vector suppressed balloon injury-induced neointima formation. Our study demonstrated for the first time that NR538.2 positively influenced VSMC proliferation during ISR.

miR-1290 induces endothelial-to-mesenchymal transition and promotes vascular restenosis after angioplasty by targeting FGF2

BACKGROUND AND AIMS

Endothelial-to-mesenchymal transition (EndMT) is an important reason for restenosis but the underlying mechanisms need to be further explored. Therefore, the purpose of this study is to screen significantly different microRNAs (miRNAs) and assess their functions and downstream pathways.

METHODS

This study screened several miRNAs with significant differences between human arterial segments from restenosis patients and healthy volunteers using whole transcriptome resequencing and real-time quantitative reverse transcription PCR (qRT-PCR). We explored the correlation between miR-1290 and EndMT using Western blot, qRT-PCR, Pearson correlation analysis and further functional gain and loss experiments. Subsequently, we identified the direct downstream target of miR-1290 by bioinformatics analysis, RNA pull-down, double Luciferase reporter gene and other functional experiments. Finally, rat carotid artery balloon injury model demonstrated the therapeutic potential of miR-1290 regulator.

RESULTS

We screened 129 differentially expressed miRNAs. Among them, miR-1290 levels were significantly higher in restenosis arteries than in healthy arteries, and as expected, EndMT was functionally enhanced with miR-1290 overexpression and comparatively weakened when miR-1290 was knocked down. In addition, fibroblast growth factor-2 (FGF2) was established as the downstream target of miR-1290. Finally, we utilized an animal model and found that low miR-1290 levels could alleviate EndMT and the progression of restenosis.

CONCLUSIONS

Our study demonstrated the strong regulatory effects of miR-1290 on EndMT, endometrial hyperplasia and restenosis, which could be useful as biomarker and therapeutic target for stent implantation in patients with arterial occlusive disease of the lower extremities.

DRug-coated Balloon for Endovascular treatment of sYmptOmatic intracraNial stenotic Disease (DR. BEYOND): the protocol of a multicentre randomised trial

BACKGROUND

Although endovascular stenting is considered an effective and safe therapeutic option for symptomatic intracranial atherosclerotic disease (sICAD), an elevated rate of restenosis remains an important issue for the conventional bare-metal stent (BMS). Recent evidence from observational studies suggests that applying drug-coated balloons (DCB) in sICAD may decrease restenosis occurrence. Additional large randomised studies are warranted to provide firmer evidence and to determine which patients would benefit most from DCB.

AIM

To design a randomised trial to examine DCB angioplasty (Taijieweiye intracranial paclitaxel-coated balloon catheter) versus BMS stenting (Wingspan intracranial stent system) in patients with sICAD.

DESIGN

This is a multicentre, prospective, randomised, open-label, blinded end-point study to assess whether DCB angioplasty reduces the risk of restenosis compared with BMS stenting in sICAD patients with high-grade stenosis (≥70%-99%). Our goal is to randomly assign 198 eligible individuals at a 1:1 ratio to undergo DCB angioplasty (intervention group) or BMS stenting (control group).

OUTCOME

The primary efficacy outcome is restenosis at 6 months post treatment, that is, >50% stenosis in or within 5 mm of the treated segment and >20% absolute luminal loss. The primary safety outcome is stroke or death within 30 days post treatment.

DISCUSSION

The DRug-coated Balloon for Endovascular treatment of sYmptOmatic intracraNial stenotic Disease trial aims to produce strong evidence on the efficacy and safety of DCB angioplasty as a promising therapeutic option for sICAD cases with high-grade stenosis.

Drug Delivery Opportunities in Esophageal Cancer: Current Treatments and Future Prospects

With one of the highest mortality rates of all malignancies, the 5-year survival rate for esophageal cancer is under 20%. Depending on the stage and extent of the disease, the current standard of care treatment paradigm includes chemotherapy or chemoradiotherapy followed by surgical esophagogastrectomy, with consideration for adjuvant immunotherapy for residual disease. This regimen has high morbidity, due to anatomic changes inherent in surgery, the acuity of surgical complications, and off-target effects of systemic chemotherapy and immunotherapy. We begin with a review of current treatments, then discuss new and emerging targets for therapies and advanced drug delivery systems. Recent and ongoing preclinical and early clinical studies are evaluating traditional tumor targets (e.g., human epidermal growth factor receptor 2), as well as promising new targets such as Yes-associated protein 1 or mammalian target of rapamycin to develop new treatments for this disease. Due the function and location of the esophagus, opportunities also exist to pair these treatments with a drug delivery strategy to increase tumor targeting, bioavailability, and intratumor concentrations, with the two most common delivery platforms being stents and nanoparticles. Finally, early results with antibody drug conjugates and chimeric antigenic receptor T cells show promise as upcoming therapies. This review discusses these innovations in therapeutics and drug delivery in the context of their successes and failures, with the goal of identifying those solutions that demonstrate the most promise to shift the paradigm in treating this deadly disease.

Drug-Coated Balloons for Treatment of Internal Carotid Artery Restenosis After Stenting: A Single-Center Mid-Term Outcome Study

PURPOSE

Endovascular and surgical treatments of stenosis of the extracranial internal carotid artery (ICA) are common procedures, yet both introduce a risk of restenosis due to endothelial hyperplasia. Drug-coated balloons (DCBs) are designed to decrease neointimal hyperplasia, however rarely used in the neurovascular setting. This study retrospectively analyzes mid-term results of DCB-treated in-stent restenosis (ISR) of the ICA.

MATERIALS AND METHODS

The medical history, comorbidities, and periprocedural data of patients receiving DCB treatment for > 50% ISR of the ICA after carotid artery stenting were analyzed. Follow-up after DCB treatment was performed with Doppler ultrasound. Suspicious cases were checked with CT- or MR-angiography and-if there was agreement between the modalities-validated with digital subtraction angiography. Potential risk factors for restenosis and differences in outcomes after PTA with three types of DCB balloons were evaluated.

RESULTS

DCB treatment was performed in 109 cases, 0.9% of which involved in-hospital major stroke; no minor strokes occurred. A total of 17 patients (15.6%) had recurrent ISR after DCB treatment, after a mean time of 30.2 months (7-85 months). Tobacco use was significantly associated with a higher incidence of recurrent ISR.

CONCLUSION

DCB angioplasty for ISR is an effective treatment that may delay and decrease restenosis. Treating comorbidities and adopting lifestyle changes may additionally help prevent ISR.

