| 1. |
- Buehler, Alexandra, et al.
(författare)
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cNGR: A novel homing sequence for CD13/APN targeted molecular imaging of murine cardiac angiogenesis in vivo
- 2006
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - : American Heart Association. - 1079-5642 .- 1524-4636. ; 26:12, s. 2681-2687
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:Previously, the peptide sequence cNGR has been shown to home specifically to CD13/APN (aminopeptidase N) on tumor endothelium. Here, we investigated the feasibility of selective imaging of cardiac angiogenesis using the cNGR-CD13/APN system.METHODS AND RESULTS:CD13/APN induction and cNGR homing were studied in the murine myocardial infarction (MI) model. By real-time polymerase chain reaction (PCR) at 7 days after MI, CD13/APN expression was 10- to 20-fold higher in the angiogenic infarct border zone and the MI area than in non-MI areas. In vivo fluorescence microscopy confirmed specific homing of fluorophore-tagged cNGR to the border zone and MI territory at 4 and 7 days after MI with a local advantage of 2.3, but not at 1 or 14 days after MI. Tissue residence half-life was 9.1+/-0.3 hours, whereas the half-life in plasma was 15.4+/-3.4 minutes. Pulse chase experiments confirmed reversible binding of cNGR in the infarct area. Fluorescent labeled cNGR conjugates or antibodies were injected in vivo, and their distribution was studied ex vivo by 2-photon laser scanning microscopy (TPLSM). cNGR co-localized exclusively with CD13/APN and the endothelial marker CD31 on vessels.CONCLUSIONS:In cardiac angiogenesis endothelial CD13/APN is upregulated. It can be targeted specifically with cNGR conjugates. In the heart cNGR binds its endothelial target only in angiogenic areas.
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| 2. |
- Baklanov, D. V., et al.
(författare)
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Comparison of transendocardial and retrograde coronary venous intramyocardial catheter delivery systems in healthy and infarcted pigs
- 2006
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Ingår i: Catheterization and cardiovascular interventions. - : Wiley-Blackwell. - 1522-1946 .- 1522-726X. ; 68:3, s. 416-423
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Tidskriftsartikel (refereegranskat)abstract
- We compared two routes for myocardial delivery of therapeutics, transendocardial (TE) delivery with an intramyocardial injection catheter, and retrograde coronary venous (RCV) delivery with a balloon occlusion catheter in the interventricular vein. Methods: TE and RCV injection of 15 mu m, neutron-activatable microspheres was compared in healthy pigs (Group I, n = 3), pigs with a 1-week-old myocardial infarction (MI; group II, n = 5), and pigs with a 2-weeks-old MI (group III, n = 4). The MI was induced by a 1-hr balloon occlusion in the LAD. Both methods were compared in the same animal using different microspheres. The RCV catheter allowed for continuous measurement of distal pressure and 2.5 x 10(6) microspheres were injected in 10 ml at 300 mmHg above balloon occlusion pressure. The TE injections were targeted to the infarct zone and 2.5 x 10(6) microspheres were distributed over 10 injections of 200 mu l. Results: The retention of microspheres decreased with increase in MI age, but was comparable between devices within the groups. RCV delivery resulted in (14.3 +/- 0.9)% microsphere retention in Group I, (10.3 +/- 0.2)% in Group II, and (6.4 +/- 0.1)% in group III (P less than 0.05 versus group I). Microsphere retention after TE was (15.1 +/- 0.7)% in group I, (18.9 +/- 0.6)% in group II, (4.1 +/- 0.1)% in Group III (P less than 0.05 versus groups I and II). The RCV catheter delivered primarily to midventricular, antero-septal segments, whereas TE targeted apical areas predominantly. Conclusions: Delivery efficacy was comparable between devices in each group however RCV targeted midventricular areas whereas TE targeted apical areas.
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| 3. |
- Baklanov, Dmitri V., et al.
(författare)
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Live 3D echo guidance of catheter-based endomyocardial injection
- 2005
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Ingår i: Catheterization and cardiovascular interventions. - : Wiley-Blackwell. - 1522-1946 .- 1522-726X. ; 65:3, s. 340-345
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Tidskriftsartikel (refereegranskat)abstract
- Local delivery of therapeutic agents into the myocardium is limited by suboptimal imaging. We evaluated the feasibility and accuracy of live 313 echo to guide left ventricular endomyocardial injection. An intramyocardial injection catheter was positioned in the left ventricle in five healthy Yorkshire pigs using fluoroscopy. All other catheter manipulations were performed with live biplane and 3D echo guidance. In each animal, a total of 12 endomyocardial injections (volume, 50-100 mu l) of echo contrast mixed with blue tissue dye were performed. Four injections, 10 mm apart, were directed to three myocardial target zones: the anterior septum at the mitral valve level (zone 1); the posterolateral wall between the heads of the papillary muscles (zone 2); and the apex (zone 3). The injections were aimed to form a transverse line in zones 1 and 2 and an inverted triangular pyramid in zone 3. The animals were sacrificed, the hearts were inspected and the left ventricular endocardium was examined to create a map of injection marks. Success, defined as a visible injection of tissue dye, was 95%, and accuracy, defined as an injection into the target zone, was 83%. There was no significant difference in accuracy between the zones. Live 3D echo can successfully guide endomyocardial injections by accurately targeting specific myocardial zones, verifying catheter apposition and, when combined with echo contrast, providing real-time visualization of injectate deposition. (c) 2005 Wiley-Liss, Inc.
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| 4. |
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| 5. |
- de Muinck, Ebo D., et al.
(författare)
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Progress and prospects: Cell based regenerative therapy for cardiovascular disease
- 2006
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Ingår i: Gene Therapy. - : Nature Publishing Group. - 0969-7128 .- 1476-5462. ; 13:8, s. 659-671
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Forskningsöversikt (refereegranskat)abstract
- Experimental and clinical studies are progressing simultaneously to investigate the mechanisms and efficacy of progenitor cell treatment after an acute myocardial infarction and in chronic congestive heart failure. Multipotent progenitor cells appear to be capable of improving cardiac perfusion and/or function; however, the mechanisms still are unclear, and the issue of whether or not trans-differentiation occurs remains unsettled. Both experimentally and clinically, cells originating from different tissues have been shown capable of restoring cardiac function, but more recently multiple groups have identified resident cardiac progenitor cells that seem to participate in regenerating the heart after injury. Clinically, cells originating from blood or bone marrow have been proven to be safe whereas injection of skeletal myoblasts has been associated with the occurrence of ventricular arrhythmias. Myoblasts can transform into rapidly beating myotubes; however, thus far convincing evidence for electro-mechanical coupling between myoblasts and cardiomyocytes is lacking. Moving forward, mechanistic studies will benefit from the use of genetic markers and Cre/lox reporter systems that are less prone to misinterpretation than fluorescent antibodies, and a more convincing answer regarding therapeutic efficacy will come from adequately powered randomized placebo controlled trials.
