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Abstract
Major advances in biomedical imaging have occurred over the last 2 decades and now allow many physiological, cellular, and molecular processes to be imaged noninvasively in small animal models of cardiovascular disease. Many of these techniques can be also used in humans, providing pathophysiological context and helping to define the clinical relevance of the model. Ultrasound remains the most widely used approach, and dedicated high-frequency systems can obtain extremely detailed images in mice. Likewise, dedicated small animal tomographic systems have been developed for magnetic resonance, positron emission tomography, fluorescence imaging, and computed tomography in mice. In this article, we review the use of ultrasound and positron emission tomography in small animal models, as well as emerging contrast mechanisms in magnetic resonance such as diffusion tensor imaging, hyperpolarized magnetic resonance, chemical exchange saturation transfer imaging, magnetic resonance elastography and strain, arterial spin labeling, and molecular imaging.
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Affiliation(s)
- David E Sosnovik
- Cardiology Division, Cardiovascular Research Center (D.E.S.), Massachusetts General Hospital and Harvard Medical School, Boston.,A.A. Martinos Center for Biomedical Imaging (D.E.S.), Massachusetts General Hospital and Harvard Medical School, Boston.,Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School and Massachusetts Institute of Technology, Cambridge (D.E.S.)
| | - Marielle Scherrer-Crosbie
- Cardiology Division, Hospital of the University of Pennsylvania and Perelman School of Medicine, Philadelphia (M.S.-C)
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2
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Abstract
Cardiomyocyte apoptosis has been observed in several cardiovascular diseases and contributes to the subsequent cardiac remodeling processes and progression to heart failure. Consequently, apoptosis imaging is helpful for noninvasively detecting the disease progression and providing treatment guidance. Here, we tested 18F-labeled 2-(5-fluoropentyl)-2-methyl-malonic acid (18F-ML-10) and 18F-labeled 2-(3-fluoropropyl)-2-methyl-malonic acid (18F-ML-8) for apoptosis imaging in rat models of myocardial infarction (MI) and compared them with 18F-fluorodeoxyglucose (18F-FDG). MI was induced in Sprague-Dawley rats by permanent left coronary artery ligation. Procedural success was confirmed by echocardiography and positron emission tomography (PET) imaging with 18F-FDG. In vivo PET imaging with 18F-ML-10 and 18F-ML-8 was performed in the MI models at different time points after operation. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays and immunohistochemical analyses were used to evaluate myocardial apoptosis. In vitro cell binding assays were performed to validate 18F-ML-8 binding to apoptotic cardiomyocytes. PET imaging demonstrated high 18F-ML-10 and 18F-ML-8 uptake where 18F-FDG uptake was absent. The focal accumulation of the two tracers was high on days 1 and 3 but was not notable on days 5 and 7 after surgery. The infarct-to-lung uptake ratio was 4.29 ± 0.30 for 18F-ML-10 and 3.51 ± 0.18 for 18F-ML-8 (n = 6, analyzed by averaging the uptake ratios on postoperative days 1 and 3, P < 0.05). The TUNEL results showed that myocardial cell apoptosis was closely related to the focal uptake of the apoptotic tracers in the infarct area. In addition, the apoptosis rates calculated from the TUNEL results were better correlated with 18F-ML-8 uptake than with 18F-ML-10 uptake. Ex vivo cell binding assays demonstrated that 18F-ML-8 accumulated in apoptotic cells but not in necrotic or normal cells. PET imaging using 18F-ML-10 or 18F-ML-8 allows the noninvasive detection of myocardial apoptosis in the early phase. In addition, 18F-ML-8 may be better than 18F-ML-10 for apoptosis imaging. We propose that PET imaging with 18F-ML-10 or 18F-ML-8 combined with 18F-FDG is an alternative for detecting and assessing MI.
