Translational Molecular imaging: Thrombosis Imaging with Positron Emission Tomography

A key focus of cardiovascular medicine is the detection, treatment, and prevention of disease, with a move towards more personalized and patient-centred treatments. To achieve this goal, novel imaging approaches that allow for early and accurate detection of disease and risk stratification are needed. At present, the diagnosis, monitoring, and prognostication of thrombotic cardiovascular diseases are based on imaging techniques that measure changes in structural anatomy and biological function. Molecular imaging is emerging as a new tool for the non-invasive detection of biological processes, such as thrombosis, that can improve identification of these events above and beyond current imaging modalities. At the forefront of these evolving techniques is the use of high-sensitivity radiotracers in conjunction with positron emission tomography imaging that could revolutionise current diagnostic paradigms by improving our understanding of the role and origin of thrombosis in a range of cardiovascular diseases.</p

Identification and proteomic profiling of exosomes in human cerebrospinal fluid

<p>Abstract</p> <p>Background</p> <p>Exosomes are released from multiple cell types, contain protein and RNA species, and have been exploited as a novel reservoir for disease biomarker discovery. They can transfer information between cells and may cause pathology, for example, a role for exosomes has been proposed in the pathophysiology of Alzheimer's disease. Although studied in several biofluids, exosomes have not been extensively studied in the cerebrospinal fluid (CSF) from humans. The objective of this study was to determine: 1) whether human CSF contains exosomes and 2) the variability in exosomal protein content across individuals.</p> <p>Methods</p> <p>CSF was collected from 5 study participants undergoing thoraco-abdominal aortic aneurysm repair (around 200 - 500 ml per participant) and low-density membrane vesicles were concentrated by ultracentrifugation. The presence of exosomes was determined by western blot for marker proteins, isopycnic centrifugation on a sucrose step gradient and transmission electron microscopy with immuno-labelling. Whole protein profiling was performed using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR).</p> <p>Results</p> <p>Flotillin 1 and tumor susceptibility gene 101 (TSG101), two exosomal marker proteins, were identified in the ultracentrifugation pellet using western blot. These markers localized to a density consistent with exosomes following isopycnic centrifugation. Transmission electron microscopy visualized structures consistent with exosomes in size and appearance that labelled positive for flotillin 1. Therefore, the pellet that resulted from ultracentrifugation of human CSF contained exosomes. FT-ICR profiling of this pellet was performed and 84-161 ions were detected per study participant. Around one third of these ions were only present in a single study participant and one third were detected in all five. With regard to ion quantity, the median coefficient of variation was 81% for ions detected in two or more samples.</p> <p>Conclusions</p> <p>Exosomes were identified in human CSF and their proteome is a potential new reservoir for biomarker discovery in neurological disorders such as Alzheimer's disease. However, techniques used to concentrate exosomes from CSF need refinement to reduce variability. In this study we used relatively large starting volumes of human CSF, future studies will focus on exosome isolation from smaller 'real life' clinical samples; a key challenge in the development of exosomes as translational tools.</p

