Refine
Has Fulltext
- yes (16)
Is part of the Bibliography
- yes (16)
Year of publication
Document Type
- Journal article (11)
- Doctoral Thesis (5)
Language
- English (16) (remove)
Keywords
- atherosclerosis (16) (remove)
Institute
- Medizinische Klinik und Poliklinik I (7)
- Institut für Experimentelle Biomedizin (5)
- Physikalisches Institut (5)
- Graduate School of Life Sciences (3)
- Deutsches Zentrum für Herzinsuffizienz (DZHI) (2)
- Institut für diagnostische und interventionelle Neuroradiologie (ehem. Abteilung für Neuroradiologie) (2)
- Rudolf-Virchow-Zentrum (2)
- Abteilung für Molekulare Innere Medizin (in der Medizinischen Klinik und Poliklinik II) (1)
- Institut für Klinische Biochemie und Pathobiochemie (1)
- Institut für Klinische Epidemiologie und Biometrie (1)
Growth, ageing and atherosclerotic plaque development alter the biomechanical forces acting on the vessel wall. However, monitoring the detailed local changes in wall shear stress (WSS) at distinct sites of the murine aortic arch over time has been challenging. Here, we studied the temporal and spatial changes in flow, WSS, oscillatory shear index (OSI) and elastic properties of healthy wildtype (WT, n = 5) and atherosclerotic apolipoprotein E-deficient (Apoe\(^{−/−}\), n = 6) mice during ageing and atherosclerosis using high-resolution 4D flow magnetic resonance imaging (MRI). Spatially resolved 2D projection maps of WSS and OSI of the complete aortic arch were generated, allowing the pixel-wise statistical analysis of inter- and intragroup hemodynamic changes over time and local correlations between WSS, pulse wave velocity (PWV), plaque and vessel wall characteristics. The study revealed converse differences of local hemodynamic profiles in healthy WT and atherosclerotic Apoe\(^{−/−}\) mice, and we identified the circumferential WSS as potential marker of plaque size and composition in advanced atherosclerosis and the radial strain as a potential marker for vascular elasticity. Two-dimensional (2D) projection maps of WSS and OSI, including statistical analysis provide a powerful tool to monitor local aortic hemodynamics during ageing and atherosclerosis. The correlation of spatially resolved hemodynamics and plaque characteristics could significantly improve our understanding of the impact of hemodynamics on atherosclerosis, which may be key to understand plaque progression towards vulnerability.
Atherosclerosis is accepted to be a chronic inflammatory disease of the arterial vessel wall. Several cellular subsets of the immune system are involved in its initiation and progression, such as monocytes, macrophages, T and B cells. Recent research has demonstrated that dendritic cells (DCs) contribute to atherosclerosis, too. DCs are defined by their ability to sense and phagocyte antigens, to migrate and to prime other immune cells, such as T cells. Although all DCs share these functional characteristics, they are heterogeneous with respect to phenotype and origin. Several markers have been used to describe DCs in different lymphoid and non-lymphoid organs; however, none of them has proven to be unambiguous. The expression of surface molecules is highly variable depending on the state of activation and the surrounding tissue. Furthermore, DCs in the aorta or the atherosclerotic plaque can be derived from designated precursor cells or from monocytes. In addition, DCs share both their marker expression and their functional characteristics with other myeloid cells like monocytes and macrophages. The repertoire of aortic DCs in healthy and atherosclerotic mice has just recently started to be explored, but yet there is no systemic study available, which describes the aortic DC compartment. Because it is conceivable that distinct aortic DC subsets exert dedicated functions, a detailed description of vascular DCs is required. The first part of this thesis characterizes DC subsets in healthy and atherosclerotic mice. It describes a previously unrecognized DC subset and also sheds light on the origin of vascular DCs. In recent years, microRNAs (miRNAs) have been demonstrated to regulate several cellular functions, such as apoptosis, differentiation, development or proliferation. Although several cell types have been characterized extensively with regard to the miRNAs involved in their regulation, only few studies are available that focus on the role of miRNAs in DCs. Because an improved understanding of the regulation of DC functions would allow for new therapeutic options, research on miRNAs in DCs is required. The second part of this thesis focuses on the role of the miRNA cluster miR- 17~92 in DCs by exploring its functions in healthy and atherosclerotic mice. This thesis clearly demonstrates for the first time an anti-inflammatory and atheroprotective role for the miR17-92 cluster. A model for its mechanism is suggested.
Background
Animal models have been instrumental in defining thrombus formation, including the role of platelet surface glycoprotein (GP) receptors, in acute ischemic stroke (AIS). However, the involvement of GP receptors in human ischemic stroke pathophysiology and their utility as biomarkers for ischemic stroke risk and severity requires elucidation.
Aims
To determine whether platelet GPIb and GPIIb/IIIa receptors are differentially expressed in patients with AIS and chronic cerebrovascular disease (CCD) compared with healthy volunteers (HV) and to identify predictors of GPIb and GPIIb/IIIa expression.