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Early Detection of Localized Immunity in Experimental Autoimmune Myocarditis Using [ 99mTc]Fucoidan SPECT. Mol Imaging Biol 2019; 22:643-652. [PMID: 31432389 DOI: 10.1007/s11307-019-01420-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
PURPOSE The aim of the study was to evaluate the ability of technetium-99m-fucoidan ([99mTc]fucoidan), a molecular imaging agent specific for selectins, in the assessment of early localized immunity in a rat model of experimental autoimmune myocarditis (EAM). PROCEDURES EAM was induced in Lewis rats and troponin T; brain natriuretic peptide (BNP) and anti-myosin antibodies were measured in plasma. Separately, [99mTc]fucoidan single-photon emission computed tomography (SPECT)/x-ray computed tomography (CT) was performed in the very early phase of myocarditis at 10, 15, and 21 days after immunization. Then, hearts were collected and used for autoradiography, well counting, histology, and flow cytometry analysis. RESULTS The EAM acute phase is characterized by extensive myocardial necrosis, release of troponin and BNP, and pericardial effusion. [99mTc]Fucoidan uptake was significantly increased in EAM compared with controls starting from D15. There was a close relationship between uptake of the tracer and myocardial content in CD45+, CD8+, CD11b+, and CD31+ cells. CONCLUSIONS [99mTc]Fucoidan SPECT/CT accurately diagnosed the autoimmune attack in the early steps of EAM and could be used to monitor disease evolution and therapy efficiency.
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Shekhar A, Heeger P, Reutelingsperger C, Arbustini E, Narula N, Hofstra L, Bax JJ, Narula J. Targeted Imaging for Cell Death in Cardiovascular Disorders. JACC Cardiovasc Imaging 2018; 11:476-493. [DOI: 10.1016/j.jcmg.2017.11.018] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/19/2017] [Accepted: 11/27/2017] [Indexed: 01/30/2023]
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5
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Papadimitriou L, Smith-Jones PM, Sarwar CM, Marti CN, Yaddanapudi K, Skopicki HA, Gheorghiade M, Parsey R, Butler J. Utility of positron emission tomography for drug development for heart failure. Am Heart J 2016; 175:142-52. [PMID: 27179733 DOI: 10.1016/j.ahj.2016.02.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Accepted: 02/22/2016] [Indexed: 12/14/2022]
Abstract
Only about 1 in 5,000 investigational agents in a preclinical stage acquires Food and Drug Administration approval. Among many reasons for this includes an inefficient transition from preclinical to clinical phases, which exponentially increase the cost and the delays the process of drug development. Positron emission tomography (PET) is a nuclear imaging technique that has been used for the diagnosis, risk stratification, and guidance of therapy. However, lately with the advance of radiochemistry and of molecular imaging technology, it became evident that PET could help novel drug development process. By using a PET radioligand to report on receptor occupancy during novel agent therapy, it may help assess the effectiveness, efficacy, and safety of such a new medication in an early preclinical stage and help design successful clinical trials even at a later phase. In this article, we explore the potential implications of PET in the development of new heart failure therapies and review PET's application in the respective pathophysiologic pathways such as myocardial perfusion, metabolism, innervation, inflammation, apoptosis, and cardiac remodeling.
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Hyafil F, Tran-Dinh A, Burg S, Leygnac S, Louedec L, Milliner M, Ben Azzouna R, Reshef A, Ben Ami M, Meilhac O, Le Guludec D. Detection of Apoptotic Cells in a Rabbit Model with Atherosclerosis-Like Lesions Using the Positron Emission Tomography Radiotracer [
18
F]ML-10. Mol Imaging 2015. [DOI: 10.2310/7290.2015.00017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Affiliation(s)
- Fabien Hyafil
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Alexy Tran-Dinh
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Samuel Burg
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Sébastien Leygnac
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Liliane Louedec
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Milan Milliner
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Rana Ben Azzouna
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Ayelet Reshef
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Miri Ben Ami
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Olivier Meilhac
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
| | - Dominique Le Guludec
- From the Department of Nuclear Medicine and Inserm Unité Mixte de Recherche 1148, Bichat University Hospital, Département Hospitalo-Universitaire FIRE, Assistance Publique – Hôpitaux de Paris, Université Paris Diderot-Paris 7, Paris, France; Aposense Ltd, Petach-Tikva, Israel; and Inserm U1188 Diabète athérothrombose Thérapies Réunion Océan Indien (DéTROI), Université de La Réunion, CHU de La Réunion, CYROI, Saint-Denis, France
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Phinikaridou A, Andia ME, Shah AM, Botnar RM. Advances in molecular imaging of atherosclerosis and myocardial infarction: shedding new light on in vivo cardiovascular biology. Am J Physiol Heart Circ Physiol 2012; 303:H1397-410. [PMID: 23064836 DOI: 10.1152/ajpheart.00583.2012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Molecular imaging of the cardiovascular system heavily relies on the development of new imaging probes and technologies to facilitate visualization of biological processes underlying or preceding disease. Molecular imaging is a highly active research discipline that has seen tremendous growth over the past decade. It has broadened our understanding of oncologic, neurologic, and cardiovascular diseases by providing new insights into the in vivo biology of disease progression and therapeutic interventions. As it allows for the longitudinal evaluation of biological processes, it is ideally suited for monitoring treatment response. In this review, we will concentrate on the major accomplishments and advances in the field of molecular imaging of atherosclerosis and myocardial infarction with a special focus on magnetic resonance imaging.
