cNGR: A Novel Homing Sequence for CD13/APN Targeted Molecular Imaging of Murine Cardiac Angiogenesis In Vivo

Objective— Previously, the peptide sequence cNGR has been shown to home specifically to CD13/APN (aminopeptidase N) on tumor endothelium. Here, we investigated the feasibility of selective imaging of cardiac angiogenesis using the cNGR-CD13/APN system.

Methods and Results— CD13/APN induction and cNGR homing were studied in the murine myocardial infarction (MI) model. By real-time polymerase chain reaction (PCR) at 7 days after MI, CD13/APN expression was 10- to 20-fold higher in the angiogenic infarct border zone and the MI area than in non-MI areas. In vivo fluorescence microscopy confirmed specific homing of fluorophore-tagged cNGR to the border zone and MI territory at 4 and 7 days after MI with a local advantage of 2.3, but not at 1 or 14 days after MI. Tissue residence half-life was 9.1±0.3 hours, whereas the half-life in plasma was 15.4±3.4 minutes. Pulse chase experiments confirmed reversible binding of cNGR in the infarct area. Fluorescent labeled cNGR conjugates or antibodies were injected in vivo, and their distribution was studied ex vivo by 2-photon laser scanning microscopy (TPLSM). cNGR co-localized exclusively with CD13/APN and the endothelial marker CD31 on vessels.

Conclusions— In cardiac angiogenesis endothelial CD13/APN is upregulated. It can be targeted specifically with cNGR conjugates. In the heart cNGR binds its endothelial target only in angiogenic areas.

Atherosclerotic plaque vulnerability as an explanation for the increased risk of stroke in elderly undergoing carotid artery stenting

BACKGROUND AND PURPOSE

Recent randomized trials showed an increased periprocedural risk for stroke with increasing age in patients undergoing carotid artery stenting. Manipulation of atherosclerotic plaques during carotid artery stenting can result in plaque rupture with subsequent superimposed thrombus formation, embolization, and cerebrovascular events. We hypothesized that atherosclerotic plaques become more unstable with increasing age and thereby might provide insight into the age-related increased risk of cerebrovascular events during carotid artery stenting.

METHODS

Carotid atherosclerotic plaques were harvested from 1385 consecutive patients undergoing carotid endarterectomy between 2002 and 2010. Carotid plaques were quantitatively analyzed for macrophages, smooth muscle cells, and microvessels; and semiquantitatively analyzed for collagen, calcifications lipid cores, and intraplaque hemorrhages. Patients were divided in 4 groups by age: <60, 60 to 69, 70 to 79, and ≥80 years. Measures of association between age as a continuous variable and histological characteristics were also calculated.

RESULTS

Increasing age was associated with a decrease in the amount of smooth muscle cells in the carotid plaque. More plaques with large atheroma and heavy plaque calcifications were observed among elderly patients. After correction for baseline differences, risk factors, and medication use, age was independently associated with a more vulnerable carotid plaque composition.

CONCLUSIONS

Plaque stability decreases gradually with age. Older patients with carotid stenosis have relatively unstable plaques with low smooth muscle cell content, a high amount of large lipid cores, and more calcified plaques as compared with younger patients. The underlying vulnerable plaque composition in the elderly might be an important contributing factor to the increased risk of stroke for older patients undergoing carotid artery stenting.

The prognostic value of highly sensitive cardiac troponin assays for adverse events in men and women with stable heart failure and a preserved vs. reduced ejection fraction

AIMS

Circulating biomarkers are important in the diagnosis, risk stratification and management of patients with heart failure (HF). Given the current lack of biomarkers in HF with preserved ejection fraction (HFpEF), we aimed to investigate the prognostic performance of the newly developed high-sensitivity (hs) assays for cardiac troponin I (hsTnI) compared with troponin T (hsTnT) for adverse events in HFpEF vs. HF with reduced ejection fraction (HFrEF). Findings in these two HF subgroups were also compared with those in the recently defined HF with mid-range ejection fraction (HFmrEF) subgroup.