Methods
This was a case-control study of 116 patients with AIS or transient ischemic attack (TIA), 117 patients with CCD, and 104 HV who were enrolled at our University hospital from 2010 to 2013. Blood sampling was performed once in the CCD and HV groups, and at several time points in patients with AIS or TIA. Linear regression and analysis of variance were used to analyze correlations between platelet GPIb and GPIIb/IIIa receptor numbers and demographic and clinical parameters.
Results
GPIb and GPIIb/IIIa receptor numbers did not significantly differ between the AIS, CCD, and HV groups. GPIb receptor expression level correlated significantly with the magnitude of GPIIb/IIIa receptor expression and the neutrophil count. In contrast, GPIIb/IIIa receptor numbers were not associated with peripheral immune-cell sub-population counts. Creactive protein was an independent predictor of GPIIb/IIIa (not GPIb) receptor numbers.
Conclusions
Platelet GPIb and GPIIb/IIIa receptor numbers did not distinguish between patient or control groups in this study, negating their potential use as a biomarker for predicting stroke risk.
Atherosclerotic lesions are populated by cells of the innate and adaptive immune system, including CD8\(^+\) T cells. The CD8\(^+\) T cell infiltrate has recently been characterized in mouse and human atherosclerosis and revealed activated, cytotoxic, and possibly dysfunctional and exhausted cell phenotypes. In mouse models of atherosclerosis, antibody-mediated depletion of CD8\(^+\) T cells ameliorates atherosclerosis. CD8\(^+\) T cells control monopoiesis and macrophage accumulation in early atherosclerosis. In addition, CD8\(^+\) T cells exert cytotoxic functions in atherosclerotic plaques and contribute to macrophage cell death and necrotic core formation. CD8\(^+\) T cell activation may be antigen-specific, and epitopes of atherosclerosis-relevant antigens may be targets of CD8\(^+\) T cells and their cytotoxic activity. CD8\(^+\) T cell functions are tightly controlled by costimulatory and coinhibitory immune checkpoints. Subsets of regulatory CD25\(^+\)CD8\(^+\) T cells with immunosuppressive functions can inhibit atherosclerosis. Importantly, local cytotoxic CD8\(^+\) T cell responses may trigger endothelial damage and plaque erosion in acute coronary syndromes. Understanding the complex role of CD8\(^+\) T cells in atherosclerosis may pave the way for defining novel treatment approaches in atherosclerosis. In this review article, we discuss these aspects, highlighting the emerging and critical role of CD8\(^+\) T cells in atherosclerosis.
Atherosclerosis is the main underlying cause for cardiovascular events such as myocardial infarction and stroke and its development might be influenced by immune cells. Dendritic cells (DCs) bridge innate and adaptive immune responses by presenting antigens to T cells and releasing a variety of cytokines. Several subsets of DCs can be discriminated that engage specific transcriptional pathways for their development. Basic leucine zipper transcription factor ATF-like 3 (Batf3) is required for the development of classical CD8α\(^{+}\) and CD103\(^{+}\) DCs. By crossing mice deficient in Batf3 with atherosclerosis-prone low density lipoprotein receptor (Ldlr\(^{−/-}\))-deficient mice we here aimed to further address the contribution of Batf3-dependent CD8α\(^{+}\) and CD103\(^{+}\) antigen-presenting cells to atherosclerosis. We demonstrate that deficiency in Batf3 entailed mild effects on the immune response in the spleen but did not alter atherosclerotic lesion formation in the aorta or aortic root, nor affected plaque phenotype in low density lipoprotein receptor-deficient mice fed a high fat diet. We thus provide evidence that Batf3-dependent antigen-presenting cells do not have a prominent role in atherosclerosis.
We used a novel approach of cytostatically induced leucocyte depletion and subsequent reconstitution with leucocytes deprived of classical \((inflammatory/Gr1^{hi})\) or non-classical \((resident/Gr1^{lo})\) monocytes to dissect their differential role in atheroprogression under high-fat diet (HFD). Apolipoprotein E-deficient \((Apoe^{-/-})\) mice lacking classical but not non-classical monocytes displayed reduced lesion size and macrophage and apoptotic cell content. Conversely, HFD induced a selective expansion of classical monocytes in blood and bone marrow. Increased CXCL1 levels accompanied by higher expression of its receptor CXCR2 on classical monocytes and inhibition of monocytosis by CXCL1-neutralization indicated a preferential role for the CXCL1/CXCR2 axis in mobilizing classical monocytes during hypercholesterolemia. Studies correlating circulating and lesional classical monocytes in gene-deficient \(Apoe^{-/-}\) mice, adoptive transfer of gene-deficient cells and pharmacological modulation during intravital microscopy of the carotid artery revealed a crucial function of CCR1 and CCR5 but not CCR2 or \(CX_3CR1\) in classical monocyte recruitment to atherosclerotic vessels. Collectively, these data establish the impact of classical monocytes on atheroprogression, identify a sequential role of CXCL1 in their mobilization and CCR1/CCR5 in their recruitment.
