G. Pasterkamp

Carotid Atherosclerotic Plaques Stabilize After Stroke. Insights Into the Natural Process of Atherosclerotic Plaque Stabilization

Objective—Rupture of unstable atherosclerotic plaques is the pathological substrate for acute ischemic events. Underlying cellular and molecular characteristics of plaque rupture have been studied extensively. However, the natural course of symptomatic plaque remodeling after ischemic events is relatively unexplored. Methods and Results—Atherosclerotic carotid plaques were obtained from 804 symptomatic (stroke=204 and TIA=426) and asymptomatic (n=174) patients undergoing carotid endarterectomy. The presence of macrophages, smooth muscle cells (SMC), collagen, calcification, and lipid-core size were assessed histologically. At protein level, inflammatory mediators (interleukin [IL]-2, IL-4, IL-5, IL-8, IL-10, IL-12p70, interferon-gamma [INF-γ], tumor necrosis factor-alpha [TNF-α], matrix degrading proteinases (MMPs), and an apoptosis marker (caspase-3) were determined. We associated plaque characteristics with time elapsed between the latest event and surgery. Early after stroke and TIA, plaques revealed an unstable phenotype. After stroke, the content of macrophages decreased significantly with time (P=0.02), whereas SMC content tended to increase. At protein level, IL-6, IL-8 expression levels and caspase activity strongly decreased after stroke or TIA. Conclusions—Symptomatic carotid lesions remodel into more stable plaques over time after stroke. Changes in IL-6 and IL-8 and caspase preceded the decrease of macrophages. These temporal phenotypic plaque alterations should be taken into account for biomarker and therapeutic target validation studies using human atherosclerotic plaques.

Role of Toll-like receptor 4 in the initiation and progression of atherosclerotic disease

The family of Toll‐like receptors (TLRs) initiates an innate immune response after recognition of pathogen‐associated molecular patterns (PAMPs). Evidence is accumulating that TLRs, and particularly TLR4, are important players in the initiation and progression of atherosclerotic disease. Not only exogenous ligands but also endogenous ligands that are expressed during arterial injury are recognized by TLR4. Mouse knockout studies and epidemiological studies of human TLR4 polymorphisms have demonstrated that the TLR4 might play a role in the initiation and progression of atherosclerosis. This review will summarize the latest progression in research on the role of TLR4 in arterial occlusive disease In addition, the potential of intervention in TLR4 signalling to influence progression of atherosclerotic disease is discussed.

Rapid, arteriovenous graft failure due to intimal hyperplasia: a porcine, bilateral, carotid arteriovenous graft model.

BACKGROUNDnThe loss of patency constitutes the major complication of arteriovenous (AV) polytetrafluoroethylene hemodialysis grafts. In most cases, this graft failure is due to intimal hyperplasia at the venous outflow tract, including proliferation of vascular, smooth muscle cells and fibroblasts with deposition of extracellular matrix proteins. Thus far, procedures developed for improving patency have proven unsuccessful, which can be partly explained by the lack of relevant animal models. For this purpose, we developed a porcine model for AV graft failure that will allow the assessment of promising therapeutic strategies in the near future.nnnMATERIALS AND METHODSnIn 14 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein using expanded polytetrafluoroethylene. Two, 4 or 8 weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis.nnnRESULTSnFrom 2 weeks onwards, a thick neo-intima developed at the venous anastomosis, predominantly consisting of alpha-actin-positive vascular smooth muscle cells (VSMC). Intimal area increased over time, coinciding with a decreased graft flow. Grafts remained patent for at least 4 weeks. At 8 weeks, patency rates declined to less than 50% due to thrombus formation superimposed on progressive neo-intima formation.nnnCONCLUSIONSnImplantation of an AV graft between the carotid artery and jugular vein in pigs causes a rapid neo-intimal response, accompanied by a loss of patency of 50% at 8 weeks after surgery. This model offers a suitable tool to study local interventions aimed at the improvement of AV graft patency rates.