Coatings for Cardiovascular Stents-An Up-to-Date Review

Cardiovascular diseases (CVDs) increasingly burden health systems and patients worldwide, necessitating the improved awareness of current treatment possibilities and the development of more efficient therapeutic strategies. When plaque deposits narrow the arteries, the standard of care implies the insertion of a stent at the lesion site. The most promising development in cardiovascular stents has been the release of medications from these stents. However, the use of drug-eluting stents (DESs) is still challenged by in-stent restenosis occurrence. DESs' long-term clinical success depends on several parameters, including the degradability of the polymers, drug release profiles, stent platforms, coating polymers, and the metals and their alloys that are employed as metal frames in the stents. Thus, it is critical to investigate new approaches to optimize the most suitable DESs to solve problems with the inflammatory response, delayed endothelialization, and sub-acute stent thrombosis. As certain advancements have been reported in the literature, this review aims to present the latest updates in the coatings field for cardiovascular stents. Specifically, there are described various organic (e.g., synthetic and natural polymer-based coatings, stents coated directly with drugs, and coatings containing endothelial cells) and inorganic (e.g., metallic and nonmetallic materials) stent coating options, aiming to create an updated framework that would serve as an inception point for future research.

A bio-inspired nanoparticle coating for vascular healing and immunomodulatory by cGMP-PKG and NF-kappa B signaling pathways

Drug-eluting stents (DESs) implantation is an effective method to tackle in-stent restenosis (ISR), which has been considered as an efficient treatment for coronary atherosclerosis. Although fruitful results have been achieved in treating coronary artery diseases (CAD), concern has arisen regarding the long-term safety and efficacy of DESs, primarily due to adverse events such as delayed re-endothelialization, persistent inflammatory response, and late stent thrombosis (LST). Taking inspiration from the immunomodulatory functions of camouflage strategies, this study designed a bio-inspired nanoparticle-coated stent. Briefly, the platelet membrane-coated poly (lactic-co-glycolic acid)/Rapamycin nanoparticles (PNP) were sprayed onto stents, forming a homogenous nanoparticle coating. The bilayer of poly (lactic-co-glycolic acid) (PLGA) and platelet membrane works synergistically to promote the sustained-release effect of rapamycin. In vitro studies revealed that the PNP-coated surfaces promoted the competitive adhesion of endothelia cells while inhibiting smooth muscle cells. Subsequent in vivo studies demonstrated that these surfaces expedite re-endothelialization and elicit immunomodulatory effects by regulating the cGMP-PKG and NF-kappa B signaling pathways, influencing the biosynthesis cofactors and immune system signaling. The study successfully deviced a novel and biomimetic drug-eluting stent system, unraveling its detailed functions and molecular mechanism of action for enhanced vascular healing.

Morphology of middle cerebral artery using computed tomography angiographic study in a tertiary care hospital

Increased tortuosity of vessel is associated with high incidence of plaque formation leading to atherosclerosis. Surgical procedures are done after analyzing morphology of middle cerebral artery (MCA). However, literature describing MCA morphology using computed tomography angiography (CTA) is limited, so this study was planned to determine its incidence in Indian population. Datasets of CTA from 289 patients (180 males and 109 females), average age: 49.29±16.16 years (range: 11 to 85 years), from a tertiary care hospital were systematically reviewed for morphology of MCA. Cases involving aneurysms and infarcts were excluded. Four shapes of MCA were recognized: straight, U, inverted U, and S-shaped. MCA was straight in 44% (254/578), U-shaped in 37% (215/578), S shaped in 15% (89/578) and inverted U-shaped in 3% (20/578) cases. In males, MCA was straight in 46% (166/360), U-shaped in 37% (134/360), S-shaped in 16% (58/360) and inverted U-shaped in 4% (14/360) cases. In females, MCA was straight in 42% cases (92/218), U-shaped in 37% (81/218), S-shaped in 17% (36/218) and inverted U-shaped in 4% (9/218). On comparing shape with various age groups using chi square test, U shaped (P≤0.001) and S-shaped (P=0.003) MCA were found to be statistically significant. The incidence of straight shape was higher in advanced age group (>60 years). Knowledge of MCA shape will be useful for clinicians and surgeons in successful endovascular recanalization. Also, this data would help surgeons during neurointerventional procedures.

Drug loaded implantable devices to treat cardiovascular disease

INTRODUCTION

It is widely acknowledged that cardiovascular diseases (CVDs) continue to be the leading cause of death globally. Furthermore, CVDs are the leading cause of diminished quality of life for patients, frequently as a result of their progressive deterioration. Medical implants that release drugs into the body are active implants that do more than just provide mechanical support; they also have a therapeutic role. Primarily, this is achieved through the controlled release of active pharmaceutical ingredients (API) at the implementation site.

AREAS COVERED

In this review, the authors discuss drug-eluting stents, drug-eluting vascular grafts, and drug-eluting cardiac patches with the aim of providing a broad overview of the three most common types of cardiac implant.

EXPERT OPINION

Drug eluting implants are an ideal alternative to traditional drug delivery because they allow for accurate drug release, local drug delivery to the target tissue, and minimise the adverse side effects associated with systemic administration. Despite the fact that there are still challenges that need to be addressed, the ever-evolving new technologies are making the fabrication of drug eluting implants a rewarding therapeutic endeavour with the possibility for even greater advances.

Hierarchy of hybrid materials. Part-II: The place of organics-on-inorganics in it, their composition and applications

Hybrid materials or hybrids incorporating organic and inorganic constituents are emerging as a very potent and promising class of materials due to the diverse but complementary nature of their properties. This complementarity leads to a perfect synergy of properties of the desired materials and products as well as to an extensive range of their application areas. Recently, we have overviewed and classified hybrid materials describing inorganics-in-organics in Part-I (Saveleva, et al., Front. Chem., 2019, 7, 179). Here, we extend that work in Part-II describing organics-on-inorganics, i.e., inorganic materials modified by organic moieties, their structure and functionalities. Inorganic constituents comprise of colloids/nanoparticles and flat surfaces/matrices comprise of metallic (noble metal, metal oxide, metal-organic framework, magnetic nanoparticles, alloy) and non-metallic (minerals, clays, carbons, and ceramics) materials; while organic additives can include molecules (polymers, fluorescence dyes, surfactants), biomolecules (proteins, carbohydtrates, antibodies and nucleic acids) and even higher-level organisms such as cells, bacteria, and microorganisms. Similarly to what was described in Part-I, we look at similar and dissimilar properties of organic-inorganic materials summarizing those bringing complementarity and composition. A broad range of applications of these hybrid materials is also presented whose development is spurred by engaging different scientific research communities.

