Granulomatous 'foreign body reactions' contribute to exaggerated in-stent restenosis

SGLT-2 inhibitors and in-stent restenosis-related events after acute myocardial infarction: an observational study in patients with type 2 diabetes

BACKGROUND

No study evaluated the incidence of intra-stent restenosis (ISR)-related events in patients with type 2 diabetes (T2DM) and acute myocardial infarction (AMI) treated or not with sodium/glucose cotransporter 2 inhibitors (SGLT2i).

METHODS

We recruited 377 patients with T2DM and AMI undergoing percutaneous coronary intervention (PCI). Among them, 177 T2DM were treated with SGLT2 inhibitors before PCI. The primary outcome was major adverse cardiovascular events (MACE) defined as cardiac death, re-infarction, and heart failure related to ISR. In patients without ISR, minimal lumen area and minimal lumen diameter were assessed by coronary CT-angiography at 1-year follow-up.

RESULTS

Glycemic control was similar in SGLT2i-treated patients and never SGLT2i-users. The incidence of ISR-related MACE was higher in never SGLT2i-users compared with SGLT2i-treated patients, an effect independent of glycemic status (HR = 0.418, 95% CI = 0.241-0.725, P = 0.002) and observed also in the subgroup of patients with HbA1c < 7% (HR = 0.393, 95% CI = 0.157-0.984, P = 0.027). In patients without the event, the stent patency was greater in SGLT2i-treated patients compared with never SGLT2i-users at 1-year follow-up.

CONCLUSIONS

SGLT2i treatment in T2DM is associated with a reduced incidence of ISR-related events, independently of glycemic control.

Coronary stent CD31-mimetic coating favours endothelialization and reduces local inflammation and neointimal development in vivo

AIMS

The rapid endothelialization of bare metal stents (BMS) is counterbalanced by inflammation-induced neointimal growth. Drug-eluting stents (DES) prevent leukocyte activation but impair endothelialization, delaying effective device integration into arterial walls. Previously, we have shown that engaging the vascular CD31 co-receptor is crucial for endothelial and leukocyte homeostasis and arterial healing. Furthermore, we have shown that a soluble synthetic peptide (known as P8RI) acts like a CD31 agonist. The aim of this study was to evaluate the effect of CD31-mimetic metal stent coating on the in vitro adherence of endothelial cells (ECs) and blood elements and the in vivo strut coverage and neointimal growth.

METHODS AND RESULTS

We produced Cobalt Chromium discs and stents coated with a CD31-mimetic peptide through two procedures, plasma amination or dip-coating, both yielding comparable results. We found that CD31-mimetic discs significantly reduced the extent of primary human coronary artery EC and blood platelet/leukocyte activation in vitro. In vivo, CD31-mimetic stent properties were compared with those of DES and BMS by coronarography and microscopy at 7 and 28 days post-implantation in pig coronary arteries (n = 9 stents/group/timepoint). Seven days post-implantation, only CD31-mimetic struts were fully endothelialized with no activated platelets/leukocytes. At day 28, neointima development over CD31-mimetic stents was significantly reduced compared to BMS, appearing as a normal arterial media with the absence of thrombosis contrary to DES.

CONCLUSION

CD31-mimetic coating favours vascular homeostasis and arterial wall healing, preventing in-stent stenosis and thrombosis. Hence, such coatings seem to improve the metal stent biocompatibility.

Balloons and Stents and Scaffolds: Preclinical Evaluation of Interventional Devices for Occlusive Arterial Disease

Atherosclerosis places a significant burden on humankind; it is the leading cause of mortality globally, and for those living with atherosclerosis, it can significantly impact quality of life. Fortunately, treatment advances have effectively reduced the morbidity and mortality related to atherosclerosis, with one such modality being percutaneous intervention (PCI) to open occluded arteries. Over the 40-year history of PCI, preclinical models have played a critical role in demonstrating proof of concept, characterizing the in vivo behavior (pharmacokinetics, degradation) and providing a reasonable assurance of biologic safety of interventional devices before entering into clinical trials. Further, preclinical models may provide insight into the potential efficacy of these devices with the appropriate study design and end points. While several species have been used in the evaluation of interventional devices, the porcine model has been the principal model used in the evaluation of safety of devices for both coronary and endovascular treatments. This article reviews the fundamentals of permanent stents, transient scaffolds, and drug-coated balloons and the models, objectives, and methods used in their preclinical evaluation.