METHODS AND RESULTS

Both hsTnI and hsTnT were measured in 1096 patients with HFrEF [left ventricular ejection fraction (LVEF) <50%; n = 853] or HFpEF (LVEF ≥50%; n = 243) enrolled in the Singapore Heart Failure Outcomes and Phenotypes (SHOP) study. Both troponin assays were more strongly associated with the composite endpoint (all-cause mortality or first rehospitalization for HF) in HFpEF than in HFrEF. The hsTnT assay provided the greatest additional prognostic value in HFpEF in comparison with hsTnI and NT-proBNP. TnI was more strongly associated with composite events in men with HFpEF [hazard ratio (HR) 3.33, 95% confidence interval (CI) 1.82-6.09; P < 0.001 per standard deviation (SD) increase in log-transformed hsTnI] than in women with HFpEF (HR 1.35, 95% CI 0.94-1.93; P = 0.10 per SD increase in log-transformed hsTnI).

CONCLUSIONS

There is a potential role for the prognostic use of high-sensitivity troponin assays, particularly hsTnT, in men and women with HFpEF. The predictive association of hsTnI with outcome appears strongest in men with HFpEF.

Associations of autozygosity with a broad range of human phenotypes

In many species, the offspring of related parents suffer reduced reproductive success, a phenomenon known as inbreeding depression. In humans, the importance of this effect has remained unclear, partly because reproduction between close relatives is both rare and frequently associated with confounding social factors. Here, using genomic inbreeding coefficients (FROH) for >1.4 million individuals, we show that FROH is significantly associated (p < 0.0005) with apparently deleterious changes in 32 out of 100 traits analysed. These changes are associated with runs of homozygosity (ROH), but not with common variant homozygosity, suggesting that genetic variants associated with inbreeding depression are predominantly rare. The effect on fertility is striking: FROH equivalent to the offspring of first cousins is associated with a 55% decrease [95% CI 44-66%] in the odds of having children. Finally, the effects of FROH are confirmed within full-sibling pairs, where the variation in FROH is independent of all environmental confounding.

Immunomodulation of the NLRP3 Inflammasome in Atherosclerosis, Coronary Artery Disease, and Acute Myocardial Infarction

Cardiovascular disease (CVD) remains the leading cause of mortality and morbidity worldwide. Atherosclerosis is responsible for the majority of cardiovascular disorders with inflammation as one of its driving processes. The nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, responsible for the release of the pro-inflammatory cytokines, interleukin-1β (IL-1β), and interleukin-18 (IL-18), has been studied extensively and showed to play a pivotal role in the progression of atherosclerosis, coronary artery disease (CAD), and myocardial ischemia reperfusion (I/R) injury. Both the NLRP3 inflammasome and its downstream cytokines, IL-1ß and IL-18, could therefore be promising targets in cardiovascular disease. This review summarizes the role of the NLRP3 inflammasome in atherosclerosis, CAD, and myocardial I/R injury. Furthermore, the current therapeutic approaches targeting the NLRP3 inflammasome and its downstream signaling cascade in atherosclerosis, CAD, and myocardial I/R injury are discussed.

Age-related changes in plaque composition

OBJECTIVE

The extent of atherosclerotic plaque burden and the incidence of atherosclerosis-related cardiovascular events accelerate with increasing age. The composition of the plaque is associated with plaque thrombosis and acute coronary occlusion. Surprisingly, however, the relation between advancing age and atherosclerotic plaque composition is still unclear. In the present study, we investigated the association between plaque characteristics and advancing age in a population of patients with haemodynamically significant carotid artery stenosis.

METHODS

Patients (N=383), ages 39-89 years, underwent carotid endarterectomy (CEA). Morphometric analysis was performed on the dissected atherosclerotic plaques to study the prevalence of fibrous and atheromatous plaques. Picro sirius red, haematoxylin eosin, alfa actin and CD68 stainings were performed to investigate the extent of collagen, calcification, smooth muscle cells and macrophages in carotid plaques, respectively. The presence of metalloproteinases-2 and -9 was assessed by ELISA.

RESULTS

With aging, a decrease in fibrous plaques and an increase in atheromatous plaques were observed. This was accompanied by an age-associated decrease in smooth muscle cell content in carotid plaques. Macrophage content slightly increased with age. In addition, total matrix metalloprotease (MMP)-2 was negatively and MMP-9 positively related with age. Differences in plaque phenotype were most prominent for the youngest age quartile compared with older age quartiles.

CONCLUSIONS

With increasing age, the morphology of atherosclerotic plaques from patients with carotid artery stenosis changes. Plaques become more atheromatous and contain less smooth muscle cells with increasing age. Local inflammation and MMP-9 levels slightly increased with age in plaques obtained from patients suffering from haemodynamically significant advanced atherosclerotic lesions.

