| 1. |
- Magnusson, Mia, 1979, et al.
(författare)
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Dynamic Enhancer Methylation - A Previously Unrecognized Switch for Tissue-Type Plasminogen Activator Expression.
- 2015
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Tissue-type plasminogen activator (t-PA), which is synthesized in the endothelial cells lining the blood vessel walls, is a key player in the fibrinolytic system protecting the circulation against occluding thrombus formation. Although classical gene regulation has been quite extensively studied in order to understand the mechanisms behind t-PA regulation, epigenetics, including DNA methylation, still is a largely unexplored field. The aim of this study was to establish the methylation pattern in the t-PA promoter and enhancer in non-cultured compared to cultured human umbilical vein endothelial cells (HUVECs), and to simultaneously examine the level of t-PA gene expression. Bisulphite sequencing was used to evaluate the methylation status, and real-time RT-PCR to determine the gene expression level. While the t-PA promoter was stably unmethylated, we surprisingly observed a rapid reduction in the amount of methylation in the enhancer during cell culturing. This demethylation was in strong negative correlation with a pronounced (by a factor of approximately 25) increase in t-PA gene expression levels. In this study, we show that the methylation level in the t-PA enhancer appears to act as a previously unrecognized switch controlling t-PA expression. Our findings, which suggest that DNA methylation is quite dynamic, have implications also for the interpretation of cell culture experiments in general, as well as in a wider biological context.
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| 2. |
- Magnusson, Mia, 1979, et al.
(författare)
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Rapid and specific hypomethylation of enhancers in endothelial cells during adaptation to cell culturing.
- 2016
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Ingår i: Epigenetics. - : Informa UK Limited. - 1559-2308 .- 1559-2294. ; 11:8, s. 614-624
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Tidskriftsartikel (refereegranskat)abstract
- Epigenetics, including DNA methylation, is one way for a cell to respond to the surrounding environment. Traditionally, DNA methylation has been perceived as a quite stable modification; however, lately, there have been reports of a more dynamic CpG methylation that can be affected by, for example, long-term culturing. We recently reported that methylation in the enhancer of the gene encoding the key fibrinolytic enzyme tissue-type plasminogen activator (t-PA) was rapidly erased during cell culturing. In the present study we used sub-culturing of human umbilical vein endothelial cells (HUVECs) as a model of environmental challenge to examine how fast genome-wide methylation changes can arise. To assess genome-wide DNA methylation, the Infinium HumanMethylation450 BeadChip was used on primary, passage 0, and passage 4 HUVECs. Almost 2% of the analyzed sites changed methylation status to passage 4, predominantly displaying hypomethylation. Sites annotated as enhancers were overrepresented among the differentially methylated sites (DMSs). We further showed that half of the corresponding genes concomitantly altered their expression, most of them increasing in expression. Interestingly, the stroke-related gene HDAC9 increased its expression several hundredfold. This study reveals a rapid hypomethylation of CpG sites in enhancer elements during the early stages of cell culturing. As many methods for methylation analysis are biased toward CpG rich promoter regions, we suggest that such methods may not always be appropriate for the study of methylation dynamics. In addition, we found that significant changes in expression arose in genes with enhancer DMSs. HDAC9 displayed the most prominent increase in expression, indicating, for the first time, that dynamic enhancer methylation may be central in regulating this important stroke-associated gene.
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| 3. |
- Forsgard, Niklas, et al.
(författare)
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Cardiac arrest in Wilson's disease after curative liver transplantation: a life-threatening complication of myocardial copper excess?
- 2019
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Ingår i: ESC Heart Failure. - : Wiley. - 2055-5822. ; 6:1, s. 228-231
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Tidskriftsartikel (refereegranskat)abstract
- We report the case of a 38-year-old man who presented with cardiac arrest 1 year after curative liver transplantation for Wilson's disease. Clinical work-up proofed myocardial copper and iron accumulation using mass spectrometry, which led most likely to myocardial fibrosis as visualized by cardiovascular magnetic resonance (unprecedented delayed enhancement pattern) and endomyocardial biopsy. Consequently, cardiac arrest due to ventricular fibrillation and subsequent episodes of sustained ventricular tachycardia were considered as primary cardiac manifestation of Wilson's disease. This can, as illustrated by our case, occur even late after curative liver transplantation, which is an important fact that treating physicians should be aware of during clinical follow-up of these patients.