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| 6. |
- De Muinck, Ebo D., et al.
(författare)
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Protection against myocardial ischemia-reperfusion injury by the angiogenic masterswitch protein PR 39 gene therapy : the roles of HIF1 alpha stabilization and FGFR1 signaling
- 2007
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Ingår i: Antioxidants and Redox Signaling. - : Mary Ann Liebert. - 1523-0864 .- 1557-7716. ; 9:4, s. 437-445
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Tidskriftsartikel (refereegranskat)abstract
- PR-39, a proline-arginine-rich angiogenic response peptide, has been implicated in myocardial ischemic reperfusion injury. The present study examined the cardioprotective abilities of PR39 gene therapy. Male C5713146 mice were randomized to intramyocardial injecton of 10(9) p.f.u. adenovirus encoding PR39 (PR39), FGFR1 dominant negative signaling construct (FGFR1-dn), empty vector (EV), or PR39 adenovirus plus 4 mu g of plasmid endcoding a HIF1 alpha dominant negative construct (PR39 + HIF1 alpha-dn). Seven days later, hearts were subjected to 20 min of ischemia (1) and 2 h. reperfusion (R) ex vivo and aortic and coronary flow, left ventricular developed pressure (LVDP), and LVdp/dt were measured. Myocardial infarct (MI) size and cardiomyocyte apoptosis were measured by TTC staining and TUNEL, respectively. PR39 expression was robust up to 14 days after gene transfer and was absent after EV and FGFR1-dn. Hemodynamics showed no differences at baseline, and heart rate remained unchanged in all groups throughout the experiment. After I-R, hemodynamics remained unchanged in PR39 hearts, but deteriorated significantly in the other groups, except for aortic flow, which remained significantly higher in FGFR1-dn than in EV and PR39 + HIF1 alpha-dn (p less than 0.05), although it was lower than in PR39 (p less than 0.05). MI was 8.7 +/- 0.9 % in PR39, 23.8 +/- 1.1 % in FGFR1-dn, 29.9 +/- 2.2% in EV, and 30.8 +/- 2.7 % in PR39 + HIF1 alpha-dn (PR39 vs. other groups: p less than 0.05; FGFR1-dn vs. EV and PR39 + HIF1 alpha-dn: p less than 0.05). In PR39, HIF-1 alpha protein was higher than in FGFR1-dn and EV. Importantly, cotransfection of HlF1 alpha-dn with PR39 completely abolished cardioprotection by PR39. Cardioprotection by PR39 is likely conveyed by protective metabolic and survival responses through HIF1-alpha stabilization and not by angiogenesis, because baseline coronary How was the same in all groups. Abrogation of FGFR1 signaling conveyed an intermediate degree of cardioprotection.
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| 7. |
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| 8. |
- de Muinck, Ebo
(författare)
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Gene and Cell Therapy for Heart Failure
- 2009
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Ingår i: Antioxidants and Redox Signaling. - : Mary Ann Liebert Inc. - 1523-0864 .- 1557-7716. ; 11, s. 2025-2042
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Tidskriftsartikel (refereegranskat)abstract
- Cardiac gene and cell therapy have both entered clinical trials aimed at ameliorating ventricular dysfunction in patients with chronic congestive heart failure. The transduction of myocardial cells with viral constructs encoding a specific cardiomyocyte Ca2+ pump in the sarcoplasmic reticulum (SR), SRCa2+-ATPase has been shown to correct deficient Ca2+ handling in cardiomyocytes and improvements in contractility in preclinical studies, thus leading to the first clinical trial of gene therapy for heart failure. In cell therapy, it is not clear whether beneficial effects are cell-type specific and how improvements in contractility are brought about. Despite these uncertainties, a number of clinical trials are under way, supported by safety and efficacy data from trials of cell therapy in the setting of myocardial infarction. Safety concerns for gene therapy center on inflammatory and immune responses triggered by viral constructs, and for cell therapy with myoblast cells, the major concern is increased incidence of ventricular arrhythmia after cell transplantation. Principles and mechanisms of action of gene and cell therapy for heart failure are discussed, together with the potential influence of reactive oxygen species on the efficacy of these treatments and the status of myocardial-delivery techniques for viral constructs and cells.
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| 9. |
- Dilip Deb, Kaushik, et al.
(författare)
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Nanotechnology in stem cells research: advances and applications
- 2012
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Ingår i: Frontiers in Bioscience. - : Frontiers in Bioscience. - 1093-9946 .- 1093-4715. ; 17, s. 1747-1760
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Tidskriftsartikel (refereegranskat)abstract
- Human beings suffer from a myriad of disorders caused by biochemical or biophysical alteration of physiological systems leading to organ failure. For a number of these conditions, stem cells and their enormous reparative potential may be the last hope for restoring function to these failing organ or tissue systems. To harness the potential of stem cells for biotherapeutic applications, we need to work at the size scale of molecules and processes that govern stem cells fate. Nanotechnology provides us with such capacity. Therefore, effective amalgamation of nanotechnology and stem cells - medical nanoscience or nanomedicine - offers immense benefits to the human race. The aim of this paper is to discuss the role and importance of nanotechnology in stem cell research by focusing on several important areas such as stem cell visualization and imaging, genetic modifications and reprogramming by gene delivery systems, creating stem cell niche, and similar therapeutic applications.
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| 10. |
- Dobrucki, Lawrence W, et al.
(författare)
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Approaches to Multimodality Imaging of Angiogenesis
- 2010
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Ingår i: Journal of Nuclear Medicine. - : The Society of Nuclear Medicine Inc. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 51, s. 66S-79S
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Tidskriftsartikel (refereegranskat)abstract
- Angiogenesis, defined as the formation of new capillaries by cellular outgrowth from existing microvessels, can be assessed by the evaluation of perfusion, function, and metabolism. However, more recently, novel, noninvasive imaging strategies for the evaluation of molecular events associated with the angiogenic process have been developed.
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| 11. |
- Gelmi, Amy, et al.
(författare)
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Direct Mechanical Stimulation of Stem Cells: A Beating Electromechanically Active Scaffold for Cardiac Tissue Engineering
- 2016
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Ingår i: Advanced Healthcare Materials. - : Wiley-Blackwell Publishing Inc.. - 2192-2640 .- 2192-2659. ; 5:12, s. 1471-1480
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Tidskriftsartikel (refereegranskat)abstract
- The combination of stem cell therapy with a supportive scaffold is a promising approach to improving cardiac tissue engineering. Stem cell therapy can be used to repair nonfunctioning heart tissue and achieve myocardial regeneration, and scaffold materials can be utilized in order to successfully deliver and support stem cells in vivo. Current research describes passive scaffold materials; here an electroactive scaffold that provides electrical, mechanical, and topographical cues to induced human pluripotent stem cells (iPS) is presented. The poly(lactic-co-glycolic acid) fiber scaffold coated with conductive polymer polypyrrole (PPy) is capable of delivering direct electrical and mechanical stimulation to the iPS. The electroactive scaffolds demonstrate no cytotoxic effects on the iPS as well as an increased expression of cardiac markers for both stimulated and unstimulated protocols. This study demonstrates the first application of PPy as a supportive electroactive material for iPS and the first development of a fiber scaffold capable of dynamic mechanical actuation.
