Publications by authors named "Christer Sylvén"

59 Publications

A Spatiotemporal Organ-Wide Gene Expression and Cell Atlas of the Developing Human Heart.

Cell 2019 Dec;179(7):1647-1660.e19

Science for Life Laboratory, Department of Gene Technology, KTH Royal Institute of Technology, Stockholm, Sweden. Electronic address:

The process of cardiac morphogenesis in humans is incompletely understood. Its full characterization requires a deep exploration of the organ-wide orchestration of gene expression with a single-cell spatial resolution. Here, we present a molecular approach that reveals the comprehensive transcriptional landscape of cell types populating the embryonic heart at three developmental stages and that maps cell-type-specific gene expression to specific anatomical domains. Spatial transcriptomics identified unique gene profiles that correspond to distinct anatomical regions in each developmental stage. Human embryonic cardiac cell types identified by single-cell RNA sequencing confirmed and enriched the spatial annotation of embryonic cardiac gene expression. In situ sequencing was then used to refine these results and create a spatial subcellular map for the three developmental phases. Finally, we generated a publicly available web resource of the human developing heart to facilitate future studies on human cardiogenesis.
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http://dx.doi.org/10.1016/j.cell.2019.11.025DOI Listing
December 2019

[Stop quibbling – of course clinical case studies are science].

Authors:
Christer Sylvén

Lakartidningen 2016 07 15;113. Epub 2016 Jul 15.

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July 2016

Wnt/β-Catenin Stimulation and Laminins Support Cardiovascular Cell Progenitor Expansion from Human Fetal Cardiac Mesenchymal Stromal Cells.

Stem Cell Reports 2016 Apr 24;6(4):607-617. Epub 2016 Mar 24.

Division of Cardiothoracic Surgery and Anesthesiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, 17177 Stockholm, Sweden; Cell Therapy Institute, Nova Southeastern University, Fort Lauderdale, FL 33314, USA. Electronic address:

The intrinsic regenerative capacity of human fetal cardiac mesenchymal stromal cells (MSCs) has not been fully characterized. Here we demonstrate that we can expand cells with characteristics of cardiovascular progenitor cells from the MSC population of human fetal hearts. Cells cultured on cardiac muscle laminin (LN)-based substrata in combination with stimulation of the canonical Wnt/β-catenin pathway showed increased gene expression of ISL1, OCT4, KDR, and NKX2.5. The majority of cells stained positive for PDGFR-α, ISL1, and NKX2.5, and subpopulations also expressed the progenitor markers TBX18, KDR, c-KIT, and SSEA-1. Upon culture of the cardiac MSCs in differentiation media and on relevant LNs, portions of the cells differentiated into spontaneously beating cardiomyocytes, and endothelial and smooth muscle-like cells. Our protocol for large-scale culture of human fetal cardiac MSCs enables future exploration of the regenerative functions of these cells in the context of myocardial injury in vitro and in vivo.
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http://dx.doi.org/10.1016/j.stemcr.2016.02.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4834052PMC
April 2016

Human fetal cardiac progenitors: The role of stem cells and progenitors in the fetal and adult heart.

Best Pract Res Clin Obstet Gynaecol 2016 Feb 10;31:58-68. Epub 2015 Sep 10.

Department of Molecular Medicine and Surgery, Division of Cardiothoracic Surgery and Anesthesiology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden; Center for Diseases of Aging (CDA) at Vaccine and Gene Therapy Institute (VGTI), Port St Lucie, FL, USA.