Bench top evaluation and clinical experience with the Szabo technique: new questions for a complex lesion

BACKGROUND

The Szabo technique has been described as a method to ensure accurate ostial stent placement. We sought to investigate this novel technique in detail both in vitro and in vivo.

METHODS AND RESULTS

The technique was subjected to bench testing and also undertaken in 26 patients. Each step was recorded with cine angiography and the stents imaged by microcomputed tomography. The ostial LAD was treated in 81% and a DES was implanted in 92%. Angiographic success was 88.5% (one case of stent dislodgement). Repeat angiography was performed in 78% and restenosis observed in two patients. MACE rate at 15.5 ± 5.1 months was 13% (1 TLR, 1 MI, 1 cardiac death). Despite a seemingly excellent immediate angiographic result, we report one case of restenosis at follow up and one case of IVUS examination (performed in four patients) in which significant stent protrusion, into the proximal main vessel, was observed. In vitro bench testing confirmed a significant and asymmetric (carina side) stent protrusion into the main branch, with the last cell of the stent undergoing significant deformation.

CONCLUSIONS

The Szabo technique is not a precise technique to implant a stent at the level of the ostium. The proximal end of the stent undergoes significant and asymmetric deformation, protruding into main branch. Additional concerns with this complex technique include the potential for stent damage or contamination before implantation and the risk of stent dislodgement. We conclude that there are more disadvantages than benefits to this technique which only partially addresses the difficulties encountered in the treating ostial lesions.

Polymer-free biolimus a9-coated stent demonstrates more sustained intimal inhibition, improved healing, and reduced inflammation compared with a polymer-coated sirolimus-eluting cypher stent in a porcine model

BACKGROUND

Drug-eluting stents effectively reduce restenosis but may increase late thrombosis and delayed restenosis. Persistent polymer, the drug, or a combination of both could be responsible. Local delivery of Biolimus A9, a rapamycin derivative, from a polymer-free BioFreedom stent (Biosensors International) may prevent these complications.

METHODS AND RESULTS

We compared high-dose (HD) (225 microg/14 mm Biolimus A9) and low-dose (LD) (112 microg/14 mm Biolimus A9) BioFreedom stents with a polymer-coated sirolimus-eluting Cypher stent (SES) and a bare-metal stent (BMS) at 28 days and 180 days in an overstretch coronary mini-swine model with histomorphometric and histological analysis. At 28 days, there was a reduction in neointimal proliferation by HD, LD, and SES compared with BMS (neointimal thickness: HD, 0.080+/-0.032; LD, 0.085+/-0.038; SES, 0.064+/-0.037; BMS, 0.19+/-0.111 mm; P<0.001; BMS > HD/LD/SES). At 180 days, both BioFreedom stents were associated with reduced neointimal proliferation, whereas SES exhibited increased neointima (neointimal thickness: HD, 0.12+/-0.034; LD, 0.10+/-0.040; SES, 0.20+/-0.111; BMS, 0.17+/-0.099 mm; P<0.001; SES > HD/LD; BMS > LD). At 180 days, BioFreedom stents showed decreased fibrin and inflammation, including granuloma and giant cells, compared with SES.

CONCLUSIONS

The polymer-free Biolimus A9-coated stent demonstrates equivalent early and superior late reduction of intimal proliferation compared with SES in a porcine model. After implantation of BioFreedom stent, delayed arterial healing was minimal, and there was no increased inflammation at 180 days compared with SES implantation. The use of polymer-free stents may have a potential long-term benefit over traditional polymeric-coated drug-eluting stents.

