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Assessing atherosclerosis severity is essential for precise patient stratification. Specifically, there is a need to identify patients with residual inflammation because these patients remain at high risk of cardiovascular events despite optimal management of cardiovascular risk factors. Molecular imaging techniques, such as PET, can have an essential role in this context. PET imaging can indicate tissue-based disease status, detect early molecular changes and provide whole-body information. Advances in molecular biology and bioinformatics continue to help to decipher the complex pathogenesis of atherosclerosis and inform the development of imaging tracers. Concomitant advances in tracer synthesis methods and PET imaging technology provide future possibilities for atherosclerosis imaging. In this Review, we summarize the latest developments in PET imaging techniques and technologies for assessment of atherosclerotic cardiovascular disease and discuss the relationship between imaging readouts and transcriptomics-based plaque phenotyping., (© 2024. Springer Nature Limited.)

Myocardial infarction, stroke, mental disorders, neurodegenerative processes, autoimmune diseases, cancer and the human immunodeficiency virus impact the haematopoietic system, which through immunity and inflammation may aggravate pre-existing atherosclerosis. The interplay between the haematopoietic system and its modulation of atherosclerosis has been studied by imaging the cardiovascular system and the activation of haematopoietic organs via scanners integrating positron emission tomography and resonance imaging (PET/MRI). In this Perspective, we review the applicability of integrated whole-body PET/MRI for the study of immune-mediated phenomena associated with haematopoietic activity and cardiovascular disease, and discuss the translational opportunities and challenges of the technology., (© 2022. Springer Nature Limited.)

Purpose: To further characterize the relationship between obstructive sleep apnea (OSA) and carotid atherosclerosis, we examined the structural and metabolic features of carotid plaque using hybrid 18-F-fluorodeoxyglucose (FDG) Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) in the Multi-Ethnic Study of Atherosclerosis (MESA)., Methods: We studied 46 individuals from the MESA-PET and MESA-Sleep ancillary studies. OSA was defined as an apnea hypopnea index [AHI] ≥ 15 events per hour (4% desaturation). PET/MRI was used to measure carotid plaque inflammation (using target-to-background-ratios [TBR]) and carotid wall thickness (CWT). Linear regression was used to assess the associations between OSA, CWT and TBR., Results: The mean age was 67.9 years (SD 8.53) and the mean BMI was 28.9 kg/m 2 (SD 4.47). There was a trend toward a higher mean CWT in the OSA (n = 11) vs. non-OSA group (n = 35), 1.51 vs. 1.41 (p = 0.098). TBR did not differ by OSA groups, and there was no significant association between OSA and carotid plaque inflammation (TBR) in adjusted analyses. Although there was a significant interaction between OSA and obesity, there were no statistically significant associations between OSA and vascular inflammation in stratified analysis by obesity., Conclusion: Despite a trend toward a higher carotid wall thickness in OSA vs. non-OSA participants, we did not find an independent association between OSA and carotid plaque inflammation using PET/MRI in MESA. Our findings suggest that simultaneous assessments of structural and metabolic features of atherosclerosis may fill current knowledge gaps pertaining to the influence of OSA on atherosclerosis prevalence and progression., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Background: Assessing inflammatory disease activity in large vessel vasculitis (LVV) can be challenging by conventional measures., Objectives: We aimed to investigate somatostatin receptor 2 (SST 2 ) as a novel inflammation-specific molecular imaging target in LVV., Methods: In a prospective, observational cohort study, in vivo arterial SST 2 expression was assessed by positron emission tomography/magnetic resonance imaging (PET/MRI) using 68 Ga-DOTATATE and 18 F-FET-βAG-TOCA. Ex vivo mapping of the imaging target was performed using immunofluorescence microscopy; imaging mass cytometry; and bulk, single-cell, and single-nucleus RNA sequencing., Results: Sixty-one participants (LVV: n = 27; recent atherosclerotic myocardial infarction of ≤2 weeks: n = 25; control subjects with an oncologic indication for imaging: n = 9) were included. Index vessel SST 2 maximum tissue-to-blood ratio was 61.8% (P < 0.0001) higher in active/grumbling LVV than inactive LVV and 34.6% (P = 0.0002) higher than myocardial infarction, with good diagnostic accuracy (area under the curve: ≥0.86; P < 0.001 for both). Arterial SST 2 signal was not elevated in any of the control subjects. SST 2 PET/MRI was generally consistent with 18 F-fluorodeoxyglucose PET/computed tomography imaging in LVV patients with contemporaneous clinical scans but with very low background signal in the brain and heart, allowing for unimpeded assessment of nearby coronary, myocardial, and intracranial artery involvement. Clinically effective treatment for LVV was associated with a 0.49 ± 0.24 (standard error of the mean [SEM]) (P = 0.04; 22.3%) reduction in the SST 2 maximum tissue-to-blood ratio after 9.3 ± 3.2 months. SST 2 expression was localized to macrophages, pericytes, and perivascular adipocytes in vasculitis specimens, with specific receptor binding confirmed by autoradiography. SSTR2-expressing macrophages coexpressed proinflammatory markers., Conclusions: SST 2 PET/MRI holds major promise for diagnosis and therapeutic monitoring in LVV. (PET Imaging of Giant Cell and Takayasu Arteritis [PITA], NCT04071691; Residual Inflammation and Plaque Progression Long-Term Evaluation [RIPPLE], NCT04073810)., Competing Interests: Funding Support and Author Disclosures This work was funded by grants to Dr Tarkin from the Wellcome Trust (Clinical Research Career Development Fellowship 211100/Z/18/Z), the National Institute for Health Research (NIHR) Imperial Biomedical Research Centre (BRC); and the British Heart Foundation (BHF) (Clinical Research Training Fellowship for Dr Ćorović [FS/CRTF/20/24035]). This work was additionally supported by the Cambridge BHF Centre of Research Excellence (18/1/34212) and the Cancer Research UK Cambridge Centre (A25177). For the purpose of open access, the lead author has applied a CC BY public copyright license to any Author Accepted Manuscript. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, or the Department of Health and Social Care. Dr Nus; authors Imaz and Lambert; Dr Frontini (FS/18/53/33863); Dr Davenport (TG/18/4/33770); and Drs Huang, Mallat, Dweck, Newby, and Bennett are supported by the BHF. Author Zulcinski is supported by the European Union’s Horizon 2020 Research and Innovation Programme (Marie Skłodowska-Curie grant agreement no. 813545). Drs Jayne, Rassl, and Graves are supported by the NIHR Cambridge BRC. Dr Fayad is supported by the National Institutes of Health/National Heart, Lung, and Blood Institute (R01HL135878). Dr Reynolds is supported by the Wellcome Trust. Dr Morgan is supported by the Medical Research Council (MRC) (MR/N011775/1), the NIHR Leeds BRC, the NIHR Leeds Medtech, and In Vitro Diagnostics Co-operative as well as an NIHR Senior Investigator award. Dr Aboagye acknowledges support from Imperial Experimental Cancer Research Centre and MRC (MR/J007986/1, MR/N020782/1); and is an inventor on the patent that developed the (18)F-FET-βAG-TOCA radiotracer. Dr Peters is supported by a UK Research and Innovation Fellowship at Health Data Research UK (MR/S004068/2). Dr Rudd is partly supported by the NIHR Cambridge BRC, the BHF, the Higher Education Funding Council for England, the Engineering and Physical Sciences Research Council, and the Wellcome Trust. Drs Gopalan, Maughan, Pericleous, Barwick, Aboagye, Peters, and Mason acknowledge support from the NIHR Imperial BRC. The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Non-Hispanic Black persons are at greater risk of cardiovascular (CV) events than other racial/ethnic groups; however, their differential vulnerability to early subclinical atherosclerosis is poorly understood., Objectives: This work aims to study the impact of race/ethnicity on early subclinical atherosclerosis in young socioeconomically disadvantaged adults., Methods: Bilateral carotid and femoral 3-dimensional vascular ultrasound examinations were performed on 436 adults (parents/caregivers and staff) with a mean age of 38.0 ± 11.1 years, 82.3% female, 66% self-reported as Hispanic, 34% self-reported as non-Hispanic Black, and no history of CV disease recruited in the FAMILIA (Family-Based Approach in a Minority Community Integrating Systems-Biology for Promotion of Health) trial from 15 Head Start preschools in Harlem (neighborhood in New York, New York, USA). The 10-year Framingham CV risk score was calculated, and the relationship between race/ethnicity and the presence and extent of subclinical atherosclerosis was analyzed with multivariable logistic and linear regression models., Results: The mean 10-year Framingham CV risk was 4.0%, with no differences by racial/ethnic category. The overall prevalence of subclinical atherosclerosis was significantly higher in the non-Hispanic Black (12.9%) than in the Hispanic subpopulation (6.6%). After adjusting for 10-year Framingham CV risk score, body mass index, fruit and vegetable consumption, physical activity, and employment status, non-Hispanic Black individuals were more likely than Hispanic individuals to have subclinical atherosclerosis (OR: 3.45; 95% CI: 1.44-8.29; P = 0.006) and multiterritorial disease (P = 0.026)., Conclusions: After adjustment for classic CV risk, lifestyle, and socioeconomic factors, non-Hispanic Black younger adults seem more vulnerable to early subclinical atherosclerosis than their Hispanic peers, suggesting that the existence of emerging or undiscovered CV factors underlying the residual excess risk (Family-Based Approach in a Minority Community Integrating Systems-Biology for Promotion of Health [FAMILIA (Project 2)]; NCT02481401)., Competing Interests: Funding Support and Author Disclosures This study was funded by the American Heart Association under grant No 14SFRN20490315 and the Stephen Gellman Children’s Outreach Program. Dr Fernandez-Jimenez is recipient of grant PI19/01704 funded by the Fondo de Investigación Sanitaria- Instituto de Salud Carlos III (ISCIII) and co-funded by the European Regional Development Fund/European Social Fund "A way to make Europe"/"Investing in your future." Dr Santos-Beneit is recipient of grant LCF/PR/MS19/12220001 funded by “la Caixa” Foundation (ID 100010434). The CNIC is supported by the ISCIII, the Ministerio de Ciencia e Innovación (MCIN) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (grant CEX2020-001041-S funded by MICIN/AEI/10.13039/501100011033). All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2022 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