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| 12. |
- Good, Elin, et al.
(författare)
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18Fluorodeoxyglucose uptake in relation to fat fraction and R2*in atherosclerotic plaques, using PET/MRI : a pilot study
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Inflammation inside Atherosclerotic plaques represents a major pathophysiological process driving plaques towards rupture. Pre-clinical studies suggest a relationship between lipid rich necrotic core, intraplaque hemorrhage and inflammation, not previously explored in patients. Therefore, we designed a pilot study to investigate the feasibility of assessing the relationship between these plaque features in a quantitative manner using PET/MRI. In 12 patients with high-grade carotid stenosis the extent of lipid rich necrotic core and intraplaque hemorrhage was quantified from fat and R2* maps acquired with a previously validated 4-point Dixon MRI sequence in a stand-alone MRI. PET/MRI was used to measure 18F-FDG uptake. T1-weighted images from both scanners were used for registration of the quantitative Dixon data with the PET images. The plaques were heterogenous with respect to their volumes and composition. The mean values for the group were as follows: fat fraction (FF) 0.17% (± 0.07), R2* 47.6 s−1 (± 10.9) and target-to-blood pool ratio (TBR) 1.49 (± 0.48). At group level the correlation between TBR and FFmean was − 0.406, p 0.19 and for TBR and R2*mean 0.259, p 0.42. The lack of correlation persisted when analysed on a patient-by-patient basis but the study was not powered to draw definitive conclusions. We show the feasibility of analysing the quantitative relationship between lipid rich necrotic cores, intraplaque haemorrhage and plaque inflammation. The 18F-FDG uptake for most patients was low. This may reflect the biological complexity of the plaques and technical aspects inherent to 18F-FDG measurements.
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| 13. |
- Good, Elin, 1983-, et al.
(författare)
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Changes in natural killer and T lymphocyte phenotypes in response to cardiovascular risk management
- 2023
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- The pro-inflammatory and regulatory roles of T lymphocytes in atherosclerosis are well established but less is known about natural killer (NK) cells and natural killer T (NKT)-like cells. The effects of cardiovascular risk management on the phenotypes of these cells are unknown. To assess changes in NK cell and lymphocyte phenotypes and circulating inflammatory proteins in response to cardiovascular risk management in patients with carotid atherosclerosis. Fifty patients were included in a prospective clinical study. Measurements were at baseline and after 12 months of cardiovascular risk management. Circulating NK, NKT-like and T lymphocyte subpopulations were phenotyped by multi-colour flow cytometry. Proximity extension assay was performed for 176 plasma proteins associated with inflammation and cardiovascular disease. At 12 months there were significant reductions in LDL (P=0.001) and blood pressure (P=0.028). NK cells responded with a reduction in pro-inflammatory (NKG2C(+)) cells (P=0.0003), an increase in anti-inflammatory (NKG2A(+)) cells (P=0.032), and a reduction in terminally differentiated (CD57(+)) NK cells. NKT-like cells showed a similar decrease in terminally differentiated subpopulations (P=0.000002). Subpopulations of T helper cells exhibited a significant reduction in central memory (P=1.09x10(-8)) and a significant increase in CD4(+) naive- (P=0.0008) and effector memory T cells (P=0.006). The protein analysis indicated that cardiovascular risk management affects proteins involved in the inflammatory NF-kappa B pathway. The consistent decrease in senescent phenotypes of NK, NKT-like and CD4(+) cells with a concomitant increase in more naive, phenotypes suggests a change towards a less pro-inflammatory lymphocyte profile in response to cardiovascular risk management.Trial registry name: CARotid MRI of Atherosclerosis (CARMA). ClinicalTrials.gov identifier NCT04835571 (08/04/2021). https://www.clinicaltrials.gov/study/NCT04835571.
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| 14. |
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| 15. |
- Good, Elin, et al.
(författare)
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High-grade carotid artery stenosis : A forgotten area in cardiovascular risk management
- 2016
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Ingår i: European Journal of Preventive Cardiology. - : Oxford University Press (OUP). - 2047-4873 .- 2047-4881. ; 23:13, s. 1453-1460
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Tidskriftsartikel (refereegranskat)abstract
- Background Patients with high-grade (≥70%) carotid artery stenosis (CAS) rank in the highest risk category for future cardiovascular (CV) events, but the quality of cardiovascular risk management in this patient group is unknown. Design Cross-sectional retrospective study. Methods Data were collected for all patients diagnosed with high-grade CAS in Östergötland county, Sweden between 1 January 2009 and 31 July 2012 regarding the quality of cardiovascular risk management, co-morbidity and outcomes during the 2-year follow-up period after a diagnosis of CAS with a carotid ultrasound scan. Patients were included regardless of whether they underwent carotid endarterectomy (CEA). Results A total of 393 patients with CAS were included in the study; 133 (33.8%) underwent CEA and 260 (66.2%) were assigned to a conservative management (CM) group. In both groups of patients the prescription of platelet inhibitors, statins and antihypertensive drugs increased significantly (p < 0.001) after diagnosis. However treatment targets were not met in the majority of patients and the low-density lipoprotein level was on target in only 13.5% of patients. During follow-up, low-density lipoprotein levels were not measured in 19.8% of patients who underwent CEA and 44.2% of patients in the CM group (p < 0.001); HbA1c was not measured in 24.4% of patients with diabetes in the CEA group and in 18.8% of patients in the CM group (p = 0.560). There was no documentation of counselling on diet, exercise, smoking cessation or adherence to medication. The combined clinical event rate (all-cause mortality, cardiovascular mortality and non-fatal cardiovascular events) was high in both groups (CEA 36.8% and CM 36.9%; p = 1.00) with no difference in the occurrence of ipsilateral ischaemic stroke. Conclusions The clinical event rate was high in patients with high-grade CAS and the management of cardiovascular risk was deficient in all aspects.