Endogenous inflammatory molecules engage Toll-like receptors in cardiovascular disease

Innate immunity is important in the pathogenesis and progression of cardiovascular disease. Innate immune cells express various pattern-recognition receptors, among which also Toll-like receptors (TLRs). TLRs occur in atherosclerotic lesions where they are triggered by both exogenous (bacterial and viral pathogens) and endogenous (tissue damage-associated) molecules. Several endogenous TLR activators are described in relation to atherosclerotic disease or ischemia-induced cardiac injury. Experimental animal models have proved the role of TLR endogenous activators in disease initiation and further development. Nowadays, researchers aim to unravel the exact mechanisms involved in the endogenous ligand-dependent TLR signaling and to discover new potential activators, released during pathological conditions such as atherosclerosis and related ischemic manifestations. This review provides an overview of the currently known endogenous molecules which trigger innate immunity via TLRs in cardiovascular disease.

Matrix metalloproteinase inhibition reduces intimal hyperplasia in a porcine arteriovenous-graft model

BACKGROUND

The patency of arteriovenous (AV) polytetrafluoroethylene grafts for hemodialysis is impaired by intimal hyperplasia (IH) at the venous outflow tract. IH mainly consists of vascular smooth muscle cells, fibroblasts, and extracellular matrix proteins. Because matrix metalloproteinases (MMPs) are enzymes able to degrade extracellular matrix proteins such as elastin and collagen and also stimulate migration of vascular smooth muscle cells, we hypothesized that BB2983 (a broad-spectrum MMP inhibitor) could reduce IH in AV grafts.

METHODS

In 12 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein. Six pigs received the oral MMP inhibitor (MMPi), and six pigs served as a control. Four weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis. Quantification of elastin content was performed on Elastin von Gieson-stained sections.

RESULTS

At the venous outflow tract, IH was strongly inhibited after MMPi when compared with the control group (1.02 +/- 0.26 mm(2) vs 2.14 +/- 0.38 mm(2); P =.027). The medial area did not differ significantly. In the control group elastin density decreased compared with nonoperated veins. This decrease was not observed in the MMPi group (nonoperated, 6.3% +/- 0.4%; MMPi, 7.2% +/- 0.7% vs untreated, 3.6% +/- 0.5%; P =.0004). Outward remodeling of the vein was not influenced by MMP inhibition.

CONCLUSION

MMPi reduces IH formation at the venous outflow tract of AV grafts in pigs, probably by inhibiting elastin degradation. These data suggest that MMP inhibitors might be useful for minimizing IH in AV grafts, thus prolonging patency rates of AV grafts in patients on hemodialysis.

Monocyte-Chemoattractant Protein-1 Levels in Human Atherosclerotic Lesions Associate With Plaque Vulnerability

[Figure: see text].

Histological characterization of restenotic carotid plaques in relation to recurrence interval and clinical presentation: a cohort study

Backgrounds and Purpose- Restenosis is an important complication after carotid endarterectomy, but little is known about plaque composition in early versus late restenosis and which plaque characteristics are associated with symptomatic clinical presentation of restenotic lesions.

METHODS

Endarterectomy specimens of 822 consecutive patients undergoing carotid endarterectomy (33 restenotic; 789 primary) were subjected to histological examination for the presence of macrophages, smooth muscle cells, collagen, calcifications, luminal thrombus, intraplaque bleeding and lipid core size.

RESULTS

Early restenotic plaques showed marked accumulation of smooth muscle cells and fibrous tissue, whereas late restenotic plaques demonstrated increased macrophage infiltration, calcification and lipid core (P trend <0.05), resembling primary plaques. Patients with symptomatic restenosis had plaques with higher macrophage infiltration (P=0.01) and a larger lipid core (P=0.02) than asymptomatic patients, independent of recurrence interval.

CONCLUSIONS

Restenosis occurring >5 years after primary carotid endarterectomy resembles primary plaques. Symptomatic presentation of restenotic lesions is independently associated with an unstable plaque phenotype.

Sex is associated with the presence of atherosclerotic plaque hemorrhage and modifies the relation between plaque hemorrhage and cardiovascular outcome

BACKGROUND AND PURPOSE

Plaque hemorrhage (PH) may lead to accelerated progression of atherosclerotic disease. The presence of local PH in the carotid plaque predicts future cardiovascular events in any vascular territory. We investigated the prevalence of local PH and the predictive value of PH for the occurrence of cardiovascular events in men and women separately.

METHODS

Atherosclerotic plaques from 1422 patients (969 men, 453 women) who underwent carotid endarterectomy were analyzed histologically for the presence of PH. Patients were monitored for 3 years for cardiovascular events (nonfatal stroke, nonfatal myocardial infarction, vascular death, and vascular intervention).