Drug-Eluting Stent Restenosis: Modern Approach to a Classic Challenge

In-stent restenosis (ISR) is a recognized complication following percutaneous coronary intervention in which the luminal diameter is narrowed through neointimal hyperplasia and vessel remodeling. Although rates of ISR have decreased in most recent years owing to newer generation drug-eluting stents, thinner struts, and better intravascular imaging modalities, ISR remains a prevalent dilemma that proves to be challenging to manage. Several factors have been proposed to contribute to ISR formation, including mechanical stent characteristics, technical factors during the coronary intervention, and biological aspects of drug-eluting stents. Presentation of ISR can range from asymptomatic to late myocardial infarction and could be difficult to differentiate from acute thrombus formation. No definite guidelines are present on the management of ISR. In this review, we will discuss the mechanisms underlying ISR and provide insight into patient-related and procedural risk factors contributing to ISR, in addition to highlighting common treatment approaches utilized in the management of ISR.

Development of Innovative Biomaterials and Devices for the Treatment of Cardiovascular Diseases

Cardiovascular diseases have become the leading cause of death worldwide. The increasing burden of cardiovascular diseases has become a major public health problem and how to carry out efficient and reliable treatment of cardiovascular diseases has become an urgent global problem to be solved. Recently, implantable biomaterials and devices, especially minimally invasive interventional ones, such as vascular stents, artificial heart valves, bioprosthetic cardiac occluders, artificial graft cardiac patches, atrial shunts, and injectable hydrogels against heart failure, have become the most effective means in the treatment of cardiovascular diseases. Herein, an overview of the challenges and research frontier of innovative biomaterials and devices for the treatment of cardiovascular diseases is provided, and their future development directions are discussed.

A Polyphenol-Network-Mediated Coating Modulates Inflammation and Vascular Healing on Vascular Stents

Localized drug delivery from drug-eluting stents (DESs) to target sites provides therapeutic efficacy with minimal systemic toxicity. However, DESs failure may cause thrombosis, delay arterial healing, and impede re-endothelialization. Bivalirudin (BVLD) and nitric oxide (NO) promote arterial healing. Nevertheless, it is difficult to combine hydrophilic signal molecules with hydrophobic antiproliferative drugs while maintaining their bioactivity. Here, we fabricated a micro- to nanoscale network assembly consisting of copper ion and epigallocatechin gallate (EGCG) via π-π interactions, metal coordination, and oxidative polymerization. The network incorporated rapamycin and immobilized BVLD by the thiol-ene "click" reaction and provided sustained rapamycin and NO release. Unlike rapamycin-eluting stents, those coated with the EGCG-Cu-rapamycin-BVLD complex favored competitive endothelial cell (EC) growth over that of smooth muscle cells, exhibited long-term antithrombotic efficacy, and attenuated the negative impact of rapamycin on the EC. In vivo stent implantation demonstrated that the coating promoted endothelial regeneration and hindered restenosis. Therefore, the polyphenol-network-mediated surface chemistry can be an effective strategy for the engineering of multifunctional surfaces.

Stent strut streamlining and thickness reduction promote endothelialization

Stent thrombosis (ST) carries a high risk of myocardial infarction and death. Lack of endothelial coverage is an important prognostic indicator of ST after stenting. While stent strut thickness is a critical factor in ST, a mechanistic understanding of its effect is limited and the role of haemodynamics is unclear. Endothelialization was tested using a wound-healing assay and five different stent strut models ranging in height between 50 and 150 µm for circular arc (CA) and rectangular (RT) geometries and a control without struts. Under static conditions, all stent strut surfaces were completely endothelialized. Reversing pulsatile disturbed flow caused full endothelialization, except for the stent strut surfaces of the 100 and 150 µm RT geometries, while fully antegrade pulsatile undisturbed flow with a higher mean wall shear stress caused only the control and the 50 µm CA geometries to be fully endothelialized. Modest streamlining and decrease in height of the stent struts improved endothelial coverage of the peri-strut and stent strut surfaces in a haemodynamics dependent manner. This study highlights the impact of the stent strut height (thickness) and geometry (shape) on the local haemodynamics, modulating reendothelialization after stenting, an important factor in reducing the risk of stent thrombosis.

Roles of MicroRNAs in Peripheral Artery In-Stent Restenosis after Endovascular Treatment

Endovascular repair including percutaneous transluminal angioplasty (PTA) and stent implantation has become the standard approach for the treatment of peripheral arterial disease; however, restenosis is still the main limited complication for the long-term success of the endovascular repair. Endothelial denudation and regeneration, inflammatory response, and neointimal hyperplasia are major pathological processes occurring during in-stent restenosis (ISR). MicroRNAs exhibit great potential in regulating several vascular biological events in different cell types and have been identified as novel therapeutic targets as well as biomarkers for ISR prevention. This review summarized recent experimental and clinical studies on the role of miRNAs in ISR modification, with the aim of unraveling the underlying mechanism and potential therapeutic strategy of ISR.

Drug-Coated Balloons for the Treatment of Symptomatic Intracranial High-Grade Stenosis: A Review of the Current Rationale

Symptomatic intracranial atherosclerotic disease (sICAD) remains a challenging disorder in the neurovascular field. Despite best medical treatment, the recurrence rate for stroke remains high in patients with intracranial high-grade stenosis (>70–99%). Furthermore, two large randomized trials (SAMMPRIS and VISSIT) failed to prove the efficacy of percutaneous transluminal angioplasty and stenting in patients with sICAD. Drug-coated balloon percutaneous transluminal angioplasty (DCB-PTA) represents an alternative treatment modality with therapeutic benefits for interventional cardiology. However, there are very few articles in the existing literature that relate to the use of DCB-PTA in sICAD patients. Here, we aimed to review the rationale underlying the use of DCB-PTA in sICAD patients and summarize recent developments in the neurovascular field.

Hierarchical Capillary Coating to Biofunctionlize Drug-Eluting Stent for Improving Endothelium Regeneration

The drug-eluting stent (DES) has become one of the most successful and important medical devices for coronary heart disease, but yet suffers from insufficient endothelial cell (EC) growth and intima repair, eventually leading to treatment failure. Although biomacromolecules such as vascular endothelial growth factor (VEGF) would be promising to promote the intima regeneration, combining hydrophilic and vulnerable biomacromolecules with hydrophobic drugs as well as preserving the bioactivity after harsh treatments pose a huge challenge. Here, we report on a design of hierarchical capillary coating, which composes a base solid region and a top microporous region for incorporating rapamycin and VEGF, respectively. The top spongy region can guarantee the efficient, safe, and controllable loading of VEGF up to 1 μg/cm2 in 1 minute, providing a distinctive real-time loading capacity for saving the bioactivity. Based on this, we demonstrate that our rapamycin-VEGF hierarchical coating impressively promoted the competitive growth of endothelial cells over smooth muscle cells (ratio of EC/SMC~25) while relieving the adverse impact of rapamycin to ECs. We further conducted the real-time loading of VEGF on stents and demonstrate that the hierarchical combination of rapamycin and VEGF showed remarkable endothelium regeneration while maintaining a very low level of in-stent restenosis. This work paves an avenue for the combination of both hydrophobic and hydrophilic functional molecules, which should benefit the next generation of DES and may extend applications to diversified combination medical devices.