Preclinical Models of Restenosis and Their Application in the Evaluation of Drug-Eluting Stent Systems

Coronary arterial disease (CAD) is the leading cause of death in the United States, the European Union, and Canada. Percutaneous coronary intervention (PCI) has revolutionized the treatment of CAD, and it is the advent of drug-eluting stent (DES) systems that has effectively allayed much of the challenge of restenosis that has plagued the success of PCI through its 30-year history. However, DES systems have not been a panacea: There yet remain the challenges associated with interventions involving bare metallic stents as well as newly arisen concerns related to the application of DES systems. To effectively address these novel and ongoing issues, animal models are relied on both to project the safety and efficacy of endovascular devices and to provide insight into the pathophysiology underlying the vascular response to injury and mechanisms of restenosis. In this review, preclinical models of restenosis are presented, and their application and limitation in the evaluation of device-based interventional technologies for the treatment of CAD are discussed.

Coronary artery stents: Part I. Evolution of percutaneous coronary intervention

The subspecialty of interventional cardiology has made significant progress in the management of coronary artery disease over the past three decades with the development of percutaneous coronary transluminal angioplasty, atherectomy, and bare-metal and drug-eluting stents (DES). Bare-metal stents (BMS) maintain vessel lumen diameter by acting as a scaffold and prevent collapse incurred by angioplasty. However, these devices cause neointimal hyperplasia leading to in-stent restenosis and requiring reintervention in more than 20% of patients by 6 mo. DES (sirolimus and paclitaxel) prevent restenosis by inhibiting neointimal hyperplasia. However, DESs also delay endothelialization, causing the stents to remain thrombogenic for an extended, yet unknown, period of time. Late stent thrombosis is associated with a 45% mortality rate. Premature discontinuation of antiplatelet therapy, particularly clopidogrel, is the strongest predictor of stent thrombosis. Sixty percent of patients receive stents for off-label (unapproved) indications, which also increases the frequency of stent thrombosis. Clopidogrel and aspirin are the cornerstone of therapy in the prevention of stent thrombosis in both BMS and DES. Recommendations pertaining to the optimal duration of dual-antiplatelet therapy have been debated. Both the Food and Drug Administration and the American Heart Association/American College of Cardiologists, in association with other major societies, have made recommendations to extend the duration of dual-antiplatelet therapy in patients with DES to 1 yr. The 6-wk duration of dual-antiplatelet therapy in patients with BMS remains unchanged. All patients with coronary stents must remain on life-long aspirin monotherapy. Since the introduction of percutaneous transluminal coronary angioplasty for the treatment of coronary atherosclerosis, the practice of percutaneous coronary intervention has undergone a dramatic transformation from simple balloon dilation catheters to sophisticated mechanical endoprostheses. These advancements have impacted the practice of perioperative medicine. In this series of two articles, in Part I we will review the evolution of percutaneous coronary intervention and discuss the issues associated with percutaneous transluminal coronary angioplasty and coronary stenting; in Part II we will discuss perioperative issues and management strategies of coronary stents during noncardiac surgery.

Cells of primarily extravascular origin in neointima formation following stent implantation: coordinated expression of endothelial progenitor, dendritic and neural crest-derived cells

OBJECTIVES

In-stent restenosis due to neointima formation is a major limitation following stent implantation. Recently, several studies reported mobilization of primarily extravascular cells to the arterial sites after balloon angioplasty. Therefore, the goal of the present study was to assess the coordinated neointimal expression of endothelial progenitor, dendritic and neural crest-derived cells after stent implantation.

METHODS

Male minipigs underwent stent implantation in abdominal aortic segments. Animals were sacrificed at 1, 7, 14, 30, 60 or 90 days. Cross sections of the injured vessels were obtained for immunohistochemistry using specific antibodies for the detection of endothelial progenitor (CD133), dendritic (S100) and neural crest-derived cells (GFAP), as well as monocytes/macrophages (CD14) and T lymphocytes (CD3).

RESULTS

As a key finding, frequency of CD133, S100, GFAP, CD14 and CD3 (18.5 +/- 3.6, 14.9 +/- 1.8, 10.6 +/- 1.1, 40.2 +/- 8.3 and 5.0 +/- 0.6%, respectively) in neointima was maximal at day 7. With ongoing neointima enlargement, expression of these cells decreased. In advanced neointima, labeled cells were predominantly localized at luminal and stented sites. Media showed almost no immunoreactivity of the markers studied, whereas adventitial zones of neovascularization revealed some signals.