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Affiliation(s)
- Alkystis Phinikaridou
- Division of Imaging Science and Biomedical Engineering, King's College London, United Kingdom.
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8
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Huang S, Chen HH, Yuan H, Dai G, Schuhle DT, Mekkaoui C, Ngoy S, Liao R, Caravan P, Josephson L, Sosnovik DE. Molecular MRI of acute necrosis with a novel DNA-binding gadolinium chelate: kinetics of cell death and clearance in infarcted myocardium. Circ Cardiovasc Imaging 2011; 4:729-37. [PMID: 21836081 DOI: 10.1161/circimaging.111.966374] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND Current techniques to image cell death in the myocardium are largely nonspecific. We report the use of a novel DNA-binding gadolinium chelate (Gd-TO) to specifically detect the exposed DNA in acutely necrotic (ruptured) cells in vivo. METHODS AND RESULTS In vivo MRI was performed in 20 mice with myocardial infarction (MI). The mice were injected with Gd-TO or Gd-DTPA at varying time points after MI. MRI was performed 2 hours after probe injection, to avoid nonspecific signal from the late gadolinium enhancement effect. Cell rupture (Gd-TO uptake) was present within 2 hours of infarction but peaked 9 to 18 hours after the onset of injury. A significant increase in the longitudinal relaxation rate (R(1)) in the infarct was seen in mice injected with Gd-TO within 48 hours of MI, but not in those injected more than 72 hours after MI (R(1)=1.24±0.08 and 0.92±0.03 s(-1), respectively, P<0.001). Gd-DTPA, unlike Gd-TO, washed completely out of acute infarcts within 2 hours of injection (P<0.001). The binding of Gd-TO to exposed DNA in acute infarcts was confirmed with fluorescence microscopy. CONCLUSIONS Gd-TO specifically binds to acutely necrotic cells and can be used to image the mechanism and chronicity of cell death in injured myocardium. Cell rupture in acute MI begins early but peaks many hours after the onset of injury. The ruptured cells are efficiently cleared by the immune system and are no longer present in the myocardium 72 hours after injury.
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Affiliation(s)
- Shuning Huang
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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9
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Abstract
The progression from acute myocardial infarction (MI) to heart failure continues to be a major cause of morbidity and mortality. Potential new therapies for improved infarct healing such as stem cells, gene therapy, and tissue engineering are being investigated. Noninvasive imaging plays a central role in the evaluation of MI and infarct healing, both clinically and in preclinical research. Traditionally, imaging has been used to assess cardiac structure, function, perfusion, and viability. However, new imaging methods can be used to assess biological processes at the cellular and molecular level. We review molecular imaging techniques for evaluating the biology of infarct healing and repair. Specifically, we cover recent advances in imaging the various phases of MI and infarct healing such as apoptosis, inflammation, angiogenesis, extracellular matrix deposition, and scar formation. Significant progress has been made in preclinical molecular imaging, and future challenges include translation of these methods to clinical practice.
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10
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Wadas TJ, Wong EH, Weisman GR, Anderson CJ. Coordinating radiometals of copper, gallium, indium, yttrium, and zirconium for PET and SPECT imaging of disease. Chem Rev 2010; 110:2858-902. [PMID: 20415480 PMCID: PMC2874951 DOI: 10.1021/cr900325h] [Citation(s) in RCA: 671] [Impact Index Per Article: 47.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Thaddeus J Wadas
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S. Kingshighway Blvd., Campus Box 8225 St. Louis, Missouri 63110, USA.