Vascular Stents Coated with Electrospun Drug-Eluting Material: Functioning in Rabbit Iliac Artery

A stenting procedure aimed at blood flow restoration in stenosed arteries significantly improves the efficiency of vascular surgery. However, the current challenge is to prevent neointimal growth, which reduces the vessel lumen, in the stented segments in the long run. We tested in vivo drug-eluting coating applied by electrospinning to metal vascular stents to inhibit the overgrowth of neointimal cells via both the drug release and mechanical support of the vascular wall. The blend of polycaprolactone with human serum albumin and paclitaxel was used for stent coating by electrospinning. The drug-eluting stents (DESs) were placed using a balloon catheter to the rabbit common iliac artery for 1, 3, and 6 months. The blood flow rate was ultrasonically determined in vivo. After explantation, the stented arterial segment was visually and histologically examined. Any undesirable biological responses (rejection or hemodynamically significant stenosis) were unobservable in the experimental groups. DESs were less traumatic and induced weaker neointimal growth; over six months, the blood flow increased by 37% versus bare-metal stents, where it increased by at least double the rate. Thus, electrospun-coated DESs demonstrate considerable advantages over the bare-metal variants.

Drug-Coated Balloon Treatment in Symptomatic Intracranial High Grade Stenosis : A Retrospective Study of 33 Patients

PURPOSE

Endovascular therapy (EVT) represents an alternative treatment modality for symptomatic intracranial high-grade atherosclerotic stenosis (sICAS); however, periprocedural complication rates as well as midterm restenosis rates represent relevant limitations of EVT. Drug-coated balloon percutaneous transluminal angioplasty (DCB-PTA) may overcome some of these shortcomings. The aim of this study was to assess feasibility and safety as well as the stroke recurrence rate in 33 patients.

METHODS

A retrospective, monocentric cohort study of sICAS patients treated with DCB-PTA. Outcome measures were the periprocedural intracranial complication rate, the recurrent stroke rate and mortality during follow-up.

RESULTS

This cohort study included 33 patients with 35 sICAS treated with DCB-PTA. The median age was 72 years (interquartile range, IQR 66-77 years); median clinical and mean radiological follow-up time was 9 months (IQR 3-22 months). Median preprocedural degree of stenosis (WASID) was 80% (IQR 73-80%) and median postprocedural residual stenosis degree (WASID) was 50% (IQR 33-60%). Intracranial periprocedural complications occurred in 2 (6%) patients. The overall restenosis rate was 15% (n = 5). In four patients a symptomatic ischemic re-event occurred within 7 months after the initial treatment. None of the patients died.

CONCLUSION

This DCB-PTA cohort study showed a relatively low intracranial complication rate of 6% with a symptomatic recurrence rate of 12%. Larger trials are needed to validate these promising observations.

Device profile of different paclitaxel-coated balloons: Neuro Elutax SV, Elutax '3' Neuro and SeQuent Please NEO for the treatment of symptomatic intracranial high-grade stenosis: overview of their feasibility and safety

Introduction: Intracranial atherosclerotic disease (ICAD) is highly prevalent and probably the most common cause of stroke worldwide. Despite best medical treatment (BMT), the rate of recurrent stroke in symptomatic ICAD patients is elevated, especially in those with high-grade stenosis. Thus, alternative treatment options are needed. So far, endovascular ICAD treatment has been considered a second-line therapy. However, recent progress in the endovascular acute stroke treatment challenges this issue. Drug-coated balloon (DCB) - percutaneous transluminal angioplasty (PTA) represents a promising alternative to BMT alone.Areas covered: In this review, current clinical studies on paclitaxel-coated DCB-PTA in symptomatic high-grade ICAD patients will be presented and discussed. Furthermore, technical profile of the different paclitaxel-coated DCB, which has been used for intracranial use (Neuro Elutax SV, Elutax '3' Neuro, and SeQuent Please NEO) are being presented.Expert opinion: Despite limited data and its experimental (off-line) use, DCB-PTA has been demonstrated to be feasible and safe in selected ICAD patients with symptomatic high-grade stenosis. DCB-PTA offers several advantages compared to alternative endovascular therapy option as well as BMT alone. Consequently, DCP-PTA might be a promising candidate for the future armamentarium in ICAD treatment.

Micelle-embedded coating with ebselen for nitric oxide generation

Nitric oxide generation is considered to be a key factor to mimic endothelial function in terms of anti-coagulation and anti-hyperplasia. Herein, ebselen which could play the similar role as glutathion peroxidase-like was loaded into micelles and was further assembled into a layer-by-layer coating. The ability of nitric oxide generation and corresponding biological effect were investigated. Endothelial-mimetic surface has now attracted huge attention in blood-contacting materials, due to its inherent ability of secreting nitric oxide. Among those categories, nitric oxide generation surface is considered to be safe and tunable in the modification of vascular biomedical devices. How to adsorb or immobilize glutathion peroxidase-like catalyst and maintain sustained/safe nitric oxide generation is full of interest. This study aimed at developing a functional coating constructed via layer-by-layer assembly to introduce the catalyst into the coating by pre-loading ebselen in micelles. We firstly introduced phenylboronic acid moiety into the micelle molecule backbone and grafted catechol moiety to chitosan backbone. Then, chitosan, micelles (containing ebselen) and heparin were adopted as polyelectrolytes and then alternatively assembled onto the substrate via layer-by-layer protocol. The catechol was conjugated to the amine groups of chitosan by Schiff base reaction to synthesize chitosan-catechol. The hydrophobic cholesterol was conjugated to the one end of the hydrophilic hyaluronic acid, and the hydroxymethylphenylboronic acid was conjugated to the other end via the esterification of carboxyl (-COOH) and hydroxyl (-OH). The modified hyaluronic acid could spontaneously form micelles in aqueous solution. Ebselen was the loaded into the as-prepared micelles. Chitosan-catechol, heparin, and micelles were alternatively assembled onto the substrate layer by layer to form a micelle-embedded coating. The micelle-embedded coating with ebselen was successfully obtained and the nitric oxide generation ability was in a safe level which was close to healthy endothelial cells. The coating could effectively inhibit platelet adhesion and smooth muscle cell proliferation. The use of ebselen preloaded into micelles could provide a sustained release of catalyst for in situ nitric oxide generation. Besides, this method could also be used to load diverse drugs and regulate desired properties. The study was approved by the Institutional Review Board of the West China Hospital in Sichuan University on March 3, 2018, with approval No. K2018044.