In recent years, cardiovascular immuno-imaging by positron emission tomography (PET) has undergone tremendous progress in preclinical settings. Clinically, two approved PET tracers hold great potential for inflammation imaging in cardiovascular patients, namely FDG and DOTATATE. While the former is a widely applied metabolic tracer, DOTATATE is a relatively new PET tracer targeting the somatostatin receptor 2 (SST2). In the current study, we performed a detailed, head-to-head comparison of DOTATATE-based radiotracers and [ 18 F]F-FDG in mouse and rabbit models of cardiovascular inflammation. For mouse experiments, we labeled DOTATATE with the long-lived isotope [ 64 Cu]Cu to enable studying the tracer's mode of action by complementing in vivo PET/CT experiments with thorough ex vivo immunological analyses. For translational PET/MRI rabbit studies, we employed the more widely clinically used [ 68 Ga]Ga-labeled DOTATATE, which was approved by the FDA in 2016. DOTATATE's pharmacokinetics and timed biodistribution were determined in control and atherosclerotic mice and rabbits by ex vivo gamma counting of blood and organs. Additionally, we performed in vivo PET/CT experiments in mice with atherosclerosis, mice subjected to myocardial infarction and control animals, using both [ 64 Cu]Cu-DOTATATE and [ 18 F]F-FDG. To evaluate differences in the tracers' cellular specificity, we performed ensuing ex vivo flow cytometry and gamma counting. In mice subjected to myocardial infarction, in vivo [ 64 Cu]Cu-DOTATATE PET showed higher differential uptake between infarcted (SUV max 1.3, IQR, 1.2-1.4, N = 4) and remote myocardium (SUV max 0.7, IQR, 0.5-0.8, N = 4, p = 0.0286), and with respect to controls (SUV max 0.6, IQR, 0.5-0.7, N = 4, p = 0.0286), than [ 18 F]F-FDG PET. In atherosclerotic mice, [ 64 Cu]Cu-DOTATATE PET aortic signal, but not [ 18 F]F-FDG PET, was higher compared to controls (SUV max 1.1, IQR, 0.9-1.3 and 0.5, IQR, 0.5-0.6, respectively, N = 4, p = 0.0286). In both models, [ 64 Cu]Cu-DOTATATE demonstrated preferential accumulation in macrophages with respect to other myeloid cells, while [ 18 F]F-FDG was taken up by macrophages and other leukocytes. In a translational PET/MRI study in atherosclerotic rabbits, we then compared [ 68 Ga]Ga-DOTATATE and [ 18 F]F-FDG for the assessment of aortic inflammation, combined with ex vivo radiometric assays and near-infrared imaging of macrophage burden. Rabbit experiments showed significantly higher aortic accumulation of both [ 68 Ga]Ga-DOTATATE and [ 18 F]F-FDG in atherosclerotic (SUV max 0.415, IQR, 0.338-0.499, N = 32 and 0.446, IQR, 0.387-0.536, N = 27, respectively) compared to control animals (SUV max 0.253, IQR, 0.197-0.285, p = 0.0002, N = 10 and 0.349, IQR, 0.299-0.423, p = 0.0159, N = 11, respectively). In conclusion, we present a detailed, head-to-head comparison of the novel SST2-specific tracer DOTATATE and the validated metabolic tracer [ 18 F]F-FDG for the evaluation of inflammation in small animal models of cardiovascular disease. Our results support further investigations on the use of DOTATATE to assess cardiovascular inflammation as a complementary readout to the widely used [ 18 F]F-FDG., (© 2022. The Author(s).)

Study Objectives: Evaluate the association between obstructive sleep apnea (OSA), coronary artery calcium (CAC) density, and cardiovascular events in the Multi-Ethnic Study of Atherosclerosis (MESA)., Methods: We analyzed 1,041 participants with nonzero CAC scores who had polysomnography and CAC density data from the fifth examination of the Multi-Ethnic Study of Atherosclerosis. OSA was defined as apnea-hypopnea index ≥ 15 events/h. Multivariable linear regression models were used to evaluate the independent association between OSA and CAC density. Additionally, we evaluated the impact of OSA on associations of CAC measures with incident cardiovascular disease events by testing for interaction in Cox proportional hazard regression models., Results: Our analytical sample was 45% female with a mean age of 70.6 +/- 9 years. Of this sample, 36.7% (n = 383/1041) had OSA (apnea-hypopnea index ≥ 15 events/h). OSA was inversely and weakly associated with CAC density ( β = -0.09; 95% CI, -0.17 to -0.02; P = .014 ) and remained significantly associated after controlling for traditional cardiovascular risk factors (β = -0.08; 95% CI, -0.16 to 0; P = .043). However, this inverse association was attenuated after controlling for body mass index (β = -0.05; 95% CI, -0.13 to 0.02; P = .174). The mean follow-up period for cardiovascular disease events was 13.3 +/- 2.8 years. Additionally, exploratory analysis demonstrated that CAC density was independently and inversely associated with cardiovascular disease events only in the non-OSA subgroup (apnea-hypopnea index ≤ 15 events/h) (hazard ratio, 0.509; 95% CI, 0.323-0.801); P = .0035)., Conclusions: OSA was associated with lower CAC density, but this association was attenuated by body mass index. Further, increased CAC density was associated with a reduced risk of cardiovascular disease events only in individuals within the non-OSA group in exploratory analysis., Citation: Newman SB, Kundel V, Matsuzaki M, et al. Sleep apnea, coronary artery calcium density, and cardiovascular events: results from the Multi-Ethnic Study of Atherosclerosis. J Clin Sleep Med . 2021;17(10):2075-2083., (© 2021 American Academy of Sleep Medicine.)