Valvular and Myocardial Fibroblast Activation in Aortic Stenosis

Activated fibroblasts drive leaflet thickening and left ventricular decompensation in aortic stenosis. Gallium-68 Fibroblast Activation Protein Inhibitor (68Ga-FAPI) binds to these key effector cells, and provides a readout of fibroblast activation. We aimed to describe the role of activated fibroblasts in patients with aortic stenosis in vivo using 68Ga-FAPI. In a prospective observational study, patients with aortic stenosis and control subjects underwent echocardiography, 68Ga-FAPI PET, CT, and MRI. Valvular and myocardial 68Ga-FAPI uptake was quantified using maximal standardised uptake values (SUVmax), and target-to-background ratio (TBRmax). Aortic stenosis severity was measured by peak velocity on echocardiography and the CT calcium score. Myocardial fibrosis was quantified by late gadolinium enhancement (LGE) on MRI. 86 patients with aortic valve disease (72±11 years, 68% male) plus 9 matched control subjects (72±9 years, 67%% male) participated. Increased 68Ga-FAPI uptake was observed in the aortic valves of patients with aortic stenosis compared with controls (p&lt;0.001). 68Ga-FAPI TBRmax correlated with peak velocity (r=0.532, p&lt;0.0010) and calcium score (r = 0.577, p&lt;0.001). 54 patients (69%) had myocardial 68Ga-FAPI uptake, of whom 30 (38%) also had LGE corresponding to the region of 68Ga-FAPI uptake. Myocardial 68Ga-FAPI uptake correlated with increased indexed left ventricular mass (r=0.429, p&lt;0.001) and indexed Extracellular Volume (r=0.404, p&lt;0.001). For the first time, we have described valvular and myocardial fibroblast activation in patients with aortic stenosis in vivo. Valvular fibroblast activation is increased in patients with aortic stenosis, correlating with increased disease severity. Myocardial fibroblast activation is seen in the majority of patients with aortic stenosis in areas with and without established fibrosis, and is associated with adverse left ventricular remodelling. 68Ga-FAPI PET can visualise the key effector cell driving aortic valve disease, and may have a role in monitoring disease modifying treatments, as well as identifying patients at high risk of myocardial decompensation. Please click on the \u27PDF\u27 for the full abstract

Choroidal and retinal thinning in chronic kidney disease independently associate with eGFR decline and are modifiable with treatment

In patients with chronic kidney disease (CKD), there is an unmet need for novel biomarkers that reliably track kidney injury, demonstrate treatment-response, and predict outcomes. Here, we investigated the potential of retinal optical coherence tomography (OCT) to achieve these ends in a series of prospective studies of patients with pre-dialysis CKD (including those with a kidney transplant), patients with kidney failure undergoing kidney transplantation, living kidney donors, and healthy volunteers. Compared to health, we observed similar retinal thinning and reduced macular volume in patients with CKD and a kidney transplant. However, choroidal thinning in CKD was not seen in patients with a kidney transplant whose choroids resembled those of healthy volunteers. In CKD, the degree of choroidal thinning related to falling eGFR and extent of kidney scarring. Following kidney transplantation, choroidal thickness increased rapidly (~10%) and was maintained over 1-year, whereas gradual choroidal thinning was observed during the 12 months following kidney donation. In patients with CKD, retinal and choroidal thickness independently associated with eGFR decline over 2 years. These observations highlight the potential for retinal OCT to act as a non-invasive monitoring and prognostic biomarker of kidney injury

Outcomes and effect of treatment according to etiology in HFrEF: an analysis of PARADIGM-HF

Objectives: The purpose of this study was to compare outcomes (and the effect of sacubitril/valsartan) according to etiology in the PARADIGM-HF (Prospective comparison of angiotensin-receptor-neprilysin inhibitor [ARNI] with angiotensin-converting-enzyme inhibitor [ACEI] to Determine Impact on Global Mortality and morbidity in Heart Failure) trial. Background: Etiology of heart failure (HF) has changed over time in more developed countries and is also evolving in non-Western societies. Outcomes may vary according to etiology, as may the effects of therapy. Methods: We examined outcomes and the effect of sacubtril/valsartan according to investigator-reported etiology in PARADIGM-HF. The outcomes analyzed were the primary composite of cardiovascular death or HF hospitalization, and components, and death from any cause. Outcomes were adjusted for known prognostic variables including N terminal pro-B type natriuretic peptide. Results: Among the 8,399 patients randomized, 5,036 patients (60.0%) had an ischemic etiology. Among the 3,363 patients (40.0%) with a nonischemic etiology, 1,595 (19.0% of all patients; 47% of nonischemic patients) had idiopathic dilated cardiomyopathy, 968 (11.5% of all patients; 28.8% of nonischemic patients) had a hypertensive cause, and 800 (9.5% of all patients, 23.8% of nonischemic patients) another cause (185 infective/viral, 158 alcoholic, 110 valvular, 66 diabetes, 30 drug-related, 14 peripartum–related, and 237 other). Whereas the unadjusted rates of all outcomes were highest in patients with an ischemic etiology, the adjusted hazard ratios (HRs) were not different from patients in the 2 major nonischemic etiology categories; for example, for the primary outcome, compared with ischemic (HR: 1.00), hypertensive 0.87 (95% confidence interval [CI]: 0.75 to 1.02), idiopathic 0.92 (95% CI: 0.82 to 1.04) and other 1.00 (95% CI: 0.85 to 1.17). The benefit of sacubitril/valsartan over enalapril was consistent across etiologic categories (interaction for primary outcome; p = 0.11). Conclusions: Just under one-half of patients in this global trial had nonischemic HF with reduced ejection fraction, with idiopathic and hypertensive the most commonly ascribed etiologies. Adjusted outcomes were similar across etiologic categories, as was the benefit of sacubitril/valsartan over enalapril. (Efficacy and Safety of LCZ696 Compared to Enalapril on Morbidity and Mortality of Patients With Chronic Heart Failure; NCT01035255