Twelve-month comparative analysis of clinical outcomes using biodegradable polymer-coated everolimus-eluting stents versus durable polymer-coated everolimus-eluting stents in all-comer patients

Aim

The purpose of the present study was to examine whether clinical differences exist between the biodegradable polymer (BDP)–coated Tetrilimus everolimus-eluting stent (EES) and the durable polymer (DP)–coated Xience EES by comparing the major adverse cardiac event (MACE) rate at 12 months in all-comer patients.

Methods

This study was designed as a multicentre, observational, retrospective, investigator-initiated study between January 2016 and October 2016. Two hundred thirteen patients who underwent percutaneous coronary intervention (PCI) with the BDP-EES were compared with 204 patients who underwent PCI with the DP-EES, irrespective of lesion complexity, comorbidities and acute presentation. The primary end point was MACE defined as a composite of cardiac death, myocardial infarction and target lesion revascularization.

Results

Baseline clinical and lesion characteristics of both the groups were similar, although the BDP-EES group had a significantly higher number of patients with diabetes mellitus (39.9% vs. 30.4%; p = 0.042) and type C lesion (67.4% vs. 48.1%; p < 0.001) than the DP-EES group. The 12-month MACE rate was 4.2% for the BDP-EES group versus 4.9% for the DP-EES group (p = 0.740). Mortality was lower in the BDP-EES group than in the DP-EES group (0.9% vs. 2.0%; p = 0.441).

Conclusion

The present comparative analysis shows that the BDP-coated Tetrilimus EES was as safe and effective as the DP-coated Xience EES during the 12-month follow-up period despite complex lesion characteristics.

Inhibition of in-stent restenosis after graphene oxide double-layer drug coating with good biocompatibility

In this study, we designed a double layer-coated vascular stent of 316L stainless steel using an ultrasonic spray system to achieve both antiproliferation and antithrombosis. The coating included an inner layer of graphene oxide (GO) loaded with docetaxel (DTX) and an outer layer of carboxymethyl chitosan (CMC) loaded with heparin (Hep). The coated surface was uniform without aggregation and shedding phenomena before and after stent expanded. The coating treatment was able to inhibit the adhesion and activation of platelets and the proliferation and migration of smooth muscle cells, indicating the excellent biocompatibility and antiproliferation ability. The toxicity tests showed that the GO/DTX and CMC/Hep coating did not cause deformity and organ abnormalities in zebrafish under stereomicroscope. The stents with GO double-layer coating were safe and could effectively prevent thrombosis and in-stent restenosis after the implantation into rabbit carotid arteries for 4–12 weeks.

Combining mathematical modelling with in vitro experiments to predict in vivo drug-eluting stent performance

In this study, we developed a predictive model of in vivo stent based drug release and distribution that is capable of providing useful insights into performance. In a combined mathematical modelling and experimental approach, we created two novel sirolimus-eluting stent coatings with quite distinct doses and release kinetics. Using readily measurable in vitro data, we then generated parameterised mathematical models of drug release. These were then used to simulate in vivo drug uptake and retention. Finally, we validated our model predictions against data on drug kinetics and efficacy obtained in a small in vivo evaluation. In agreement with the in vivo experimental results, our mathematical model predicted consistently higher sirolimus content in tissue for the higher dose stents compared with the lower dose stents. High dose stents resulted in statistically significant improvements in three key efficacy measures, providing further evidence of a basic relationship between dose and efficacy within DES. However, our mathematical modelling suggests a more complex relationship is at play, with efficacy being dependent not only on delivering an initial dose of drug sufficient to achieve receptor saturation, but also on the consequent drug release rate being tuned to ensure prolonged saturation. In summary, we have demonstrated that our combined in vitro experimental and mathematical modelling framework may be used to predict in vivo DES performance, opening up the possibility of an in silico approach to optimising the drug release profile and ultimately the effectiveness of the device.

Micelle-Embedded Layer-by-Layer Coating with Catechol and Phenylboronic Acid for Tunable Drug Loading, Sustained Release, Mild Tissue Response, and Selective Cell Fate for Re-endothelialization

Tunable/sustained drug loading/releasing are of significance in addressing low cytotoxicity, long-term performance, and localized mild healing response in biomedical applications. With an ingenious design, a self-healing sandwiched layer-by-layer (LBL) coating was constructed by using chitosan/heparin as adopted polyelectrolytes with embedding of micelles, in which the chitosan backbone was grafted with catechol and the micelle was modified with exposed phenylboronic acid, endowing the coating with enhanced stability by abundant interactions among coating components (e.g., boric acid ester bond formation, weak intermolecular cross-linking, π-π interactions, and H-bonding). Moreover, rapamycin and atorvastatin calcium were selected as drug candidates and loaded into micelles, followed by drug-releasing behavior study. It was found that the LBL coating maintained a linear growth mode up to 30 cycles, giving a favorable tunability of coating construction and drug loading. The coating could also support sustained release of payloads and provide wild tissue response. With the systematic in vitro and in vivo study, such catechol-phenylboronic acid-enhanced LBL coating with drug loading would also address enhanced antiplatelet adhesion/activation and direct cell fate of endothelial cells and smooth muscle cells via tuning of coating cycles and loaded drugs. With modular assembly, such coating indicated potential for achieving enhanced re-endothelialization for vascular implants.

In vitro and in vivo evaluation of a dextran-graft-polybutylmethacrylate copolymer coated on CoCr metallic stent

Introduction: The major complications of stent implantation are restenosis and late stent thrombosis. PBMA polymers are used for stent coating because of their mechanical properties. We previously synthesized and characterized Dextrangraft-polybutylmethacrylate copolymer (Dex-PBMA) as a potential stent coating. In this study, we evaluated the haemocompatibility and biocompatibility properties of Dex-PBMA in vitro and in vivo. Methods: Here, we investigated: (1) the effectiveness of polymer coating under physiological conditions and its ability to release Tacrolimus®, (2) the capacity of Dex-PBMA to inhibit Staphylococcus aureus adhesion, (3) the thrombin generation and the human platelet adhesion in static and dynamic conditions, (4) the biocompatibility properties in vitro on human endothelial colony forming cells ( ECFC) and on mesenchymal stem cells (MSC) and in vivo in rat models, and (5) we implanted Dex-PBMA and Dex-PBMA_TAC coated stents in neointimal hyperplasia restenosis rabbit model. Results: Dex-PBMA coating efficiently prevented bacterial adhesion and release Tacrolimus®. Dex-PBMA exhibit haemocompatibility properties under flow and ECFC and MSC compatibility. In vivo, no pathological foreign body reaction was observed neither after intramuscular nor intravascular aortic implantation. After Dex-PBMA and Dex-PBMA_TAC coated stents 30 days implantation in a restenosis rabbit model, an endothelial cell coverage was observed and the lumen patency was preserved. Conclusion: Based on our findings, Dex-PBMA exhibited vascular compatibility and can potentially be used as a coating for metallic coronary stents.