Background and Aims: Electronic cigarette (EC) use is popular among youth, touted as a safer alternative to smoking and promoted as a tool to aid in smoking cessation. EC cardiovascular safety however is not well established. The aim of this study was to examine cardiovascular consequences of EC use by evaluating their effect on the entire atherosclerotic cascade in young adults using noninvasive combined positron emission tomography (PET)/magnetic resonance imaging (MR) and comparing EC use with age matched smokers of traditional cigarettes and nonsmoking controls., Methods: Carotid PET/MR was applied to look at vascular inflammation (18-fluorodeoxyglucose (FDG)-PET) and plaque burden (multi-contrast MR of vessel wall) from 60 18-30 year-old subjects (20 electronic cigarette users, 20 traditional smokers and 20 nonsmokers)., Results: Groups were reasonably well balanced in terms of age, gender, demographics, cardiovascular risk and most biomarkers. There were no differences in vascular inflammation as measured by 18-FDG-PET target to background ratios (TBR) between EC users, traditional cigarette smokers and nonsmokers. However, measures of carotid plaque burden - wall area, normalized wall index, and wall thickness - measured from MR were significantly higher in both traditional smokers and EC users than in nonsmokers., Conclusions: Young adult EC users, smokers and nonsmokers in our study did not exhibit vascular inflammation as defined by 18-F-FDG-PET TBR max, but smokers and EC users had significantly more carotid plaque burden compared to matched nonsmokers. Results could indicate that vaping does not cause an increase in vascular inflammation as measured by FDG-PET., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Macrophages play a central role in the pathogenesis of atherosclerosis. The inflammatory properties of these cells are dictated by their metabolism, of which the mechanistic target of rapamycin (mTOR) signaling pathway is a key regulator. Using myeloid cell-specific nanobiologics in apolipoprotein E-deficient ( Apoe -/- ) mice, we found that targeting the mTOR and ribosomal protein S6 kinase-1 (S6K1) signaling pathways rapidly diminished plaque macrophages' inflammatory activity. By investigating transcriptome modifications, we identified Psap , a gene encoding the lysosomal protein prosaposin, as closely related with mTOR signaling. Subsequent in vitro experiments revealed that Psap inhibition suppressed both glycolysis and oxidative phosphorylation. Transplantation of Psap ) mice led to a reduction in atherosclerosis development and plaque inflammation. Last, we confirmed the relationship between -/- expression and inflammation in human carotid atherosclerotic plaques. Our findings provide mechanistic insights into the development of atherosclerosis and identify prosaposin as a potential therapeutic target.Ldlr -/- ) mice led to a reduction in atherosclerosis development and plaque inflammation. Last, we confirmed the relationship between PSAP expression and inflammation in human carotid atherosclerotic plaques. Our findings provide mechanistic insights into the development of atherosclerosis and identify prosaposin as a potential therapeutic target., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Accurate quantification and characterization of atherosclerotic plaques with MRI requires high spatial resolution acquisitions with excellent image quality. The intrinsically better signal-to-noise ratio (SNR) at high-field clinical 7T compared to the widely employed lower field strengths of 1.5 and 3T may yield significant improvements to vascular MRI. However, 7T atherosclerosis imaging also presents specific challenges, related to local transmit coils and B1 field inhomogeneities, which may overshadow these theoretical gains. We present the development and evaluation of 3D, black-blood, ultra-high resolution vascular MRI on clinical high-field 7T in comparison lower-field 3T. These protocols were applied for in vivo imaging of atherosclerotic rabbits, which are often used for development, testing, and validation of translatable cardiovascular MR protocols. Eight atherosclerotic New Zealand White rabbits were imaged on clinical 7T and 3T MRI scanners using 3D, isotropic, high (0.63 mm3) and ultra-high (0.43 mm3) spatial resolution, black-blood MR sequences with extensive spatial coverage. Following imaging, rabbits were sacrificed for validation using fluorescence imaging and histology. Image quality parameters such as SNR and contrast-to-noise ratio (CNR), as well as morphological and functional plaque measurements (plaque area and permeability) were evaluated at both field strengths. Using the same or comparable imaging parameters, SNR and CNR were in general higher at 7T compared to 3T, with a median (interquartiles) SNR gain of +40.3 (35.3-80.1)%, and a median CNR gain of +68.1 (38.5-95.2)%. Morphological and functional parameters, such as vessel wall area and permeability, were reliably acquired at 7T and correlated significantly with corresponding, widely validated 3T vessel wall MRI measurements. In conclusion, we successfully developed 3D, black-blood, ultra-high spatial resolution vessel wall MRI protocols on a 7T clinical scanner. 7T imaging was in general superior to 3T with respect to image quality, and comparable in terms of plaque area and permeability measurements., Competing Interests: The authors have read the journal's policy and have the following competing interests: IS is a paid employee of Takeda Pharmaceutical Company Limited, and HD is a paid employee of Hyperfine Research Inc. There are no patents, products in development or marketed products associated with this research to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Atherosclerotic plaques prone to rupture may cause acute myocardial infarction (MI) but can also heal without causing an event. Certain common histopathological features, including inflammation, a thin fibrous cap, positive remodelling, a large necrotic core, microcalcification, and plaque haemorrhage are commonly found in plaques causing an acute event. Recent advances in imaging techniques have made it possible to detect not only luminal stenosis and overall coronary atherosclerosis burden but also to identify such adverse plaque characteristics. However, the predictive value of identifying individual adverse atherosclerotic plaques for future events has remained poor. In this Position Paper, the relationship between vulnerable plaque imaging and MI is addressed, mainly for non-invasive assessments but also for invasive imaging of adverse plaques in patients undergoing invasive coronary angiography. Dynamic changes in atherosclerotic plaque development and composition may indicate that an adverse plaque phenotype should be considered at the patient level rather than for individual plaques. Imaging of adverse plaque burden throughout the coronary vascular tree, in combination with biomarkers and biomechanical parameters, therefore holds promise for identifying subjects at increased risk of MI and for guiding medical and invasive treatment., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)

Study Objectives: The objectives of this study were to evaluate the independent association between sleep-disordered breathing (SDB) using overnight polysomnography and left ventricular (LV) scar using cardiac magnetic resonance (CMR) with late-gadolinium enhancement in a community-based cohort of the Multi-Ethnic Study of Atherosclerosis., Methods: Our analytical sample includes 934 participants from the fifth examination of the Multiethnic Study of Atherosclerosis who underwent both polysomnography and CMR. SDB was categorized as follows: no-SDB (apnea-hypopnea index [AHI] < 5 events/h), mild SDB (5 events/h ≤ AHI < 15 events/h), and moderate-severe SDB (AHI ≥ 15 events/h). LV scar was considered present if there was presence of scar on CMR (late-gadolinium enhancement > 0%). Logistic regression with multivariable adjustment for confounders (age, sex, race/ethnicity, body mass index, and cardiometabolic risk factors) was used to examine the independent association of SDB with LV scar. Confounders were identified using directed acyclic graphs., Results: The mean age of our sample was 67.0 ± 8.5 years (SD), with 49% (n = 461) females and a prevalence of SDB (AHI ≥ 5 events/h) of 63% (n = 590). LV scar was more prevalent in individuals with SDB (9.5%) versus those without SDB (3.8%; P < .01), and 88% of all LV scars were clinically unrecognized. After multivariable adjustment, both mild SDB and moderate-severe SDB were independently associated with LV scar (odds ratio, 2.53; 95% confidence interval, 1.13-5.64 and odds ratio, 2.31; 95% confidence interval, 1.01-5.24, respectively)., Conclusions: In a community-based cohort, SDB (including mild) is independently associated with a more than 2-fold increase in the odds of LV scar presence measured using CMR with late-gadolinium enhancement. Most LV scars were clinically unrecognized. The impact of SDB treatment on subclinical myocardial infarction needs to be investigated in future studies., (© 2020 American Academy of Sleep Medicine.)

