Pathological analysis of local delivery of paclitaxel via a polymer-coated stent

Current Management of In-Stent Restenosis

In-stent restenosis (ISR) remains the primary cause of target lesion failure following percutaneous coronary intervention (PCI), resulting in 10-year incidences of target lesion revascularization at a rate of approximately 20%. The treatment of ISR is challenging due to its inherent propensity for recurrence and varying susceptibility to available strategies, influenced by a complex interplay between clinical and lesion-specific conditions. Given the multiple mechanisms contributing to the development of ISR, proper identification of the underlying substrate, especially by using intravascular imaging, becomes pivotal as it can indicate distinct therapeutic requirements. Among standalone treatments, drug-coated balloon (DCB) angioplasty and drug-eluting stent (DES) implantation have been the most effective. The main advantage of a DCB-based approach is the avoidance of an additional metallic layer, which may otherwise enhance neointimal hyperplasia, provide the substratum for developing neoatherosclerosis, and expose the patient to a persistently higher risk of coronary ischemic events. On the other hand, target vessel scaffolding by DES implantation confers relevant mechanical advantages over DCB angioplasty, generally resulting in larger luminal gain, while drug elution from the stent surface ensures the inhibition of neointimal hyperplasia. Nevertheless, repeat stenting with DES also implies an additional permanent metallic layer that may reiterate and promote the mechanisms leading to ISR. Against this background, the selection of either DCB or DES on a patient- and lesion-specific basis as well as the implementation of adjuvant treatments, including cutting/scoring balloons, intravascular lithotripsy, and rotational atherectomy, hold the potential to improve the effectiveness of ISR treatment over time. In this review, we comprehensively assessed the available evidence from randomized trials to define contemporary interventional treatment of ISR and provide insights for future directions.

Selection criteria in the era of perfect competition for drug-eluting stents - a survey of interventional cardiologists in Japan: the selection-DES study

BACKGROUND

More than 20 years have passed since the first company introduced drug-eluting stent (DES) in 2002, but competing companies still have improved their DESs under regulatory approval. This study aimed to investigate the criteria for interventional cardiologists performing percutaneous coronary intervention (PCI) in selecting a DES.

RESEARCH DESIGN AND METHODS

From 10 April 2023, to 30 April 2023, 3,422 cardiologists were requested to complete a questionnaire, of whom 126 responded to the survey.

RESULTS

Overall, 86.5% of the respondents used Xience cobalt-chromium everolimus-eluting stent (Xience) in > 10% of PCI procedures. For Xience, brand loyalty and calcified lesions were important independent variables for the DES selection criteria. Ultimaster sirolimus-eluting stent (Ultimaster) was not affected by the clinical data delivered by the company, whereas the respondents were shown to seek support for their activities from the Ultimaster supplier. The relationship with the company and/or sales representative and the planned surgical procedure affected the use of Coroflex ISAR NEO sirolimus-eluting polymer-free stent.

CONCLUSIONS

Patient background and lesion characteristics had little impact on the DES selection criteria, suggesting that DES performance has already reached its physical limitations to the extent that respondents may not value further improvements in performance or characteristics of DES.

An extracellular matrix-mimetic coating with dual bionics for cardiovascular stents

Anti-inflammation and anti-coagulation are the primary requirements for cardiovascular stents and also the widely accepted trajectory for multi-functional modification. In this work, we proposed an extracellular matrix (ECM)-mimetic coating for cardiovascular stents with the amplified functionalization of recombinant humanized collagen type III (rhCOL III), where the biomimetics were driven by structure mimicry and component/function mimicry. Briefly, the structure-mimic was constructed by the formation of a nanofiber (NF) structure via the polymerization of polysiloxane with a further introduction of amine groups as the nanofibrous layer. The fiber network could function as a three-dimensional reservoir to support the amplified immobilization of rhCoL III. The rhCOL III was tailored for anti-coagulant, anti-inflammatory and endothelialization promotion properties, which endows the ECM-mimetic coating with desired surface functionalities. Stent implantation in the abdominal aorta of rabbits was conducted to validate the in vivo re-endothelialization of the ECM-mimetic coating. The mild inflammatory responses, anti-thrombotic property, promotion of endothelialization and suppression of excessive neointimal hyperplasia confirmed that the ECM-mimetic coating provided a promising approach for the modification of vascular implants.

The Ranger drug-coated balloon: advances in drug-coated technology for treatment of femoropopliteal segment arterial disease

Paclitaxel drug-coated balloons (DCBs) have been shown to improve patency and lower revascularization rates compared with plain old balloon angioplasty. DCBs continue to evolve by improving balloon-coating techniques that minimize the quantity of particles washed off into the bloodstream while maximizing drug retention and vascular-healing profile. Against this backdrop, it is clear that the future of antiproliferatives for the superficial femoral artery will focus on enhancements in device coating materials that will improve the efficiency of drug delivery. The Ranger DCB system recently gained US FDA approval for use. This review discusses the background of DCBs and how the Ranger DCB builds on these previous platforms based on experimental and clinical data.

Angioscopic Evaluation of Vascular Response After Fluoropolymer-Based Drug-Eluting Stent Implantation for Femoropopliteal Artery Lesions

BACKGROUND

Although favorable clinical outcomes have been demonstrated for fluoropolymer-based paclitaxel-eluting stents (FP-DES) in the treatment of femoropopliteal lesions, the vascular response after implantation has not been systematically studied through intravascular imaging.Methods and Results: We angioscopically compared FP-DES: 24 in the early phase (mean [±SD] 3±1 months), 26 in the middle phase (12±3 months), and 20 in the late phase (≥18 months) after implantation. The dominant neointimal coverage grade, heterogeneity of neointimal coverage grade, and thrombus adhesion in the stent segment were evaluated. Neointimal coverage was graded as follows: Grade 0, stent struts exposed; Grade 1, struts bulging into the lumen, although covered; Grade 2, struts embedded in the neointima, but visible; Grade 3, struts fully embedded and invisible. Dominant neointimal coverage and heterogeneity grades were significantly higher in the middle and late phases than in the early phase (all P<0.05), but did not differ significantly between the middle and late phases. The incidence of thrombus adhesion was recorded for all stents in each of the 3 different phases.

CONCLUSIONS

The middle and late phases after FP-DES implantation were associated with significantly higher dominant neointimal coverage and heterogeneity grades than the early phase. However, thrombus adhesion was observed in all phases after FP-DES implantation. Arterial healing may not be completed even in the late phase after FP-DES implantation.

Nanoparticle coatings for controlled release of quercetin from an angioplasty balloon

Peripheral artery disease (PAD) is a systemic vascular disease of the legs that results in a blockage of blood flow from the heart to the lower extremities. Now one of the most common causes of mortality in the U.S., the first line of therapy for PAD is to mechanically open the blockages using balloon angioplasty. Coating the balloons with antiproliferative agents can potentially reduce vessel re-narrowing, or restenosis after surgical intervention, but current drug-coated balloons releasing chemotherapy agents like paclitaxel have in some cases shown increased mortality long-term. Our aim was to design a novel drug-coated balloon using a polymeric nanodelivery system for a sustained release of polyphenols that reduce restenosis but with reduced toxicity compared to chemotherapy agents. Poly (lactic-co-glycolic acid) (PLGA) nanoparticles with entrapped quercetin, a dimethoxy quercetin (rhamnazin), as well as quercetin covalently attached to PLGA, were developed. Balloon catheters were coated with polymeric nanoparticles using an ultrasonic method, and nanoparticle characteristics, drug loading, coating uniformity and drug release were determined. The adhesion of nanoparticles to vascular smooth muscle cells and the antiproliferative effect of nano-delivered polyphenols were also assessed. Of the nanoparticle systems tested, those with covalently attached quercetin provided the most sustained release over a 6-day period. Although these particles adhered to cells to a smaller extent compared to other nanoparticle formulations, their attachment was resistant to washing. These particles also exhibited the greatest anti-proliferative effect. In addition, their attachment was not altered when the cells were grown in calcifying conditions, and in PAD tissue calcification is typically a condition that impedes drug delivery. Moreover, the ultrasonic coating method generated a uniform balloon coating. The polymeric nanoparticle system with covalently attached quercetin developed herein is thus proposed as a promising platform to reduce restenosis post-angioplasty.