CONCLUSIONS

Endothelial progenitor, dendritic, neural crest-derived and inflammatory cells are consistently recruited into arterial neointima, mostly at early time points after stent implantation.

Granulation encapsulated stent: a new therapeutic approach for vascular implantation

OBJECTIVES

To determine if stents could be encapsulated with immunocompatible granulation tissue for the treatment of vascular diseases.

METHODS

Bare metal stents were implanted in New Zealand white rabbits so they would be encapsulated with immunocompatible granulation tissue. The granulation encapsulated stents (GES) were then treated with either mitomycin C or saline, and implanted into rabbit iliac arteries for 4 weeks. To test whether the effect of mitomycin C was retained, we co-cultured smooth muscle cells for 3 h with subcutaneous tissue (as control) or with granulation tissue from GES treated with mitomycin C and saline.

RESULTS

Vessels with GES treated with mitomycin C (MS) and washed with saline had significantly less neointimal area (NA) after 4 weeks (0.27 (SD 0.03) mm(2) than vessels containing bare metal stents (B) (1.15 (SD 0.10) mm(2), n = 5, p<0.05) or GES treated with saline (S) (4.78 (SD 0.72) mm(2), n = 5, p<0.05). The average vessel injury score was not significantly different among these three groups (S: 1.98 (SD 0.51), MS: 1.46 (SD 0.18) and B: 1.51 (SD 0.32)). GES treated with saline had significantly less NA than the other two groups and also blocked blood flow in the contralateral iliac artery in the abdominal aortic bifurcation immediately after implantation and 4 weeks later. Histology also showed neointimal overgrowth in the vessel wall over the contralateral iliac artery.

CONCLUSIONS

GES treated with mitomycin C can significantly inhibit neointimal formation in rabbit arteries due to the formation of granulation tissue. GES treated with saline demonstrated significantly increased NA and resisted normal rabbit artery pressures.

Reduced thrombogenicity of nitinol stents--in vitro evaluation of different surface modifications and coatings

The material and the surface patterns of intravascular stents play a pivotal role in activating platelets and triggering adherence of inflammatory cells that consecutively leads to renarrowing caused by neointimal hyperplasia. To improve these features, besides mechanical and chemical modifications, ways of masking the stent by covering have been developed. In addition, polymer-coated stents are used as vehicle for local drug delivery. But as substances used for this application are described to possess an inflammatory potential, this aspect has to be evaluated. In the present study we compared different approaches to surface alterations applied to a nitinol stent design. Besides commonly used techniques like passivation and electropolishing, we evaluated coatings with heparin, aluminium and a polyurethane polymer regarding their thrombogenic and inflammatory characteristics. By weaving thin elastomer fibres a graft was generated. The previously described Chandler loop was used to simulate arterial flow conditions ex vivo using rotating PVC tubings filled with human blood. All stents received 120 min of blood contact. To determine thrombocyte activation and inflammatory reaction, the platelet count and levels of beta-TG, TAT and PMN-elastase were assessed. Scanning electron microscopy was used to visualize the reactions. Mechanical polishing and passivation did not improve the stent surface characteristics while sandblasting, electropolishing and aluminium covering decreased activation of the coagulation cascade. In terms of thrombogenicity, the heparin coating had no beneficial effect. The lowest thrombogenic potential was found in the Polyurethane-coated stent group. All stents showed similar levels of polymorph nuclear granulocyte elastase except for the membrane design. While mechanical and chemical modifications are able to reduce thrombogenicity, coating with this particular polyurethane polymer seems to be superior to these approaches regarding the parameters assessed in this experimental setting. The Chandler loop is a valuable tool to test polymeric coatings ex vivo since these modifications may reduce drug performance by inducing inflammatory reaction themselves.

Eosinophilic infiltration in restenotic tissue following coronary stent implantation

OBJECTIVES

The aim of our study was to compare the histopathological features of restenotic tissue after balloon angioplasty and after stent placement. We emphasized on specific types of inflammatory cells to evaluate the type of tissue immune response in both situations.