The human fetal heart is formed early during embryogenesis as a result of cell migrations, differentiation, and formative blood flow. It begins to beat around gestation day 22. Progenitor cells are derived from mesoderm (endocardium and myocardium), proepicardium (epicardium and coronary vessels), and neural crest (heart valves, outflow tract septation, and parasympathetic innervation). A variety of molecular disturbances in the factors regulating the specification and differentiation of these cells can cause congenital heart disease. This review explores the contribution of different cardiac progenitors to the embryonic heart development; the pathways and transcription factors guiding their expansion, migration, and functional differentiation; and the endogenous regenerative capacity of the adult heart including the plasticity of cardiomyocytes. Unfolding these mechanisms will become the basis for understanding the dynamics of specific congenital heart disease as well as a means to develop therapy for fetal as well as postnatal cardiac defects and heart failure.
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http://dx.doi.org/10.1016/j.bpobgyn.2015.08.008DOI Listing
February 2016

Meta-Analysis of Cell-based CaRdiac stUdiEs (ACCRUE) in patients with acute myocardial infarction based on individual patient data.

Circ Res 2015 Apr 19;116(8):1346-60. Epub 2015 Feb 19.

Rationale: The meta-Analysis of Cell-based CaRdiac study is the first prospectively declared collaborative multinational database, including individual data of patients with ischemic heart disease treated with cell therapy.

Objective: We analyzed the safety and efficacy of intracoronary cell therapy after acute myocardial infarction (AMI), including individual patient data from 12 randomized trials (ASTAMI, Aalst, BOOST, BONAMI, CADUCEUS, FINCELL, REGENT, REPAIR-AMI, SCAMI, SWISS-AMI, TIME, LATE-TIME; n=1252).

Methods And Results: The primary end point was freedom from combined major adverse cardiac and cerebrovascular events (including all-cause death, AMI recurrance, stroke, and target vessel revascularization). The secondary end point was freedom from hard clinical end points (death, AMI recurrence, or stroke), assessed with random-effects meta-analyses and Cox regressions for interactions. Secondary efficacy end points included changes in end-diastolic volume, end-systolic volume, and ejection fraction, analyzed with random-effects meta-analyses and ANCOVA. We reported weighted mean differences between cell therapy and control groups. No effect of cell therapy on major adverse cardiac and cerebrovascular events (14.0% versus 16.3%; hazard ratio, 0.86; 95% confidence interval, 0.63-1.18) or death (1.4% versus 2.1%) or death/AMI recurrence/stroke (2.9% versus 4.7%) was identified in comparison with controls. No changes in ejection fraction (mean difference: 0.96%; 95% confidence interval, -0.2 to 2.1), end-diastolic volume, or systolic volume were observed compared with controls. These results were not influenced by anterior AMI location, reduced baseline ejection fraction, or the use of MRI for assessing left ventricular parameters.

Conclusions: This meta-analysis of individual patient data from randomized trials in patients with recent AMI revealed that intracoronary cell therapy provided no benefit, in terms of clinical events or changes in left ventricular function.

Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01098591.
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http://dx.doi.org/10.1161/CIRCRESAHA.116.304346DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4509791PMC
April 2015

Rosuvastatin inhibits TIMP-2 and promotes myocardial angiogenesis.

Pharmacology 2014 17;93(3-4):178-84. Epub 2014 May 17.

Department of Laboratory Medicine, Care Sciences and Society (Clinical Geriatrics), Karolinska University Hospital Huddinge and Karolinska Institute, Stockholm, Sweden.

Background: Angiogenesis is usually driven by inflammation. Matrix metalloproteinases MMP-3 and MMP-9 and tissue inhibitors of metalloproteinases TIMP-1 and TIMP-2 are implicated in vascular remodeling. TIMP-2 exhibits antiangiogenic properties. Statins show benefits that are additional to lipid lowering including pro- and antiangiogenic properties. Atherosclerotic lesions in the coronary arteries have been well studied, but less is known about the fine terminal branches of the myocardial vasculature.

Methods: To examine this, we studied rosuvastatin (RSV) treatment in ApoE knockout (ApoE(-/-)) mice fed a high cholesterol (HC) diet. Hearts from ApoE(-/-) mice on a normal diet, HC diet and HC diet with RSV were harvested to determine MMP-3, MMP-9, TIMP-1, TIMP-2, vascular endothelial growth factor (VEGF)-A and estrogen receptor-α (ER-α) mRNA.