A review on current research status of the surface modification of Zn-based biodegradable metals

Recently, zinc and its alloys have been proposed as promising candidates for biodegradable metals (BMs), owning to their preferable corrosion behavior and acceptable biocompatibility in cardiovascular, bone and gastrointestinal environments, together with Mg-based and Fe-based BMs. However, there is the desire for surface treatment for Zn-based BMs to better control their biodegradation behavior. Firstly, the implantation of some Zn-based BMs in cardiovascular environment exhibited intimal activation with mild inflammation. Secondly, for orthopedic applications, the biodegradation rates of Zn-based BMs are relatively slow, resulting in a long-term retention after fulfilling their mission. Meanwhile, excessive Zn2+ release during degradation will cause in vitro cytotoxicity and in vivo delayed osseointegration. In this review, we firstly summarized the current surface modification methods of Zn-based alloys for the industrial applications. Then we comprehensively summarized the recent progress of biomedical bulk Zn-based BMs as well as the corresponding surface modification strategies. Last but not least, the future perspectives towards the design of surface bio-functionalized coatings on Zn-based BMs for orthopedic and cardiovascular applications were also briefly proposed.

A single-centre, retrospective analysis of mortality over 80 months comparing paclitaxel-coated balloon versus standard balloon angioplasty in the treatment of dysfunctional arteriovenous access

AIM

Percutaneous transluminal angioplasty (PTA) is a standard treatment for arteriovenous fistula (AVF) stenosis to preserve haemodialysis vascular access, promoting improved dialysis adequacy and better outcomes for those dependent on renal replacement therapy. Drug coated balloons (DCB) may help reduce the rate of neointimal hyperplasia and recurrent stenosis, but their use in femoropopliteal angioplasty has been associated with increased mortality at 2 and 5 year follow-up. This study aims to address the long-term safety of PTA for AVF stenosis with clinical correlation to participant co-morbidity and mortality.

METHODS

All patients undergoing PTA for AVF stenosis at a single centre between 2013 and 2017 were identified and grouped according to the use of DCB versus standard balloon angioplasty. All data was anonymised and correlated to verify independent predictors of mortality.

RESULTS

481 (400 standard balloon; 81 DCB) procedures were performed in 313 patients (250 standard balloon; 63 DCB). Follow-up at 80 months did not show any difference in mortality (p = 0.546). Multivariate analysis identified time on dialysis (p < 0.001), age (p = 0.001) and Charlson comorbidity index (p = 0.02) as independent predictors of mortality.

CONCLUSIONS

In this study, mortality was not associated with the use of DCBs, but was related to established factors of dialysis longevity, age and comorbidity.

Inhibition of edge stenosis of endografts in swine iliac arteries by a novel endograft with biodegradable coating at both ends

Objective

This study evaluated the effectiveness and safety of a novel endograft with a biodegradable coating at both ends in preventing edge stenosis in swine iliac arteries. The biodegradable coating was composed of polylactide and paclitaxel.

Methods

Four types of endograft were implanted in the iliac arteries of healthy swine: an endograft without coating (control group) and endografts with polylactide and paclitaxel coating containing 0.1, 0.3, or 3.6 μg/mm² of paclitaxel. The edge stenosis of these endografts in swine iliac arteries was assessed using angiographic image data at 30, 90, and 180 days after the operation. After terminal angiography, histologic evaluation of the treated arteries was performed. The treated sections of iliac arteries and blood samples were obtained at 1, 7, 30, 90, and 180 days for pharmacokinetic analysis.

Results

The results of angiographic and histologic evaluation demonstrated that intimal hyperplasia contributed to edge stenosis and polylactide-paclitaxel coating effectively inhibited edge stenosis. At 30 days, edge stenosis was observed at both the proximal and distal edges of the endograft without coating. At 90 days, edge stenosis was detected for the endograft coated with 0.1 μg/mm² paclitaxel, and ectasia dilation occurred at the proximal and distal edges of the endograft coated with 3.6 μg/mm² paclitaxel. No edge stenosis or other adverse effects were observed at 90 and 180 days for the endograft coated with 0.3 μg/mm² paclitaxel. In addition, for the endograft coated with 0.3 μg/mm² paclitaxel, a pharmacokinetic analysis showed that the paclitaxel concentration of treated segments decreased from 14 264 ± 1020 ng/g at day 1 to 80 ± 70 ng/g at day 90, and 20 ± 40 ng/g at day 180. The plasma paclitaxel concentration was low at day 1 and no longer detected after 7 days.

Conclusions

Polylactide and paclitaxel coating containing 0.3 μg/mm² paclitaxel at both ends of endografts effectively and safely inhibits edge stenosis in swine iliac arteries.

Aneurysmal degeneration of fluoropolymer-coated paclitaxel-eluting stent in the superficial femoral artery: a rising concern

BACKGROUND

Although several clinical reports demonstrated a durable patency rate after a novel fluoropolymer-coated paclitaxel-eluting stent (Eluvia; Boston Scientific, Marlborough, MA, USA) placement, aneurysmal degeneration after drug-eluting stent (Eluvia) placement has raised clinical concerns. Here, we report a case with progressive aneurysm formation on serial angiography and intravascular ultrasound over 50 months after drug-eluting stent (Eluvia) placement for a superficial femoral artery atheromatous plaque.

CASE PRESENTATION

A 79-year-old woman with right leg intermittent claudication at 100 m distance was referred to our hospital. Pre-procedural angiography showed long-segment severe stenosis from the middle-to-distal part of the right superficial femoral artery, and a 7 mm wide drug-eluting stent (Eluvia) was placed. However, the patient had a recurrence of intermittent claudication in the right lower extremity 25 months thereafter. Angiography revealed de novo stenosis in the distal part of the popliteal artery and proximal superficial femoral artery in-stent restenosis. Subsequently, the patient underwent endovascular therapy for these lesions. In addition, intravascular ultrasound at the time of endovascular therapy revealed femoral artery enlargement with a maximum vessel diameter of 10.0 mm at the distal edge of the stent. Intermittent claudication on the right side recurred again 50 months after drug-eluting stent (Eluvia). Angiography demonstrated de novo severe stenosis from the distal part of the superficial femoral artery to the middle part of the popliteal artery. Peri-stent contrast staining was found at the distal part of the drug-eluting stent (Eluvia) site. Intravascular ultrasound showed a further enlargement of maximum vessel diameter to 12.0 mm at the distal edge of the stent.

CONCLUSIONS

We report a case with progressive aneurysm degeneration on serial angiography and intravascular ultrasound over 50 months after drug-eluting stent (Eluvia) placement for a superficial femoral artery stenosis.

Results of drug-eluting stent in significant restenosis of the hemodialysis access: An initial study

BACKGROUND

This study aimed to report the 12-month results of drug-eluting stent (DES) for the treatment of significant restenosis of the hemodialysis access.