METHODS

A total of 32 patients underwent elective directional coronary atherectomy; 16 patients had restenosis after balloon angioplasty, 16 patients had in-stent restenosis (ISR). Atherectomy specimens were stained with antibodies against T cells, eosinophils, smooth muscle cell actin, macrophages and with antibodies against T cell activation markers. Quantitative morphometric analysis was performed using image analysis software.

RESULTS

In-stent restenotic tissue contained more smooth muscle cells (P < 0.001), anti-CD3 positive T cells (P < 0.001) and eosinophils (P = 0.012). Anti-CD40L positive activated T cells were more numerous in ISR lesions (P = 0.003) and were frequently clustered around stent imprints in the tissue. Five ISR specimens contained grossly visible stent fragments amidst the restenotic tissue. In all cases of balloon restenosis, T cells and eosinophils (if present) were concentrated around lipid rich tissue.

CONCLUSIONS

Our study indicates involvement of inflammatory responses in both types of restenosis, with significantly more eosinophils encountered in case of in-stent restenosis. In contrast with clustering of inflammatory cells around stent struts after stent placement, the inflammatory cells in balloon restenosis were located in association with lipid rich tissue, suggesting different inflammatory triggers in balloon restenosis and in-stent restenosis.

Stent-based delivery of ABT-578 via a phosphorylcholine surface coating reduces neointimal formation in the porcine coronary model

Stent-based delivery of the antiproliferative and immunosuppressive macrocyclic lactone sirolimus reduces neointimal formation and restenosis by cytostatic inhibition of vascular smooth muscle cell proliferation. The objective of this study was to determine the feasibility and efficacy of stent-based delivery of ABT-578, a structurally unique macrocyclic lactone. Stainless steel balloon-expandable stents were coated with thin layer of phosphorylcholine (PC) or PC with ABT-578 (10 microg/mm). Fifteen juvenile domestic pigs underwent placement of oversized bare metal (n = 15), PC (n = 8), and PC with ABT-578 (n = 9) stents in the coronary arteries. At 28 days, histology demonstrated similar mean injury scores for the control, PC-, and ABT-578-coated stents. The mean neointimal area (mm2) was significantly reduced for ABT-578 (1.70 +/- 0.47) as compared with PC (2.82 +/- 1.24) and control (2.89 +/- 1.91) stents (P < or = 0.05). The 40% reduction in neointimal area resulted in significantly less mean percent diameter stenosis for ABT-578 (19.4% +/- 4.0%) as compared with PC (30.3 +/- 12.1 %) and control (29.4% +/- 15.5%) stents (P < or = 0.03). Twelve of the 45 bare metal stent cross-sections (26.7%) exhibited a giant cell reaction, while none of the sections from the ABT-578-eluting stents had a giant cell reaction (P = 0.004). Stent-based delivery of ABT-578 via a PC surface coating inhibits neointimal formation at 28 days in the porcine coronary model. Further study is necessary to determine the dose-response and long-term effects ABT-578-eluting stents in the porcine coronary model.

Chronic platelet and neutrophil adhesion: a causal role for neointimal hyperplasia in in-stent restenosis

PURPOSE

To investigate the relationship between platelets and neutrophils and the progression of neointimal hyperplasia after angioplasty versus stenting of porcine coronary arteries.

METHODS

Balloon angioplasty or implantation of a balloon-expandable stent was randomly performed in the left and right coronary arteries of 16 Yorkshire swine; the animals were euthanized 1 hour (n=6), 24 hours (n=4), or 1 month (n=6) after the interventions. The adhesion of chromium 51-labeled platelets and indium 111-labeled neutrophils was quantified (per cm2), and histological and morphometric analyses were performed.

RESULTS

The acute adhesion of platelets and neutrophils observed on the injured segments 1 hour after the interventions was similar between the treated groups. However, at 24 hours, stenting was associated with 2-fold more platelets and 3-fold more neutrophils (p<0.05) than was dilation, and stented arteries remained more thrombogenic at 1 month (p<0.05). Neointimal formation was more intense after stent implantation (3.80+/-0.77 mm, p<0.05) than after dilation (0.81+/-0.21 mm), and it correlated positively with the adhesion of platelets (r=0.81, p<0.002) and neutrophils (r=0.69, p<0.01).