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| 16. |
- Good, Elin, 1983-
(författare)
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Interrogating Atherosclerotic Plaque Biology Through Responses to Cardiovascular Risk Management and Imaging
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atherosclerosis causes more deaths than any other disease worldwide, and the cause of death is most commonly a rupture of a vulnerable atherosclerotic plaque, resulting in a thrombotic event in the heart or brain. The major risk factors for plaque progression are well known, but all the mechanisms that drive atherosclerotic plaques towards catastrophic events are not yet fully elucidated. This thesis revolves around the atherosclerotic plaque; how plaques can be analysed using cardiovascular magnetic resonance imaging and the study of biological responses to cardiovascular risk management. In Study I we interrogated the quality of cardiovascular risk management in patients diagnosed with high-grade carotid stenosis and found that cardiovascular risk management was deficient in all aspects, despite the very high risk for events in these patients. Thus, we designed the next two studies to address the unmet clinical need for improved cardiovascular risk management in patients with carotid atherosclerosis while at the same time asking mechanistic questions about the effect of this approach on lymphocyte phenotypes (Study II) and on plaque composition (Study III). In Study II, the effect of cardiovascular risk management on Natural Killer cell, Natural Killer T cell and T lymphocyte subpopulations were studied in patients with carotid atherosclerosis. Our results show a polarisation away from a senescent phenotype towards more naïve i.e., juvenile cell types suggesting a transition towards a possibly less pro-inflammatory lymphocyte profile. In Study III, we applied a newly developed quantitative Dixon MRI technique to the quantification of lipid rich necrotic core and hemorrhage inside atherosclerotic plaques. Employing this technique, we explored the relationships between these high-risk plaque compositional features and circulating lipoproteins as they changed over time in response to cardiovascular risk management. In the current study there was no evidence for such a linear relationship. To further study the associations between inflammation and quantitative plaque measurements we explored in Study IV the relationship between inflammation in atherosclerotic plaques as measured by 18F-FDG uptake and features of high-risk plaque as measured by quantitative Dixon MRI. To facilitate the use of carotid MRI in larger cohorts we developed in Study V a technique for the segmentation of the carotid artery using supervised machine learning. Taken together these studies describe the importance of cardiovascular risk management, the complexity of atherosclerotic plaque biology and they propose new strategies for quantitative plaque imaging.
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| 17. |
- Good, Elin, 1983-, et al.
(författare)
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Quantitative Magnetic Resonance Imaging Assessment of the Relationships Between Fat Fraction and R2*Inside Carotid Plaques, and Circulating Lipoproteins
- 2022
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 55:4, s. 1260-1270
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Tidskriftsartikel (refereegranskat)abstract
- Background Lipid-rich necrotic core (LRNC) and intraplaque hemorrhage (IPH) are morphological features of high-risk atherosclerotic plaques. However, their relationship to circulating lipoproteins is unclear. Purpose To study associations between changes in lipoproteins vs. changes in LRNC (represented by fat fraction [FF]) and IPH (represented by R2*). Study Type Prospective. Subjects Fifty-two patients with carotid plaques, 33 males (63.5%), mean age 72 (+/- 5). Field Strength/Sequence Four-point fast gradient Dixon magnetic resonance imaging (MRI) was used to quantify FF and R2* (to measure IPH) inside plaques and in vessel wall. Turbo-spin echo was used for T-1 weighted sequences to guide manual segmentation. Assessment Carotid MRI and serum lipid levels were assessed at baseline and at 1-year follow-up. For patients, lipid-lowering therapy was customized to reduce low-density lipoprotein (LDL) levels below 1.8 mmol/L. Segmentation was performed with one set of regions of interest for the plaque and one for the vessel wall at the location of the plaque. Thereby MRI data for FF, R2*, and volumes in plaque- and vessel-wall segmentations could be obtained from baseline and follow-up, as well as changes over the study year. Statistical Tests Pearson correlation coefficient for correlations. Paired samples t-test for changes over time. Significance at P < 0.05, 95% confidence interval. Results LDL decreased significantly (2.19-1.88 mmol/L, Z - 2.9), without correlation to changes in plaque composition, nor to the significant reduction in vessel-wall volume (-106.3 mm(3)). Plaque composition remained unchanged, FF +8.5% (P = 0.366) and R2* +3.5% (P = 0.304). Compared to plaque segmentations, R2* was significantly lower in the vessel-wall segmentations both at baseline (-9.3%) and at follow-up (-9.1%). Data Conclusion The absence of correlations between changes in lipoproteins and changes in plaque composition indicates more complex relationships between these parameters than previously anticipated. The significant differences in both R2* and volume dynamics comparing plaque segmentations and vessel-wall segmentations suggest differences in their pathobiology of atherosclerosis. Level of Evidence 1 Technical Efficacy Stage 4
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| 18. |
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| 19. |
- Gustafsson, Håkan, et al.
(författare)
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Visualization of oxidative stress in ex vivo biopsies using electron paramagnetic resonance imaging
- 2015
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Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 73:4, s. 1682-1691
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The purpose of this study was to develop an X-Band electron paramagnetic resonance imaging protocol for visualization of oxidative stress in biopsies.METHODS: The developed electron paramagnetic resonance imaging protocol was based on spin trapping with the cyclic hydroxylamine spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine and X-Band EPR imaging. Computer software was developed for deconvolution and back-projection of the EPR image. A phantom containing radicals of known spatial characteristic was used for evaluation of the developed protocol. As a demonstration of the technique electron paramagnetic resonance imaging of oxidative stress was performed in six sections of atherosclerotic plaques. Histopathological analyses were performed on adjoining sections.RESULTS: The developed computer software for deconvolution and back-projection of the EPR images could accurately reproduce the shape of a phantom of known spatial distribution of radicals. The developed protocol could successfully be used to image oxidative stress in six sections of the three ex vivo atherosclerotic plaques.CONCLUSIONS: We have shown that oxidative stress can be imaged using a combination of spin trapping with the cyclic hydroxylamine spin probe cyclic hydroxylamine spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine and X-Band EPR imaging. A thorough and systematic evaluation on different types of biopsies must be performed in the future to validate the proposed technique. Magn Reson Med, 2014.
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| 20. |
- Koppal, Sandeep, et al.