RESULTS

Plaques from men showed a significantly higher prevalence of PH compared with women (67% versus 54%; P<0.001). In 1353 patients with available follow-up data, with a median duration of 2.9 years, 270 events had occurred in men (29%) and 94 in women (22%). Stratified by presence of PH, the event rate was 32% in men with PH versus 23% in men without PH, and 23% in women with PH versus 21% in women without PH. A multivariable Cox proportional hazards model found a significant interaction between sex and PH. PH was significantly associated with events in men (adjusted hazard ratio, 1.9; 95% CI, 1.2-2.8) but not in women (adjusted hazard ratio, 1.0; 95% CI, 0.6-1.7).

CONCLUSIONS

Atherosclerotic carotid plaques obtained from men reveal a higher prevalence of PH compared with women. Local PH is strongly related to secondary manifestations of cardiovascular disease in men but not in women.

Carotid atherosclerotic plaque matrix metalloproteinase-12-positive macrophage subpopulation predicts adverse outcome after endarterectomy

Background

Matrix metalloproteinase-12 (MMP-12) promotes atherosclerosis in animal models. MMP-12 is expressed in only a subset of foam-cell macrophages (FCMs) in human plaques. We investigated whether the prevalence of this MMP-12–expressing subpopulation is a prognostic indicator of adverse outcome in patients after carotid endarterectomy (CEA).

Methods and Results

Serial sections of culprit lesions from 236 patients who underwent CEA and had undergone 3 years of clinical follow-up were stained immunocytochemically for MMP-12 and for CD68, and the MMP-12/CD68 ratio was used to quantify the MMP-12–expressing subpopulation. A high MMP-12/CD68 ratio correlated with a high content of lipid and total macrophages and a low content of vascular smooth muscle cells, as well as with MMP-8 (R=0.211, P=0.001), MMP-9 (R=0.251, P<0.001), and cleaved caspase-3 (R=0.142, P=0.036) activity measured in a neighboring segment. Dual immunohistochemical examination confirmed the location of MMP-12 in a subpopulation of MMP-8– and MMP-9–positive FCMs, whereas all apoptotic FCMs were MMP-12 positive. Patients who yielded plaques within the highest quartile compared with the lowest quartile of MMP-12/CD68 ratio had a 2.4-fold (hazard ratio, 2.4; 95% CI, 1.1- to 5.1-fold; adjusted P=0.027) increased risk of major adverse cardiovascular event and a 3.4-fold (3.4; 1.2- to 9.6-fold, P=0.024) increased risk for stroke.

Conclusions

The prevalence of an MMP-12–positive subset of FCMs is a prognostic marker for adverse clinical outcome after CEA.

Statin Treatment Is Not Associated With Consistent Alterations in Inflammatory Status of Carotid Atherosclerotic Plaques

BACKGROUND AND PURPOSE

Anti-inflammatory qualities are held partially responsible for the reduction of cardiovascular events after statin treatment. We examined the phenotype of carotid atherosclerotic plaques harvested during carotid endarterectomy in relation to the previous use of different statins prescribed in clinical practice.

METHODS

Three hundred and seventy-eight patients were included. Atherosclerotic plaques were harvested, immunohistochemically stained and semiquantitively examined for the presence of macrophages (CD68), smooth muscle cells, collagen and fat. Adjacent atherosclerotic plaques were used to study protease activity and interleukin levels. Patients' demographics were recorded and blood samples were stored.

RESULTS

Serum cholesterol, low-density lipoprotein, apolipoprotein B, and C-reactive protein levels were lower in patients treated with statins compared with patients without statin treatment. Atheromatous plaques were less prevalent in patients receiving statins compared with patients without statin therapy (29% versus 42%, P=0.04). An increase of CD68 positive cells was observed in patients receiving statins compared with nonstatin treatment (P=0.05). This effect was specifically related to atorvastatin treatment. In patients treated with atorvastatin, the increased amount of CD68 positive cells were not associated with increased protease activity. In contrast, a dose-dependent decrease in protease activity was shown in the atorvastatin group. Interleukin 6 expression was lower in plaques obtained from patients treated with statins (P=0.04).

CONCLUSIONS

Statin use may exert pleiotropic effects on plaque phenotype. However, not the presence of macrophages but activation with subsequent protease and cytokine release may be attenuated by statin use.