Cardiovascular disease due to atherosclerosis is still the main cause of morbidity and mortality worldwide. This disease is a complex systemic disorder arising from a network of pathological processes within the arterial vessel wall, and, outside of the vasculature, in the hematopoietic system and organs involved in metabolism. Recent years have seen tremendous efforts in the development and validation of quantitative imaging technologies for the noninvasive evaluation of patients with atherosclerotic cardiovascular disease. Specifically, the advent of combined positron emission tomography and magnetic resonance imaging scanners has opened new exciting opportunities in cardiovascular imaging. In this review, we will describe how combined positron emission tomography/magnetic resonance imaging scanners can be leveraged to evaluate atherosclerotic cardiovascular disease at the whole-body level, with specific focus on preclinical animal models of disease, from mouse to nonhuman primates. We will broadly describe 3 major areas of application: (1) vascular imaging, for advanced atherosclerotic plaque phenotyping and evaluation of novel imaging tracers or therapeutic interventions; (2) assessment of the ischemic heart and brain; and (3) whole-body imaging of the hematopoietic system. Finally, we will provide insights on potential novel technical developments which may further increase the relevance of integrated positron emission tomography/magnetic resonance imaging in preclinical atherosclerosis studies.

The immune system's role in atherosclerosis has long been an important research topic and is increasingly investigated for therapeutic and diagnostic purposes. Therefore, noninvasive imaging of hematopoietic organs and immune cells will undoubtedly improve atherosclerosis phenotyping and serve as a monitoring method for immunotherapeutic treatments. Among the available imaging techniques, positron emission tomography's unique features make it an ideal tool to quantitatively image the immune response in the context of atherosclerosis and afford reliable readouts to guide medical interventions in cardiovascular disease. Here, we summarize the state of the art in the field of atherosclerosis positron emission tomography immunoimaging and provide an outlook on current and future applications.

Nanotherapy has recently emerged as an experimental treatment option for atherosclerosis. To fulfill its promise, robust noninvasive imaging approaches for subject selection and treatment evaluation are warranted. To that end, we present here a positron emission tomography (PET)-based method for quantification of liposomal nanoparticle uptake in the atherosclerotic vessel wall. We evaluated a modular procedure to label liposomal nanoparticles with the radioisotope zirconium-89 ( 89 Zr). Their biodistribution and vessel wall targeting in a rabbit atherosclerosis model was evaluated up to 15 days after intravenous injection by PET/computed tomography (CT) and PET/magnetic resonance imaging (PET/MRI). Vascular permeability was assessed in vivo using three-dimensional dynamic contrast-enhanced MRI (3D DCE-MRI) and ex vivo using near-infrared fluorescence (NIRF) imaging. The 89 Zr-radiolabeled liposomes displayed a biodistribution pattern typical of long-circulating nanoparticles. Importantly, they markedly accumulated in atherosclerotic lesions in the abdominal aorta, as evident on PET/MRI and confirmed by autoradiography, and this uptake moderately correlated with vascular permeability. The method presented herein facilitates the development of nanotherapy for atherosclerotic disease as it provides a tool to screen for nanoparticle targeting in individual subjects' plaques.

Objectives: This study sought to develop an integrative positron emission tomography (PET) with magnetic resonance imaging (MRI) procedure for accurate atherosclerotic plaque phenotyping, facilitated by clinically approved and nanobody radiotracers., Background: Noninvasive characterization of atherosclerosis remains a challenge in clinical practice. The limitations of current diagnostic methods demonstrate that, in addition to atherosclerotic plaque morphology and composition, disease activity needs to be evaluated., Methods: We screened 3 nanobody radiotracers targeted to different biomarkers of atherosclerosis progression, namely vascular cell adhesion molecule (VCAM)-1, lectin-like oxidized low-density lipoprotein receptor (LOX)-1, and macrophage mannose receptor (MMR). The nanobodies, initially radiolabeled with copper-64 ( 64 Cu), were extensively evaluated in Apoe -/- mice and atherosclerotic rabbits using a combination of in vivo PET/MRI readouts and ex vivo radioactivity counting, autoradiography, and histological analyses., Results: The 3 nanobody radiotracers accumulated in atherosclerotic plaques and displayed short circulation times due to fast renal clearance. The MMR nanobody was selected for labeling with gallium-68 ( 68 Ga), a short-lived radioisotope with high clinical relevance, and used in an ensuing atherosclerosis progression PET/MRI study. Macrophage burden was longitudinally studied by 68 Ga-MMR-PET, plaque burden by T2-weighted MRI, and neovascularization by dynamic contrast-enhanced (DCE) MRI. Additionally, inflammation and microcalcifications were evaluated by fluorine-18 ( 18 F)-labeled fluorodeoxyglucose ( 18 F-FDG) and 18 F-sodium fluoride ( 18 F-NaF) PET, respectively. We observed an increase in all the aforementioned measures as disease progressed, and the imaging signatures correlated with histopathological features., Conclusions: We have evaluated nanobody-based radiotracers in rabbits and developed an integrative PET/MRI protocol that allows noninvasive assessment of different processes relevant to atherosclerosis progression. This approach allows the multiparametric study of atherosclerosis and can aid in early stage anti-atherosclerosis drug trials., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Nanomedicine research produces hundreds of studies every year, yet very few formulations have been approved for clinical use. This is due in part to a reliance on murine studies, which have limited value in accurately predicting translational efficacy in larger animal models and humans. Here, we report the scale-up of a nanoimmunotherapy from mouse to large rabbit and porcine atherosclerosis models, with an emphasis on the solutions we implemented to overcome production and evaluation challenges. Specifically, we integrated translational imaging readouts within our workflow to both analyze the nanoimmunotherapeutic's in vivo behavior and assess treatment response in larger animals. We observed our nanoimmunotherapeutic's anti-inflammatory efficacy in mice, as well as rabbits and pigs. Nanoimmunotherapy-mediated reduction of inflammation in the large animal models halted plaque progression, supporting the approach's translatability and potential to acutely treat atherosclerosis., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Atherosclerosis is a chronic disease of the large arteries and the underlying cause of myocardial infarction and stroke. Atherosclerosis is driven by cholesterol accumulation and subsequent inflammation in the vessel wall. Despite the clinical successes of lipid-lowering treatments, atherosclerosis remains one of the major threats to human health worldwide. Over the past 20 years, insights into cardiovascular immunopathology have provided a plethora of new potential therapeutic targets to reduce the risk of atherosclerosis and have shifted the therapeutic focus from lipids to inflammation. In 2017, the CANTOS trial demonstrated for the first time the beneficial effects of targeting inflammation to treat cardiovascular disease by showing that IL-1β inhibition can reduce the recurrence rate of cardiovascular events in a large cohort of patients. At the same time, preclinical studies have highlighted nanotechnology approaches that facilitate the specific targeting of innate immune cells, which could potentially generate more effective immunomodulatory treatments to induce disease regression and prevent the recurrence of cardiovascular events. The clinical translation of such nanoimmunotherapies and their application to treat patients with ischaemic heart disease are challenges that lie ahead.

Macrophage accumulation in atherosclerosis is directly linked to the destabilization and rupture of plaque, causing acute atherothrombotic events. Circulating monocytes enter the plaque and differentiate into macrophages, where they are activated by CD4 + T lymphocytes through CD40-CD40 ligand signalling. Here, we report the development and multiparametric evaluation of a nanoimmunotherapy that moderates CD40-CD40 ligand signalling in monocytes and macrophages by blocking the interaction between CD40 and tumour necrosis factor receptor-associated factor 6 (TRAF6). We evaluated the biodistribution characteristics of the nanoimmunotherapy in apolipoprotein E-deficient (Apoe -/- ) mice and in non-human primates by in vivo positron-emission tomography imaging. In Apoe -/- mice, a 1-week nanoimmunotherapy treatment regimen achieved significant anti-inflammatory effects, which was due to the impaired migration capacity of monocytes, as established by a transcriptome analysis. The rapid reduction of plaque inflammation by the TRAF6-targeted nanoimmunotherapy and its favourable toxicity profiles in both mice and non-human primates highlights the translational potential of this strategy for the treatment of atherosclerosis.

