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Chen Y, Lim P, Rogers KA, Rutt BK, Ronald JA. In Vivo MRI of Amyloid Plaques in a Cholesterol-Fed Rabbit Model of Alzheimer’s Disease. J Alzheimers Dis 2018; 64:911-923. [DOI: 10.3233/jad-180207] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Yuanxin Chen
- Robarts Research Institute, Western University, London, ON, Canada
| | - Patrick Lim
- Robarts Research Institute, Western University, London, ON, Canada
| | - Kem A. Rogers
- Department of Anatomy and Cell Biology, Western University, London, ON, Canada
| | - Brian K. Rutt
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - John A. Ronald
- Robarts Research Institute, Western University, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
- Lawson Health Research Institute, London, ON, Canada
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Pham TA, Hua N, Phinikaridou A, Killiany R, Hamilton J. Early in vivo discrimination of vulnerable atherosclerotic plaques that disrupt: A serial MRI study. Atherosclerosis 2015; 244:101-7. [PMID: 26606442 DOI: 10.1016/j.atherosclerosis.2015.11.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/08/2015] [Accepted: 11/10/2015] [Indexed: 11/19/2022]
Abstract
BACKGROUND AND AIMS MRI has been validated as a suitable imaging modality for in vivo, non-invasive detection of atherosclerosis and has provided quantitative predictors of high-risk plaque. Here, we apply serial MRI to monitor the natural progression of plaques over a 3-month period in a rabbit model of atherothrombosis to determine differences over time between plaques that ultimately disrupt to form a luminal mural thrombus and plaques that remain stable. METHODS Atherosclerotic plaques were induced in 12 male New Zealand White (NZW) rabbits by aortic endothelial injury and a 1% cholesterol diet. The rabbits were imaged 5 times: at baseline, 1, 2, and 3 months, and 48hr after pharmacological triggering for plaque disruption. RESULTS Starting at 2 months, plaques that disrupted after triggering exhibited a higher remodeling ratio (RR, 1.05 ± 0.11 vs 0.97 ± 0.10, p = 0.0002) and a larger vessel wall area (VWA, 6.99 ± 1.54 mm(2) vs 6.30 ± 1.37 mm(2), p = 0.0072) than the stable non-disrupted plaques. The same trends were observed at 3 months: plaques that disrupted had a higher RR (1.04 ± 0.02 vs 0.99 ± 0.01, p = 0.0209), VWA (8.19 ± 2.69 mm(2) vs 6.81 ± 1.60 mm(2), p = 0.0001), and increased gadolinium uptake (75.51 ± 13.77% for disrupted vs 31.02 ± 6.45% for non-disrupted, p = 0.0022). CONCLUSIONS MR images of plaques that disrupted revealed larger VWAs, RRs, and increased gadolinium uptake at 2 months and continued progression of these vulnerable features between 2 and 3 months. Non-disrupted plaques had an independent history without these hallmarks of vulnerability. Our results show that MRI can provide early detection of plaques at a higher-risk for luminal thrombosis.
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Affiliation(s)
- Tuan A Pham
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Ning Hua
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA
| | - Alkystis Phinikaridou
- Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom
| | - Ronald Killiany
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, USA
| | - James Hamilton
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA; Department of Biomedical Engineering, Boston University, Boston, MA, USA.
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Rajendran R, Minqin R, Ronald JA, Rutt BK, Halliwell B, Watt F. Does iron inhibit calcification during atherosclerosis? Free Radic Biol Med 2012; 53:1675-9. [PMID: 22940067 PMCID: PMC4831625 DOI: 10.1016/j.freeradbiomed.2012.07.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 05/31/2012] [Accepted: 07/16/2012] [Indexed: 11/26/2022]
Abstract
Oxidative stress has been implicated in the etiology of atherosclerosis and even held responsible for plaque calcification. Transition metals such as iron aggravate oxidative stress. To understand the relation between calcium and iron in atherosclerotic lesions, a sensitive technique is required that is quantitatively accurate and avoids isolation of plaques or staining/fixing tissue, because these processes introduce contaminants and redistribute elements within the tissue. In this study, the three ion-beam techniques of scanning transmission ion microscopy, Rutherford backscattering spectrometry, and particle-induced X-ray emission have been combined in conjunction with a high-energy (MeV) proton microprobe to map the spatial distribution of the elements and quantify them simultaneously in atherosclerotic rabbit arteries. The results show that iron and calcium within the atherosclerotic lesions exhibit a highly significant spatial inverse correlation. It may be that iron accelerates the progression of atherosclerotic lesion development, but suppresses calcification. Alternatively, calcification could be a defense mechanism against atherosclerotic progression by excluding iron.