Gender differences in health-related quality of life in patients undergoing coronary angiography

Background

Health-related quality of life (HRQOL) reflects the general well-being of individuals. In patients with coronary artery disease (CAD), HRQOL is compromised. Female patients with CAD have been reported to have lower HRQOL. In this study, we investigate gender differences in HRQOL and in associations of patient characteristics with HRQOL in patients with coronary angiography (CAG).

Methods

We cross-sectionally analysed patients from the Utrecht Coronary Biobank undergoing CAG. All patients filled in an HRQOL questionnaire (RAND-36 and EuroQoL) on inclusion. RAND-36 and EuroQoL HRQOL measures were compared between the genders across indications for CAG, CAD severity and treatment of CAD. RAND-36 HRQOL measures were compared with the general Dutch population. Additionally, we assessed interactions of gender with patient characteristics in their association with HRQOL (EuroQoL).

Results

We included 1421 patients (1020 men and 401 women) with a mean age of 65 in our analysis. Women reported lower HRQOL measures than men (mean EuroQoL self-rated health grade 6.84±1.49 in men, 6.46±1.40 in women, p<0.001). The reduction in RAND-36 HRQOL as compared with the general Dutch population was larger in women than in men. From regression analysis, we found that diabetes, a history of cardiovascular disease and symptoms of shortness of breath determined HRQOL (EuroQoL) more strongly in men than in women.

Conclusions

Women reported lower HRQOL than men throughout all indications for CAG and regardless of CAD severity or treatment. As compared with the general population, the reduction in HRQOL was more extreme in women than in men. Evident gender differences were found in determinants of HRQOL in patients undergoing CAG, which deserve attention in future research.

Trial registration

NCT02304744 (clinicaltrials.gov).

Human Validation of Genes Associated With a Murine Atherosclerotic Phenotype

OBJECTIVE

The genetically modified mouse is the most commonly used animal model for studying the pathogenesis of atherosclerotic disease. We aimed to assess if mice atherosclerosis-related genes could be validated in human disease through examination of results from genome-wide association studies.

APPROACH AND RESULTS

We performed a systematic review to identify atherosclerosis-causing genes in mice and carried out gene-based association tests of their human orthologs for an association with human coronary artery disease and human large artery ischemic stroke. Moreover, we investigated the association of these genes with human atherosclerotic plaque characteristics. In addition, we assessed the presence of tissue-specific cis-acting expression quantitative trait loci for these genes in humans. Finally, using pathway analyses we show that the putative atherosclerosis-causing genes revealed few associations with human coronary artery disease, large artery ischemic stroke, or atherosclerotic plaque characteristics, despite the fact that the majority of these genes have cis-acting expression quantitative trait loci.

CONCLUSIONS

A role for genes that has been observed in mice for atherosclerotic lesion development could scarcely be confirmed by studying associations of disease development with common human genetic variants. The value of murine atherosclerotic models for selection of therapeutic targets in human disease remains unclear.

Intersecting single-cell transcriptomics and genome-wide association studies identifies crucial cell populations and candidate genes for atherosclerosis

Aims

Genome-wide association studies (GWASs) have discovered hundreds of common genetic variants for atherosclerotic disease and cardiovascular risk factors. The translation of susceptibility loci into biological mechanisms and targets for drug discovery remains challenging. Intersecting genetic and gene expression data has led to the identification of candidate genes. However, previously studied tissues are often non-diseased and heterogeneous in cell composition, hindering accurate candidate prioritization. Therefore, we analysed single-cell transcriptomics from atherosclerotic plaques for cell-type-specific expression to identify atherosclerosis-associated candidate gene–cell pairs.

Methods and results

We applied gene-based analyses using GWAS summary statistics from 46 atherosclerotic and cardiovascular disease, risk factors, and other traits. We then intersected these candidates with single-cell RNA sequencing (scRNA-seq) data to identify genes specific for individual cell (sub)populations in atherosclerotic plaques. The coronary artery disease (CAD) loci demonstrated a prominent signal in plaque smooth muscle cells (SMCs) (SKI, KANK2, and SORT1) P-adj. = 0.0012, and endothelial cells (ECs) (SLC44A1, ATP2B1) P-adj. = 0.0011. Finally, we used liver-derived scRNA-seq data and showed hepatocyte-specific enrichment of genes involved in serum lipid levels.