MATERIALS AND METHODS

A total of 14 patients (seven men and seven women; median age 70 years; range of 50-83 years) with significant restenosis of hemodialysis accesses were enrolled from January 2017 to December 2018. A total of 10 arteriovenous graft (AVG) and four arteriovenous fistulae were treated with DES. Study outcomes included primary patency of the target lesion and circuit.

RESULTS

Venous anastomosis of the AVG was the most common target lesion for DES insertion (nine hemodialysis accesses). The range of follow-up time was 12-36 months. Primary patency rates of target lesion before DES (patency for last conventional balloon angioplasty [CBA]) versus target lesion after DES at 6 and 12 months were 29% versus 100% and 7% versus 86% (p < 0.001). Primary patency rates of pre-DES circuit (patency for last CBA) versus post-DES circuit at 6 and 12 months were 29% versus 64% and 7% versus 29%, respectively (p = 0.058).

CONCLUSION

DES might improve the patency rate of target lesion in patients with significant restenosis of the hemodialysis access.

The Use of Bioactive Polymers for Intervention and Tissue Engineering: The New Frontier for Cardiovascular Therapy

Coronary heart disease remains one of the leading causes of death in most countries. Healthcare improvements have seen a shift in the presentation of disease with a reducing number of ST-segment elevation myocardial infarctions (STEMIs), largely due to earlier reperfusion strategies such as percutaneous coronary intervention (PCI). Stents have revolutionized the care of these patients, but the long-term effects of these devices have been brought to the fore. The conceptual and technologic evolution of these devices from bare-metal stents led to the creation and wide application of drug-eluting stents; further research introduced the idea of polymer-based resorbable stents. We look at the evolution of stents and the multiple advantages and disadvantages offered by each of the different polymers used to make stents in order to identify what the stent of the future may consist of whilst highlighting properties that are beneficial to the patient alongside the role of the surgeon, the cardiologist, engineers, chemists, and biophysicists in creating the ideal stent.

Dexamethasone eluting 3D printed metal devices for bone injuries

Aim: Additively manufactured (3D printed), stainless steel implants were coated with dexamethasone using gelatin, chondroitin sulfate for use in bone graft surgeries. Materials & methods: The drug and polymers were deposited on the implants with a rough surface using a high precision air brush. The gelatin-chondroitin sulfate layers were cross-linked using glutaraldehyde. Results: The drug content uniformity was within 100 ± 5%, and the thickness of the polymer layer was 410 ± 5.2 μm. The in vitro release studies showed a biphasic pattern with an initial burst release followed by slow release up to 3 days. Conclusion: These results are very promising as the slow release implants can be further tested in vivo in large animals, such as cattle and horses to prevent the inflammatory cascade following surgeries.

Recent Advances in Manufacturing Innovative Stents

Cardiovascular diseases are the most distributed cause of death worldwide. Stenting of arteries as a percutaneous transluminal angioplasty procedure became a promising minimally invasive therapy based on re-opening narrowed arteries by stent insertion. In order to improve and optimize this method, many research groups are focusing on designing new or improving existent stents. Since the beginning of the stent development in 1986, starting with bare-metal stents (BMS), these devices have been continuously enhanced by applying new materials, developing stent coatings based on inorganic and organic compounds including drugs, nanoparticles or biological components such as genes and cells, as well as adapting stent designs with different fabrication technologies. Drug eluting stents (DES) have been developed to overcome the main shortcomings of BMS or coated stents. Coatings are mainly applied to control biocompatibility, degradation rate, protein adsorption, and allow adequate endothelialization in order to ensure better clinical outcome of BMS, reducing restenosis and thrombosis. As coating materials (i) organic polymers: polyurethanes, poly(ε-caprolactone), styrene-b-isobutylene-b-styrene, polyhydroxybutyrates, poly(lactide-co-glycolide), and phosphoryl choline; (ii) biological components: vascular endothelial growth factor (VEGF) and anti-CD34 antibody and (iii) inorganic coatings: noble metals, wide class of oxides, nitrides, silicide and carbide, hydroxyapatite, diamond-like carbon, and others are used. DES were developed to reduce the tissue hyperplasia and in-stent restenosis utilizing antiproliferative substances like paclitaxel, limus (siro-, zotaro-, evero-, bio-, amphi-, tacro-limus), ABT-578, tyrphostin AGL-2043, genes, etc. The innovative solutions aim at overcoming the main limitations of the stent technology, such as in-stent restenosis and stent thrombosis, while maintaining the prime requirements on biocompatibility, biodegradability, and mechanical behavior. This paper provides an overview of the existing stent types, their functionality, materials, and manufacturing conditions demonstrating the still huge potential for the development of promising stent solutions.

Comparative Analysis of the Paclitaxel-Eluting Peripheral Igaki-Tamai Stent and the Drug-Free Igaki-Tamai Stent Using Optical Coherence Tomography and Histological Analysis in a Porcine Iliac Artery Model

BACKGROUND

The combination of a bioresorbable scaffold and antiproliferative drugs is a promising treatment for peripheral artery disease. The novel paclitaxel-eluting peripheral Igaki-Tamai stent (PTX-ITS) has the same backbone design as the drug-free peripheral Igaki-Tamai stent and a paclitaxel coating. Arterial responses to the PTX-ITS and ITS using optical coherence tomography (OCT) and histological analysis in a porcine iliac artery model were compared.Methods and Results:In total, 6 PTX-ITSs and 6 ITSs implanted in porcine iliac arteries were evaluated. Quantitative measurements of the scaffold, lumen, neointimal areas, and percent area stenosis were performed using OCT at 1 and 3 months. Histological evaluations (PTX-ITS [n=5], ITS [n=4]) were performed following euthanasia at 3 months. Injury, inflammation, endothelialization, and fibrin scores were measured. Baseline angiographic characteristics were similar in both groups. The ITS group showed significantly smaller scaffold areas than the PTX-ITS group at 1 month (18.50±3.62 mm²vs. 23.54±3.64 mm²; P=0.037) and 3 months (15.82±2.57 mm²vs. 21.67±3.57 mm²; P=0.009). Percent area stenosis was significantly lower in the PTX-ITS group at 3 months (28.70±7.24% vs. 40.36±7.07%; P=0.018). Histological evaluations revealed similar low-grade inflammatory reactions for both scaffolds.

CONCLUSIONS

PTX-ITSs showed significantly better suppression of late scaffold shrinkage and lower in-scaffold stenosis for up to 3 months. Additionally, PTX-ITSs exhibited high biocompatibility, which is comparable to ITSs.

1-Year All-Comers Analysis of the Eluvia Drug-Eluting Stent for Long Femoropopliteal Lesions After Suboptimal Angioplasty

OBJECTIVES

The aim of this study was to assess the performance of the fluoropolymer-based paclitaxel-eluting stent (PES) in long femoropopliteal lesions.

BACKGROUND

The new-generation fluoropolymer-based PES showed promising outcomes in short femoropopliteal lesions. The main feature of the stent is its controlled and sustained paclitaxel release over 12 months. However, the safety and efficacy of this technology in longer femoropopliteal lesions remain unclear.

METHODS

Between March 2016 and March 2017, 62 patients were included in this analysis. Indications for fluoropolymer-based PES deployment were insufficient luminal gain or flow-limiting dissection after plain old balloon angioplasty in a femoropopliteal lesion. Primary patency, freedom from target lesion revascularization, amputation-free survival, and paclitaxel-related adverse events were retrospectively analyzed for up to 1 year of follow-up.