Electrospun Produced 3D Matrices for Covering of Vascular Stents: Paclitaxel Release Depending on Fiber Structure and Composition of the External Environment

Paclitaxel is a natural, highly lipophilic anti proliferative drug widely used in medicine. We have studied the release of tritium-labeled paclitaxel (³H-PTX) from matrices destined for the coating of vascular stents and produced by the electrospinning method from the solutions of polycaprolactone (PCL) with paclitaxel (PTX) in hexafluoisopropanol (HFIP) and/or solutions of PCL with PTX and human serum albumin (HSA) in HFIP or HIFP-dimethyl sulphoxide (DMSO) blend. The release of PTX has been shown to depend on the composition of electrospinning solution, as well as the surrounding medium, particularly the concentration of free PTX and PTX-binding biomolecules present in human serum. It was shown that 3D matrices can completely release PTX without weight loss. Two-phase PTX release from optimized 3D matrices was obtained: ~27% of PTX was released in the first day, another 8% were released over the next 26 days. Wherein ~2.8%, ~2.3%, and ~0.25% of PTX was released on day 3, 9, and 27, respectively. Considering PTX toxicity, the rate of its diffusion through the arterial wall, and the data obtained the minimum cytostatic dose of the drug in the arterial wall will be maintained for at least three months.

Middle cerebral artery geometric features are associated with plaque distribution and stroke

OBJECTIVE

We aimed to investigate the geometric features of the middle cerebral artery (MCA) and their relevance to plaque distribution and ischemic stroke.

METHODS

We reviewed our institutional vessel wall imaging database. Patients with symptomatic MCA atherosclerosis, asymptomatic MCA atherosclerosis, or without MCA atherosclerosis were included. The MCA geometric features, including M1 segment shape and M1 curve orientation, were defined on magnetic resonance angiography. Plaque distribution and other plaque parameters were identified on vessel wall imaging. The association among MCA geometric features, plaque distribution, and ischemic stroke were analyzed.

RESULTS

A total of 977 MCAs were analyzed (87 atherosclerotic symptomatic MCAs, 459 atherosclerotic asymptomatic MCAs, and 431 plaque-free MCAs). Overall, curved M1 segments were the predominant shape across all groups. In 91.1% of curved atherosclerotic MCAs, the plaque involved the inner wall of the curve. Plaque not involving the inner wall was shorter (p < 0.0001) and thinner (p = 0.005) compared to plaque involving the inner wall. Inferior plaque was observed in 39.9% of inferior-oriented M1 curves compared to 21.7% in non-inferior-oriented M1 curves (p < 0.0001). The absence of an inferior-oriented M1 curve (odds ratio 0.45, 95% confidence interval 0.27-0.77) and presence of superior plaque (odds ratio 2.67, 95% confidence interval 1.52-4.67) were independently associated with stroke after adjusting for plaque length and thickness, degree of stenosis, and remodeling ratio.

CONCLUSIONS

MCA geometric features are associated with plaque distribution and stroke. Our findings provide insight into the vascular pathophysiology of MCA atherosclerosis.

Multifunctional coatings that mimic the endothelium: surface bound active heparin nanoparticles with in situ generation of nitric oxide from nitrosothiols

Multifunctional coatings that mimic the endothelial function in terms of nitric oxide generation and membrane-bound active heparin species are prepared via the immobilization of cystamine-modified heparin/polyethyleneimine (Hep-Cys/PEI) nanoparticles. Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS) were conducted to confirm the coating formation. Functions of active heparin release and nitric oxide (NO) generation are obtained on the material surface after the immobilization of Hep-Cys/PEI nanoparticles. Moreover, a nanoparticle-immobilized coating is sufficiently flexible to resist the deformation of a 316L SS stent without any destruction. With the introduction of heparin, the antithrombin III (AT-III) binding ability was significantly enhanced with prolonged APTT time. Besides, a Hep-Cys/PEI nanoparticle immobilized coating surface not only significantly suppressed the platelet adhesion and activation, but also promoted EC proliferation and inhibited SMC proliferation. Besides, a milder tissue response was observed on the NP immobilized surface. With the synergistic effect of heparin and nitric oxide generating moieties, such multifunctional coatings presented potential for the modification of vascular materials.

Understanding the role of non-coding RNA (ncRNA) in stent restenosis

Coronary heart disease (CHD) is one of the leading disorders with the highest mortality rate. Percutaneous angioplasty and stent implantation are the currently available standard methods for the treatment of obstructive coronary artery disease. However, the stent being an exogenous substance causes several complications by promoting the proliferation of vascular smooth muscle cells, immune responses and neointima formation after implantation, leading to post-stent restenosis (ISR) and late thrombosis. The prevention of these adverse vascular events is important to achieve long-term proper functioning of the heart after stent implantation. Non-coding ribonucleic acids (ncRNAs) are RNA molecules not translated into proteins, theyhave a great potential in regulating endothelial cell and vascular smooth muscle function as well as inflammatory reactions. In this review, we outline the regulatory functions of different classes of ncRNA in cardiovascular disease and propose ncRNAs as new targets for stent restonosis treatment.

Comparative study of different polymeric coatings for the next-generation magnesium-based biodegradable stents

Development of next-generation bioabsorbable stents based on magnesium alloys is gaining lots of attention. However, finding an appropriate coating in order to enhance its corrosion resistance along with preserving other requirements is still a challenge. In this study, three FDA-approved polymers, namely poly(lactic acid), polycaprolactone and poly(lactic-co-glycolic acid), have been investigated as potential coatings for magnesium-based stents to enhance their corrosion resistance, biocompatibility and haemocompatibility. Potentiodynamic and electrochemical impedance spectroscopy results demonstrated that PLA and PLGA coating performed better in improving corrosion resistance in comparison with uncoated and other coated samples. Although all coated and bare samples displayed desirable results of haemocompatibility assays, PLA-coated samples showed better outcome in terms of biocompatibility. The results revealed that PLA can be considered as a potential coating material to enhance the main characteristics of magnesium-based bioabsorbable stents.