CONCLUSIONS

These results indicate that stent implantation is associated with a more intense acute and chronic, low-grade inflammatory response than is dilation. It appears that the chronic inflammatory response is, at least in part, platelet- and neutrophil-driven and contributes to the progression of neointimal proliferation after stenting.

Localized Hypersensitivity and Late Coronary Thrombosis Secondary to a Sirolimus-Eluting Stent

Background— The US Food and Drug Administration recently issued a warning of subacute thrombosis and hypersensitivity reactions to sirolimus-eluting stents (Cypher). The cause and incidence of these events have not been determined.

Methods and Results— We present findings of a 58-year-old man who died of late stent thrombosis 18 months after receiving 2 Cypher stents for unstable angina. Although angiographic and intravascular ultrasound results at 8 months demonstrated the absence of neointimal formation, vessel enlargement was present. An autopsy showed aneurysmal dilation of the stented arterial segments with a severe localized hypersensitivity reaction consisting predominantly of T lymphocytes and eosinophils.

Conclusions— The known pharmacokinetic elution profile of Cypher stents and the presence of polymer fragments surrounded by giant cells and eosinophils suggest that a reaction to the polymer may have caused late stent thrombosis. Careful long-term follow-up of patients with vessel enlargement after Cypher stent placement is recommended.

Pressure rinsing of coronary stents immediately before implantation reduces inflammation and neointimal hyperplasia

OBJECTIVES

This study evaluates whether rinsing stents with high pressure immediately before implantation minimizes stent-induced inflammation and neointimal formation.

BACKGROUND

Several reports indicate that manual stent manipulation before implantation results in foreign body contamination and increased neointimal hyperplasia.

METHODS

A stent-cleaning chamber was developed to rinse stents at a sustained hydrodynamic pressure of 4 atm for 10 s. Commercial pre-mounted stents were examined with different levels of manipulation: 1) untouched stents: no stent manipulation before implantation; 2) handled stents: manual stent re-crimping on the balloon; 3) rinsed stents: pressure-rinsed with the stent-cleaning chamber. In vitro surface analysis was evaluated by scanning electron microscopy. Neointimal hyperplasia and inflammation around stent struts were also assessed in the pig in-stent restenosis model.

RESULTS

In vitro analysis revealed fewer contaminants on rinsed stents compared with untouched (p = 0.01) and handled stents (p < 0.001). In vivo, neointimal thickness, neointimal area and vessel percent stenosis were significantly reduced in rinsed, compared with not-rinsed, stents (p = 0.002, p = 0.007, p = 0.008 respectively). In addition, a significant reduction in the inflammatory infiltrate around struts was observed in untouched, compared with handled, stents (p = 0.04) and in rinsed, compared with not-rinsed, stents (p < 0.001). Regression analysis accounting for injury and neointimal thickness showed significant differences in slopes between "handled + not-rinsed" and "handled + rinsed" stents (p = 0.004), and between "untouched + not-rinsed" and "untouched + rinsed stents" (p = 0.037).

CONCLUSIONS

Rinsing stents under high pressure immediately before coronary implantation results in less inflammation around struts and thinner neointima at 28 days in this pig model.

Modulation of protein expression and activity by radiation: relevance to intracoronary radiation for the prevention of restenosis

Restenosis is a common complication of percutaneous transluminal coronary angioplasty. Recent studies have demonstrated a striking reduction in the neointimal hyperplasia characteristic of restenosis following intracoronary radiation (IR), but the mechanisms by which radiation reduces neointima formation following balloon overstretch injury are not elucidated fully. In addition to direct antimitotic effects mediated via oxygen free radicals, ionizing radiation can induce the expression of numerous genes and thereby mediate indirect effects. Additionally, IR prevents restenosis at the cost of decreased healing and increased thrombosis, and we suggest that these adverse reactions can be modulated by adjunct pharmacology or gene-based strategies. This review discusses several genes and proteins modulated by radiation in the context of arterial injury, and their possible therapeutic relevance.