Qualitative and quantitative analysis of 18F-GP1 positron emission tomography in thrombotic cardiovascular disease

Abstract 18F-GP1 is a novel highly specific radiotracer that binds to activated platelets and thrombus. We aimed to establish the observer repeatability of coronary, carotid and cerebral 18F-GP1 uptake in patients presenting with acute myocardial infarction or ischaemic stroke. Forty-three patients presenting with acute myocardial infarction or ischaemic stroke underwent hybrid positron emission tomography (PET) and computed tomography (CT) angiography. Qualitative and quantitative assessment of 18F-GP1 uptake was performed on coronary arteries, carotid arteries and brain parenchyma. Qualitative uptake of 18F-GP1 had excellent intraobserver and interobserver agreement, with complete agreement for the presence or absence of visual 18F-GP1 uptake. For quantitative analysis, there were excellent intraclass correlation coefficients for intraobserver repeatability for coronary artery, carotid artery and brain parenchymal SUVmax and TBRmax measurements (all ≥ 0.92). Coronary artery and brain parenchymal analyses showed the strongest agreement in SUVmax values with mean biases of − 0.04 (limits of agreement − 0.21 to 0.20) and 0.02 (limits of agreement − 0.29 to 0.32) respectively. There was good interclass correlation coefficients for interobserver repeatability for coronary artery, carotid artery and brain parenchymal SUVmax and TBRmax measurements (all ≥ 0.89). The strongest interobserver agreement was seen with brain parenchymal SUVmax (mean SUVmax 1.95 ± 0.94) and TBRmax (mean TBRmax 9.55 ± 6.56) with mean biases of − 0.05 (limits of agreement − 0.37 to 0.27) and 0.04 (limits of agreement − 0.59 to 0.52) respectively. Visual qualitative and quantitative 18F-GP1 PET-CT image analyses provide robust and repeatable measurements of activated platelets and thrombi within the coronary arteries, carotid arteries and brain parenchyma

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Novel loci associated with increased risk of sudden cardiac death in the context of coronary artery disease

BACKGROUND: Recent genome-wide association studies (GWAS) have identified novel loci associated with sudden cardiac death (SCD). Despite this progress, identified DNA variants account for a relatively small portion of overall SCD risk, suggesting that additional loci contributing to SCD susceptibility await discovery. The objective of this study was to identify novel DNA variation associated with SCD in the context of coronary artery disease (CAD).METHODS AND FINDINGS: Using the MetaboChip custom array we conducted a case-control association analysis of 119,117 SNPs in 948 SCD cases (with underlying CAD) from the Oregon Sudden Unexpected Death Study (Oregon-SUDS) and 3,050 controls with CAD from the Wellcome Trust Case-Control Consortium (WTCCC). Two newly identified loci were significantly associated with increased risk of SCD after correction for multiple comparisons at: rs6730157 in the RAB3GAP1 gene on chromosome 2 (P = 4.93×10(-12), OR = 1.60) and rs2077316 in the ZNF365 gene on chromosome 10 (P = 3.64×10(-8), OR = 2.41).CONCLUSIONS: Our findings suggest that RAB3GAP1 and ZNF365 are relevant candidate genes for SCD and will contribute to the mechanistic understanding of SCD susceptibility.</p