Multifunctional mussel-inspired copolymerized epigallocatechin gallate (EGCG)/arginine coating: the potential as an ad-layer for vascular materials

Surface properties are considered to be important factors in addressing proper functionalities. In this paper, a multifunctional mussel-inspired coating was prepared via the direct copolymerization of epigallocatechin gallate (EGCG) and arginine. The coating formation was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectra. The EGCG/arginine coating contained diverse functional groups like amines, phenols and carboxyls, whose densities were also tunable. Such mussel-inspired coating could also be applied as an ad-layer for its secondary reactivity, demonstrated by quartz crystal microbalance technique. Moreover, the tunable surface density of phenols showed potential ability in modulating endothelial cell and smooth muscle cell viability. The coatings rich in phenols presented excellent free radical scavenging property. Current results strongly indicated the potential of EGCG/arginine coatings to be applied as an ad-layer for vascular materials.

Primary Stenting of Totally Occluded Native Coronary Arteries III (PRISON III): a randomised comparison of sirolimus-eluting stent implantation with zotarolimus-eluting stent implantation for the treatment of total coronary occlusions

AIMS

We investigated whether sirolimus-eluting stents (SES) are superior to next-generation zotarolimus-eluting stents (ZES) in treating patients with total coronary occlusions (TCO).

METHODS AND RESULTS

In a prospective, randomised trial we compared the SES with the zotarolimus-eluting stent (ZES; Endeavor or Resolute) after successful recanalisation of TCO. During the first phase of the trial, 51 patients were assigned to receive the SES and 46 patients to receive the Endeavor ZES. In the second phase we randomised 103 patients to the SES group and 104 patients to the Resolute ZES group. The primary endpoint was in-segment late lumen loss at eight-month follow-up. At eight months, patients in the SES group had less in-segment and in-stent late loss as compared to the Endeavor group: -0.13±0.3 mm vs. 0.27±0.6 mm (p=0.0002) and -0.13±0.5 mm vs. 0.54±0.5 mm (p<0.0001), respectively. In contrast, the SES and the Resolute ZES showed comparable amounts of in-segment (-0.03±0.7 mm vs. -0.10±0.7 mm, p=0.6) and in-stent (0.03±0.8 mm vs. 0.05±0.8 mm, p=0.9) late loss.

CONCLUSIONS

In the treatment of TCOs, the SES was associated with superior angiographic outcomes compared to the Endeavor ZES. On the other hand, the SES and the Resolute ZES showed comparable angiographic outcomes.

Bioresorbable drug-eluting scaffolds for treatment of vascular disease

INTRODUCTION

Theoretical advantages of fully bioresorbable scaffold (BRS) stem from transient vessel support without rigid caging. Therefore, it could reduce long-term adverse events associated with the presence of foreign materials.

AREAS COVERED

This article will provide an overview of: drug-eluting BRS for various applications in the treatment of vascular disease; The mechanisms of active agent release from such scaffolds; currently available drug-eluting BRS and their future applications are also discussed.

EXPERT OPINION

The current BRS have been developed in order to achieve optimal vascular patency while providing long-term safety. The clinical efficacy and safety of BRS in coronary treatment have been reported as equal to that of the current metallic drug eluting stents in simple lesions. The application of BRS can potentially be expanded to other vascular beds. The research in bioengineering for the appropriate materials should not only focus on biocompatibility but also should be tailored according to the sites of implantation, which may require different strength and supporting period. The ultimate goal in this field is to develop a biocompatible device that provides equivalent and complementary therapy to other devices, and is able to disappear when the mechanical support and drug delivery are no longer required.

A NEW WAY TO OPTIMIZE DRUG RELEASE RATE OF DRUG ELUTING STENT (DES)

Local hemodynamic environment is a determinant factor in drug delivery from a drug eluting stent (DES) to the target arterial tissue. By using a simplified model of a DES, we demonstrated that if a DES had a drug release mode of uniform rate the drug released from the stent will distribute non-uniformly along the stent due to the flowing blood, with a significantly higher drug concentration at the distal part of the stent than that at the proximal one. This may explain why a DES could retard neointimal formation and vascular remodeling in downstream coronary segments. To solve this problem, we thereafter optimized the drug release mode of the DES as an exponential function. The simulation results showed that the optimized drug release mode could lead to a fairly uniform drug concentration distribution along the stent. Therefore, the present study suggested that to achieve a more effective result, optimization of drug eluting strategy (drug release mode) for the DES would be essential.

Polymer-Free Drug-Eluting Stents: An Overview of Coating Strategies and Comparison with Polymer-Coated Drug-Eluting Stents

Clinical evaluations have proven the efficacy of drug-elution stents (DES) in reduction of in-stent restenosis rates as compared to drug-free bare metal stents (BMS). Typically, DES are metal stents that are covered with a polymer film loaded with anti-inflammatory or antiproliferative drugs that are released in a sustained manner. However, although favorable effects of the released drugs have been observed, the polymer coating as such has been associated with several adverse clinical effects, such as late stent thrombosis. Elimination of the polymeric carrier of DES may therefore potentially lead to safer DES. Several technologies have been developed to design polymer-free DES, such as the use of microporous stents and inorganic coatings that can be drug loaded. Several drugs, including sirolimus, tacrolimus, paclitaxel, and probucol have been used in the design of carrier-free stents. Due to the function of the polymeric coating to control the release kinetics of a drug, polymer-free stents are expected to have a faster drug elution rate, which may affect the therapeutic efficacy. However, several polymer-free stents have shown similar efficacy and safety as the first-generation DES, although the superiority of polymer-free DES has not been established in clinical trials.

Controlled Slow-Release Drug-Eluting Stents for the Prevention of Coronary Restenosis: Recent Progress and Future Prospects

Drug-eluting stents (DES) have become more widely used by cardiologists than bare metal stents (BMS) because of their better ability to control restenosis. However, recognized negative events, particularly including delayed or incomplete endothelialization and late stent thrombosis, have caused concerns over the long-term safety of DES. Although stent-based drug delivery can facilitate a drug's release directly to the restenosis site, a burst of drug release can seriously affect the pharmacological action and is a major factor accounting for adverse effects. Therefore, the drug release rate has become an important criterion in evaluating DES. The factors affecting the drug release rate include the drug carrier, drug, coating methods, drug storage, elution direction, coating thickness, pore size in the coating, release conditions (release medium, pH value, temperature), and hemodynamics after the stent implantation. A better understanding of how these factors influence drug release is particularly important for the reasonable use of efficient control strategies for drug release. This review summarizes the factors influencing the drug release from DES and presents strategies for enhancing the control of the drug's release, including the stent design, the application of absorbable stents, the development of new polymers, and the application of nanocarriers and improvements in the coating technology. Therefore, this paper provides a reference for the preparation of novel controlled slow-release DES.