Atherosclerosis is an inflammatory disease of large and medium-sized arteries, characterized by the growth of atherosclerotic lesions (plaques). These plaques often develop at inner curvatures of arteries, branchpoints, and bifurcations, where the endothelial wall shear stress is low and oscillatory. In conjunction with other processes such as lipid deposition, biomechanical factors lead to local vascular inflammation and plaque growth. There is also evidence that low and oscillatory shear stress contribute to arterial remodeling, entailing a loss in arterial elasticity and, therefore, an increased pulse-wave velocity. Although altered shear stress profiles, elasticity and inflammation are closely intertwined and critical for plaque growth, preclinical and clinical investigations for atherosclerosis mostly focus on the investigation of one of these parameters only due to the experimental limitations. However, cardiovascular magnetic resonance imaging (MRI) has been demonstrated to be a potent tool which can be used to provide insights into a large range of biological parameters in one experimental session. It enables the evaluation of the dynamic process of atherosclerotic lesion formation without the need for harmful radiation. Flow-sensitive MRI provides the assessment of hemodynamic parameters such as wall shear stress and pulse wave velocity which may replace invasive and radiation-based techniques for imaging of the vascular
function and the characterization of early plaque development. In combination with inflammation imaging, the analyses and correlations of these parameters could not only significantly advance basic preclinical investigations of atherosclerotic lesion formation and progression, but also the diagnostic clinical evaluation for early identification of high-risk plaques, which are prone to rupture. In this review, we summarize the key applications of magnetic resonance imaging for the evaluation of plaque characteristics through flow sensitive and morphological measurements. The simultaneous measurements of functional and structural parameters will further preclinical research on atherosclerosis and has the potential to fundamentally improve the detection of inflammation and vulnerable plaques in patients.
Functional versus morphological assessment of vascular age in patients with coronary heart disease
(2021)
Communicating cardiovascular risk based on individual vascular age (VA) is a well acknowledged concept in patient education and disease prevention. VA may be derived functionally, e.g. by measurement of pulse wave velocity (PWV), or morphologically, e.g. by assessment of carotid intima-media thickness (cIMT). The purpose of this study was to investigate whether both approaches produce similar results. Within the context of the German subset of the EUROASPIRE IV survey, 501 patients with coronary heart disease underwent (a) oscillometric PWV measurement at the aortic, carotid-femoral and brachial-ankle site (PWVao, PWVcf, PWVba) and derivation of the aortic augmentation index (AIao); (b) bilateral cIMT assessment by high-resolution ultrasound at three sites (common, bulb, internal). Respective VA was calculated using published equations. According to VA derived from PWV, most patients exhibited values below chronological age indicating a counterintuitive healthier-than-anticipated vascular status: for VA(PWVao) in 68% of patients; for VA\(_{AIao}\) in 52% of patients. By contrast, VA derived from cIMT delivered opposite results: e.g. according to VA\(_{total-cIMT}\) accelerated vascular aging in 75% of patients. To strengthen the concept of VA, further efforts are needed to better standardise the current approaches to estimate VA and, thereby, to improve comparability and clinical utility.
Background Transgenic mouse models are increasingly used to study the pathophysiology of human cardiovascular diseases. The aortic pulse wave velocity (PWV) is an indirect measure for vascular stiffness and a marker for cardiovascular risk. Results This work presents three MR-methods that allow the determination of the PWV in the descending murine aorta by analyzing blood flow waveforms, arterial distension waveforms, and a method that uses the combination of flow and distension waveforms. Systolic flow pulses were recorded with a temporal resolution of 1 ms applying phase velocity encoding. In a first step, the MR methods were validated by pressure waveform measurements on pulsatile elastic vessel phantoms. In a second step, the MR methods were applied to measure PWVs in a group of five eight-month-old apolipoprotein E deficient (ApoE(-/-)) mice and an age matched group of four C57Bl/6J mice. The ApoE(-/-) group had a higher mean PWV than the C57Bl/6J group. Depending on the measurement technique, the differences were or were not statistically significant. Conclusions The findings of this study demonstrate that high field MRI is applicable to non-invasively determine and distinguish PWVs in the arterial system of healthy and diseased groups of mice.
Atherosclerosis is an important risk factor in the development of cardiovascular diseases. In addition to increased plasma lipid concentrations, irregular/oscillatory shear stress and inflammatory processes trigger atherosclerosis. Inhibitors of the transcription modulatory bromo- and extra-terminal domain (BET) protein family (BETi) could offer a possible therapeutic approach due to their epigenetic mechanism and anti-inflammatory properties. In this study, the influence of laminar shear stress, inflammation and BETi treatment on human endothelial cells was investigated using global protein expression profiling by ion mobility separation-enhanced data independent acquisition mass spectrometry (IMS-DIA-MS). For this purpose, primary human umbilical cord derived vascular endothelial cells were treated with TNFα to mimic inflammation and exposed to laminar shear stress in the presence or absence of the BRD4 inhibitor JQ1. IMS-DIA-MS detected over 4037 proteins expressed in endothelial cells. Inflammation, shear stress and BETi led to pronounced changes in protein expression patterns with JQ1 having the greatest effect. To our knowledge, this is the first proteomics study on primary endothelial cells, which provides an extensive database for the effects of shear stress, inflammation and BETi on the endothelial proteome.