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| 4. |
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| 5. |
- Ulfhammer, Erik, 1974, et al.
(författare)
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Dependence of Proximal GC Boxes and Binding Transcription Factors in the Regulation of Basal and Valproic Acid-Induced Expression of t-PA.
- 2016
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Ingår i: International journal of vascular medicine. - : Hindawi Limited. - 2090-2824 .- 2090-2832. ; 2016
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Endothelial tissue-type plasminogen activator (t-PA) release is a pivotal response to protect the circulation from occluding thrombosis. We have shown that the t-PA gene is epigenetically regulated and greatly induced by the histone deacetylase (HDAC) inhibitor valproic acid (VPA). We now investigated involvement of known t-PA promoter regulatory elements and evaluated dependence of potential interacting transcription factors/cofactors. Methods. A reporter vector with an insert, separately mutated at either the t-PA promoter CRE or GC box II or GC box III elements, was transfected into HT-1080 and HUVECs and challenged with VPA. HUVECs were targeted with siRNA against histone acetyl transferases (HAT) and selected transcription factors from the Sp/KLF family. Results. An intact VPA-response was observed with CRE mutated constructs, whereas mutation of GC boxes II and III reduced the magnitude of the induction by 54 and 79% in HT-1080 and 49 and 50% in HUVECs, respectively. An attenuated induction of t-PA mRNA was observed after Sp2, Sp4, and KLF5 depletion. KLF2 and p300 (HAT) were identified as positive regulators of basal t-PA expression and Sp4 and KLF9 as repressors. Conclusion. VPA-induced t-PA expression is dependent on the proximal GC boxes in the t-PA promoter and may involve interactions with Sp2, Sp4, and KLF5.
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| 6. |
- Glise, Lars, 1988, et al.
(författare)
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Disturbed Laminar Blood Flow Causes Impaired Fibrinolysis and Endothelial Fibrin Deposition In Vivo
- 2019
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Ingår i: Thrombosis and Haemostasis. - : Georg Thieme Verlag KG. - 0340-6245 .- 2567-689X. ; 119:2, s. 223-233
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Tidskriftsartikel (refereegranskat)abstract
- Endothelial expression of tissue-type plasminogen activator (t-PA) is crucial for maintaining an adequate endogenous fibrinolysis. It is unknown how endothelial t-PA expression and fibrinolysis are affected by blood flow in vivo. In this study, we investigated the impact of different blood flow profiles on endothelial t-PA expression and fibrinolysis in the arterial vasculature. Induction of disturbed laminar blood flow (D-flow) in the mouse carotid artery potently reduced endothelial t-PA messenger ribonucleic acid and protein expression, and caused fibrin deposition. En face immunohistochemistry demonstrated that arterial areas naturally exposed to D-flow had markedly lower endothelial t-PA levels than areas with sustained laminar blood flow (S-flow), and displayed pronounced fibrin deposition despite an intact endothelium. In t-PA and plasminogen-deficient mice, fibrin deposition did not extend into S-flow areas, indicating that areas of D-flow and S-flow differ, not only in fibrinolytic capacity, but also in coagulation. Furthermore, plasminogen accumulation was found at D-flow areas, and infusion of recombinant t-PA activated fibrinolysis and significantly reduced the fibrin deposits. In conclusion, D-flow potently impairs the fibrinolytic capacity and causes endothelial fibrin deposition in vivo. Our data also indicate that t-PA is the limiting factor for efficient fibrinolysis at the thrombosis-prone D-flow areas in the arterial vasculature.
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| 7. |
- Simsa, Robin, et al.