Objectives: The authors sought to develop combined positron emission tomography (PET) dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) to quantify plaque inflammation, permeability, and burden to evaluate the efficacy of a leukotriene A4 hydrolase (LTA4H) inhibitor in a rabbit model of atherosclerosis., Background: Multimodality PET/MRI allows combining the quantification of atherosclerotic plaque inflammation, neovascularization, permeability, and burden by combined 18 F-fluorodeoxyglucose ( 18 F-FDG) PET, DCE-MRI, and morphological MRI. The authors describe a novel, integrated PET-DCE/MRI protocol to noninvasively quantify these parameters in aortic plaques of a rabbit model of atherosclerosis. As proof-of-concept, the authors apply this protocol to assess the efficacy of the novel LTA4H inhibitor BI691751., Methods: New Zealand White male rabbits (N = 49) were imaged with integrated PET-DCE/MRI after atherosclerosis induction and 1 and 3 months after randomization into 3 groups: 1) placebo; 2) high-dose BI691751; and 3) low-dose BI691751. All animals were euthanized at the end of the study., Results: Among the several metrics that were quantified, only maximum standardized uptake value and target-to-background ratio by 18 F-FDG PET showed a modest, but significant, reduction in plaque inflammation in rabbits treated with low-dose BI691751 (p = 0.03), whereas no difference was detected in the high-fat diet and in the high-dose BI691751 groups. No differences in vessel wall area by MRI and area under the curve by DCE-MRI were detected in any of the groups. No differences in neovessel and macrophage density were found at the end of study among groups., Conclusions: The authors present a comprehensive, integrated 18 F-FDG PET and DCE-MRI imaging protocol to noninvasively quantify plaque inflammation, neovasculature, permeability, and burden in a rabbit model of atherosclerosis on a simultaneous PET/MRI scanner. A modest reduction was found in plaque inflammation by 18 F-FDG PET in the group treated with a low dose of the LTA4H inhibitor BI691751., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Oxidation-specific epitopes (OSEs) are proinflammatory, and elevated levels in plasma predict cardiovascular events., Objectives: The purpose of this study was to develop novel positron emission tomography (PET) probes to noninvasively image OSE-rich lesions., Methods: An antigen-binding fragment (Fab) antibody library was constructed from human fetal cord blood. After multiple rounds of screening against malondialdehyde-acetaldehyde (MAA) epitopes, the Fab LA25 containing minimal nontemplated insertions in the CDR3 region was identified and characterized. In mice, pharmacokinetics, biodistribution, and plaque specificity studies were performed with Zirconium-89 ( 89 Zr)-labeled LA25. In rabbits, 89 Zr-LA25 was used in combination with an integrated clinical PET/magnetic resonance (MR) system. 18 F-fluorodeoxyglucose PET and dynamic contrast-enhanced MR imaging were used to evaluate vessel wall inflammation and plaque neovascularization, respectively. Extensive ex vivo validation was carried out through a combination of gamma counting, near infrared fluorescence, autoradiography, immunohistochemistry, and immunofluorescence., Results: LA25 bound specifically to MAA epitopes in advanced and ruptured human atherosclerotic plaques with accompanying thrombi and in debris from distal protection devices. PET/MR imaging 24 h after injection of 89 Zr-LA25 showed increased uptake in the abdominal aorta of atherosclerotic rabbits compared with nonatherosclerotic control rabbits, confirmed by ex vivo gamma counting and autoradiography. 18 F-fluorodeoxyglucose PET, dynamic contrast-enhanced MR imaging, and near-infrared fluorescence signals were also significantly higher in atherosclerotic rabbit aortas compared with control aortas. Enhanced liver uptake was also noted in atherosclerotic animals, confirmed by the presence of MAA epitopes by immunostaining., Conclusions: 89 Zr-LA25 is a novel PET radiotracer that may allow noninvasive phenotyping of high-risk OSE-rich lesions., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Several animal models have been developed to study atherosclerosis. Here we present a rabbit atherosclerosis model generated by surgical denudation of the aortic endothelium in combination with a high-fat and cholesterol-enriched diet. This model is characterized by the formation of vascular lesions that exhibit several hallmarks of human atherosclerosis. Due to the rabbit's relative large size, as compared to rodents, this model is suited for the imaging-guided evaluation of novel therapeutic strategies using clinical scanners. In this chapter, we present an extensive outline of the procedures to induce aortic atherosclerotic lesions in rabbits as well as methods to evaluate the disease, including noninvasive in vivo multiparametric imaging and histopathology.

Atherosclerosis is a leading cause of worldwide morbidity and mortality whose management could benefit from novel targeted therapeutics. Nanoparticles are emerging as targeted drug delivery systems in chronic inflammatory disorders. To optimally exploit nanomedicines, understanding their biological behavior is crucial for further development of clinically relevant and efficacious nanotherapeutics intended to reduce plaque inflammation. Here, three clinically relevant nanomedicines, i.e., high-density lipoprotein ([S]-HDL), polymeric micelles ([S]-PM), and liposomes ([S]-LIP), that are loaded with the HMG-CoA reductase inhibitor simvastatin [S], were evaluated in the apolipoprotein E-deficient (Apoe -/- ) mouse model of atherosclerosis. We systematically employed quantitative techniques, including in vivo positron emission tomography imaging, gamma counting, and flow cytometry to evaluate the biodistribution, nanomedicines' uptake by plaque-associated macrophages/monocytes, and their efficacy to reduce macrophage burden in atherosclerotic plaques. The three formulations demonstrated distinct biological behavior in Apoe -/- mice. While [S]-PM and [S]-LIP possessed longer circulation half-lives, the three platforms accumulated to similar levels in atherosclerotic plaques. Moreover, [S]-HDL and [S]-PM showed higher uptake by plaque macrophages in comparison to [S]-LIP, while [S]-PM demonstrated the highest uptake by Ly6C high monocytes. Among the three formulations, [S]-PM displayed the highest efficacy in reducing macrophage burden in advanced atherosclerotic plaques. In conclusion, our data demonstrate that [S]-PM is a promising targeted drug delivery system, which can be advanced for the treatment of atherosclerosis and other inflammatory disorders in the clinical settings. Our results also emphasize the importance of a thorough understanding of nanomedicines' biological performance, ranging from the whole body to the target cells, as well drug retention in the nanoparticles. Such systematic investigations would allow rational applications of nanomaterials', beyond cancer, facilitating the expansion of the nanomedicine horizon., (Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.)

Hyaluronan is a biologically active polymer, which can be formulated into nanoparticles. In our study, we aimed to probe atherosclerosis-associated inflammation by using hyaluronan nanoparticles and to determine whether they can ameliorate atherosclerosis. Hyaluronan nanoparticles (HA-NPs) were prepared by reacting amine-functionalized oligomeric hyaluronan (HA) with cholanic ester and labeled with a fluorescent or radioactive label. HA-NPs were characterized in vitro by several advanced microscopy methods. The targeting properties and biodistribution of HA-NPs were studied in apoe -/- mice, which received either fluorescent or radiolabeled HA-NPs and were examined ex vivo by flow cytometry or nuclear techniques. Furthermore, three atherosclerotic rabbits received 89 Zr-HA-NPs and were imaged by PET/MRI. The therapeutic effects of HA-NPs were studied in apoe -/- mice, which received weekly doses of 50 mg/kg HA-NPs during a 12-week high-fat diet feeding period. Hydrated HA-NPs were ca. 90 nm in diameter and displayed very stable morphology under hydrolysis conditions. Flow cytometry revealed a 6- to 40-fold higher uptake of Cy7-HA-NPs by aortic macrophages compared to normal tissue macrophages. Interestingly, both local and systemic HA-NP-immune cell interactions significantly decreased over the disease progression. 89 Zr-HA-NPs-induced radioactivity in atherosclerotic aortas was 30% higher than in wild-type controls. PET imaging of rabbits revealed 6-fold higher standardized uptake values compared to the muscle. The plaques of HA-NP-treated mice contained 30% fewer macrophages compared to control and free HA-treated group. In conclusion, we show favorable targeting properties of HA-NPs, which can be exploited for PET imaging of atherosclerosis-associated inflammation. Furthermore, we demonstrate the anti-inflammatory effects of HA-NPs in atherosclerosis.