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11
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Bayturan O, Uno K, Lavoie A, Nicholls SJ. Future requirement for arterial wall imaging modalities in the evaluation of novel anti-atherosclerotic therapies. Curr Med Res Opin 2010; 26:753-7. [PMID: 20092390 DOI: 10.1185/03007990903547582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND While arterial wall imaging has been used to characterize progression of atherosclerosis, there remain limitations to this approach. SCOPE A selective overview of emerging modalities to image the artery wall and highlight how they may be used to evaluate emerging anti-atherosclerotic agents. FINDINGS Ongoing developments appear to enable assessment of composition and molecular properties of plaque in addition to quantitation of burden. Non-invasiveness and correlation with clinical outcome remains a challenge. CONCLUSION New developments in imaging should enhance the ability to provide early characterization of the potential therapeutic efficacy of experimental agents.
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12
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Imaging the molecular signatures of apoptosis and injury with radiolabeled annexin V. Ann Am Thorac Soc 2009; 6:469-76. [PMID: 19687221 DOI: 10.1513/pats.200901-001aw] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Annexin V is a ubiquitous intracellular protein in humans that has a variety of intriguing characteristics, including a nanomolar affinity for the membrane-bound constitutive anionic phospholipid known as phosphatidylserine (PS). PS is selectively expressed on the surface of apoptotic or physiologically stressed cells. As such, radiolabeled forms of annexin V have been used in both animal models and human Phase I and Phase II trials to determine if this tracer can be employed as an early surrogate marker of therapeutic efficacy in NSCLC and non-Hodgkin's lymphoma. Many other pulmonary imaging applications of radiolabeled annexin V are also possible, including the detection and monitoring of active pulmonary inflammation and other pathophysiologic stressors in a variety of diseases. In this article, the salient molecular features of apoptosis (and other forms of cell death) that permits imaging with radiolabeled annexin V will be discussed. The latest results from Phase II imaging trials with NSCLC and non-Hodgkin's lymphoma will be also be detailed. Finally, the potential future application of this tracer for the imaging of other pulmonary pathologies will be outlined.
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Sosnovik DE, Nahrendorf M, Panizzi P, Matsui T, Aikawa E, Dai G, Li L, Reynolds F, Dorn GW, Weissleder R, Josephson L, Rosenzweig A. Molecular MRI detects low levels of cardiomyocyte apoptosis in a transgenic model of chronic heart failure. Circ Cardiovasc Imaging 2009; 2:468-75. [PMID: 19920045 DOI: 10.1161/circimaging.109.863779] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND The ability to image cardiomyocyte (CM) apoptosis in heart failure could facilitate more accurate diagnostics and optimize targeted therapeutics. We thus aimed to develop a platform to image CM apoptosis quantitatively and specifically in heart failure in vivo. The myocardium in heart failure, however, is characterized by very low levels of CM apoptosis and normal vascular permeability, factors thought to preclude the use of molecular MRI. METHODS AND RESULTS Female mice with overexpression of Gaq were studied. Two weeks postpartum, these mice develop a cardiomyopathy characterized by low levels of CM apoptosis and minimal myocardial necrosis or inflammation. The mice were injected with the annexin-labeled nanoparticle (AnxCLIO-Cy5.5) or a control probe (CLIO-Cy5.5) and imaged in vivo at 9.4 T. Uptake of AnxCLIO-Cy5.5 occurred in isolated clusters, frequently in the subendocardium. Myocardial T2* was significantly lower (7.6+/-1.5 versus 16.8+/-2.7 ms, P<0.05) in the mice injected with AnxCLIO-Cy5.5 versus CLIO-Cy5.5, consistent with the uptake of AnxCLIO-Cy5.5 by apoptotic CMs. A strong correlation (r(2)=0.86, P<0.05) was seen between in vivo T2* (AnxCLIO-Cy5.5 uptake) and myocardial caspase-3 activity. CONCLUSIONS The ability of molecular MRI to image sparsely expressed targets in the myocardium is demonstrated in this study. Moreover, a novel platform for high-resolution and specific imaging of CM apoptosis in heart failure is established. In addition to providing novel insights into the pathogenesis of CM apoptosis, the developed platform could facilitate the development of novel antiapoptotic therapies in heart failure.