(författare)
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Optimal validering av MR-bildtagning av aterosklerotiska plack genom användning av multi-modal MR och 3D histologi
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- BAKGRUND: Magnetkamera (MR) kan identifiera aterosklerotiska plack som löper risk att brista och därmed orsaka stroke eller hjärtinfarkt. Metoden är dock bristfälligt validerad på grund av den osäkerhet som uppstår då 2D histologiska snitt ska registreras med 3D MR-bilder.SYFTE: Att optimera validering av MR-bildtagning av aterosklerotiska plack genom användning av multi-modal MR och 3D histologi.MATERIAL och METOD: Patienter som skulle opereras för att avlägsna aterosklerotiska plack från arteria karotis genomgick dedikerad plack-MR där följande parametrar undersöktes: plackets fettinnehåll, blödning inuti placket och maximal intensitet av turbulent blodflöde. Undersökningarna gjordes med en Philips 3T MR-kamera: (a) 4-punkt Dixon 3D gradient-eko, (b) T1-viktad spin-eko, (c) 4D fas-kontrast. Upplösningen var 0.6x0.6x0.7mm, 0.35x0.35x3mm respektive 1.14x1.25x1.14mm x 25ms. Vatten-, fett- and R2*-bilder (blödning) beräknades utifrån Dixon-sekvensen.Efter operation bäddades placken in i paraffin och enface-bilder togs varje 50µm i Z-riktning. Bilderna registrerades i ImageJ/Fiji och användes för att bygga en 3D-volym av placket. Vid varje 200µm togs snitt för biologiska markörer och histologiska färgningar. De färgade snitten registrerades med motsvarande enface-bilder. Detta resulterade i 3D-volymer med en upplösning på 1.02x1.02x200µm. Den histologiska 3D-volymen registrerades manuellt med uppsamplade och co-registrerade MR-bilder.RESULTAT: T1-viktade bilder var bäst för registrering av plack inom varje snitt. Registrering av kärlets lumen optimerades genom en kombination av 4D fas-kontrast, det första Dixon-ekot och vatten-bilder. Registrering av fett och R2* från MR-bilder med fett och blödning från 3D histologi uppvisade god överensstämmelse.SLUTSATS: Optimal validering av MR-bilder av aterosklerotiska plack kan åstadkommas genom att kombinera olika anatomiska landmärken från multimodala MR-bilder av plack och 3D-histologi. Genom att använda 3D-histologi korrigerar man för registreringsproblem som är relaterade till ”out-of-plane” vinklingar av vävnadssnitt och krympning och deformering till följd av histologiskt bearbetning av placket. Den detaljerade biologiska informationen från 3D-histologi kan förväntas förstärka fynden från in vivo MR-bilder.
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| 21. |
- Koppal, Sandeep, et al.
(författare)
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Quantitative fat and R2* mapping in vivo to measure lipid-rich necrotic core and intraplaque hemorrhage in carotid atherosclerosis
- 2017
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Ingår i: Magnetic Resonance in Medicine. - : John Wiley & Sons. - 0740-3194 .- 1522-2594. ; 78:1, s. 285-296
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this work was to quantify the extent of lipid-rich necrotic core (LRNC) and intraplaque hemorrhage (IPH) in atherosclerotic plaques. Methods: Patients scheduled for carotid endarterectomy underwent four-point Dixon and T1-weighted magnetic resonance imaging (MRI) at 3 Tesla. Fat and R2* maps were generated from the Dixon sequence at the acquired spatial resolution of 0.60×0.60×0.70mm voxel size. MRI and three-dimensional (3D) histology volumes of plaques were registered. The registration matrix was applied to segmentations denoting LRNC and IPH in 3D histology to split plaque volumes in regions with and without LRNC and IPH. Results: Five patients were included. Regarding volumes of LRNC identified by 3D histology, the average fat fraction by MRI was significantly higher inside LRNC than outside: 12.64±0.2737% versus 9.294±0.1762% (mean±standard error of the mean [SEM]; P<0.001). The same was true for IPH identified by 3D histology, R2* inside versus outside IPH was: 71.81±1.276 s-1 versus 56.94±0.9095 s-1 (mean±SEM; P<0.001). There was a strong correlation between the cumulative fat and the volume of LRNC from 3D histology (R2=0.92) as well as between cumulative R2* and IPH (R2=0.94). Conclusion: Quantitative mapping of fat and R2* from Dixon MRI reliably quantifies the extent of LRNC and IPH.
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| 22. |
- Listz Maurice, Roch, et al.
(författare)
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Characterization of atherosclerotic plaques and mural thrombi with intravascular ultrasound elastography : A potential method evaluated in an aortic rabbit model and a human coronary artery
- 2008
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Ingår i: IEEE transactions on information technology in biomedicine. - : Institute of Electrical and Electronics Engineers (IEEE). - 1089-7771 .- 1558-0032. ; 12:3, s. 290-298
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Tidskriftsartikel (refereegranskat)abstract
- Plaque rupture is correlated with the plaque morphology, composition, mechanical properties, and with the blood pressure. Whereas the geometry can accurately be assessed with intravascular ultrasound (IVUS) imaging, intravascular elastography (IVE) is capable of extracting information on the plaque local mechanical properties and composition. This paper reports additional IVE validation data regarding reproducibility and potential to characterize atherosclerotic plaques and mural thrombi. In a first investigation, radio frequency (RF) data were acquired from the abdominal aorta of an atherosclerotic rabbit model. In a second investigation, IVUS RF data were recorded from the left coronary artery of a patient referred for angioplasty. In both cases, Galaxy IVUS scanners (Boston Scientific, Freemont, CA), equipped with 40 MHz Atlantis catheters, were used. Elastograms were computed using two methods, the Lagrangian speckle model estimator (LSME) and the scaling factor estimator (SFE). Corroborated with histology, the LSME and the SFE both clearly detected a soft thrombus attached to the vascular wall. Moreover, shear elastograms, only available with the LSME, confirmed the presence of the thrombus. Additionally, IVE was found reproducible with consistent elastograms between cardiac cycles (CCs). Regarding the human dataset, only the LSME was capable of identifying a plaque that presumably sheltered a lipid core. Whereas such an assumption could not be certified with histology, radial shear and tangential strain LSME elastograms enabled the same conclusion. It is worth emphasizing that this paper reports the first ever in vivo tangential strain elastogram with regards to vascular imaging, due to the LSME. It is concluded that the IVE was reproducible exhibiting consistent strain patterns between CCs. The IVE might provide a unique tool to assess coronary wall lesions.
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| 23. |
- Mandinov, L., et al.
(författare)
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Inhibition of in-stent restenosis by oral copper chelation in porcine coronary arteries
- 2006
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Ingår i: American Journal of Physiology. Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 291:6, s. H2692-H2697
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Tidskriftsartikel (refereegranskat)abstract
- Stress-induced release of IL-1 alpha and fibroblast growth factor-1 is dependent on intracellular copper and is a major driver of neointimal hyperplasia. Therefore, we assessed the effect of tetrathiomolybdate (TTM), a clinically proven copper chelator, on in-stent restenosis. Nine pigs were treated with TTM (5 mg/kg po) twice daily for 2 wk before stent implantation and for 4 wk thereafter, and nine pigs served as controls. In-stent restenosis was assessed by quantitative coronary angiography (QCA), intravascular ultrasound (IVUS), and histomorphometry. Serum ceruloplasmin activity was used as a surrogate marker of copper bioavailability. In TTM-treated animals, ceruloplasmin dropped 70 +/- 10% below baseline levels. Baseline characteristics were comparable in TTM-treated and control animals. At 4-wk follow-up, all parameters relevant to in-stent restenosis were significantly reduced in TTM-treated animals: minimal lumen diameter by QCA was 2.03 +/- 0.57 and 1.47 +/- 0.45 mm in TTM-treated and control animals, respectively (P less than 0.05), percent stenosis diameter was 39% less in TTM-treated animals (27.1 +/- 16.6% vs. 44.5 +/- 16.1%, P less than 0.05), minimal lumen area by IVUS was 60% larger in TTM-treated animals (4.27 +/- 1.56 vs. 2.67 +/- 1.19 mm(2), P less than 0.05), and neointimal volume by histomorphometry was 37% less in TTM-treated animals (34.9 +/- 11.5 vs. 55.2 +/- 19.6 mm(3), P less than 0.05). We conclude that systemic copper chelation with a clinically approved chelator significantly inhibits in-stent restenosis.