Immunological complexity in atherosclerosis warrants targeted treatment of specific inflammatory cells that aggravate the disease. With the initiation of large phase III trials investigating immunomodulatory drugs for atherosclerosis, cardiovascular disease treatment enters a new era. We here propose a radically different approach: implementing and evaluating in vivo a combinatorial library of nanoparticles with distinct physiochemical properties and differential immune cell specificities. The library's nanoparticles are based on endogenous high-density lipoprotein, which can preferentially deliver therapeutic compounds to pathological macrophages in atherosclerosis. Using the apolipoprotein E-deficient (Apoe -/- ) mouse model of atherosclerosis, we quantitatively evaluated the library's immune cell specificity by combining immunological techniques and in vivo positron emission tomography imaging. Based on this screen, we formulated a liver X receptor agonist (GW3965) and abolished its liver toxicity while still preserving its therapeutic function. Screening the immune cell specificity of nanoparticles can be used to develop tailored therapies for atherosclerosis and other inflammatory diseases., Competing Interests: The authors declare no conflict of interest.

Background: Evidence suggests that interleukin (IL)-1β is important in the pathogenesis of atherosclerosis and its complications and that inhibiting IL-1β may favorably affect vascular disease progression., Objectives: The goal of this study was to evaluate the effects of IL-1β inhibition with canakinumab versus placebo on arterial structure and function, determined by magnetic resonance imaging., Methods: Patients (N = 189) with atherosclerotic disease and either type 2 diabetes mellitus or impaired glucose tolerance were randomized to receive placebo (n = 94) or canakinumab 150 mg monthly (n = 95) for 12 months. They underwent magnetic resonance imaging of the carotid arteries and aorta., Results: There were no statistically significant differences between canakinumab compared with placebo in the primary efficacy and safety endpoints. There was no statistically significant change in mean carotid wall area and no effect on aortic distensibility, measured at 3 separate anatomic sites. The change in mean carotid artery wall area was -3.37 mm 2 after 12 months with canakinumab versus placebo. High-sensitivity C-reactive protein was significantly reduced by canakinumab compared with placebo at 3 months (geometric mean ratio [GMR]: 0.568; 95% confidence interval [CI]: 0.436 to 0.740; p < 0.0001) and 12 months (GMR: 0.56; 95% CI: 0.414 to 0.758; p = 0.0002). Lipoprotein(a) levels were reduced by canakinumab compared with placebo (-4.30 mg/dl [range: -8.5 to -0.55 mg/dl]; p = 0.025] at 12 months), but triglyceride levels increased (GMR: 1.20; 95% CI: 1.046 to 1.380; p = 0.01). In these patients with type 2 diabetes mellitus or impaired glucose tolerance, canakinumab had no effect compared with placebo on any of the measures assessed by using a standard oral glucose tolerance test., Conclusions: There were no statistically significant effects of canakinumab on measures of vascular structure or function. Canakinumab reduced markers of inflammation (high-sensitivity C-reactive protein and interleukin-6), and there were modest increases in levels of total cholesterol and triglycerides. (Safety & Effectiveness on Vascular Structure and Function of ACZ885 in Atherosclerosis and Either T2DM or IGT Patients; NCT00995930)., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

Objectives: The goal of this study was to develop and validate a noninvasive imaging tool to visualize the in vivo behavior of high-density lipoprotein (HDL) by using positron emission tomography (PET), with an emphasis on its plaque-targeting abilities., Background: HDL is a natural nanoparticle that interacts with atherosclerotic plaque macrophages to facilitate reverse cholesterol transport. HDL-cholesterol concentration in blood is inversely associated with risk of coronary heart disease and remains one of the strongest independent predictors of incident cardiovascular events., Methods: Discoidal HDL nanoparticles were prepared by reconstitution of its components apolipoprotein A-I (apo A-I) and the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine. For radiolabeling with zirconium-89 ((89)Zr), the chelator deferoxamine B was introduced by conjugation to apo A-I or as a phospholipid-chelator (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-deferoxamine B). Biodistribution and plaque targeting of radiolabeled HDL were studied in established murine, rabbit, and porcine atherosclerosis models by using PET combined with computed tomography (PET/CT) imaging or PET combined with magnetic resonance imaging. Ex vivo validation was conducted by radioactivity counting, autoradiography, and near-infrared fluorescence imaging. Flow cytometric assessment of cellular specificity in different tissues was performed in the murine model., Results: We observed distinct pharmacokinetic profiles for the two (89)Zr-HDL nanoparticles. Both apo A-I- and phospholipid-labeled HDL mainly accumulated in the kidneys, liver, and spleen, with some marked quantitative differences in radioactivity uptake values. Radioactivity concentrations in rabbit atherosclerotic aortas were 3- to 4-fold higher than in control animals at 5 days' post-injection for both (89)Zr-HDL nanoparticles. In the porcine model, increased accumulation of radioactivity was observed in lesions by using in vivo PET imaging. Irrespective of the radiolabel's location, HDL nanoparticles were able to preferentially target plaque macrophages and monocytes., Conclusions: (89)Zr labeling of HDL allows study of its in vivo behavior by using noninvasive PET imaging, including visualization of its accumulation in advanced atherosclerotic lesions. The different labeling strategies provide insight on the pharmacokinetics and biodistribution of HDL's main components (i.e., phospholipids, apo A-I)., (Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Slowing of progression and inducing the regression of atherosclerosis with medical therapy have been shown to be associated with an extensive reduction in risk of cardiovascular events. This proof of concept was obtained with invasive angiographic studies but these are, for obvious reasons, impractical for sequential investigations. Non-invasive imaging has henceforth replaced the more cumbersome invasive studies and has proven extremely valuable in numerous occasions. Because of excellent reproducibility and no radiation exposure, magnetic resonance imaging (MRI) has become the non-invasive method of choice to assess the efficacy of anti-atherosclerotic drugs. The high accuracy of this technology is particularly helpful in rare diseases where the small number of affected patients makes the conduct of outcome-trials in large cohorts impractical. With MRI it is possible to assess the extent, as well as the composition, of atherosclerotic plaques and this further enhances the utility of this technology., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Major focus has been placed on the identification of vulnerable plaques as a means of improving the prediction of myocardial infarction. However, this strategy has recently been questioned on the basis that the majority of these individual coronary lesions do not in fact go on to cause clinical events. Attention is, therefore, shifting to alternative imaging modalities that might provide a more complete pan-coronary assessment of the atherosclerotic disease process. These include markers of disease activity with the potential to discriminate between patients with stable burnt-out disease that is no longer metabolically active and those with active atheroma, faster disease progression, and increased risk of infarction. This review will examine how novel molecular imaging approaches can provide such assessments, focusing on inflammation and microcalcification activity, the importance of these processes to coronary atherosclerosis, and the advantages and challenges posed by these techniques., (© 2016 The Authors.)