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Affiliation(s)
- David E Sosnovik
- Center for Molecular Imaging Research, the Cardiology Division, and Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, Masss, USA.
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Abstract
Recent advances in molecular imaging have permitted the noninvasive imaging of apoptosis, a critical process underlying the pathogenesis of many diseases of the cardiovascular system including atherosclerotic vascular disease, myocardial ischemia and reperfusion injury, chronic heart failure, myocarditis, and cardiac allograft rejection. Multiple molecular targets including phosphatidylserine, phosphatidylinositol 3-kinase, and caspases have been targeted by a variety of imaging agents and modalities such as nuclear scintigraphy, PET, MRI, and fluorescent and bioluminescent imaging. Translationally, methods utilizing radiolabeled annexin V have proven promising in several clinical trials of ischemia-reperfusion injury and cardiac allograft rejection. New approaches using novel molecular imaging agents show great potential for the ability to image apoptosis in the research and clinical setting. Ultimately the ability to detect apoptosis noninvasively would help to identify patients for emerging anti-apoptotic therapies and guide clinical management with the aim of maximal myocardial preservation.
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Technetium 99m–Labeled Annexin V Scintigraphy of Platelet Activation in Vegetations of Experimental Endocarditis. Circulation 2008; 117:781-9. [DOI: 10.1161/circulationaha.107.718114] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
The pathophysiology of infective endocarditis involves a pathogen/host tissue interaction, leading to formation of infected thrombotic vegetations. Annexin V is a ligand of phosphatidylserines exposed by activated platelets and apoptotic cells. Because vegetations are platelet-fibrin clots in which platelet proaggregant activity is enhanced by bacterial colonization, we investigated the ability of annexin V labeled with technetium Tc 99m (
99m
Tc-ANX) to provide functional imaging of these vegetations in experimental models of infective endocarditis. This ability was assessed in rabbits and rats because of the different interest of these 2 species in preclinical analysis.
Methods and Results—
Nonbacterial thrombotic endocarditis was induced with the use of a catheter left indwelling through the aortic or tricuspid valve, and animals were injected with either a bacterial inoculum or saline. Scintigraphic investigations were performed 5 days later and showed a higher
99m
Tc-ANX uptake by vegetations in infected versus noninfected animals (ratio, 1.3 for in vivo acquisitions and 2 for autoradiography;
P
<0.0001 for all), whereas no significant uptake was present in controls. Right-sided endocarditis was associated with pulmonary uptake foci corresponding to emboli. Histological analysis of vegetations showed a specific uptake of
99m
Tc-ANX at the interface between circulating blood and vegetation. In parallel, underlying myocardial tissue showed myocyte apoptosis and mucoid degeneration, without extracellular matrix degradation at this stage.
Conclusions—
99m
Tc-ANX is suitable for functional imaging of platelet-fibrin vegetations in endocarditis, as well as embolic events.
99m
Tc-ANX uptake reflects mainly platelet activation in the luminal layer of vegetations. This uptake is enhanced by bacterial colonization.