Chorioretinal thinning in chronic kidney disease links to inflammation and endothelial dysfunction

The Engineering and Sciences Library was formed in 1990,incorporating the C. S. Davis Mathematics Library and the Thomas Parnell Memorial Physics Library. In 1997 the library was refurbished and merged with the Geology Library collection. The library was named the Dorothy Hill Physical Sciences and Engineering Library, after the late Professor Dorothy Hill, and opened officially on 26 August 1997. In 2011, the name was changed to the Dorothy Hill Engineering and Sciences Library, when the collections were merged with those of the Biological Sciences Library

Chorioretinal thinning in chronic kidney disease links to inflammation and endothelial dysfunction

BACKGROUND. Chronic kidney disease (CKD) is strongly associated with cardiovascular disease and there is an established association between vasculopathy affecting the kidney and eye. Optical coherence tomography (OCT) is a novel, rapid method for high-definition imaging of the retina and choroid. Its use in patients at high cardiovascular disease risk remains unexplored. METHODS. We used the new SPECTRALIS OCT machine to examine retinal and retinal nerve fiber layer (RNFL) thickness, macular volume, and choroidal thickness in a prospective cross-sectional study in 150 subjects: 50 patients with hypertension (defined as a documented clinic BP greater than or equal to 140/90 mmHg (prior to starting any treatment) with no underlying cause identified); 50 with CKD (estimated glomerular filtration rate (eGFR) 8–125 ml/min/1.73 m(2)); and 50 matched healthy controls. We excluded those with diabetes. The same, masked ophthalmologist carried out each study. Plasma IL-6, TNF-α , asymmetric dimethylarginine (ADMA), and endothelin-1 (ET-1), as measures of inflammation and endothelial function, were also assessed. RESULTS. Retinal thickness, macular volume, and choroidal thickness were all reduced in CKD compared with hypertensive and healthy subjects (for retinal thickness and macular volume P < 0.0001 for CKD vs. healthy and for CKD vs. hypertensive subjects; for choroidal thickness P < 0.001 for CKD vs. healthy and for CKD vs. hypertensive subjects). RNFL thickness did not differ between groups. Interestingly, a thinner choroid was associated with a lower eGFR (r = 0.35, P <0.0001) and, in CKD, with proteinuria (r = –0.58, P < 0.001) as well as increased circulating C-reactive protein (r = –0.57, P = 0.0002), IL-6 (r = –0.40, P < 0.01), ADMA (r = –0.37, P = 0.02), and ET-1 (r = –0.44, P < 0.01). Finally, choroidal thinning was associated with renal histological inflammation and arterial stiffness. In a model of hypertension, choroidal thinning was seen only in the presence of renal injury. CONCLUSIONS. Chorioretinal thinning in CKD is associated with lower eGFR and greater proteinuria, but not BP. Larger studies, in more targeted groups of patients, are now needed to clarify whether these eye changes reflect the natural history of CKD. Similarly, the associations with arterial stiffness, inflammation, and endothelial dysfunction warrant further examination. TRIAL REGISTRATION. Registration number at www.clinicalTrials.gov: NCT02132741. SOURCE OF FUNDING. TR was supported by a bursary from the Erasmus Medical Centre, Rotterdam. JJMHvB was supported by a bursary from the Utrecht University. JRC is supported by a Rowling Scholarship. SB was supported by a Wellcome Trust funded clinical research fellowship from the Scottish Translational Medicine and Therapeutics Initiative, and by a Rowling Scholarship, at the time of this work. ND is supported by a British Heart Foundation Intermediate Clinical Research Fellowship (FS/13/30/29994)