RESULTS

Lesions were de novo in 84% of patients. Mean lesion length was 20 ± 12 cm, and 79% of the lesions (n = 49) were chronic total occlusions. Moderate or severe calcification was present in 42% of the lesions (n = 26). Stent implantation involved the distal superficial femoral artery and the proximal popliteal artery in 76% (n = 47) and 44% (n = 27) of patients, respectively. The Kaplan-Meier estimate of primary patency and freedom from target lesion revascularization was 87%. Amputation-free survival was 100% for patients with claudication (n = 32 [52%]) and 87% in patients with critical limb ischemia (n = 30 [48%]) (hazard ratio: 6.3; 95% confidence interval: 1.25 to 31.54; p = 0.052). Five aneurysm formations of the treated segments (8%) were thought to be attributable to paclitaxel.

CONCLUSIONS

The fluoropolymer-based PES showed promising 1-year clinical and angiographic outcomes in real-world long femoropopliteal lesions. The long-term impact of aneurysm formation remains to be further investigated.

Recent Advances in Polymeric Implants

Implantable drug delivery systems, such as drug pumps and polymeric drug depots, have emerged as means of providing predetermined drug release profiles at the desired site of action. While initial implants aimed at providing an enduring drug supply, developments in polymer chemistry and pharmaceutical technology and the growing need for refined drug delivery patterns have prompted the design of sophisticated drug delivery implants such as on-demand drug-eluting implants and personalized 3D printed implants. The types of cargo loaded into these implants range from small drug molecules to hormones and even therapeutic cells. This review will shed light upon recent advances in materials and composites used for polymeric implant fabrication, highlight select approaches employed in polymeric implant fabrication, feature medical applications where polymeric implants have a significant impact, and report recent advances made in these areas.

Current concepts regarding drug dosing for peripheral stents

Drug-eluting stent (DES) are the mainstay therapy for the treatment of coronary artery disease. Stent design and drug-elution strategies have evolved over the years leading to the last generation DES which shows optimal safety and efficacy outcome. Peripheral arteries have different mechanical and biological features and the lessons learned from the coronary field have been difficult to introduce into the development of peripheral vascular technologies. First, due to its complex biomechanical behavior the use of metallic stents is limited in some vascular segments (i.e., distal superficial fermoral artery [SFA]). Also, peripheral vascular atherosclerosis is different containing higher levels of plaque burden and calcium. Finally, peripheral arterial disease tends to be more aggressive including longer lesions and higher incidence of total chronic occlusion. In general terms, restenosis in the peripheral vascular territory is more aggressive and occurs at a later time (~12 months) requiring a different pharmacokinetic profile compared to coronary technologies. Several strategies have been evaluated in the peripheral arteries raging from the bare metal stent to the drug coated balloon and drug eluting stent with outcome varying depending on the different field of application (i.e. SFA and below-the-knee). Results coming from the clinical trial are encouraging but further studies and direct comparison among the different technologies are demanded to determine the best therapy for peripheral vascular disease.

Targeted Delivery of Bioactive Molecules for Vascular Intervention and Tissue Engineering

Cardiovascular diseases are the leading cause of death in the United States. Treatment often requires surgical interventions to re-open occluded vessels, bypass severe occlusions, or stabilize aneurysms. Despite the short-term success of such interventions, many ultimately fail due to thrombosis or restenosis (following stent placement), or incomplete healing (such as after aneurysm coil placement). Bioactive molecules capable of modulating host tissue responses and preventing these complications have been identified, but systemic delivery is often harmful or ineffective. This review discusses the use of localized bioactive molecule delivery methods to enhance the long-term success of vascular interventions, such as drug-eluting stents and aneurysm coils, as well as nanoparticles for targeted molecule delivery. Vascular grafts in particular have poor patency in small diameter, high flow applications, such as coronary artery bypass grafting (CABG). Grafts fabricated from a variety of approaches may benefit from bioactive molecule incorporation to improve patency. Tissue engineering is an especially promising approach for vascular graft fabrication that may be conducive to incorporation of drugs or growth factors. Overall, localized and targeted delivery of bioactive molecules has shown promise for improving the outcomes of vascular interventions, with technologies such as drug-eluting stents showing excellent clinical success. However, many targeted vascular drug delivery systems have yet to reach the clinic. There is still a need to better optimize bioactive molecule release kinetics and identify synergistic biomolecule combinations before the clinical impact of these technologies can be realized.

Efficacy and safety of drug-eluting stent for the intracranial atherosclerotic disease: A systematic review and meta-analysis

Drug-eluting stent (DES) is a potential endovascular treatment for patients with symptomatic intracranial atherosclerotic disease (sICAD). However, evidence regarding the treatment of ICAD with DES is lacking. We systematically searched Pubmed, Embase, Cochrane database (before 2017-12-21) for literature reporting the application of DES in the treatment of sICAD. The main outcomes were as follows: the incidence of any stroke or death within 30 days (perioperative complications), ischemic stroke in the territory of the qualifying artery beyond 30 days (long-term complications), in-stent restenosis rate (ISR) and symptomatic ISR during follow-up. Those studies with mean stenosis rate greater than 70% and less than 70% were defined as severe and moderate stenosis group, respectively. The random effect model was used to pool the data. Of 518 articles, 13 studies were eligible and included in our analysis (N = 336 patients with 364 lesions). After the implantation of DES, perioperative complications (mortality = 0) occurred in 6.0% (95%CI 2.0%-11.9%), long-term complications occurred in 2.2% (95%CI 0.7%-4.5%), ISR rate was 4.1% (95%CI 1.6%-7.7%) and the symptomatic ISR rate was only 0.5% (95%CI 0-2.2%). In addition, subgroup analysis showed that the perioperative complication rate in severe stenosis group [10.6% (95%CI 6.5%-15.7%)] was significantly (p < 0.01) higher than that in moderate stenosis group [1.0% (95%CI 0.3%-3.5%)]. In summary, endovascular DES implantation is a relatively safe and effective method compared with stents or medical management group in SAMMPRIS and VISSIT trials. However, a higher preoperative stenosis rate may imply a higher risk of perioperative complications. Further studies are needed.

Understanding the Impact of Stent and Scaffold Material and Strut Design on Coronary Artery Thrombosis from the Basic and Clinical Points of View

The technology of percutaneous coronary intervention (PCI) is constantly being refined in order to overcome the shortcomings of present day technologies. Even though current generation metallic drug-eluting stents (DES) perform very well in the short-term, concerns still exist about their long-term efficacy. Late clinical complications including late stent thrombosis (ST), restenosis, and neoatherosclerosis still exist and many of these events may be attributed to either the metallic platform and/or the drug and polymer left behind in the arterial wall. To overcome this limitation, the concept of totally bioresorbable vascular scaffolds (BRS) was invented with the idea that by eliminating long-term exposure of the vessel wall to the metal backbone, drug, and polymer, late outcomes would improve. The Absorb-bioabsorbable vascular scaffold (Absorb-BVS) represented the most advanced attempt to make such a device, with thicker struts, greater vessel surface area coverage and less radial force versus contemporary DES. Unfortunately, almost one year after its initial approval by the U.S. Food and Drug Administration, this scaffold was withdrawn from the market due to declining devise utilization driven by the concerns about scaffold thrombosis (ScT) seen in both early and late time points. Additionally, the specific causes of ScT have not yet been fully elucidated. In this review, we discuss the platform, vascular response, and clinical data of past and current metallic coronary stents with the Absorb-BVS and newer generation BRS, concentrating on their material/design and the mechanisms of thrombotic complications from the pre-clinical, pathologic, and clinical viewpoints.