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In vivo dynamic imaging of myocardial cell death using 99mTc-labeled C2A domain of synaptotagmin I in a rat model of ischemia and reperfusion. Nucl Med Biol 2007; 34:907-15. [PMID: 17998092 DOI: 10.1016/j.nucmedbio.2007.07.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 07/18/2007] [Accepted: 07/21/2007] [Indexed: 11/21/2022]
Abstract
OBJECTIVES This study was designed to investigate the capability of a small-animal SPECT imager, FastSPECT II, for dynamic rat heart imaging and to characterize the in vivo kinetic properties of 99mTc-C2A-glutathione-s-transferase (GST), a molecular probe targeting apoptosis and necrosis, in detecting cell death in ischemic-reperfused rat hearts. METHODS C2A-GST was radiolabeled with 99mTc via 2-iminothiolane thiolation. Myocardial ischemia-reperfusion was induced by 30-min ligation of the left coronary artery followed by 120-min reperfusion in seven rats. FastSPECT II cardiac images of 99mTc-C2A-GST in list-mode acquisition were recorded for 2 h using FastSPECT II. RESULTS Tomographic images showed a focal radioactive accumulation (hot spot) in the lateral and anterior walls of the left ventricle. The hot spot was initially visualized 10 min after injection and persisted on the 2-h images. Quantitative analysis demonstrated that the hot-spot radioactivity increased significantly within 30 min postinjection and experienced no washout up to the end of the 2-h study. The ratio of the hot spot/viable myocardium was 4.52+/-0.24, and infarct-to-lung ratio was 8.22+/-0.63 at 2 h postinjection. The uptake of 99mTc-C2A-GST in the infarcted myocardium was confirmed by triphenyl tetrazolium chloride staining and autoradiography analysis. CONCLUSIONS FastSPECT II allows quantitative dynamic imaging and functional determination of radiotracer kinetics in rat hearts. An in vivo kinetic profile of 99mTc-C2A-GST in the ischemic-reperfused rat heart model was characterized successfully. The pattern of accelerated 99mTc-C2A-GST uptake in the ischemic area at risk after reperfusion may be useful in detecting and quantifying ongoing myocardial cell loss induced by ischemia-reperfusion.
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Sarda-Mantel L, Hervatin F, Michel JB, Louedec L, Martet G, Rouzet F, Lebtahi R, Merlet P, Khaw BA, Le Guludec D. Myocardial uptake of 99mTc-annexin-V and 111In-antimyosin-antibodies after ischemia-reperfusion in rats. Eur J Nucl Med Mol Imaging 2007; 35:158-65. [PMID: 17805532 DOI: 10.1007/s00259-007-0559-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Accepted: 07/25/2007] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Phosphatidylserin exposure on cell surfaces occurs early during apoptosis and is detected in vivo by using (99m)Tc-annexin-V (ANX). Cardiomyocyte membrane disruption is detected in vivo by using (111)In-antimyosin-antibodies (AM). We aimed to determine if ANX and AM allow evaluation of the time-course of these two distinct cell death events after myocardial ischemia-reperfusion. METHODS Coronary tying (20 min) followed by reperfusion (IR) was performed in 31 rats. Twelve of the rats were injected with ANX, 11 with AM, and eight with both tracers. Myocardial uptake of tracers was studied 1-2 h, 4 h, or 24 h after IR by scintigraphy (ANX, n = 14) and autoradiography (all cases), and compared to histology and Apostain staining. RESULTS Scintigraphy was positive in all rats 2 h after IR and in three of five rats at 24 h. On autoradiography, ANX activity was intense in myocardial lesions as early as 1 h post-IR, whereas AM activity was mild at 2 h then increased at 4 h post-IR. ANX and AM uptakes evolved from mid-myocardium to endocardial and epicardial regions from 2 h to 24 h post-IR. Apostain staining was significant in myocardial lesions (p < 10(6) compared to six sham-operated rats). On histology, myocardial lesion was characterized by interstitial oedema, myocytes necrosis, and dramatic thinning at 24 h. CONCLUSION These data suggest that ANX and AM allow temporal and regional evaluations of PS exposure and membrane disruption, respectively, during myocytes death after 20-min myocardial ischemia followed by reperfusion. Also, (i) apoptosis starts very early in injured myocardium, (ii) myocyte necrosis occurs later (3-4 h post-reperfusion), and (iii) most dead cells are removed from mid-myocardium between 6 h and 24 h after reperfusion.