Conclusion

We discovered novel and known gene–cell pairs pointing to new biological mechanisms of atherosclerotic disease. We highlight that loci associated with CAD reveal prominent association levels in mainly plaque SMC and EC populations. We present an intuitive single-cell transcriptomics-driven workflow rooted in human large-scale genetic studies to identify putative candidate genes and affected cells associated with cardiovascular traits. Collectively, our workflow allows for the identification of cell-specific targets relevant for atherosclerosis and can be universally applied to other complex genetic diseases and traits.

Systemic Mesenchymal Stem Cell-Derived Exosomes Reduce Myocardial Infarct Size: Characterization With MRI in a Porcine Model

The observations that mesenchymal stem cells (MSCs) exert cardiac protection and repair via their secretome with the active component(s) identified as exosomes underpinned our test of the efficacy of MSC exosomes in a porcine model of myocardial infarction (MI) when administered systemically by the convenient method of intravenous (IV) bolus injection. Results show that 7 days of IV exosomes results in clear reduction (30-40%) of infarct size measured at both 7 and 28 days post-MI, despite near identical release of hs Troponin T. Together with reduced infarct size, exosome treatment reduced transmurality and lessened wall thinning in the infarct zone. Exosome treated pigs showed relative preservation of LV function with significant amelioration of falls in fractional wall thickening compared with control. However, global measures of LV function were less protected by exosome treatment. It is possible that greater preservation of global LV function may have been attenuated by increased cardiac fibrosis, as T1 values showed significant increase in the exosome pigs compared to control particularly in the infarct related segments. Taken together, these results show clear effects of IV exosomes administered over 7 days to reduce infarct size with relatively preserved cardiac function compared to control treated infarct pigs.

Spectroscopic intravascular photoacoustic imaging of lipids in atherosclerosis

The natural history of atherosclerosis is marked by changes in the lipid biochemistry in the diseased arterial wall. As lesions become more vulnerable, different cholesterol species accumulate in the plaque. Understanding unstable atherosclerosis as a pharmacological and interventional therapeutic target requires chemically specific imaging of disease foci. In this study, we aim to image atherosclerotic plaque lipids and other vessel wall constituents with spectroscopic intravascular photoacoustics (sIVPA). sIVPA imaging can identify lipids in human coronary atherosclerotic plaque by relying on contrast in the near-infrared absorption spectra of the arterial wall components. Using reference spectra acquired on pure compounds, we analyzed sIVPA data from human coronary plaques ex vivo, to image plaque composition in terms of cholesterol and cholesterol ester content. In addition, we visualized the deeper lying connective tissue layers of the adventitia, as well as the fatty acid containing adipose cells in the peri-adventitial tissue. We performed simultaneous coregistered IVUS imaging to obtain complementary morphological information. Results were corroborated by histopathology. sIVPA imaging can distinguish the most prevalent lipid components of human atherosclerotic plaques and also visualize the connective tissue layers of the adventitia and the fatty acid containing adipose cells in the peri-adventitial tissue.

RANTES/CCL5 and risk for coronary events: results from the MONICA/KORA Augsburg case-cohort, Athero-Express and CARDIoGRAM studies

BACKGROUND

The chemokine RANTES (regulated on activation, normal T-cell expressed and secreted)/CCL5 is involved in the pathogenesis of cardiovascular disease in mice, whereas less is known in humans. We hypothesised that its relevance for atherosclerosis should be reflected by associations between CCL5 gene variants, RANTES serum concentrations and protein levels in atherosclerotic plaques and risk for coronary events.

METHODS AND FINDINGS

We conducted a case-cohort study within the population-based MONICA/KORA Augsburg studies. Baseline RANTES serum levels were measured in 363 individuals with incident coronary events and 1,908 non-cases (mean follow-up: 10.2±4.8 years). Cox proportional hazard models adjusting for age, sex, body mass index, metabolic factors and lifestyle factors revealed no significant association between RANTES and incident coronary events (HR [95% CI] for increasing RANTES tertiles 1.0, 1.03 [0.75-1.42] and 1.11 [0.81-1.54]). None of six CCL5 single nucleotide polymorphisms and no common haplotype showed significant associations with coronary events. Also in the CARDIoGRAM study (>22,000 cases, >60,000 controls), none of these CCL5 SNPs was significantly associated with coronary artery disease. In the prospective Athero-Express biobank study, RANTES plaque levels were measured in 606 atherosclerotic lesions from patients who underwent carotid endarterectomy. RANTES content in atherosclerotic plaques was positively associated with macrophage infiltration and inversely associated with plaque calcification. However, there was no significant association between RANTES content in plaques and risk for coronary events (mean follow-up 2.8±0.8 years).