Matrix Metalloproteinases: A Therapeutic Target in Cardiovascular Disease

Cardiovascular disease is the leading cause of death in Western society. Extracellular matrix turnover is important in many cardiovascular pathologies, such as arterial remodeling, plaque rupture, restenosis, aneurysm formation and heart failure. Matrix metalloproteinases (MMPs) belong to a group of zinc and calcium dependent proteases and cause breakdown of the extracellular matrix. MMP inhibitors have been developed and tested for their effect on the outcome of oncological disease [1]. Recent preclinical research revealed that these MMP inhibitors could also have great potential in the field of cardiovascular disease. This preclinical research has encouraged investigators to design and start the first clinical studies with cardiovascular endpoints. In the present paper, the various aspects of MMP participation in cardiovascular disease will be summarized. Preclinical animal studies that demonstrated the effect and potential of applicable MMP inhibitors on different cardiovascular disease entities will be discussed. We will specifically focus on the role of MMPs and the potential of their inhibitors in de novo atherosclerotic plaque destabilization, arterial remodeling, restenosis after ballon angioplasty and stenting, aneurysm formation and heart failure. We conclude that MMP inhibitors are likely to be useful in the development of pharmacological approaches to reduce cardiovascular death, considering the positive outcomes after usage of MMP inhibitors in restenosis and arterial remodeling.

Carotid Atherosclerotic Plaque Characteristics Are Associated With Microembolization During Carotid Endarterectomy and Procedural Outcome

Background and Purpose— During carotid endarterectomy (CEA), microemboli may occur, resulting in perioperative adverse cerebral events. The objective of the present study was to investigate the relation between atherosclerotic plaque characteristics and the occurrence of microemboli or adverse events during CEA. Methods— Patients (n=200, 205 procedures) eligible for CEA were monitored by perioperative transcranial Doppler. The following phases were discriminated during CEA: dissection, shunting, release of the clamp, and wound closure. Each carotid plaque was stained for collagen, macrophages, smooth muscle cells, hematoxylin, and elastin. Semiquantitative analyses were performed on all stainings. Plaques were categorized into 3 groups based on overall appearance (fibrous, fibroatheromatous, or atheromatous). Results— Fibrous plaques were associated with the occurrence of more microemboli during clamp release and wound closure compared with atheromatous plaques (P=0.04 and P=0.02, respectively). Transient ischemic attacks and minor stroke occurred in 5 of 205 (2.4%) and 6 of 205 (2.9%) patients, respectively. Adverse cerebral outcome was significantly related to the number of microembolic events during dissection (P=0.003) but not during shunting, clamp release, or wound closure. More cerebrovascular adverse events occurred in patients with atheromatous plaques (7/69) compared with patients with fibrous or fibroatheromatous plaques (4/138) (P=0.04). Conclusions— Intraoperatively, a higher number of microemboli were associated with the presence of a fibrous but not an atheromatous plaque. However, atheromatous plaques were more prevalent in patients with subsequent immediate adverse events. In addition, specifically the number of microemboli detected during the dissection phase were related to immediate adverse events.

Modulation of Collagen Turnover in Cardiovascular Disease

Collagen fibers are the most abundant components of the extracellular matrix in arteries and myocardium. Disturbances in the collagen turnover (synthesis and degradation) have been linked to inflammatory diseases including cardiovascular pathological syndromes. In the myocardium, changes in collagen turnover may result in ventricle dilatation and subsequent contractile dysfunction. In arteries, collagen synthesis and degradation are associated with the progression of atherosclerotic disease and intimal hyperplasia following injury. Collagen synthesis is tightly regulated at several levels: synthesis of procollagens, suitable folding of polypeptides, secretion and cross-linking of mature fibers. On the other hand, degradation of newly synthesised procollagen and mature collagen fibers depends on the action of Matrix-Metalloproteinases (MMPs). The major role of collagen turnover in cardiovascular disorders has stimulated the search for pharmacological agents that interfere with collagen turnover at different levels. These drugs can theoretically act through modulation of the synthesis of procollagens or by interference with their post-translational modifications. Another group of pharmacological agents inhibit collagen breakdown (MMP inhibitors). Beneficial effects of compounds that target collagen metabolism have been reported. Unfortunately, many of these compounds also give rise to serious adverse effects due to interference with vital biological processes in which collagen plays an important role. In this paper, we will review cardiovascular diseases in which altered local collagen turnover is a key feature. Subsequently, the effect of compounds that have been developed and tested to modulate collagen synthesis, cross-linking or breakdown will be discussed.