Background: Atherosclerosis is an inflammatory condition with calcification apparent late in the disease process. The extent and progression of coronary calcification predict cardiovascular events. Relatively little is known about noncoronary vascular calcification., Objectives: This study investigated noncoronary vascular calcification and its influence on changes in vascular inflammation., Methods: A total of 130 participants in the dal-PLAQUE (Safety and efficacy of dalcetrapib on atherosclerotic disease using novel non-invasive multimodality imaging) study underwent fluorodeoxyglucose positron emission tomography/computed tomography at entry and at 6 months. Calcification of the ascending aorta, arch, carotid, and coronary arteries was quantified. Cardiovascular risk factors were related to arterial calcification. The influences of baseline calcification and drug therapy (dalcetrapib vs. placebo) on progression of calcification were determined. Finally, baseline calcification was related to changes in vascular inflammation., Results: Age >65 years old was consistently associated with higher baseline calcium scores. Arch calcification trended to progress more in those with calcification at baseline (p = 0.055). There were no significant differences between progression of vascular calcification with dalcetrapib compared to that with placebo. Average carotid target-to-background ratio indexes declined over 6 months if carotid calcium was absent (single hottest slice [p = 0.037], mean of maximum target-to-background ratio [p = 0.010], and mean most diseased segment [p < 0.001]), but did not significantly change if calcification was present at baseline., Conclusions: Across multiple arterial regions, higher age is consistently associated with higher calcium scores. The presence of vascular calcification at baseline is associated with progressive calcification; in the carotid arteries, calcification appears to influence vascular inflammation. Dalcetrapib therapy did not affect vascular calcification., (Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Rationale: Local plaque macrophage proliferation and monocyte production in hematopoietic organs promote progression of atherosclerosis. Therefore, noninvasive imaging of proliferation could serve as a biomarker and monitor therapeutic intervention., Objective: To explore (18)F-FLT positron emission tomography-computed tomography imaging of cell proliferation in atherosclerosis., Methods and Results: (18)F-FLT positron emission tomography-computed tomography was performed in mice, rabbits, and humans with atherosclerosis. In apolipoprotein E knock out mice, increased (18)F-FLT signal was observed in atherosclerotic lesions, spleen, and bone marrow (standardized uptake values wild-type versus apolipoprotein E knock out mice, 0.05 ± 0.01 versus 0.17 ± 0.01, P<0.05 in aorta; 0.13 ± 0.01 versus 0.28 ± 0.02, P<0.05 in bone marrow; 0.06 ± 0.01 versus 0.22 ± 0.01, P<0.05 in spleen), corroborated by ex vivo scintillation counting and autoradiography. Flow cytometry confirmed significantly higher proliferation of macrophages in aortic lesions and hematopoietic stem and progenitor cells in the spleen and bone marrow in these mice. In addition, (18)F-FLT plaque signal correlated with the duration of high cholesterol diet (r(2)=0.33, P<0.05). Aortic (18)F-FLT uptake was reduced when cell proliferation was suppressed with fluorouracil in apolipoprotein E knock out mice (P<0.05). In rabbits, inflamed atherosclerotic vasculature with the highest (18)F-fluorodeoxyglucose uptake enriched (18)F-FLT. In patients with atherosclerosis, (18)F-FLT signal significantly increased in the inflamed carotid artery and in the aorta., Conclusions: (18)F-FLT positron emission tomography imaging may serve as an imaging biomarker for cell proliferation in plaque and hematopoietic activity in individuals with atherosclerosis., (© 2015 American Heart Association, Inc.)

Drug delivery to atherosclerotic plaques via liposomal nanoparticles may improve therapeutic agents' risk-benefit ratios. Our paper details the first clinical studies of a liposomal nanoparticle encapsulating prednisolone (LN-PLP) in atherosclerosis. First, PLP's liposomal encapsulation improved its pharmacokinetic profile in humans (n=13) as attested by an increased plasma half-life of 63h (LN-PLP 1.5mg/kg). Second, intravenously infused LN-PLP appeared in 75% of the macrophages isolated from iliofemoral plaques of patients (n=14) referred for vascular surgery in a randomized, placebo-controlled trial. LN-PLP treatment did however not reduce arterial wall permeability or inflammation in patients with atherosclerotic disease (n=30), as assessed by multimodal imaging in a subsequent randomized, placebo-controlled study. In conclusion, we successfully delivered a long-circulating nanoparticle to atherosclerotic plaque macrophages in patients, whereas prednisolone accumulation in atherosclerotic lesions had no anti-inflammatory effect. Nonetheless, the present study provides guidance for development and imaging-assisted evaluation of future nanomedicine in atherosclerosis., From the Clinical Editor: In this study, the authors undertook the first clinical trial using long-circulating liposomal nanoparticle encapsulating prednisolone in patients with atherosclerosis, based on previous animal studies. Despite little evidence of anti-inflammatory effect, the results have provided a starting point for future development of nanomedicine in cardiovascular diseases., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The present study describes the development of a good manufacturing practice (GMP)-grade liposomal nanotherapy containing prednisolone phosphate for the treatment of inflammatory diseases. After formulation design, GMP production was commenced which yielded consistent, stable liposomes sized 100nm±10nm, with a prednisolone phosphate (PLP) incorporation efficiency of 3%-5%. Pharmacokinetics and toxicokinetics of GMP-grade liposomal nanoparticles were evaluated in healthy rats, which were compared to daily and weekly administration of free prednisolone phosphate, revealing a long circulatory half-life with minimal side effects. Subsequently, non-invasive multimodal clinical imaging after liposomal nanotherapy's intravenous administration revealed anti-inflammatory effects on the vessel wall of atherosclerotic rabbits. The present program led to institutional review board approval for two clinical trials with patients with atherosclerosis., From the Clinical Editor: In drug discovery, bringing production to industrial scale is an essential process. In this article the authors describe the development of an anti-inflammatory nanoparticle according to good manufacturing practice. As a result, this paves the way for translating laboratory studies to clinical trials in humans., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: Although it is accepted that macrophage glycolysis is upregulated under hypoxic conditions, it is not known whether this is linked to a similar increase in macrophage proinflammatory activation and whether specific energy demands regulate cell viability in the atheromatous plaque., Approach and Results: We studied the interplay between macrophage energy metabolism, polarization, and viability in the context of atherosclerosis. Cultured human and murine macrophages and an in vivo murine model of atherosclerosis were used to evaluate the mechanisms underlying metabolic and inflammatory activity of macrophages in the different atherosclerotic conditions analyzed. We observed that macrophage energetics and inflammatory activation are closely and linearly related, resulting in dynamic calibration of glycolysis to keep pace with inflammatory activity. In addition, we show that macrophage glycolysis and proinflammatory activation mainly depend on hypoxia-inducible factor and on its impact on glucose uptake, and on the expression of hexokinase II and ubiquitous 6-phosphofructo-2-kinase. As a consequence, hypoxia potentiates inflammation and glycolysis mainly via these pathways. Moreover, when macrophages' ability to increase glycolysis through 6-phosphofructo-2-kinase is experimentally attenuated, cell viability is reduced if subjected to proinflammatory or hypoxic conditions, but unaffected under control conditions. In addition to this, granulocyte-macrophage colony-stimulating factor enhances anerobic glycolysis while exerting a mild proinflammatory activation., Conclusions: These findings, in human and murine cells and in an animal model, show that hypoxia potentiates macrophage glycolytic flux in concert with a proportional upregulation of proinflammatory activity, in a manner that is dependent on both hypoxia-inducible factor -1α and 6-phosphofructo-2-kinase., (© 2015 American Heart Association, Inc.)