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Affiliation(s)
- Reshmi Rajendran
- Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore 117542
| | - Ren Minqin
- Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore 117542
| | | | | | - Barry Halliwell
- Department of Biochemistry, National University of Singapore, Singapore 117542
| | - Frank Watt
- Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore 117542
- Corresponding author. (F.Watt)
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Ander BP, Edel AL, McCullough R, Rodriguez-Leyva D, Rampersad P, Gilchrist JSC, Lukas A, Pierce GN. Distribution of omega-3 fatty acids in tissues of rabbits fed a flaxseed-supplemented diet. Metabolism 2010; 59:620-7. [PMID: 19913851 DOI: 10.1016/j.metabol.2009.09.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 09/03/2009] [Accepted: 09/04/2009] [Indexed: 01/07/2023]
Abstract
Diets rich in omega-3 polyunsaturated fatty acids are associated with decreased incidences of cardiovascular disease. The extent of incorporation and distribution of these beneficial fats into body tissues is uncertain. Rabbits were fed regular rabbit chow or a diet containing 10% ground flaxseed that is highly enriched with the omega-3 polyunsaturated fatty acid alpha-linolenic acid (ALA). The high-flaxseed diet resulted in an incorporation of ALA in all tissues, but mostly in the heart and liver with little in the brain. Docosahexaenoic and eicosapentaenoic acid levels were also selectively increased in some tissues, and the effects were not as large as ALA. Arachidonic acid and the ratio of omega-6/omega-3 fatty acids were decreased in all tissues obtained from the flax-supplemented group. Consumption of dietary flaxseed appears to be an effective means to increase ALA content in body tissues, but the degree will depend upon the tissues examined.
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Affiliation(s)
- Bradley P Ander
- Department of Physiology, Faculty of Medicine, Canadian Centre for Agri-Food Research in Health and Medicine and Institute of Cardiovascular Sciences, St Boniface General Hospital Research Centre, University of Manitoba, Winnipeg, Canada
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Fitzgerald TN, Muto A, Fancher TT, Brown PB, Martin KA, Muhs BE, Rothman DL, Constable RT, Sampath S, Dardik A. Surgically implantable magnetic resonance angiography coils improve resolution to allow visualization of blood flow dynamics. Ann Vasc Surg 2009; 24:242-53. [PMID: 20036497 DOI: 10.1016/j.avsg.2009.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2009] [Revised: 08/28/2009] [Accepted: 10/23/2009] [Indexed: 10/20/2022]
Abstract
BACKGROUND Magnetic resonance angiography (MRA) is clinically useful but of limited applicability to small animal models due to poor signal resolution, with typical voxel sizes of 1 mm(3) that are insufficient to analyze vessels of diameter <1 mm. We determined whether surgically implantable, extravascular MRA coils increase signal resolution adequately to examine blood flow dynamics METHODS A custom MRA coil was surgically implanted near the carotid artery of a New Zealand White rabbit. A stenosis was created in the carotid artery to induce complicated, non-laminar flow. Phase contrast images were obtained on multiple axial planes with 3T MRA and through-plane velocity profiles were calculated under laminar and complicated flow conditions. These velocity profiles were fit to a laminar flow model using ordinary least squares in order to quantify the degree of flow complication (Matlab). Flow was also measured with a Doppler flow probe; vessel diameters and flow velocities were compared with duplex ultrasound RESULTS Carotid artery blood flow was 24.7 +/- 2.6 ml/min prior to stenosis creation and reduced to 12.0 +/- 1.7 ml/min following injury (n=3). An MRA voxel size of 0.1 x 0.1 x 5 mm was achieved. The control carotid artery diameter was 1.9 +/- 0.1 mm, and cross-sectional images containing 318 +/- 22 voxels were acquired (n=26). Velocity profiles resembled laminar flow proximal to the stenosis, and then became more complicated just proximal and distal to the stenosis. Laminar flow conditions returned downstream of the stenosis CONCLUSION Implantable, extra-vascular coils enable small MRA voxel sizes to reproducibly calculate complex velocity profiles under both laminar and complicated flow in a small animal model. This technique may be applied to study blood flow dynamics of vessel remodeling and atherogenesis.