Results: RSV inhibited TIMP-1 and TIMP-2 expression and enhanced myocardial VEGF-A and ER-α expression, independently of plasma lipid level changes, but had no effect on MMP-3 and MMP-9 expression.

Conclusions: These modulations of TIMPs, VEGF and ER-α expression induced by RSV may act as local stimulating factors for arteriolar growth in the myocardium.
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http://dx.doi.org/10.1159/000360860DOI Listing
January 2015

Relation between N-terminal pro-brain natriuretic peptide levels and response to enhanced external counterpulsation in chronic angina pectoris.

Coron Artery Dis 2014 Jan;25(1):45-51

Department of Cardiology M52, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.

Objective: Although enhanced external counterpulsation (EECP) provides symptom reduction in many patients with severe angina pectoris, one-quarter of patients fail to respond. Earlier reports have not clearly established whether and how EECP responders may be identified pre-hoc. We hypothesized that clinical and biochemical data may be used to predict EECP response.

Methods: We explored a database of n=53 patients who had undergone clinically indicated EECP during 35 1-h sessions in our unit (65±7 years; 49 male), and sought to clarify which factors are predictive of response. Efficiency of counterpulsation was measured as the diastolic augmentation (DA) ratio, and was recorded both at beginning and end of the EECP treatment course. An increase in 6-min walk (6MW) distance of 5% was indicative of clinical response.

Results: Response occurred in 28 patients (53%; nonresponse in n=25, 47%). Responders had shorter baseline 6MW distance (377±81 vs. 445±62 m; P<0.01), lower left ventricular ejection fraction (48±9 vs. 54±8%; P<0.05), frequently had an increase in DA ratio during the EECP treatment course (23/28 vs. 5/28 with unchanged or decreased DA ratio; P<0.05), and higher levels of N-terminal pro-brain natriuretic peptide [NT-proBNP; 256 (123-547) vs. 62 (26-444) ng/l, P<0.01]. In multivariate logistic regression, response was independently predicted by baseline 6MW distance and baseline NT-proBNP levels (P<0.05 for both; model sensitivity: 82%, specificity: 72%, accuracy: 79%).

Conclusion: There is larger clinical benefit of EECP in patients with greater functional impairment and higher levels of NT-proBNP.
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http://dx.doi.org/10.1097/MCA.0000000000000057DOI Listing
January 2014

Electrocardiographic artefacts mimicking atrial tachycardia resulted in unnecessary diagnostic and therapeutic measures.

Korean J Intern Med 2013 Mar 27;28(2):224-30. Epub 2013 Feb 27.

Department of Cardiology, Karolinska University Hospital, Stockholm, Sweden. shams.younis-hassan@ karolinska.se

Electrocardiographic (ECG) artefacts may closely simulate both supraventricular and ventricular tachycardias. We describe a case initially diagnosed as rapid atrial fibrillation, based on 12-lead surface ECG (especially the limb leads) and monitor tracing. The arrhythmia was resistant to beta blockers. Because of the at times apparently regular rhythm, an esophageal ECG recording was performed, and adenosine was administered. When the presumed atrial fibrillation terminated after sodium pentothal was administered while preparing for electrical cardioversion, the oesophageal ECG recordings and the ECGs during adenosine administration were reviewed. An ECG artefact diagnosis was suspected, and then confirmed, during relapse of the "arrhythmia," with simple palpation of the radial pulse and cardiac auscultation.
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http://dx.doi.org/10.3904/kjim.2013.28.2.224DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3604613PMC
March 2013

Exploration of human, rat, and rabbit embryonic cardiomyocytes suggests K-channel block as a common teratogenic mechanism.

Cardiovasc Res 2013 Jan 20;97(1):23-32. Epub 2012 Sep 20.

Department of Cardiology, Karolinska University Hospital, Huddinge, SE-141 86, Stockholm, Sweden.