CONCLUSIONS

High RANTES plaque levels were associated with an unstable plaque phenotype. However, the absence of associations between (i) RANTES serum levels, (ii) CCL5 genotypes and (iii) RANTES content in carotid plaques and either coronary artery disease or incident coronary events in our cohorts suggests that RANTES may not be a novel coronary risk biomarker. However, the potential relevance of RANTES levels in platelet-poor plasma needs to be investigated in further studies.

Low levels of Nogo-B in human carotid atherosclerotic plaques are associated with an atheromatous phenotype, restenosis, and stenosis severity

OBJECTIVE

Reticulon-4/Nogo (Nogo-B) protects mouse arteries from lumen loss by reducing smooth muscle cell (SMC) migration and intimal thickening. Our goal was to determine plaque and circulating levels of Nogo-B in atherosclerotic and control subjects. Therefore, we studied the relationships between local Nogo-B, plaque characteristics, and clinical data in patients undergoing carotid endarterectomy.

METHODS AND RESULTS

Western blot analysis showed that endarterectomy specimens from the femoral (n=19) and carotid arteries (n=145) contained significantly less Nogo-B than nonatherosclerotic mammary arteries (n=8; P<0.003) and aortas (n=15; P=0.03). Immunohistochemistry revealed that in atherosclerotic lesions, Nogo-B was expressed by macrophage/foam cells, SMC rich, and neo-vascularized areas. Atheromatous plaques (>40% fat content) showed a significant reduction in Nogo-B expression (P=0.002). Nogo-B expression levels were significantly lower in patients with more than 90% of carotid stenosis (P=0.04) or restenotic lesions after prior carotid intervention (duplex; P=0.01). In contrast, plasmatic levels of Nogo-B (soluble Nogo-B) did not differ between atherosclerotic subjects (n=68) and risk-factor matched controls (n=63; P=0.5).

CONCLUSION

Our findings suggest that local reduction of Nogo-B in atherosclerotic tissue might contribute to plaque formation and/or instability triggering luminal narrowing. In contrast, plasma Nogo-B levels are not associated with clinically manifested atherosclerotic disease.

Functional role for toll-like receptors in atherosclerosis and arterial remodeling

PURPOSE OF REVIEW

Activation of inflammatory cascades is causally related to the development of atherosclerotic disease. Toll-like receptors are innate immune receptors that recognize pathogen-associated molecular patterns. In this review the pathways by which toll-like receptors might play a role in the development and progression of atherosclerosis will be discussed according to recent literature.

RECENT FINDINGS

Toll-like receptors are expressed in atherosclerotic tissue. Next to pathogens, endogenous toll-like receptor ligands have been linked with the development of arterial occlusive disease. In mouse models of hyperlipidemia, a potential role for the toll-like receptor pathway has been suggested in hypercholesterolemia-induced atherosclerosis. Recent in-vitro studies revealed a mechanism by which toll-like receptor ligation results in a strong inhibition of cholesterol efflux from macrophages. In addition, oxidized lipoproteins interact with toll-like receptors. Furthermore, activation of the apoptotic cascade, which is important during atherogenesis, enhances the toll-like receptor pathway resulting in upregulation of proinflammatory cytokines. Human epidemiologic studies have linked TLR4 polymorphism with atherosclerosis. However, data on the association between atherosclerosis progression and TLR4 polymorphisms are conflicting. Next to plaque growth, arterial remodeling is an important determinant of luminal narrowing in atherosclerosis. Recently, a possible role for TLR4 signaling in arterial remodeling has been revealed in mouse models.

SUMMARY

A clarification of the molecule [corrected] mechanisms by which the toll-like receptor signaling cascade influences atherosclerosis might [corrected] lead to novel strategies to intervene in the development of this life-threatening disease.

Circulating leukocyte and carotid atherosclerotic plaque telomere length: interrelation, association with plaque characteristics, and restenosis after endarterectomy

OBJECTIVE

Shorter leukocyte telomeres are associated with atherosclerosis and predict future heart disease. The goal of the present study was to determine whether leukocyte telomere length is related to atherosclerotic plaque telomere length and whether it is associated with plaque characteristics or recurrence of disease.