The Foreign Body Response Demystified

The human body is endowed with an uncanny ability to distinguish self from foreign. The implantation of a foreign object inside a mammalian host activates complex signaling cascades, which lead to biological encapsulation of the implant. This reaction by the host system to a foreign object is known as foreign body response (FBR). Over the last few decades, it has been increasingly important to have a deeper insight into the mechanisms of FBR is needed to develop biomaterials for better integration with living systems. In the light of recent advances in tissue engineering and regenerative medicine, particularly in the field of biosensors and biodegradable tissue engineering scaffolds, the classical concepts related to the FBR have acquired new dimensions. The aim of this review is to provide a holistic view of the FBR, while critically analyzing the challenges, which need to be addressed in the future to overcome this innate response. In particular, this review discusses the relevant experimental methodology to assess the host response. The role of erosion and degradation behavior on FBR with biodegradable polymers is largely explored. Apart from the discussion on temporal progression of FBR, an emphasis has been given to the design of next-generation biomaterials with favorable host response.

Mid-term clinical outcomes after bailout drug-eluting stenting for suboptimal drug-coated balloon results: Insights from a Milan registry

BACKGROUND

Drug-coated balloon (DCB) is an alternative to drug-eluting stent (DES) for the treatment of small vessel or in-stent restenosis (ISR) lesions, with bailout stenting reserved for poor results after DCB inflation (residual stenosis or dissection). Data regarding bailout stenting with DES are limited. The aim of this study was to evaluate clinical outcomes after bailout stenting with DES for suboptimal DCB results.

METHODS

From June 2009 to December 2015, patients who underwent bailout DES implantation for suboptimal results after DCB (residual stenosis > 30% or type C-F dissection) in 2 high-volume centers in Italy were analyzed. The primary endpoint was target lesion failure (TLF) defined as composite of cardiac mortality, target vessel myocardial infarction (MI) and target lesion revascularization (TLR).

RESULTS

A total of 103 patients (125 lesions) were analyzed. Mean age was 68.8 ± 9.5 years, 21.4% were diabetic, and 92.2% underwent PCI for stable angina. The left anterior descending artery was most commonly treated (35.2%), followed by right coronary artery (17.6%) and left circumflex artery (17.6%). Lesion complexity was high (type B2/C: 88.8%) and 24.8% were ISR lesions. During the follow-up period (median: 858 days [interquartile range: 467-1665]), the TLF rate was 4.3% at 1 year and 15.4% at 2 years, and mainly driven by TLR (3.3% at 1 year, 14.5% at 2 years, respectively). There were no target vessel MI or definite/probable stent thrombosis events.

CONCLUSIONS

Bailout stenting with DES for suboptimal DCB results is a feasible and safe strategy at mid-term follow-up.

Efficacy and safety of a second-generation biodegradable polymer sirolimus-eluting stent: One-year results of the CREDIT 2 trial

AIMS

We performed a multicenter, randomized controlled trial to determine the noninferiority of a novel biodegradable polymer drug-eluting stent (BP-DES), the EXCEL 2 stent, to the first-generation BP-DES, the EXCEL stent.

METHODS AND RESULTS

Patients (n = 419) scheduled to undergo percutaneous coronary intervention (PCI) were randomized to receive either the EXCEL 2 stent (n = 208) or the EXCEL stent (n = 211) from 15 Chinese centers. At 9 months, primary endpoint in-stent late loss (LL) difference was -0.03 mm (95% confidence interval: -0.09 mm to 0.04 mm) between the EXCEL 2 group (0.14 ± 0.26 mm) and the EXCEL group (0.16 ± 0.36 mm), demonstrating the noninferiority of EXCEL 2 to EXCEL in terms of in-stent LL (P for noninferiority < .0001). Besides, target lesion failure (TLF) was statistically lower in EXCEL 2 group compared with EXCEL through 1 year (HR [95%CI] = 0.45 [0.20,0.98], P_log-rank  = .04). Definite/probable ST was observed in 0.0% vs 1.9% (P = .12) of EXCEL 2 vs EXCEL-treated subjects.

CONCLUSIONS

The second-generation BP-DES (EXCEL 2) was noninferior to the first-generation BP-DES (EXCEL) for the primary endpoint of in-stent LL at 9 months. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT02057978.

Development of Microporous Covered Stents: Geometrical Design of the Luminal Surface

To reduce in-stent restenosis rates we have developed newly designed covered stents, in which a stent strut is buried into a microporous elastomeric cover film to provide a physical barrier against tissue ingrowth and a pharmacological reservoir for drug-eluting.

The covered stents were prepared by dip-coating balloon expandable stents mounted on a stainless steel rod in a segmented polyurethane (SPU) solution, and were subsequently subjected to laser-processed microporing (pore diameter, 100 μm; interpore distance, 200 μm). The covered stents, which possessed flat luminal surfaces and micropores that were homogeneously arranged on the whole surface of the covering film, were deployed into the bilateral common carotid arteries of normal New Zealand white rabbits. Angiography after one month of implantation showed all stents were patent with little thrombus formation. The mean thickness of the formed neointimal layers was 292 ± 177 μm (n=8), which was close to the size in non-covered bare stent (231 ± 58 μm, n=7), but markedly decreased (about 2/3) from that in the previously developed wrapping-type covered stents (415 ± 173 μm, P<0.01, n=8).

A water-soluble nucleolin aptamer-paclitaxel conjugate for tumor-specific targeting in ovarian cancer

Paclitaxel (PTX) is among the most commonly used first-line drugs for cancer chemotherapy. However, its poor water solubility and indiscriminate distribution in normal tissues remain clinical challenges. Here we design and synthesize a highly water-soluble nucleolin aptamer-paclitaxel conjugate (NucA-PTX) that selectively delivers PTX to the tumor site. By connecting a tumor-targeting nucleolin aptamer (NucA) to the active hydroxyl group at 2' position of PTX via a cathepsin B sensitive dipeptide bond, NucA-PTX remains stable and inactive in the circulation. NucA facilitates the uptake of the conjugated PTX specifically in tumor cells. Once inside cells, the dipeptide bond linker of NucA-PTX is cleaved by cathepsin B and then the conjugated PTX is released for action. The NucA modification assists the selective accumulation of the conjugated PTX in ovarian tumor tissue rather than normal tissues, and subsequently resulting in notably improved antitumor activity and reduced toxicity.

Delivery of Antioxidant and Anti-inflammatory Agents for Tissue Engineered Vascular Grafts

The treatment of patients with severe coronary and peripheral artery disease represents a significant clinical need, especially for those patients that require a bypass graft and do not have viable veins for autologous grafting. Tissue engineering is being investigated to generate an alternative graft. While tissue engineering requires surgical intervention, the release of pharmacological agents is also an important part of many tissue engineering strategies. Delivery of these agents offers the potential to overcome the major concerns for graft patency and viability. These concerns are related to an extended inflammatory response and its impact on vascular cells such as endothelial cells. This review discusses the drugs that have been released from vascular tissue engineering scaffolds and some of the non-traditional ways that the drugs are presented to the cells. The impact of antioxidant compounds and gasotransmitters, such as nitric oxide and carbon monoxide, are discussed in detail. The application of tissue engineering and drug delivery principles to biodegradable stents is also briefly discussed. Overall, there are scaffold-based drug delivery techniques that have shown promise for vascular tissue engineering, but much of this work is in the early stages and there are still opportunities to incorporate additional drugs to modulate the inflammatory process.