Aims: Several drugs blocking the rapidly activating potassium (K(r)) channel cause malformations (including cardiac defects) and embryonic death in animal teratology studies. In humans, these drugs have an established risk for acquired long-QT syndrome and arrhythmia. Recently, associations between cardiac defects and spontaneous abortions have been reported for drugs widely used in pregnancy (e.g. antidepressants), with long-QT syndrome risk. To investigate whether a common embryonic adverse-effect mechanism exists in the human, rat, and rabbit embryos, we made a comparative study of embryonic cardiomyocytes from all three species.

Methods And Results: Patch-clamp and quantitative-mRNA measurements of K(r) and slowly activating K (K(s)) channels were performed on human, rat, and rabbit primary cardiomyocytes and cardiac samples from different embryo-foetal stages. The K(r) channel was present when the heart started to beat in all species, but was, in contrast to human and rabbit, lost in rats in late organogenesis. The specific K(r)-channel blocker E-4031 prolonged the action potential in a species- and development-dependent fashion, consistent with the observed K(r)-channel expression pattern and reported sensitive periods of developmental toxicity. E-4031 also increased the QT interval and induced 2:1 atrio-ventricular block in multi-electrode array electrographic recordings of rat embryos. The K(s) channel was expressed in human and rat throughout the embryo-foetal period but not in rabbit.

Conclusion: This first comparison of mRNA expression, potassium currents, and action-potential characteristics, with and without a specific K(r)-channel blocker in human, rat, and rabbit embryos provides evidence of K(r)-channel inhibition as a common mechanism for embryonic malformations and death.
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http://dx.doi.org/10.1093/cvr/cvs296DOI Listing
January 2013

Ischemia-reperfusion injury and pregnancy initiate time-dependent and robust signs of up-regulation of cardiac progenitor cells.

PLoS One 2012 9;7(5):e36804. Epub 2012 May 9.

Division of Cardiology, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.

To explore how cardiac regeneration and cell turnover adapts to disease, different forms of stress were studied for their effects on the cardiac progenitor cell markers c-Kit and Isl1, the early cardiomyocyte marker Nkx2.5, and mast cells. Adult female rats were examined during pregnancy, after myocardial infarction and ischemia-reperfusion injury with/out insulin like growth factor-1(IGF-1) and hepatocyte growth factor (HGF). Different cardiac sub-domains were analyzed at one and two weeks post-intervention, both at the mRNA and protein levels. While pregnancy and myocardial infarction up-regulated Nkx2.5 and c-Kit (adjusted for mast cell activation), ischemia-reperfusion injury induced the strongest up-regulation which occurred globally throughout the entire heart and not just around the site of injury. This response seems to be partly mediated by increased endogenous production of IGF-1 and HGF. Contrary to c-Kit, Isl1 was not up-regulated by pregnancy or myocardial infarction while ischemia-reperfusion injury induced not a global but a focal up-regulation in the outflow tract and also in the peri-ischemic region, correlating with the up-regulation of endogenous IGF-1. The addition of IGF-1 and HGF did boost the endogenous expression of IGF and HGF correlating to focal up-regulation of Isl1. c-Kit expression was not further influenced by the exogenous growth factors. This indicates that there is a spatial mismatch between on one hand c-Kit and Nkx2.5 expression and on the other hand Isl1 expression. In conclusion, ischemia-reperfusion injury was the strongest stimulus with both global and focal cardiomyocyte progenitor cell marker up-regulations, correlating to the endogenous up-regulation of the growth factors IGF-1 and HGF. Also pregnancy induced a general up-regulation of c-Kit and early Nkx2.5+ cardiomyocytes throughout the heart. Utilization of these pathways could provide new strategies for the treatment of cardiac disease.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0036804PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3348899PMC
September 2012

Coronary artery perforation and regrowth of a side branch occluded by a polytetrafluoroethylene-covered stent implantation.

ISRN Cardiol 2011 26;2011:212851. Epub 2011 Apr 26.

Department of Cardiology, Karolinska Institute at Karolinska University Hospital, Huddinge, 141 86 Stockholm, Sweden.