METHODS AND RESULTS

Telomere length was measured by real-time quantitative polymerase chain reaction in atherosclerotic plaques and leukocytes in patients with carotid atherosclerosis undergoing carotid endarterectomy (n=684) and of leukocytes in age- and gender-balanced subjects without clinical atherosclerosis (n=780). Leukocyte telomere length was shorter in patients versus controls (0.99 [interquartile range (IQR): 0.79 to 1.26] versus 1.06 [0.80 to 1.39]; P=0.0007). Plaque telomeres were longer than leukocyte telomeres (1.42 [IQR: 1.21 to 1.77] versus 1.01 [IQR: 0.75 to 1.34]; P<1.00×10(-6)) and independent of age. Leukocyte and plaque telomere length were only weakly correlated (correlation coefficient r2=0.04, P=0.03). Patients, whose plaques showed marked macrophage infiltration and large lipid core, had longer plaque telomeres (1.61 [IQR: 1.32 to 2.04] versus 1.40 [IQR: 1.15 to 1.57]; P=0.006) and shorter leukocyte telomeres (0.88 [IQR: 0.75 to 1.20] versus 1.03 [IQR: 0.83 to 1.34]; P=0.02). Plaque telomere length was associated with restenosis 1 year after endarterectomy (OR 1.58±0.206; P=0.026 per SD decrease of plaque telomere length).

CONCLUSIONS

Leukocyte telomere length is associated with the presence of atherosclerotic carotid plaques but is not a proxy for local plaque telomere length. Plaque telomere length is related to plaque characteristics and development of restenosis following endarterectomy.

In Vivo Generation of Post-infarct Human Cardiac Muscle by Laminin-Promoted Cardiovascular Progenitors

Regeneration of injured human heart muscle is limited and an unmet clinical need. There are no methods for the reproducible generation of clinical-quality stem cell-derived cardiovascular progenitors (CVPs). We identified laminin-221 (LN-221) as the most likely expressed cardiac laminin. We produced it as human recombinant protein and showed that LN-221 promotes differentiation of pluripotent human embryonic stem cells (hESCs) toward cardiomyocyte lineage and downregulates pluripotency and teratoma-associated genes. We developed a chemically defined, xeno-free laminin-based differentiation protocol to generate CVPs. We show high reproducibility of the differentiation protocol using time-course bulk RNA sequencing developed from different hESC lines. Single-cell RNA sequencing of CVPs derived from hESC lines supported reproducibility and identified three main progenitor subpopulations. These CVPs were transplanted into myocardial infarction mice, where heart function was measured by echocardiogram and human heart muscle bundle formation was identified histologically. This method may provide clinical-quality cells for use in regenerative cardiology.

Clinical prediction rule to estimate the absolute 3-year risk of major cardiovascular events after carotid endarterectomy

BACKGROUND AND PURPOSE

Prognosis after carotid endarterectomy is mainly determined by the occurrence of major adverse cardiovascular events (MACEs). Optimal medical treatment to reduce risk is the mainstay of MACE prevention. The level of risk of MACE may determine the initiation and aggressiveness of medical treatment, yet a prediction rule to assess that absolute MACE risk after carotid endarterectomy is currently unavailable.

METHODS

The prediction model was developed in a consecutive cohort of 1138 patients who underwent carotid endarterectomy between 2002 and 2009. Primary end point was MACE and encompassed myocardial infarction, stroke, and cardiovascular death. Fourteen potential clinical predictors were entered into a Cox proportional hazard model. After backward stepwise regression, internal validation was conducted with bootstrapping techniques to correct for overfitting. To provide an easily applicable clinical tool, a score chart was constructed, dividing patients into 4 risk groups. Model performance was assessed in terms of discrimination, calibration, and risk stratification.

RESULTS

During a mean follow-up of 2.28 (± 0.95) years, 148 events occurred, corresponding to a cumulative incidence of 13%. Clinical predictors in the final model were age, history of coronary or peripheral artery disease, smoking, systolic blood pressure, use of antihypertensive drugs, clinical presentation, presence of contralateral carotid stenosis, and serum creatinine levels. Discrimination of the final model, in terms of a C statistic, was 0.69 (0.64-0.73) and calibration showed a good overall fit (Gronnesby and Borgan, P=0.39). The observed incidence of MACE in the 4 risk groups was 6%, 9%, 19%, and 35%, respectively, indicating good overall risk stratification.

CONCLUSIONS

The clinical prediction model for MACE in the first 3 years after carotid endarterectomy may be used to identify high-risk patients to help optimize medical treatment and risk factor management as part of secondary prevention to increase life expectancy free from MACE. Despite our success in stratifying risk among these patients, even the lowest stratum remains at high risk and all of these patients should receive maximal secondary preventive measures.