Coronary stents and vascular response to implantation: literature review

Drug-eluting stents (DESs) have minimized the limitations of bare-metal stents (BMSs) after percutaneous coronary interventions. Nevertheless, serious concerns remain about possible late complications of stenting, such as stent thrombosis (ST) and in-stent restenosis (ISR), although the introduction of second-generation DESs seems to have softened the phenomenon, compared to the first-generation ones. ST is a potentially catastrophic event, which has been markedly reduced by optimization of stent implantation, novel stent designs, and dual antiplatelet therapy. The exact mechanism to explain its occurrence is under investigation, and, realistically, multiple factors are responsible. ISR of BMSs has been previously considered as a stable condition with an early peak (at 6 months) of intimal hyperplasia, followed by a regression period beyond 1 year. On the contrary, both clinical and histologic studies of DESs have demonstrated evidence of continuous neointimal growth during long-term follow-up, named “late catch-up” phenomenon. The acknowledgment that ISR is a relatively benign clinical condition has been recently challenged by evidences which reported that patients with ISR can experience acute coronary syndromes. Intracoronary imaging is an invasive technology that allows identifying features of atherosclerotic plaque of stent implanted and of vascular healing after stenting; it is often used to complete diagnostic coronary angiography and to drive interventional procedures. Intracoronary optical coherence tomography is currently considered a state-of-the-art imaging technique; it provides, compared to intravascular ultrasound, better resolution (at least >10 times), allowing the detailed characterization of the superficial structure of the vessel wall. Imaging studies “in vivo,” in agreement with histological findings, suggest that chronic inflammation and/or endothelial dysfunction may induce late de novo “neoatherosclerosis” inside both BMSs and DESs. So, neoatherosclerosis has become the prime suspect in the pathogenesis of late stent failure.

Phenotypic switching prevention and proliferation/migration inhibition of vascular smooth muscle cells by the ruthenium nitrosyl complex trans-[Ru(NO)Cl(cyclam](PF6 )2

OBJECTIVES

Vascular smooth muscle cell (VSMC) migration and proliferation at sites of vascular injury are both critical steps in the development of intimal hyperplasia (IH). Local delivery of nitric oxide (NO) largely prevents these events. Among the NO donors, tetraazamacrocyclic nitrosyl complexes, such as trans-[Ru(NO)Cl(cyclam)](PF₆ )₂ (cyclamNO), gained attention for their features, which include the possibility of being embedded in solid matrices, and ability to participate in a nitrite/NO catalytic conversion cycle.

METHODS

Methods used to evaluate cyclamNO activity: safety margin by NR and MTT; cell proliferation by 3H-thymidine incorporation and proliferating cell nuclear antigen (PCNA) expression; antimigratory properties by transwell and wound healing; prevention of cell phenotypic switching under platelet-derived growth factor type BB (PDGF-BB) stimuli by analysis of alpha smooth muscle actin (α-SMA) expression.

KEY FINDINGS

Cell proliferation and migration induced by PDGF-BB were significantly inhibited by cyclamNO. The ~60% reduction on expression of contractile protein α-SMA induced by PDGF-BB revealed VSMC phenotypic switching which is significantly prevented by cyclamNO. Compared to the NO donor sodium nitroprusside, cyclamNO showed to be significantly less cytotoxic.

CONCLUSIONS

With great potential to maintain VSMC functionality and prevent IH-associated events, cyclamNO might be a promissory drug for several applications in cardiovascular medicine, as in stents.

Coronary Artery Aneurysms: A Review of the Epidemiology, Pathophysiology, Diagnosis, and Treatment

Coronary artery aneurysms (CAAs) are uncommon and describe a localized dilatation of a coronary artery segment more than 1.5-fold compared with adjacent normal segments. The incidence of CAAs varies from 0.3 to 5.3%. Ever since the dawn of the interventional era, CAAs have been increasingly diagnosed on coronary angiography. Causative factors include atherosclerosis, Takayasu arteritis, congenital disorders, Kawasaki disease (KD), and percutaneous coronary intervention. The natural history of CAAs remains unclear; however, several recent studies have postulated the underlying molecular mechanisms of CAAs, and genome-wide association studies have revealed several genetic predispositions to CAA. Controversies persist regarding the management of CAAs, and emerging findings support the importance of an early diagnosis in patients predisposed to CAAs, such as in children with KD. This review aims to summarize the present knowledge of CAAs and collate the recent advances regarding the epidemiology, etiology, pathophysiology, diagnosis, and treatment of this disease.

Neointimal response to everolimus-eluting bioresorbable scaffolds implanted at bifurcating coronary segments: insights from optical coherence tomography

Heterogeneity of neointimal thickness is observed after drug-eluting stents implantation in bifurcation lesions (BL). We evaluated the vascular response of everolimus-eluting bioresorbable scaffold (BRS) struts deployed at BL using optical coherence tomography (OCT). 50 patients (64 scaffolds) underwent follow-up OCT after BRS implantation. Cross-sectional areas of each BL with a side branch more than 1.5 mm were analyzed using OCT every 200 µm. All images were divided into three regions according to shear stress: the 1/2 circumference of the vessel opposite to the ostium (OO), the vessel wall adjacent to the ostium (AO) and the side-branch ostium (SO). The %uncovered strut and the averaged neointimal thickness (NIT) were calculated. Overall, there were significant differences in both NIT and %uncovered strut among the three regions (OO, 119.2 ± 68.5 μm vs. AO, 94.2 ± 35.7 μm vs. SO, 80.5 ± 41.4 μm, p = 0.03; OO, 0.4 %vs. AO, 1.4 %vs. SO, 4.8 %, p = 0.02). Scaffolds were divided into two groups: a large-ratio side-branch group (LRSB; n = 32) and a small-ratio side-branch group (SRSB; n = 32), based on the median value of the ratio of the diameter of side branch ostium (Ds) to that of the main branch (Dm). In the LRSB alone, there were significant differences in both NIT and %uncovered strut among the three regions (OO, 128.0 ± 61.1 μm vs. AO, 97.3 ± 34.3 μm vs. SO, 75.9 ± 39.4 μm, p < 0.01; OO, 0.3 % vs. AO, 2.3 % vs. SO, 8.7 %, p < 0.01). After BRS implantation in BL, neointimal response was pronounced at the vessel wall opposite to the side branch ostium, especially in those with large side branches.

Oral Mycophenolate Mofetil Prevents In-Stent Intimal Hyperplasia Without Edge Effect

Neointimal hyperplasia is in the forefront in in-stent restenosis. Prevention of in-stent restenosis is possible by reducing and inhibiting the hyperplasia of smooth muscle cells. The authors planned this study to test the hypothesis that when administered orally, mycophenolate mofetil (MMF) could inhibit in-stent neointimal hyperplasia. The study included 14 New Zealand rabbits. The rabbits were allocated to 2 different groups: Group 1 included 7 rabbits that were given MMF, 40 mg/kg/day by oral route. Group 2 included 7 rabbits that were not given MMF after the stenting. Sampling materials were taken before and after stenting by incising the artery so as to cover a 5-mm area. The samples taken from the edge of the stent in Group 1 showed focal neointimal cell proliferation, but it was less than that from the control group. Neointimal thickness was 0.048 ±0.009 mm and neointimal area was 0.0925 ±0.019 mm2. Apparent neointimal cell proliferation and thickening of the intimal layer were observed in Group 2. Neointimal thickness at the stent edge was 0.147 ±0.051 mm and the neointimal area was 0.154 ±0.023 mm2. The differences between groups in terms of neointimal thickness and neointimal area were statistically significant (p=0.001 for thickness and p=0.001 for area). In-stent artery samples of Group 1 showed that some subjects had no neointimal cell proliferation, while others had very limited focal intimal thickening. Neointimal thickening was 0.071 ±0.003 mm and neointimal area was 0.073 ±0.003 mm2. In Group 2 apparent, and mostly focal, neointimal cell proliferation and formation of intimal layer were observed in the stent. Neointimal thickening was 0.154 ±0.069 mm and neointimal area was 0.279 ±0.059 mm2. The comparison between groups showed significant differences (p=0.011 for thickness and p=0.001 for area). It was established in the third month that endothelialization was completed in both groups. Oral MMF decreased in-stent intimal hyperplasia without edge effect. It was concluded that for the prevention of in-stent restenosis, studies should be conducted for using systemic immunosuppressive treatments in humans as well.