Stenting of the right coronary artery stenosis caused coronary perforation and profound dye (blood) extravasation in a 69-year-old female patient. Instantaneous balloon inflation followed by implantation of a polytetrafluoroethylene- (PTFE-)covered stent sealed the coronary perforation, restored the blood flow, and perceivably caused acute occlusion of a large side branch (SB). The immediate in situ balloon inflation prevented the development of cardiac tamponade. Surprisingly, followup coronary angiography 4 and 11 months later showed spontaneous recanalization of the SB occluded by PTFE-covered stent. The SB was filled through a channel beginning at the end of the covered stent streaming retrogradely beneath it toward the SB ostium. Up to the best of our knowledge, this is the first described case of late spontaneous recanalization of as SB occluded by a PTFE-covered stent.
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http://dx.doi.org/10.5402/2011/212851DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3262528PMC
August 2012

[Takotsubo syndrome possible also in obstructive coronary vessel disease. The conditions do not exclude each other according to two case reports].

Lakartidningen 2011 Apr 13-19;108(15):864-7

Hjartkliniken, Karolinska universitetssjukhuset, Stockholm.

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June 2011

Estrogen receptors do not influence angiogenesis after myocardial infarction.

Scand Cardiovasc J 2011 Aug 12;45(4):215-22. Epub 2011 Apr 12.

Department of Cardiology, Karolinska Institute, Clinical Research Center, Stockholm, Sweden.

Background: There is controversy on whether estrogen receptors are present and functioning in the myocardium. Aims. To explore if after myocardial infarction (MI) estrogen receptors α (ERα) and β (ERβ) are upregulated in myocardial tissue and to explore if the presence/ absence of ERα or ERβ influences angiogenesis after MI.

Methods: MI was induced by ligation of the left anterior descending artery in knockout (KO) mice, ERαKO and ERβKO, respectively, and non-KO littermate-controls, C57Bl/6 mice. The hearts were harvested after 12 days. A part of the periinfarct tissue was collected for ERα and ERβ mRNA expression determination by real-time polymerase chain reaction. Using immunohistochemistry, ERα and ERβ protein expression and capillary and arteriolar densities were blindly determined in the periinfarct area.

Results: In myocardium disrupted mRNA was upregulated in both ERαKO and ERβKO, (p < 0.005) and did not change after MI. There was no change in mRNA expression of ERα or ERβ in wild type mice after MI. Expression of ERβ in ERαKO and of ERα in ERβKO did not change. Following MI ERα or ERβ could not be demonstrated by immunohistochemistry in either wild type or ERαKO or ERβKO. The capillary and arteriolar densities after MI did not differ between the groups in the periinfarct area.

Conclusions: Although disrupted ER mRNA is upregulated in myocardium of ER knockout mice, no change in these or native receptors occurs following MI. At least in this model ER therefore seems not to have a role in myocardial arteriogenesis and angiogenesis after MI.
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http://dx.doi.org/10.3109/14017431.2011.569941DOI Listing
August 2011

A Novel Descriptive, Intelligible and Ordered (DINO) classification of coronary bifurcation lesions. Review of current classifications.

Circ J 2011 24;75(2):299-305. Epub 2010 Dec 24.

Department of Cardiology, Karolinska Institute, Karolinska University Hospital, Huddinge, S-141 86 Stockholm.

Background: Several classification systems for coronary artery bifurcation lesions (CABL) have been described in the literature, but despite the commendable effort to simplify a difficult subject in interventional cardiology, all of them have certain limitations and shortcomings.

Methods And Results: The proposed Descriptive, INtelligible and Ordered (DINO) is a new descriptive and clinically oriented system of classifying CABLs. This classification system takes into consideration more details of the side branch angulation relative to the main branch. It uses self-explanatory terms and mnemonic characters (acronyms related to the branches of the bifurcation and the shape of side branch angulation). The DINO classification describes the extent of CABL distribution and designates its localization at the bifurcation region. Moreover, systematized simple and easy to remember terms may form a relevant classification basis for multicenter and meta-analysis investigations.