Progress and prospects of endothelial progenitor cell therapy in coronary stent implantation

Drug-eluting stents (DES) have been widely used to treat coronary artery disease (CAD) since their clinical use has significantly reduced the occurrence of in-stent restenosis (ISR) as compared with the initially applied bare-metal stents (BMS). However, analyses of long-term clinical outcome have raised concerns about the serious safety problem of DES, such as ISR caused by late or very late thrombosis. Various studies showed that those complications were associated with vascular endothelial injury/dysfunction or endothelialization delaying. Recently, through biological characterization of endothelial progenitor cells (EPCs), mechanistic understanding of rapid re-endothelialization of the vascular injury sites after coronary stenting has become possible and is a new research hotspot in the prevention of ISR and late/very late stent thrombosis. It has been well recognized that the formation of a functional endothelial layer from EPCs requires a coordinated sequence of multistep and signaling events, which includes cell mobilization, adhesion, migration and finally the differentiation to vascular endothelial cells (VECs). In this review, we summarize and discuss the currently relevant information about EPCs, the mechanism of DES interfering with the natural vascular healing process in preventing or delaying the formation of a functional endothelial layer, and EPCs-mediated acceleration of re-endothelialization at vascular injury sites. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1237-1247, 2016.

A new stent with streamlined cross-section can suppress monocyte cell adhesion in the flow disturbance zones of the endovascular stent

We proposed a new stent with streamlined cross-sectional wires, which is different from the clinical coronary stents with square or round cross-sections. We believe the new stent might have better hemodynamic performance than the clinical metal stents. To test the hypothesis, we designed an experimental study to compare the performance of the new stent with the clinical stents in terms of monocyte (U-937 cells) adhesion. The results showed that when compared with the clinical stents, the adhesion of U-937 cells were much less in the new stent. The results also showed that, when Reynolds number increased from 180 (the rest condition for the coronary arteries) to 360 (the strenuous exercise condition for the coronary arteries), the flow disturbance zones in the clinical stents became larger, while they became smaller with the new stent. The present experimental study therefore suggests that the optimization of the cross-sectional shape of stent wires ought to be taken into consideration in the design of endovascular stents.

Sodium ferulate inhibits neointimal hyperplasia in rat balloon injury model

Background/Aim

Neointimal formation after vessel injury is a complex process involving multiple cellular and molecular processes. Inhibition of intimal hyperplasia plays an important role in preventing proliferative vascular diseases, such as restenosis. In this study, we intended to identify whether sodium ferulate could inhibit neointimal formation and further explore potential mechanisms involved.

Methods

Cultured vascular smooth muscle cells (VSMCs) isolated from rat thoracic aorta were pre-treated with 200 µmol/L sodium ferulate for 1 hour and then stimulated with 1 µmol/L angiotensin II (Ang II) for 1 hour or 10% serum for 48 hours. Male Sprague-Dawley rats subjected to balloon catheter insertion were administrated with 200 mg/kg sodium ferulate (or saline) for 7 days before sacrificed.

Results

In presence of sodium ferulate, VSMCs exhibited decreased proliferation and migration, suppressed intracellular reactive oxidative species production and NADPH oxidase activity, increased SOD activation and down-regulated p38 phosphorylation compared to Ang II-stimulated alone. Meanwhile, VSMCs treated with sodium ferulate showed significantly increased protein expression of smooth muscle α-actin and smooth muscle myosin heavy chain protein. The components of Notch pathway, including nuclear Notch-1 protein, Jagged-1, Hey-1 and Hey-2 mRNA, as well as total β-catenin protein and Cyclin D1 mRNA of Wnt signaling, were all significantly decreased by sodium ferulate in cells under serum stimulation. The levels of serum 8-iso-PGF2α and arterial collagen formation in vessel wall were decreased, while the expression of contractile markers was increased in sodium ferulate treated rats. A decline of neointimal area, as well as lower ratio of intimal to medial area was observed in sodium ferulate group.

Conclusion

Sodium ferulate attenuated neointimal hyperplasia through suppressing oxidative stress and phenotypic switching of VSMCs.

Mmp-9 expression after metallic stent placement in patients with colorectal cancer: association with in-stent restenosis

PURPOSE

To verify the expression of matrix metalloproteinase (MMP)-9 in stent-induced hyperplastic tissue from patients with colorectal cancer who received colorectal stents as a bridge to surgery.

MATERIALS AND METHODS

This prospective study was institutional review board-approved, and informed consent was obtained from all patients. Eleven patients (nine men, two women; mean age, 67 years; age range, 53-82 years) with malignant colorectal obstructions who received a colorectal stent between May and December 2010 were included. Tissue specimens were analyzed for MMP-9 and MMP-2 expression. After resection, the tissue was segmented into three parts: tumor tissue, stent-induced tissue hyperplasia, and normal colon tissue. MMP-9 and MMP-2 expression were determined by using zymography, Western blot analysis, and real-time reverse-transcription (qRT) polymerase chain reaction (PCR). Significance of differences between groups was evaluated with Friedman analysis of variance test. Signed-rank test was used to determine differences between malignant tumor tissue and stent-induced hyperplastic tissue groups.

RESULTS

Stent placement was technically successful in all 11 patients. Stent-induced hyperplastic tissues were found in all patients. Zymography (P = .003) and Western blot analysis (P = .008) showed that expression of MMP-9 was higher in malignant tumor tissue and stent-induced hyperplastic tissue groups compared with normal colorectal tissue group, demonstrating significant differences between groups but no significant differences between malignant tumor and stent-induced hyperplastic tissues. As for results of qRT PCR analysis, the stent-induced hyperplastic tissue group showed increases in messenger RNA expression level of MMP-9 compared with the malignant tumor tissue group (50.42-fold ± 66.30 higher).

CONCLUSION

High expression of MMP-9 is closely associated with stent-induced colorectal tissue hyperplasia in patients with colorectal cancer.

Electrografting of a biodegradable layer as a primer adhesion coating onto a metallic stent: in vitro and in vivo evaluations

Drug-eluting stents have been developed to reduce the risk of restenosis after angioplasty. To facilitate the adhesion of a poly(lactic acid) (PLA) overlayer loaded with rapamycin (20 wt%), a biodegradable macromonomer based on poly(lactic acid) (HEMA-PLA) was grafted onto the metallic stent by electrografting in a one-step reaction involving the immobilization of aryl diazonium onto the metal followed by an in situ surface electro-polymerization. The HEMA-PLA coating was chemically characterized. Mechanical performance during stent expansion was tested. Morphology examinations showed a strong adhesion of PLA topcoat in the presence of the electrografted layer. Biocompatibility and degradation of the coating were studied in vitro and in vivo in rabbit iliac arteries. These 28 days implantations resulted in a minimal inflammatory process with a partial degradation of the coating. These results suggest that this kind of anchoring of a biodegradable layer shows great potential for drug-eluting stents.