A New Method of Heparinizing PLLA Film by Surface Entrapment

A new method of surface heparinizing biodegradable polymers was designed. A heparin-modified poly(L-lactic acid) (PLLA) system was developed by physically entrapping the heparin on the PLLA surface. The surface characterization and biological performance of these materials were carried out by SEM, attenuated-total-reflection spectroscopy, contact angle measurements, and platelet adhesion evaluations. The modification strategy was performed by reversible swelling of the PLLA surface following exposure to a solvent–nonsolvent mixture. This process resulted in the localized physical entrapment of the diffused heparin. X-ray photoelectron spectroscopy was used to confirm that control over the heparin surface density can be achieved by using set polymer treatment times. Platelet adhesion tests showed significant improvement in blood compatibility by the PLLA surfaces after modification.

Optical coherence tomography to evaluate coronary stent implantation and complications

Coronary optical coherence tomography (OCT) is now an established imaging technique in many catheterization laboratories worldwide. With its near-histological view of the vessel wall and lumen interface, it offers unprecedented imaging quality to improve our understanding of the pathophysiology of atherosclerosis, plaque vulnerability, and vascular biology. Not only is OCT used to accurately detect atherosclerotic plaque and optimize stent position, but it can further characterize plaque composition, quantify stent apposition, and assess stent tissue coverage. Given that its resolution of 15 μm is well above that of angiography and intravascular ultrasound, OCT has become the invasive imaging method of choice to examine the interaction between stents and the vessel wall. This review focuses on the application of OCT to examine coronary stents, the mechanisms of stent complications, and future directions of OCT-guided intervention.

Relative dose and vascular response after drug-eluting stent implantation: A dosimetric 3D-intravascular ultrasound study

BACKGROUND

In drug-eluting stents (DESs), the theoretical drug dose exposed to the vessel wall per stent surface area may vary due to the fixed loading dose and differences in the stent surface area once expanded in varying vessel sizes. The aim of this study was to evaluate the potential effects of different dose intensities, as estimated by 3D-IVUS dosimetry, on vascular response after DES implantation.

METHODS

Follow-up (6-9 months) 3D-IVUS was performed in 840 coronary lesions treated with a single DES of the following types: sirolimus (SES, n=148), paclitaxel (PES, n=162), Endeavor zotarolimus (E-ZES, n=233), Resolute zotarolimus (R-ZES, n=147), and everolimus (EES, n=150). Volume index (volume/length, mm(3)/mm) was obtained for vessel, lumen, plaque, stent, and neointima. In each lesion, exposed dose intensity was calculated as known loading dose divided by measured luminal surface area of the stented segment. Lesions were divided into tertiles based on the exposed dose intensity: high, medium, and low dose groups.

RESULTS

The exposed dose intensity ranged 0.74-1.76 μg/mm(2) for SES, 0.41-1.18 μg/mm(2) for PES, 0.71-1.57 μg/mm(2) for E-ZES, 0.72-1.63 μg/mm(2) for R-ZES, and 0.40-0.99 μg/mm(2) for EES. All types of DES showed no significant difference in neointimal hyperplasia among the 3 groups, except that E-ZES showed significantly less neointimal hyperplasia in the high dose group.

CONCLUSIONS

Detailed 3D-IVUS revealed significant lesion-to-lesion variability in dose intensity exposed to the vessel wall following DES implantation. However, the major types of DES appear to yield equally effective neointimal suppression, despite the varying dose intensity, except for E-ZES.

Metallic zinc exhibits optimal biocompatibility for bioabsorbable endovascular stents

Although corrosion resistant bare metal stents are considered generally effective, their permanent presence in a diseased artery is an increasingly recognized limitation due to the potential for long-term complications. We previously reported that metallic zinc exhibited an ideal biocorrosion rate within murine aortas, thus raising the possibility of zinc as a candidate base material for endovascular stenting applications. This study was undertaken to further assess the arterial biocompatibility of metallic zinc. Metallic zinc wires were punctured and advanced into the rat abdominal aorta lumen for up to 6.5months. This study demonstrated that metallic zinc did not provoke responses that often contribute to restenosis. Low cell densities and neointimal tissue thickness, along with tissue regeneration within the corroding implant, point to optimal biocompatibility of corroding zinc. Furthermore, the lack of progression in neointimal tissue thickness over 6.5months or the presence of smooth muscle cells near the zinc implant suggest that the products of zinc corrosion may suppress the activities of inflammatory and smooth muscle cells.

Optimization of Drug Delivery by Drug-Eluting Stents

Drug-eluting stents (DES), which release anti-proliferative drugs into the arterial wall in a controlled manner, have drastically reduced the rate of in-stent restenosis and revolutionized the treatment of atherosclerosis. However, late stent thrombosis remains a safety concern in DES, mainly due to delayed healing of the endothelial wound inflicted during DES implantation. We present a framework to optimize DES design such that restenosis is inhibited without affecting the endothelial healing process. To this end, we have developed a computational model of fluid flow and drug transport in stented arteries and have used this model to establish a metric for quantifying DES performance. The model takes into account the multi-layered structure of the arterial wall and incorporates a reversible binding model to describe drug interaction with the cells of the arterial wall. The model is coupled to a novel optimization algorithm that allows identification of optimal DES designs. We show that optimizing the period of drug release from DES and the initial drug concentration within the coating has a drastic effect on DES performance. Paclitaxel-eluting stents perform optimally by releasing their drug either very rapidly (within a few hours) or very slowly (over periods of several months up to one year) at concentrations considerably lower than current DES. In contrast, sirolimus-eluting stents perform optimally only when drug release is slow. The results offer explanations for recent trends in the development of DES and demonstrate the potential for large improvements in DES design relative to the current state of commercial devices.

The GPER agonist G-1 induces mitotic arrest and apoptosis in human vascular smooth muscle cells independent of GPER

The G protein-coupled estrogen receptor (GPER) has been implicated in the regulation of smooth muscle cell (SMC) proliferation. The GPER selective agonist G-1 has been a useful tool for exploring the biological roles of GPER in a variety of experimental settings, including SMC proliferation. The present study, originally designed to investigate cellular and signaling mechanisms underlying the regulatory role of GPER in vascular SMC proliferation using G-1, unexpectedly revealed off-target effects of G-1. G-1(1-10 μM) inhibited bromodeoxyuridine (BrdU) incorporation of human SMCs and caused G2/M cell accumulation. G-1 treatment also increased mitotic index concurrent with a decrease in phosphorylation of Cdk1 (Tyr 15) and an increase in phosphorylation of the mitotic checkpoint protein BuBR1. Furthermore, G-1 caused microtubule disruption, mitotic spindle damage, and tubulin depolymerization. G-1 induced cell apoptosis as indicated by the appearance of TUNEL-positive and annexin V-positive cells with enhanced cleavage of caspases 3 and 9. However, neither the GPER antagonist G-15 nor the MAPK kinase inhibitor PD98059 prevented these G-1 effects. Down-regulation of GPER or p44/42 MAPK with siRNA transfection also did not affect the G-1-induced apoptosis. We conclude that G-1 inhibits proliferation of SMCs through mechanisms involving mitotic arrest and apoptosis, independent of GPER and the MAPK pathway.