Conclusions: The DINO is the first verbally anchored, all-inclusive classification system of CABLs. It describes precisely side branch angulation, using self-explanatory and instructive terms that describe both the extent of the lesion's distribution and its localization. The current coronary bifurcation lesion classifications are reviewed.
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http://dx.doi.org/10.1253/circj.cj-10-0614DOI Listing
May 2011

Cyclic variability of stromal cell-derived factor-1 and endothelial progenitor cells during the menstrual cycle.

Int J Mol Med 2011 Feb 2;27(2):221-6. Epub 2010 Dec 2.

Department of Clinical Science, Intervention and Technology (CLINTEC), Division of Transplantation Surgery, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden.

The endometrium goes through a unique cycle of physiological angiogenesis during the normal menstrual cycle (MC). We studied whether there is a correlation between endothelial progenitor cells (EPCs) and plasma and endometrial levels of angiogenic growth factors during the MC. Ten healthy, regularly menstruating women provided blood samples and another 16 supplied endometrial biopsies. Blood samples were obtained over a single MC: twice in the proliferative and once in the secretory phase and at ovulation. Endometrial biopsies were provided in the proliferative or in the secretory phase. We assessed plasma levels of vascular endothelial and fibroblast growth factors, granulocyte and granulocyte-macrophage colony-stimulating factors and stromal cell-derived factor-1 (SDF-1) by ELISA; EPCs by a colony-forming unit (CFU) assay; immunostaining for endometrial SDF-1 by computer-assisted software; and endothelial cell (EC) markers by flow cytometry. In the proliferative phase, SDF-1 levels were significantly higher than during the secretory phase. EPC-CFUs correlated negatively to SDF-1 levels. Endometrial SDF-1 expression tended to be higher in the secretory than in the proliferative phase. Furthermore, vascular endothelial growth factor receptors and Tie-2 EPCs showed a cyclic pattern over the MC. Our results point to SDF-1 as a novel mediator of EPC trafficking during the MC.
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http://dx.doi.org/10.3892/ijmm.2010.570DOI Listing
February 2011

Anti-endothelial cell antibodies are increased in patients with previous myocardial infarction.

Scand Cardiovasc J 2010 Oct 8;44(5):255-9. Epub 2010 Jun 8.

Division of Transplantation Surgery, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden.

Objectives: Atherosclerosis is an inflammatory disease of multifactorial origin, in which immune cells together with metabolic risk factors may initiate, propagate, and activate lesions in the arterial tree. We investigated the role of auto-antibodies against endothelial cells in patients with previous myocardial infarction.

Design: One hundred and four patients were studied four to five years after acute myocardial infarction (aged 36-84 years) and 83 sex-matched healthy controls (aged 32-70 years). Anti-endothelial cells IgM and IgG auto-antibodies (AECA) were quantified in plasma using flow cytometry.

Results: IgM and IgG AECA were significantly higher (23.08 ± 0.81 and 10.63 ± 0.31 channel shifts, respectively; p < 0.001) in patients as compared to controls (13.40 ± 0.95 and 3.53 ± 0.54 channel shifts, respectively). Further, patients who got an invasive treatment had significantly higher levels of AECA as compared to patients with only medical treatment. Plasma concentration of IgG was positively (p < 0.05) correlated to the levels of high-sensitivity C-reactive protein (hsCRP).

Conclusions: We report for the first time evidence that AECA are related to signs of inflammation and are increased in patients with atherosclerosis and previous myocardial infarction and with further increase with severity of disease.
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http://dx.doi.org/10.3109/14017431003797168DOI Listing
October 2010

Islet-1 cells are cardiac progenitors present during the entire lifespan: from the embryonic stage to adulthood.

Stem Cells Dev 2010 Oct;19(10):1601-15

Department of Medicine, Division of Cardiology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.