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| 24. |
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| 25. |
- Moreno, Rodrigo, 1973-, et al.
(författare)
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Robust Estimation of Distance Between Sets of Points
- 2013
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Ingår i: Pattern Recognition Letters. - : Elsevier. - 0167-8655 .- 1872-7344. ; 34:16, s. 2192-2198
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a new methodology for computing Hausdorff distances between sets of points in a robust way. In a first step, robust nearest neighbor distance distributions between the two sets of points are obtained by considering reliability measures in the computations through a Monte Carlo scheme. In a second step, the computed distributions are operated using random variables algebra in order to obtain probability distributions of the average, minimum or maximum distances. In the last step, different statistics are computed from these distributions. A statistical test of significance, the nearest neighbor index, in addition to the newly proposed divergence and clustering indices are used to compare the computed measurements with respect to values obtained by chance. Results on synthetic and real data show that the proposed method is more robust than the standard Hausdorff distance. In addition, unlike previously proposed methods based on thresholding, it is appropriate for problems that can be modeled through point processes.
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| 26. |
- Shen, Li, et al.
(författare)
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An interactive 3D visualization and manipulation tool foreffective assessment of angiogenesis and arteriogenesis usingcomputed tomographic angiography
- 2005
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Ingår i: Progress in Biomedical Optics and Imaging. - : SPIE. - 1605-7422 .- 1042-4687. ; 5744:II, s. 848-858
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents IVM, an Interactive Vessel Manipulation tool that can help make effective and efficient assessmentof angiogenesis and arteriogenesis in computed tomographic angiography (CTA) studies. IVM consistsof three fundamental components: (1) a visualization component, (2) a tracing component, and (3) a measurementcomponent. Given a user-specified threshold, IVM can create a 3D surface visualization based on it. Sincevessels are thin and tubular structures, using standard isosurface extraction techniques usually cannot yieldsatisfactory reconstructions. Instead, IVM directly renders the surface of a derived binary 3D image. The imagevolumes collected in CTA studies often have a relatively high resolution. Thus, compared with more complicatedvessel extraction and visualization techniques, rendering the binary image surface has the advantages of beingeffective, simple and fast. IVM employs a semi-automatic approach to determine the threshold: a user can adjustthe threshold by checking the corresponding 3D surface reconstruction and make the choice. Typical tracingsoftware often defines ROIs on 3D image volumes using three orthogonal views. The tracing component in IVMtakes one step further: it can perform tracing not only on image slices but also in a 3D view. We observe thatdirectly operating on a 3D view can help a tracer identify ROIs more easily. After setting a threshold and tracingan ROI, a user can use IVM’s measurement component to estimate the volume and other parameters of vesselsin the ROI. The effectiveness of the IVM tool is demonstrated on rat vessel/bone images collected in a previousCTA study.
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| 27. |
- Sherman, Jonathan A., et al.
(författare)
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Humoral and cellular factors responsible for coronary collateral formation
- 2006
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Ingår i: American Journal of Cardiology. - : Elsevier. - 0002-9149 .- 1879-1913. ; 98:9, s. 1194-1197
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Tidskriftsartikel (refereegranskat)abstract
- Clinical observations suggest that patients with coronary artery disease (CAD) display a marked heterogenerty in collateral formation despite similar degrees of coronary obstruction. The development of coronary collaterals helps protect the myocardium from ischemic damage, yet the factors responsible for collateral formation are poorly understood. To better understand the biochemical and cellular mechanisms of collateral artery formation, monocyte function and circulating levels of pro- and antiangiogenic factors were measured in 101 patients with angiographically assessed CAD and extensively developed (score 2, n = 33) or absent (score 0, n = 68) collateral circulations. Compared with patients with score 0, those with score 2 were slightly older and had more advanced CAD. The score 2 group, was also more likely to have had a previous myocardial infarction or coronary artery bypass grafting and a family history of CAD. At the same time, there were no significant differences between groups with regard to circulating levels of vascular endothelial growth factor-A(165), platelet-derived growth factor-beta beta, fibroblast growth factor-2, fibroblast growth factor-4, hepatocyte growth factor, tumor necrosis factor-alpha, interleukin-1 beta, endostatin, matrix metalloproteinase-9, promatrix metalloproteinase-1, and CD40 ligand. Monocytes isolated from patients with score 2 and 0 collateral circulations demonstrated no differences in migration assays. However, adhesion to fibrinogen and collagen was significantly higher for monocytes from patients with score 0 (p = 0.05 and 0.04, respectively). In conclusion, these data suggest that the degree of coronary collateral formation is not determined by differences in systemically measurable levels of pro- or antiangiogenic factors assessed in this study. Rather, cellular properties, such as cell adhesion, or genetic differences between patients may be the driving force for collateral development. (c) 2006 Elsevier Inc. All rights reserved.
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| 28. |
- Sherrell, Peter, 1986-, et al.
(författare)
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Rational Design of a Conductive Collagen Heart Patch
- 2017
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Ingår i: Macromolecular Bioscience. - : Wiley-VCH Verlagsgesellschaft. - 1616-5187 .- 1616-5195. ; 17:7
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Tidskriftsartikel (refereegranskat)abstract
- Cardiovascular diseases, including myocardial infarction, are the cause of significant morbidity and mortality globally. Tissue engineering is a key emerging treatment method for supporting and repairing the cardiac scar tissue caused by myocardial infarction. Creating cell supportive scaffolds that can be directly implanted on a myocardial infarct is an attractive solution. Hydrogels made of collagen are highly biocompatible materials that can be molded into a range of shapes suitable for cardiac patch applications. The addition of mechanically reinforcing materials, carbon nanotubes, at subtoxic levels allows for the collagen hydrogels to be strengthened, up to a toughness of 30 J m-1 and a two to threefold improvement in Youngs' modulus, thus improving their viability as cardiac patch materials. The addition of carbon nanotubes is shown to be both nontoxic to stem cells, and when using single-walled carbon nanotubes, supportive of live, beating cardiac cells, providing a pathway for the further development of a cardiac patch.
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| 29. |
- Wickham, Abeni, et al.