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Affiliation(s)
- Tamara N Fitzgerald
- Department of Surgery, Yale University School of Medicine, New Haven, CT, USA
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Ronald JA, Chen JW, Chen Y, Hamilton AM, Rodriguez E, Reynolds F, Hegele RA, Rogers KA, Querol M, Bogdanov A, Weissleder R, Rutt BK. Enzyme-sensitive magnetic resonance imaging targeting myeloperoxidase identifies active inflammation in experimental rabbit atherosclerotic plaques. Circulation 2009; 120:592-9. [PMID: 19652086 DOI: 10.1161/circulationaha.108.813998] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Inflammation undermines the stability of atherosclerotic plaques, rendering them susceptible to acute rupture, the cataclysmic event that underlies clinical expression of this disease. Myeloperoxidase is a central inflammatory enzyme secreted by activated macrophages and is involved in multiple stages of plaque destabilization and patient outcome. We report here that a unique functional in vivo magnetic resonance agent can visualize myeloperoxidase activity in atherosclerotic plaques in a rabbit model. METHODS AND RESULTS We performed magnetic resonance imaging of the thoracic aorta of New Zealand White rabbits fed a cholesterol (n=14) or normal (n=4) diet up to 2 hours after injection of the myeloperoxidase sensor bis-5HT-DTPA(Gd) [MPO(Gd)], the conventional agent DTPA(Gd), or an MPO(Gd) analog, bis-tyr-DTPA(Gd), as controls. Delayed MPO(Gd) images (2 hours after injection) showed focal areas of increased contrast (>2-fold) in diseased wall but not in normal wall (P=0.84) compared with both DTPA(Gd) (n=11; P<0.001) and bis-tyr-DTPA(Gd) (n=3; P<0.05). Biochemical assays confirmed that diseased wall possessed 3-fold elevated myeloperoxidase activity compared with normal wall (P<0.01). Areas detected by MPO(Gd) imaging colocalized and correlated with myeloperoxidase-rich areas infiltrated by macrophages on histopathological evaluations (r=0.91, P<0.0001). Although macrophages were the main source of myeloperoxidase, not all macrophages secreted myeloperoxidase, which suggests that distinct subpopulations contribute differently to atherogenesis and supports our functional approach. CONCLUSIONS The present study represents a unique approach in the detection of inflammation in atherosclerotic plaques by examining macrophage function and the activity of an effector enzyme to noninvasively provide both anatomic and functional information in vivo.
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Affiliation(s)
- John A Ronald
- Robarts Research Institute, London, Ontario, Canada.
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Rajendran R, Ronald JA, Ye T, Minqin R, Chen JW, Weissleder R, Rutt BK, Halliwell B, Watt F. Nuclear microscopy: a novel technique for quantitative imaging of gadolinium distribution within tissue sections. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2009; 15:338-344. [PMID: 19575834 PMCID: PMC2802450 DOI: 10.1017/s1431927609090813] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
All clinically-approved and many novel gadolinium (Gd)-based contrast agents used to enhance signal intensity in magnetic resonance imaging (MRI) are optically silent. To verify MRI results, a "gold standard" that can map and quantify Gd down to the parts per million (ppm) levels is required. Nuclear microscopy is a relatively new technique that has this capability and is composed of a combination of three ion beam techniques: scanning transmission ion microscopy, Rutherford backscattering spectrometry, and particle induced X-ray emission used in conjunction with a high energy proton microprobe. In this proof-of-concept study, we show that in diseased aortic vessel walls obtained at 2 and 4 h after intravenous injection of the myeloperoxidase-sensitive MRI agent, bis-5-hydroxytryptamide-diethylenetriamine-pentaacetate gadolinium, there was a time-dependant Gd clearance (2 h = 18.86 ppm, 4 h = 8.65 ppm). As expected, the control animal, injected with the clinically-approved conventional agent diethylenetriamine-pentaacetate gadolinium and sacrificed 1 week after injection, revealed no significant residual Gd in the tissue. Similar to known in vivo Gd pharmacokinetics, we found that Gd concentration dropped by a factor of 2 in vessel wall tissue in 1.64 h. Further high-resolution studies revealed that Gd was relatively uniformly distributed, consistent with random agent diffusion. We conclude that nuclear microscopy is potentially very useful for validation studies involving Gd-based magnetic resonance contrast agents.
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Affiliation(s)
- Reshmi Rajendran
- Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore.