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Fang W, Wang F, Ji S, Zhu X, Meier HT, Hellman RS, Brindle KM, Davletov B, Zhao M. SPECT imaging of myocardial infarction using 99mTc-labeled C2A domain of synaptotagmin I in a porcine ischemia-reperfusion model. Nucl Med Biol 2007; 34:917-23. [PMID: 17998093 DOI: 10.1016/j.nucmedbio.2007.06.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2006] [Revised: 06/18/2007] [Accepted: 06/25/2007] [Indexed: 11/26/2022]
Abstract
INTRODUCTION The C2A domain of synaptotagmin I recognizes necrotic and apoptotic cells by binding to exposed anionic phospholipids. The goal is to explore the potential imaging utility of 99mTc-labeled C2A in the detection of acute cardiac cell death in a porcine model that resembles human cardiovascular physiology. METHODS Ischemia (20-25 min) was induced in pigs (M/F, 20-25 kg) using balloon angioplasty. 99mTc-C2A-GST (n=7) or 99mTc-BSA (n=2) was injected intravenously 1-2 h after reperfusion. Noninfarct animals were injected with 99mTc-C2A-GST (n=4). SPECT images were acquired at 3 and 6 h postinjection. Cardiac tissues were analyzed to confirm the presence of cell death. RESULTS Focal uptake was detected in five out of seven subjects at 3 h and in all infarct subjects at 6 h postinjection but not in infarct animals injected with 99mTc-BSA or in noninfarct animals with 99mTc-C2A-GST. Gamma counting of infarct versus normal myocardium yielded a 10.2+/-5.7-fold elevation in absolute radioactivity, with histologically confirmed infarction. CONCLUSIONS We present data on imaging myocardial cell death in the acute phase of infarction in pigs. C2A holds promise and warrants further development as an infarct-avid molecular probe.
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Affiliation(s)
- Wei Fang
- Department of Nuclear Medicine, Cardiovascular Institute and Fu Wai Hospital, Chinese Academy of Medical Sciences, Beijing 100037, China
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Abstract
New therapies aimed at molecular abnormalities are often more efficacious and less toxic than nontargeted therapies; however, with current technology, major treatment decisions are being made with inadequate data. This problem needs to be fixed by molecular imaging technology, enabling he noninvasive establishment of the presence of a molecular target, its spatial distribution and heterogeneity, and how this changes over time. This article discusses the status of molecular imaging in clinical trails today, and looks forward to what physicians would like it to become.
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Sarda-Mantel L, Coutard M, Rouzet F, Raguin O, Vrigneaud JM, Hervatin F, Martet G, Touat Z, Merlet P, Le Guludec D, Michel JB. 99m
Tc-Annexin-V Functional Imaging of Luminal Thrombus Activity in Abdominal Aortic Aneurysms. Arterioscler Thromb Vasc Biol 2006; 26:2153-9. [PMID: 16857952 DOI: 10.1161/01.atv.0000237605.25666.13] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
The mural thrombus of abdominal aortic aneurysms (AAA) is involved in aneurysm progression via several interdependent biological processes including platelet activation.
99m
Tc-annexin V (ANX) is a scintigraphic tracer that binds to phosphatidylserine exposed on activated platelets and apoptotic cells. Here, we evaluated the potential of ANX imaging to assess mural thrombus biological activity in an experimental AAA model. The clinical applicability was further tested ex vivo on human samples of excised AAA thrombi.
Methods and Results—
Experimental AAA was created by infusing elastase into infrarenal abdominal aorta in 17 rats, and 6 sham-operated rats were used as controls. Abdominal ANX scintigraphy was performed 2 weeks later followed by quantitative autoradiography and histological studies. Among the 13 rats which developed AAA, 11 displayed intense ANX uptake within AAA by scintigraphy. ANX uptake in the aneurysms on planar and single-photon emission computed tomography (SPECT) imaging was higher than that observed in infrarenal aorta of sham-operated controls (target/background ratio: 5.7±0.9 versus 1.33±0.21;
P
<0.005 for SPECT). Aneurysm-to-background activity ratios obtained by scintigraphy correlated with ANX activity in corresponding autoradiograms (
R
=0.69;
P
<0.02). This activity was located in the thrombus area where activated platelets and polymorphonuclear leukocytes accumulated. Similar patterns were also found in all of the 7 human AAA thrombi harvested during surgery.
Conclusions—
ANX imaging may assess mural thrombus renewal activity linked to permanent flowing blood interface.
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Affiliation(s)
- Laure Sarda-Mantel
- Service de Médecine Nucléaire, Hôpital Bichat, 46 rue Henri Huchard, 75018 Paris, France.
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Bengel FM. One life to live, but many ways to die—imaging of cardiomyocyte death. Eur J Nucl Med Mol Imaging 2005; 33:237-8. [PMID: 16283182 DOI: 10.1007/s00259-005-1911-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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