(författare)
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Influence of Polycaprolactone Scaffold Topography on Progenitor and Mesenchymal Cell Proliferation
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Polycaprolactone (PCL) is a frequently used polymer for tissue engineering applications and has been suggested as a suitable scaffold for cardiac regeneration. PCL can be effectively procesed using electrospinning to form fibrous scaffolds with defined topographies. The topography, as well as the materials and suraface properties, signficanltly effect the performance and host response of the scaffold. We have investigated the effect of PCL scaffold topology on protein adsorption and how this translate to cell adhesion and proliferation. PCL sheets are relatively hydrophobic with a water contact angle of 72o. The surface energy of PCL (20 mJ m‐2) was obatined using the Good van OSS and Chaudhury (GvOC) method, and is in the range of many antifouling materials. Non-specific protein adsorption on PCL sheets was yet substantial (0.45 mg cm‐2) when exposed to serum. A lower protein surface concentration was seen on fibrous PCL scaffolds prepared by electrospinning, presumably as a consequence of the lower diffusion in the scaffold. Proliferation of mesenchymal stem cells and cardiac progenitor cells was significantly improved when cultured on PCL sheets pre-treated with serum, but significantly lower than for fibrous PCL scaffolds. For the latter, no significant effect of serum pretreatment was observed, indicating that for PCL, fibre dimensions and scaffold topography has a larger influence on cell adhesion and proliferation than a high surface concentration of adsorbed proteins.
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| 30. |
- Yu, Jun, et al.
(författare)
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Endothelial nitric oxide synthase is critical for ischemic remodeling, mural cell recruitment, and blood flow reserve
- 2005
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 102:31, s. 10999-11004
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Tidskriftsartikel (refereegranskat)abstract
- The genetic loss of endothelial-derived nitric oxide synthase (eNOS) in mice impairs vascular endothelial growth factor (VEGF) and ischemia-initiated blood flow recovery resulting in critical limb ischemia. This result may occur through impaired arteriogenesis, angiogenesis, or mobilization of stem and progenitor cells. Here, we show that after ischemic challenge, eNOS knockout mice [eNOS (-/-)] have defects in arteriogenesis and functional blood flow reserve after muscle stimulation and pericyte recruitment, but no impairment in endothelial progenitor cell recruitment. More importantly, the defects in blood flow recovery, clinical manifestations of ischemia, ischemic reserve capacity, and pericyte recruitment into the growing neovasculature can be rescued by local intramuscular delivery of an adenovirus encoding a constitutively active allele of eNOS, eNOS S1179D, but not a control virus. Collectively, our data suggest that endogenous eNOS-derived NO exerts direct effects in preserving blood flow, thereby promoting arteriogenesis, angiogenesis, and mural cell recruitment to immature angiogenic sprouts.
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| 31. |
- Zhuang, Zhen W., et al.
(författare)
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Arteriogenesis: Noninvasive quantification with multi-detector row CT angiography and three-dimensional volume rendering in rodents
- 2006
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Ingår i: Radiology. - : Radiological Society of North America (RSNA). - 0033-8419 .- 1527-1315. ; 240:3, s. 698-707
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE:To evaluate two-dimensional (2D) multi-detector row computed tomographic (CT) angiography and three-dimensional (3D) volume rendering for depiction of patterns of arterial growth and quantification of blood vessel density and volume.MATERIALS AND METHODS:The institutional animal care and use committee approved this study. The right femoral artery and its branches were ligated and excised in 16 inbred Lewis rats; animals were randomly assigned to receive 70 microL Dulbecco's modified Eagle's medium (DMEM) or 1.5 x 10(7) bone marrow-derived mononuclear cells (BMC) from isogenic donor rats in 70 microL DMEM. At 2 weeks, CT angiography was performed with injection of 0.45 mL barium sulfate suspension at 0.7 mL/min, followed by silver staining. Number of blood vessels, area, mean area, volume, and blood vessel size distribution derived from digitally subtracted 2D CT angiographic sections were quantified; 3D images were reconstructed. Two-way analysis of variance and paired and unpaired Student t tests were performed.RESULTS:CT angiography showed two patterns of arterial growth: collateral arterial formation and branching arteriogenesis. Two-way analysis of variance indicated that differences within subjects (ischemic vs nonischemic legs) and between subjects (BMC vs DMEM treatment) were significant for total blood vessel area, total blood vessel volume, and mean of blood vessel area (P < .001). In the BMC group, there were significantly more arteries (mean, 241.6 +/- 77.0 [standard deviation] vs 196.4 +/- 75.2, P = .028), but mean cross-sectional area of these arteries was smaller in ischemic versus nonischemic legs (5.4 mm(2) +/- 1.2 vs 6.8 mm(2) +/- 1.3, P = .006). Total arterial area and volume did not differ significantly between ischemic and nonischemic legs.CONCLUSION:BMC injection had a substantial effect on arteriogenesis, with normalization of total arterial area and volume in the BMC group; this effect was successfully depicted.
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| 32. |
- Ziegler, Magnus, et al.
(författare)
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Automated segmentation of the individual branches of the carotid arteries in contrast-enhanced MR angiography using DeepMedic
- 2021
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Ingår i: BMC Medical Imaging. - : BMC. - 1471-2342. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundNon-invasive imaging is of interest for tracking the progression of atherosclerosis in the carotid bifurcation, and segmenting this region into its constituent branch arteries is necessary for analyses. The purpose of this study was to validate and demonstrate a method for segmenting the carotid bifurcation into the common, internal, and external carotid arteries (CCA, ICA, ECA) in contrast-enhanced MR angiography (CE-MRA) data.MethodsA segmentation pipeline utilizing a convolutional neural network (DeepMedic) was tailored and trained for multi-class segmentation of the carotid arteries in CE-MRA data from the Swedish CardioPulmonsary bioImage Study (SCAPIS). Segmentation quality was quantitatively assessed using the Dice similarity coefficient (DSC), Matthews Correlation Coefficient (MCC), F-2, F-0.5, and True Positive Ratio (TPR). Segmentations were also assessed qualitatively, by three observers using visual inspection. Finally, geometric descriptions of the carotid bifurcations were generated for each subject to demonstrate the utility of the proposed segmentation method.ResultsBranch-level segmentations scored DSC=0.800.13, MCC=0.80 +/- 0.12, F-2=0.82 +/- 0.14, F-0.5=0.78 +/- 0.13, and TPR=0.84 +/- 0.16, on average in a testing cohort of 46 carotid bifurcations. Qualitatively, 61% of segmentations were judged to be usable for analyses without adjustments in a cohort of 336 carotid bifurcations without ground-truth. Carotid artery geometry showed wide variation within the whole cohort, with CCA diameter 8.6 +/- 1.1 mm, ICA 7.5 +/- 1.4 mm, ECA 5.7 +/- 1.0 mm and bifurcation angle 41 +/- 21 degrees .ConclusionThe proposed segmentation method automatically generates branch-level segmentations of the carotid arteries that are suitable for use in further analyses and help enable large-cohort investigations.
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| 33. |
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| 34. |
- Ziegler, Magnus, et al.