Activation of the Innate Immune System in Atherosclerotic Disease

Innate immunity is the first line of defence against invading micro-organisms. The family of Toll-like receptors (TLRs) recognizes pathogen-associated molecular patterns (PAMPs) that are carried by the invading micro-organisms. Infectious pathogens have been implicated to play an important role in atherosclerosis. Nowadays, evidence is accumulating that TLRs play an important role in the initiation and progression of atherosclerosis too. A lot is known about the exogenous ligands that are able to activate the TLRs, but it is also known that endogenous ligands have the capacity to activate TLRs when exogenous ligands are absent. Studies on knockout mice, epidemiological studies and even human polymorphism studies confirmed the important role of TLRs in development and progression of atherosclerotic disease. Studies with antagonists against TLR ligands and vaccination studies demonstrated that TLR signaling might be a potential target for intervention in the initiation and progression of atherosclerosis.

Heart failure with preserved ejection fraction in women: the Dutch Queen of Hearts program

Heart failure (HF) poses a heavy burden on patients, their families and society. The syndrome of HF comes in two types: with reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF). The latter is on the increase and predominantly present in women, especially the older ones. There is an urgent need for mortality-reducing drugs in HFpEF, a disease affecting around 5xa0% of those aged 65xa0years and over. HFpEF develops in patients with risk factors and comorbidities such as obesity, hypertension, diabetes, COPD, but also preeclampsia. These conditions are likely to drive microvascular disease with involvement of the coronary microvasculature, which may eventually evolve into HFpEF. Currently, the diagnosis of HFPEF relies mainly on echocardiography. There are no biomarkers that can help diagnose female microvascular disease or facilitate the diagnosis of (early stages of) HFpEF. Recently a Dutch consortium was initiated, Queen of Hearts, with support from the Netherlands Heart Foundation, with the aim to discover and validate biomarkers for diastolic dysfunction and HFpEF in women. These biomarkers come from innovative blood-derived sources such as extracellular vesicles and circulating cells. Within the Queen of Hearts consortium, we will pursue female biomarkers that have the potential for further evolution in assays with point of care capabilities. As a spin-off, the consortium will gain knowledge on gender-specific pathology of HFpEF, possibly opening up novel treatment options.

Plasma extracellular vesicle protein content for diagnosis and prognosis of global cardiovascular disease

Cardiovascular disease is a major public health problem worldwide. Its growing burden is particularly ominous in Asia, due to increasing rates of major risk factors such as diabetes, obesity and smoking. There is an urgent need for early identification and treatment of individuals at risk of adverse cardiovascular events. Plasma extracellular vesicle proteins are novel biomarkers that have been shown to be useful in the diagnosis, risk stratification and prognostication of patients with cardiovascular disease. Ongoing parallel biobank initiatives in European (the Netherlands) and Asian (Singapore) populations offer a unique opportunity to validate these biomarkers in diverse ethnic groups.

Characterization and In Vitro and In Vivo Testing of CB2-Receptor- and NGAL-Targeted Paramagnetic Micelles for Molecular MRI of Vulnerable Atherosclerotic Plaque

PurposeAtherosclerotic plaque macrophages express the peripheral cannabinoid receptor (CB2-R) and promote fibrous cap degradation by secretion of neutrophil gelatinase-associated lipocalin 2 (NGAL). In this study, we report the preparation, characterization, and in vitro and in vivo testing of double-labeled (MR and fluorescent) CB2-R- and NGAL-targeted micelles.Procedures/ResultsSpecific CB2-R agonists or antibodies directed to 24p3 (mouse homolog of NGAL) were incorporated into di-oleoyl-polyethylene glycol-phosphatidylethanolamine 1000 (DOPE-PEG1000) micelles or di-stearoyl-polyethylene glycol-phosphatidylethanolamine 2000 (DSPE-PEG2000) micelles. The hydrodynamic diameter, determined by dynamic light scattering, was 16.5 and 19.0xa0nm for CB2-R-targeted DOPE-PEG1000 and DSPE-PEG2000 micelles, respectively, and 23.0xa0nm for Ab-conjugated DSPE-PEG2000 micelles. In vitro and in vivo MRI and fluorescence microscopy showed specific binding of CB2-R-targeted and 24p3-targeted micelles to in vitro systems and to aortic plaque in apoE−/−/eNOS−/− mice, respectively.ConclusionsCB2-R- and NGAL-targeted micelles show promise as tools for in vivo characterization of vulnerable plaque.