Effect of anti-ApoA-I antibody-coating of stents on neointima formation in a rabbit balloon-injury model

Background and Aims

Since high-density lipoprotein (HDL) has pro-endothelial and anti-thrombotic effects, a HDL recruiting stent may prevent restenosis. In the present study we address the functional characteristics of an apolipoprotein A-I (ApoA-I) antibody coating in vitro. Subsequently, we tested its biological performance applied on stents in vivo in rabbits.

Materials and Methods

The impact of anti ApoA-I- versus apoB-antibody coated stainless steel discs were evaluated in vitro for endothelial cell adhesion, thrombin generation and platelet adhesion. In vivo, response to injury in the iliac artery of New Zealand white rabbits was used as read out comparing apoA-I-coated versus bare metal stents.

Results

ApoA-I antibody coated metal discs showed increased endothelial cell adhesion and proliferation and decreased thrombin generation and platelet adhesion, compared to control discs. In vivo, no difference was observed between ApoA-I and BMS stents in lumen stenosis (23.3±13.8% versus 23.3±11.3%, p=0.77) or intima surface area (0.81±0.62 mm² vs 0.84±0.55 mm², p=0.85). Immunohistochemistry also revealed no differences in cell proliferation, fibrin deposition, inflammation and endothelialization.

Conclusion

ApoA-I antibody coating has potent pro-endothelial and anti-thrombotic effects in vitro, but failed to enhance stent performance in a balloon injury rabbit model in vivo.

Effects of Paclitaxel on the Ability of Aspirin and Clopidogrel to Inhibit Platelet Aggregation

The aim of this study was to investigate the effects of different paclitaxel concentrations on platelet aggregation induced by adenosine diphosphate (ADP). This experiment involved platelet suspensions that were obtained from fasting morning blood specimens from healthy adult male volunteers aged 22 to 28 years. The effect of paclitaxel on platelet aggregation induced by ADP and the inhibition rate of platelet aggregation were calculated in 6 groups with varying concentrations of paclitaxel, respectively. The optimal incubation time and concentration of ADP were 10 minutes and 10 μmol/mL, respectively. When the concentration of paclitaxel increased, platelet aggregation induced by ADP increased accordingly. When the concentration of paclitaxel exceeded 0.1 ng/mL, the ability of ADP to induce platelet aggregation increased significantly with increasing paclitaxel concentrations. In all the 3 experimental groups, that is A, C, and AC groups, the ability to inhibit platelet aggregation was weakened as paclitaxel concentration increased. Paclitaxel can enhance platelet aggregation induced by ADP, and this ability was observed to increase as paclitaxel concentration increased. In conclusion, paclitaxel can reduce the ability of aspirin, clopidogrel, and aspirin combined with clopidogrel to inhibit platelet aggregation. Furthermore, the ability to inhibit platelet aggregation was weakened as paclitaxel concentration increased in all 3 experimental groups.

Vascular Response After Zilver PTX Stent Implantation for Superficial Femoral Artery Lesions

Purpose: To compare the vascular response after paclitaxel-coated nitinol drug-eluting stent (Zilver PTX) implantation for superficial femoral artery lesions after 6 and 12 months using optical coherence tomography (OCT). Methods: Serial OCT examinations were performed in 5 patients (4 men; mean age 78.4±6.8 years) with 9 Zilver PTX stents at 6- and 12-month follow-up. Variables evaluated included neointimal thickness and apposition on each strut, the incidence of extrastent lumen (ESL), peristrut low-intensity area (PLIA), and neovascularization at 1-mm intervals. Results: A total of 249 matched cross-section images were evaluated and included 4788 and 4826 struts at 6 and 12 months, respectively. Mean neointimal thickness significantly increased from 480 to 540 µm between 6 and 12 months (p<0.001). The percentage of uncovered struts tended to decrease at 12 months (3% vs. 2.3%, p=0.054), whereas the percentage of malapposed struts were similar at both examinations (0.2% vs. 0.2%, p>0.99). Although the incidence of ESL in cross sections was not different (35% vs. 31%, p=0.29), median ESL area significantly increased from 6 to 12 months [0.12 (0.04–0.36) vs. 0.31 (0.14–0.59) mm2, p=0.003)]. The presence of PLIA (29% vs. 44%, p<0.001) and neovascularization (14% vs. 27%, p<0.001) increased from 6 to 12 months. Conclusion: These findings suggest that delayed vascular healing and persistent peristent inflammation may be present even at 12 months after Zilver PTX implantation.

Chronic treatment with trimetazidine after discharge reduces the incidence of restenosis in patients who received coronary stent implantation: a 1-year prospective follow-up study

BACKGROUND

The incidence of stent restenosis (SR) has risen with as more patients are being treated with drug-eluting stents (DESs). Trimetazidine has multiple favorable effects on the cardiovascular system. Here, we aimed to evaluate whether chronic treatment with trimetazidine reduced the incidence of SR.

METHODS

From January 2009 to December 2011 at Chinese PLA General Hospital, 768 patients were enrolled and randomized into the trimetazidine treatment group (TG, n = 384) and control group (CG, n = 384). After DES implantation, all patients were treated with regular medication. In the TG, trimetazidine was administrated at 20mg tid for at least 30days. All patients received follow-up angiography 9-13 months after discharge. Major adverse cardiac and cerebrovascular events (MACCEs) were recorded.

RESULTS

Six hundred thirty-five patients were included in the final analysis (TG, n = 312; CG, n = 323). SR occurred in 49 (7.7%) patients. The TG had a lower incidence of SR compared to the CG (4.2% vs. 11.1%, p = 0.001). At the 30-day follow-up, the TG exhibited a higher left ventricular ejection fraction than the CG (65.4 ± 10.7 vs. 63.1 ± 10.4, p = 0.006). The incidence of MACCEs was also lower in the TG at the 1-year follow-up (6.1% vs. 10.8%, p = 0.032). Further multivariate analysis revealed that trimetazidine treatment was a predictor for SR (OR: 0.376; 95% CI: 0.196-0.721; p = 0.003).

CONCLUSIONS

Trimetazidine treatment effectively reduced the incidence of SR and MACCEs after DES implantation at the 1-year follow-up.

Highly porous drug-eluting structures: from wound dressings to stents and scaffolds for tissue regeneration

For many biomedical applications, there is need for porous implant materials. The current article focuses on a method for preparation of drug-eluting porous structures for various biomedical applications, based on freeze drying of inverted emulsions. This fabrication process enables the incorporation of any drug, to obtain an "active implant" that releases drugs to the surrounding tissue in a controlled desired manner. Examples for porous implants based on this technique are antibiotic-eluting mesh/matrix structures used for wound healing applications, antiproliferative drug-eluting composite fibers for stent applications and local cancer treatment, and protein-eluting films for tissue regeneration applications. In the current review we focus on these systems. We show that the release profiles of both types of drugs, water-soluble and water-insoluble, are affected by the emulsion's formulation parameters. The former's release profile is affected mainly through the emulsion stability and the resulting porous microstructure, whereas the latter's release mechanism occurs via water uptake and degradation of the host polymer. Hence, appropriate selection of the formulation parameters enables to obtain desired controllable release profile of any bioactive agent, water-soluble or water-insoluble, and also fit its physical properties to the application.