(författare)
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Exploring the Relationships Between Hemodynamic Stresses in the Carotid Arteries
- 2021
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Ingår i: Frontiers in Cardiovascular Medicine. - : Frontiers Media S.A.. - 2297-055X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Background: Atherosclerosis manifests as a focal disease, often affecting areas with complex hemodynamics such as the carotid bifurcation. The magnitude and regularity of the hemodynamic shear stresses acting on the vessel wall are thought to generate risk patterns unique to each patient and play a role in the pathogenesis of atherosclerosis. The involvement of different expressions of shear stress in the pathogenesis of carotid atherosclerosis highlights the need to characterize and compare the differential impact of the various expressions of shear stress in the atherosclerotic carotid bifurcation. Therefore, the aim of this study is to characterize and compare hemodynamic wall shear stresses (WSS) in the carotid arteries of subjects with asymptomatic atherosclerotic plaques. Shear stresses were also compared against vessel diameter and bifurcation angle to examine the relationships with the geometry of the carotid bifurcation. Methods: 4D Flow MRI and contrast-enhanced MRA data were acquired for 245 subjects with atherosclerotic plaques of at least 2.7 mm in conjunction with the Swedish CArdioPulmonary bioImage Study (SCAPIS). Following automatic segmentation and geometric analysis, time-resolved WSS and near-wall turbulent kinetic energy (nwTKE) were derived from the 4D Flow data. Whole-cycle parameters including time-averaged WSS and nwTKE, and the oscillatory shear index (OSI) were calculated. Pairwise Spearman rank-correlation analyses were used to investigate relationships among the hemodynamic as well as geometric parameters. Results: One hundred and seventy nine subjects were successfully segmented using automated tools and subsequently geometric and hemodynamic analyses were performed. Temporally resolved WSS and nwTKE were strongly correlated, rho = 0.64. Cycle-averaged WSS and nwTKE were moderately correlated, rho = 0.57. Cycle-average nwTKE was weakly correlated to OSI (rho = -0.273), revealing that nwTKE provides information about disturbed flow on the vessel wall that OSI does not. In this cohort, there was large inter-individual variation for both WSS and nwTKE. Both WSS and nwTKE varied most within the external carotid artery. WSS, nwTKE, and OSI were weakly correlated to vessel diameter and bifurcation angle. Conclusion: The turbulent and mean component of WSS were examined together in vivo for the first time, and a strong correlation was found between them. nwTKE presents the opportunity to quantify turbulent wall stresses in vivo and gain insight into the effects of disturbed flow on the vessel wall. Neither vessel diameter nor bifurcation angle were found to be strongly correlated to the turbulent or mean component of WSS in this cohort.
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| 35. |
- Ziegler, Magnus, 1990-
(författare)
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Improving Assessments of Hemodynamics and Vascular Disease
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Blood vessels are more than simple pipes, passively enabling blood to pass through them. Their form and function are dynamic, changing with both aging and disease. This process involves a feedback loop wherein changes to the shape of a blood vessel affect the hemodynamics, causing yet more structural adaptation. This feedback loop is driven in part by the hemodynamic forces generated by the blood flow, and the distribution and strength of these forces appear to play a role in the initiation, progression, severity, and the outcome of vascular diseases.Magnetic Resonance Imaging (MRI) offers a unique platform for investigating both the form and function of the vascular system. The form of the vascular system can be examined using MR-based angiography, to generate detailed geometric analyses, or through quantitative techniques for measuring the composition of the vessel wall and atherosclerotic plaques. To complement these analyses, 4D Flow MRI can be used to quantify the functional aspect of the vascular system, by generating a full time-resolved three-dimensional velocity field that represents the blood flow.This thesis aims to develop and evaluate new methods for assessing vascular disease using novel hemodynamic markers generated from 4D Flow MRI and quantitative MRI data towards the larger goal of a more comprehensive non-invasive examination oriented towards vascular disease. In Paper I, we developed and evaluated techniques to quantify flow stasis in abdominal aortic aneurysms to measure this under-explored aspect of aneurysmal hemodynamics. In Paper II, the distribution and intensity of turbulence in the aorta was quantified in both younger and older men to understand how aging changes this aspect of hemodynamics. A method to quantify the stresses generated by turbulence that act on the vessel wall was developed and evaluated using simulated flow data in Paper III, and in Paper V this method was utilized to examine the wall stresses of the carotid artery. The hemodynamics of vascular disease cannot be uncoupled from the anatomical changes the vessel wall undergoes, and therefore Paper IV developed and evaluated a semi-automatic method for quantifying several aspects of vessel wall composition. These developments, taken together, help generate more valuable information from imaging data, and can be pooled together with other methods to form a more comprehensive non-invasive examination for vascular disease.
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| 36. |
- Ziegler, Magnus, et al.
(författare)
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Towards Automated Quantification of Vessel Wall Composition Using MRI
- 2020
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Ingår i: Journal of Magnetic Resonance Imaging. - : WILEY. - 1053-1807 .- 1522-2586. ; 52:3, s. 710-719
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Tidskriftsartikel (refereegranskat)abstract
- Background MRI can be used to generate fat fraction (FF) and R2* data, which have been previously shown to characterize the plaque compositional features lipid-rich necrotic core (LRNC) and intraplaque hemorrhage (IPH) in the carotid arteries (CAs). Previously, these data were extracted from CA plaques using time-consuming manual analyses. Purpose To design and demonstrate a method for segmenting the CA and extracting data describing the composition of the vessel wall. Study Type Prospective. Subjects 31 subjects from the Swedish CArdioPulmonary bioImage Study (SCAPIS). Field Strength/Sequences T-1-weighted (T1W) quadruple inversion recovery, contrast-enhanced MR angiography (CE-MRA), and 4-point Dixon data were acquired at 3T. Assessment The vessel lumen of the CA was automatically segmented using support vector machines (SVM) with CE-MRA data, and the vessel wall region was subsequently delineated. Automatically generated segmentations were quantitatively measured and three observers visually compared the segmentations to manual segmentations performed on T(1)w images. Dixon data were used to generate FF and R2* maps. Both manually and automatically generated segmentations of the CA and vessel wall were used to extract compositional data. Statistical Tests Two-tailedt-tests were used to examine differences between results generated using manual and automated analyses, and among different configurations of the automated method. Interobserver agreement was assessed with Fleiss kappa. Results Automated segmentation of the CA using SVM had a Dice score of 0.89 +/- 0.02 and true-positive ratio 0.93 +/- 0.03 when compared against ground truth, and median qualitative score of 4/5 when assessed visually by multiple observers. Vessel wall regions of 0.5 and 1 mm yielded compositional information similar to that gained from manual analyses. Using the 0.5 mm vessel wall region, the mean difference was 0.1 +/- 2.5% considering FF and 1.1 +/- 5.7[1/s] for R2*. Level of Evidence 1. Technical Efficacy Stage 1. J. Magn. Reson. Imaging 2020;52:710-719.
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