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Ronald JA, Chen Y, Belisle AJL, Hamilton AM, Rogers KA, Hegele RA, Misselwitz B, Rutt BK. Comparison of gadofluorine-M and Gd-DTPA for noninvasive staging of atherosclerotic plaque stability using MRI. Circ Cardiovasc Imaging 2009; 2:226-34. [PMID: 19808597 DOI: 10.1161/circimaging.108.826826] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND Inflammation and neovascularization play critical roles in the stability of atherosclerotic plaques. Whole-body quantitative assessment of these plaque features may improve patient risk-stratification for life-threatening thromboembolic events and direct appropriate intervention. In this report, we determined the utility of the MR contrast agent gadofluorine-M (GdF) for staging plaque stability and compared this to the conventional agent Gd-DTPA. METHODS AND RESULTS Five control and 7 atherosclerotic rabbits were sequentially imaged after administration of Gd-DTPA (0.2 mmol/kg) and GdF (0.1 mmol/kg) using a T(1)-weighted pulse sequence on a 3-T MRI scanner. Diseased aortic wall could be distinguished from normal wall based on wall-to-muscle contrast-to-noise values after GdF administration. RAM-11 (macrophages) and CD-31 (endothelial cells) immunostaining of MR-matched histological sections revealed that GdF accumulation was related to the degree of inflammation at the surface of plaques and the extent of core neovascularization. Importantly, an MR measure of GdF accumulation at both 1 and 24 hours after injection but not Gd-DTPA at peak enhancement was shown to correlate with a quantitative histological morphology index related to these 2 plaque features. CONCLUSIONS GdF-enhanced MRI of atherosclerotic plaques allows noninvasive quantitative information about plaque composition to be acquired at multiple time points after injection (within 1 and up to 24 hours after injection). This dramatically widens the imaging window for assessing plaque stability that is currently attainable with clinically approved MR agents, therefore opening the possibility of whole-body (including coronary) detection of unstable plaques in the future and potentially improved mitigation of cataclysmic cardiovascular events.
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Affiliation(s)
- John A Ronald
- Robarts Research Institute, Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.
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Ronald JA, Chen Y, Bernas L, Kitzler HH, Rogers KA, Hegele RA, Rutt BK. Clinical field-strength MRI of amyloid plaques induced by low-level cholesterol feeding in rabbits. ACTA ACUST UNITED AC 2009; 132:1346-54. [PMID: 19293239 PMCID: PMC2677794 DOI: 10.1093/brain/awp031] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Two significant barriers have limited the development of effective treatment of Alzheimer's disease. First, for many cases the aetiology is unknown and likely multi-factorial. Among these factors, hypercholesterolemia is a known risk predictor and has been linked to the formation of β-amyloid plaques, a pathological hallmark this disease. Second, standardized diagnostic tools are unable to definitively diagnose this disease prior to death; hence new diagnostic tools are urgently needed. Magnetic resonance imaging (MRI) using high field-strength scanners has shown promise for direct visualization of β-amyloid plaques, allowing in vivo longitudinal tracking of disease progression in mouse models. Here, we present a new rabbit model for studying the relationship between cholesterol and Alzheimer's disease development and new tools for direct visualization of β-amyloid plaques using clinical field-strength MRI. New Zealand white rabbits were fed either a low-level (0.125–0.25% w/w) cholesterol diet (n = 5) or normal chow (n = 4) for 27 months. High-resolution (66 × 66 × 100 µm3; scan time = 96 min) ex vivo MRI of brains was performed using a 3-Tesla (T) MR scanner interfaced with customized gradient and radiofrequency coils. β-Amyloid-42 immunostaining and Prussian blue iron staining were performed on brain sections and MR and histological images were manually registered. MRI revealed distinct signal voids throughout the brains of cholesterol-fed rabbits, whereas minimal voids were seen in control rabbit brains. These voids corresponded directly to small clusters of extracellular β-amyloid-positive plaques, which were consistently identified as iron-loaded (the presumed source of MR contrast). Plaques were typically located in the hippocampus, parahippocampal gyrus, striatum, hypothalamus and thalamus. Quantitative analysis of the number of histologically positive β-amyloid plaques (P < 0.0001) and MR-positive signal voids (P < 0.05) found in cholesterol-fed and control rabbit brains corroborated our qualitative observations. In conclusion, long-term, low-level cholesterol feeding was sufficient to promote the formation of extracellular β-amyloid plaque formation in rabbits, supporting the integral role of cholesterol in the aetiology of Alzheimer's disease. We also present the first evidence that MRI is capable of detecting iron-associated β-amyloid plaques in a rabbit model of Alzheimer's disease and have advanced the sensitivity of MRI for plaque detection to a new level, allowing clinical field-strength scanners to be employed. We believe extension of these technologies to an in vivo setting in rabbits is feasible and that our results support future work exploring the role of MRI as a leading imaging tool for this debilitating and life-threatening disease.
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Affiliation(s)
- John A Ronald
- Robarts Research Institute, University of Western Ontario, 100 Perth Drive, 1st Floor, London, ON, Canada N6A 5K8.
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