The aim of this study was to longitudinally characterize the distribution of cells actively expressing the progenitor transcription factor islet-1 (Isl1+) during the embryonic life, the postnatal period, and adulthood. In this study, we have used direct immunohistochemical staining toward the protein Isl1 in a longitudinal rat model. Cells actively expressing Isl1 were traced in embryos from gestational day (GD) 11 until adulthood. In early cardiac development (GD 11), the Isl1+ progenitors were located in a greater abundance in the paracardiac regions, areas suggested to be the second heart field. To a lesser extent, Isl1+ cells were present within the bulbotruncal region and the truncus arteriosus. During the following days until GD 15, the Isl1+ cells were mainly observed at the proximal outflow tract (OFT) and at the inflow area of the right atrium. No Isl1+ cells were detected in the left ventricle. Compared with GD 11, more Isl1+ cells seemed to co-express cardiomyocyte markers and a minority of the Isl1+ cells was undifferentiated. Unexpectedly, only few undifferentiated Isl1+ cells were Ki67+ while a lot of TnT+ cardiomyocytes were proliferating in the ventricles. After birth, immature Isl1+ cells were still present in the OFT where they resided until adulthood. Our data suggest that during embryogenesis, Isl1+ cells migrate from extracardiac regions into the proximal part of the heart, proliferating and giving rise to cardioblasts. Unexpectedly, only a minority of the Isl1+ cells while a majority of ventricular cardiomyocytes were proliferating. The Isl1+ cell pool persists into adulthood, which might open up new strategies to repair damaged myocardium.
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http://dx.doi.org/10.1089/scd.2009.0483DOI Listing
October 2010

Depressed expression of angiogenic growth factors in the subacute phase of myocardial ischemia: a mechanism behind the remodeling plateau?

Coron Artery Dis 2010 Mar;21(2):65-71

Department of Medicine, Division of Cardiology, Section of Integrative Physiology, Karolinska University Hospital, Karolinska Institutet, 141 86 Stockholm, Sweden.

Background And Aims: To investigate whether, in the subacute phase of acute myocardial infarction, in the peri-infarcted area the expressions of the vascular endothelial growth factor (VEGF-A) and angiopoietin (Ang) ligand receptors are depressed, and whether overexpression of these angiogens counteracts a downregulation of myocardial function.

Methods: Acute myocardial infarction was induced by left anterior descending artery ligation and overexpression through injection of human VEGF-A165 and Ang-1 plasmids. The capillary and arteriolar densities, Akt-1 phosphorylation and citrate synthase activity were measured concurrent with the expression of VEGF-A, VEGFR1 and R2, Ang-1, Ang-2 and Tie-2.

Results: One day after AMI, VEGR-2 was unchanged but all other measured factors in the two families were upregulated. After day 2, the Ang-2 expression increased but other measured factors decreased. After gene transfer, the vascular supply, Akt phosphorylation and citrate synthase activity were higher in the peri-infarcted area, where also the endogenous angiogenic growth factor expressions were increased.

Conclusion: A rapid decrease in angiogenic stimulating factors occurs in the subacute phase of AMI and is related to a progressive decrease in myocardial contraction. A negative consequence of such a circuit is a successive reduction in the vascular supply and contractility in areas with reduced perfusion. These negative adaptations can be counteracted by angiogen overexpression.
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http://dx.doi.org/10.1097/MCA.0b013e3283349cbbDOI Listing
March 2010

Early first trimester human embryonic cardiac Islet-1 progenitor cells and cardiomyocytes: Immunohistochemical and electrophysiological characterization.

Stem Cell Res 2010 Jan 6;4(1):69-76. Epub 2009 Nov 6.

Karolinska Institute at Clinical Research Centre, Novum, Sweden.