Objectives: This study evaluated the effect of p38 mitogen-activated protein kinase (p38MAPK) inhibitor, BMS-582949, on atherosclerotic plaque inflammation, using (18)FDG-PET imaging. p38MAPK is an important element of inflammatory pathways in atherothrombosis and its inhibition may lead to reduced inflammation within atherosclerotic plaques., Methods: Subjects with documented atherosclerosis (n = 72) on stable low-dose statin therapy and having at least one lesion with active atherosclerotic plaque inflammation in either aorta or carotid arteries were randomized to BMS-582949 (100 mg once daily), placebo, or atorvastatin (80 mg once daily), for 12 weeks. Arterial inflammation was assessed using (18)FDG-PET/CT imaging of the carotid arteries and aorta. Uptake of arterial (18)FDG was assessed as target-to-background ratio (TBR): 1) as a mean of all slices of the index vessel, and 2) within active slices of all vessels (AS: which includes only slices with significant inflammation (TBR ≥ 1.6) at the baseline)., Results: Treatment with BMS-582949 did not reduce arterial inflammation relative to placebo, (ΔTBR index: 0.10 [95% CI: -0.11, 0.30], p = 0.34; ΔTBR AS: -0.01 [-0.31, 0.28], p = 0.93) or hs-CRP (median %ΔCRP [IQR]: 33.83% [153.91] vs. 16.71% [133.45], p = 0.61). In contrast, relative to placebo, statin intensification was associated with significant reduction of hs-CRP (%ΔCRP [IQR]: -17.44% [54.68] vs. 16.71% [133.45], p = 0.04) and arterial inflammation in active slices (ΔTBRAS = -0.24 [95% CI: -0.46, -0.01], p = 0.04)., Conclusions: The findings of this study demonstrates that in stable atherosclerosis, 12 weeks of treatment with BMS-582949 did not reduce arterial inflammation or hs-CRP compared to placebo, whereas intensification of statin therapy significantly decreased arterial inflammation., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Purpose: To determine if manganese (Mn) G8 dendrimers targeted to oxidation-specific epitopes (OSE) allow for in vivo detection of atherosclerotic lesions., Materials and Methods: OSE have been identified as key factors in atherosclerotic plaque progression and destabilization. Mn offers a potentially clinically translatable alternative to gadolinium-based agents when bioretention and potential toxicity of gadolinium is anticipated. However, to be effective, high payloads of Mn must accumulate intracellularly in macrophages. It was hypothesized that G8 dendrimers targeted to OSE may allow delivery of high Mn payloads, thereby enabling in vivo detection of macrophage-rich plaques. G8 dendrimers were modified to allow conjugation with MnDTPA (758 Mn ion) and the antibody MDA2 that is targeted to malondialdehyde (MDA)-lysine epitopes. Both the untargeted and targeted G8 dendrimers were characterized and their in vivo efficacy evaluated in apoE(-/-) mice over a 96-hour time period after bolus administration of a 0.05 mmol Mn/kg dose using a clinical MR system (3T)., Results: Significant enhancement (normalized enhancement >60%, P = 0.0013) of atherosclerotic lesions was observed within a 72-hour time period following administration of the targeted dendrimers. The presence of Mn within atherosclerotic lesions was confirmed using spectroscopic methods (>8 μg Mn/g). Limited signal attenuation (<18%) and Mn deposition (<1 μg Mn/g) was observed in the arterial wall following injection of the untargeted material., Conclusion: This study demonstrates that manganese-labeled dendrimers, allowing a high Mn payload, targeted to OSE may allow in vivo image of atherosclerotic lesions., (© 2014 Wiley Periodicals, Inc.)

Bioengineering provides unique opportunities to better understand and manage atherosclerotic disease. The field is entering a new era that merges the latest biological insights into inflammatory disease processes with targeted imaging and nanomedicine. Preclinical cardiovascular molecular imaging allows the in vivo study of targeted nanotherapeutics specifically directed toward immune system components that drive atherosclerotic plaque development and complication. The first multicenter trials highlight the potential contribution of multimodality imaging to more efficient drug development. This review describes how the integration of engineering, nanotechnology, and cardiovascular immunology may yield precision diagnostics and efficient therapeutics for atherosclerosis and its ischemic complications., (Copyright © 2014, American Association for the Advancement of Science.)

Background: Hypoxia is an important microenvironmental factor influencing atherosclerosis progression by inducing foam-cell formation, metabolic adaptation of infiltrated macrophages, and plaque neovascularization. Therefore, imaging plaque hypoxia could serve as a marker of lesions at risk., Methods and Results: Advanced aortic atherosclerosis was induced in 18 rabbits by atherogenic diet and double balloon endothelial denudation. Animals underwent (18)F-fluoromisonidazole positron emission tomographic and (18)F-fluorodeoxyglucose positron emission tomographic imaging after 6 to 8 months (atherosclerosis induction) and 12 to 16 months (progression) of diet initiation. Four rabbits fed standard chow served as controls. Radiotracer uptake of the abdominal aorta was measured using standardized uptake values. After imaging, plaque hypoxia (pimonidazole), macrophages (RAM-11), neovessels (CD31), and hypoxia-inducible factor-1α were assessed by immunohistochemistry.(18)F-fluoromisonidazole uptake increased with time on diet (standardized uptake value mean, 0.10±0.01 in nonatherosclerotic animals versus 0.20±0.03 [P=0.002] at induction and 0.25±0.03 [P<0.001] at progression). Ex vivo positron emission tomographic imaging corroborated the (18)F-fluoromisonidazole uptake by the aorta of atherosclerotic rabbits. (18)F-fluorodeoxyglucose uptake also augmented in atherosclerotic animals, with an standardized uptake value mean of 0.43±0.02 at induction versus 0.35±0.02 in nonatherosclerotic animals (P=0.031) and no further increase at progression. By immunohistochemistry, hypoxia was mainly located in the macrophage-rich areas within the atheromatous core, whereas the macrophages close to the lumen were hypoxia-negative. Intraplaque neovessels were found predominantly in macrophage-rich hypoxic regions (pimonidazole(+)/hypoxia-inducible factor-1α(+)/RAM-11(+))., Conclusions: Plaque hypoxia increases with disease progression and is present in macrophage-rich areas associated with neovascularization. (18)F-fluoromisonidazole positron emission tomographic imaging emerges as a new tool for the detection of atherosclerotic lesions.

Therapeutic and diagnostic nanomaterials are being intensely studied for several diseases, including cancer and atherosclerosis. However, the exact mechanism by which nanomedicines accumulate at targeted sites remains a topic of investigation, especially in the context of atherosclerotic disease. Models to accurately predict transvascular permeation of nanomedicines are needed to aid in design optimization. Here we show that an endothelialized microchip with controllable permeability can be used to probe nanoparticle translocation across an endothelial cell layer. To validate our in vitro model, we studied nanoparticle translocation in an in vivo rabbit model of atherosclerosis using a variety of preclinical and clinical imaging methods. Our results reveal that the translocation of lipid-polymer hybrid nanoparticles across the atherosclerotic endothelium is dependent on microvascular permeability. These results were mimicked with our microfluidic chip, demonstrating the potential utility of the model system.

Background: The presence of subclinical atherosclerosis is a likely predictor of cardiovascular events; however, factors associated with the early stages and progression of atherosclerosis are poorly defined., Objective: The PESA study examines the presence of subclinical atherosclerosis by means of noninvasive imaging and prospectively analyzes the determinants associated with its development and progression in a middle-aged population., Methods: The PESA study is an observational, longitudinal and prospective cohort study in a target population of 4000 healthy subjects (40-54 years old, 35% women) based in Madrid (Spain). Recruitment began in June 2010 and will be completed by the end of 2013. Baseline examination consists of (1) assessment for cardiovascular risk factors (including lifestyle and psychosocial factors); (2) screening for subclinical atherosclerosis using 2D/3D ultrasound in carotid, abdominal aorta and iliofemoral arteries, and coronary artery calcium score (CACS) by computed tomography; and (3) blood sampling for determination of traditional risk factors, advanced "omics" and biobanking. In addition, a subgroup of 1300 participants with evidence of atherosclerosis on 2D/3D ultrasound or CACS will undergo a combined (18)F-fluorodeoxyglucose-positron emission tomography/magnetic resonance imaging ((18)FDG PET/MRI) study of carotid and iliofemoral arteries. Follow-up at 3 and 6 years will include a repetition of baseline measurements, except for the (18)FDG PET/MRI study, which will be repeated at 6 years., Conclusions: The PESA study is expected to identify new imaging and biological factors associated with the presence and progression of atherosclerosis in asymptomatic people and will help to establish a more personalized management of medical care., (© 2013.)