(författare)
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Effect of fluid dynamics on decellularization efficacy and mechanical properties of blood vessels
- 2019
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 14:8
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Tidskriftsartikel (refereegranskat)abstract
- Decellularization of blood vessels is a promising approach to generate native biomaterials for replacement of diseased vessels. The decellularization process affects the mechanical properties of the vascular graft and thus can have a negative impact for in vivo functionality. The aim of this study was to determine how detergents under different fluid dynamics affects decellularization efficacy and mechanical properties of the vascular graft. We applied a protocol utilizing 1% TritonX, 1% Tributyl phosphate (TnBP) and DNase on porcine vena cava. The detergents were applied to the vessels under different conditions; static, agitation and perfusion with 3 different perfusion rates (25, 100 and 400 mL/min). The decellularized grafts were analyzed with histological, immunohistochemical and mechanical tests. We found that decellularization efficacy was equal in all groups, however the luminal ultrastructure of the static group showed remnant cell debris and the 400 mL/min perfusion group showed local damage and tearing of the luminal surface. The mechanical stiffness and maximum tensile strength were not influenced by the detergent application method. In conclusion, our results indicate that agitation or low-velocity perfusion with detergents are preferable methods for blood vessel decellularization.
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| 8. |
- Simsa, Robin, et al.
(författare)
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Systematic in vitro comparison of decellularization protocols for blood vessels.
- 2018
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- Decellularization of native blood vessels is a promising technology to generate 3D biological scaffolds for vascular grafting. Blood vessel decellularization has been performed in previous studies under various experimental conditions, that complicates comparison and optimization of suitable protocols. The goal of this work was to systematically compare the decellularization and recellularization efficacy of 5 different protocols utilizing the detergents sodium dodecyl sulfate (SDS), sodium deoxycholate (SDC), CHAPS and TritonX-100 together with DNA-removing enzymes on porcine vena cava in a perfusion bioreactor setup. Additionally, we tested the effect of DNase on the extracellular matrix (ECM) properties. We found that all protocols could efficiently decellularize blood vessels. Mechanical strength, collagen preservation and ECM integrity were similar among all tested detergents, yet TritonX protocols required long-term DNase application for complete decellularization. However, TritonX-based protocols showed the greatest recellularization efficacy with HUVECs in vitro. Furthermore, we developed a novel protocol for TritonX which improved recellularization and reduced total process time and ECM stiffness compared to previous protocols. SDS, SDC and CHAPS based protocols had a lower recellularization potential. In conclusion, decellularization of blood vessels can be achieved with all tested reagents, but TritonX treated ECM can be most efficiently recellularized with endothelial cells.
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| 9. |
- Spanos, Elias, et al.
(författare)
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Cardioprotection of the enkephalin analog Eribis peptide 94 in a rat model of ischemia and reperfusion is highly dependent on dosing regimen and timing of administration
- 2015
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Ingår i: European Journal of Pharmacology. - : Elsevier BV. - 0014-2999. ; 747, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Eribis Peptide 94 (EP94) is an enkephalin analog with cardioprotective properties in ischemia and reperfusion. The aim of the present study was to define the optimal timing and dosing of the administration of EP94 during ischemia and reperfusion in a rat model. 172 anesthetized and mechanically ventilated male Sprague-Dawley rats were randomly assigned to different administration protocols of EP94 and subjected to 30 or 40min of coronary artery occlusion followed by 2h of reperfusion. EP94 was administered intravenously at different doses and time intervals. Area at risk (AAR) and infarct size (IS) were determined by staining with Evans Blue (EB) and Triphenyl tetrazolium chloride (TTC), respectively. EP94 reduced IS/AAR when administered as a double bolus (0.5µg/kg per dose), whereas single (1μg/kg) or triple boluses (0.5μg/kg per dose) did not confer any protection. Reduction of IS/AAR was of highest magnitude if EP94 was administered 5 and 0min before the 30min ischemic period (47% reduction, P<0.05), with declining cardioprotective effect with later administration during ischemia. When EP94 was administered after 15 and 20min of a 40-min ischemic period, reduction of IS/AAR was of the same magnitude as when given after 5 and 10min of a 30-min ischemic period. It is concluded that EP94 confers cardioprotection after double bolus administration. The effects are highly dependent on the timing of administration in relation to ischemia and reperfusion. Time of reperfusion from drug administration seems to be more critical than the total duration of ischemia.
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| 10. |
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