The aims of this study were to systematically characterize the distribution, proliferation, and differentiation of Islet-1(+)(Isl1(+)) progenitor cells in the early first trimester human embryonic heart during which period most of the organogenesis takes place. In hearts of gestational week 5 to 10 Isl1(+)cells were identified and mainly clustered in the outflow tract and to a lesser extent in the atria and in the right ventricle. Some of the clusters were also troponin T(+). Unexpectedly a only few Isl1(+)cells were Ki67(+)while in the ventricles a majority of Isl1(-)troponinT(+)cells were Ki67(+). Cultures derived from the digested embryonic heart developed into spontaneously beating cardiospheres. At harvest cells in these cardiospheres showed frequent expression of troponin T(+)and Nkx2.5(+), while Isl1 was expressed only in scattered cells. Only a minority of the cultured cells expressed Ki67. The cardiospheres could be frozen, thawed, and recultured to beating cardiospheres. In a multielectrode array system, the beating cardiospheres were responsive to adrenergic stimulation and exhibited rate-dependent action potential duration. In conclusion, the early first trimester human embryonic heart expresses clusters of Isl1(+)cells, some of which differentiate into cardiomyocytes. Unexpectedly, only a minority of the Isl1(+)cells, while a majority of ventricular cardiomyocytes, were proliferating. Spontaneously beating cardiospheres could be derived from the human embryonic heart and these cardiospheres showed functional frequency control.
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http://dx.doi.org/10.1016/j.scr.2009.10.001DOI Listing
January 2010

The ischemic preconditioning effect of adenosine in patients with ischemic heart disease.

Cardiovasc Ultrasound 2009 Nov 5;7:52. Epub 2009 Nov 5.

The Karolinska Institute, Department of Cardiology, Karolinska University Hospital, Huddinge, Stockholm, Sweden.

Introduction: In vivo and in vitro evidence suggests that adenosine and its agonists play key roles in the process of ischemic preconditioning. The effects of low-dose adenosine infusion on ischemic preconditioning have not been thoroughly studied in humans.

Aims: We hypothesised that a low-dose adenosine infusion could reduce the ischemic burden evoked by physical exercise and improve the regional left ventricular (LV) systolic function.

Materials And Methods: We studied nine severely symptomatic male patients with severe coronary artery disease. Myocardial ischemia was induced by exercise on two separate occasions and quantified by Tissue Doppler Echocardiography. Prior to the exercise test, intravenous low-dose adenosine or placebo was infused over ten minutes according to a randomized, double blind, cross-over protocol. The LV walls were defined as ischemic if a reduction, no increment, or an increment of < 15% in peak systolic velocity (PSV) was observed during maximal exercise compared to the baseline values observed prior to placebo-infusion. Otherwise, the LV walls were defined as non-ischemic.

Results: PSV increased from baseline to maximal exercise in non-ischemic walls both during placebo (P = 0.0001) and low-dose adenosine infusion (P = 0.0009). However, in the ischemic walls, PSV increased only during low-dose adenosine infusion (P = 0.001), while no changes in PSV occurred during placebo infusion (P = NS).

Conclusion: Low-dose adenosine infusion reduced the ischemic burden and improved LV regional systolic function in the ischemic walls of patients with exercise-induced myocardial ischemia, confirming that adenosine is a potential preconditioning agent in humans.
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http://dx.doi.org/10.1186/1476-7120-7-52DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2779183PMC
November 2009

Preconditioning effects of adenosine in patients with severe coronary artery disease but preserved coronary flow reserve.

Coron Artery Dis 2009 Aug;20(5):354-9

Department of Cardiology, Karolinska Institute, Karolinska University Hospital, Huddinge, 141 86 Stockholm, Sweden.

Background: Adenosine plays a key role in different protective and adaptive responses to ischemia and has been suggested to induce ischemic preconditioning.

Aim: To investigate whether a low-dose adenosine infusion reduces the ischemic burden induced by pharmacological stress without affecting the coronary flow reserve (CFR).

Materials And Methods: Myocardial ischemia was induced by dobutamine stress test and quantified by tissue Doppler echocardiography in 11 patients with advanced coronary artery disease. CFR was quantified during high-dose adenosine infusion by contrast echocardiography. Before the dobutamine stress test and contrast echocardiography, intravenous low-dose adenosine or placebo was infused over 15 min according to a randomized, double-blind, cross-over protocol. Echocardiographic left ventricular (LV) apical images and flow pattern of left anterior descending coronary artery (LAD) were obtained at baseline, during adenosine/placebo infusion, maximal, and recovery phases.Furthermore, the LV walls were categorized as ischemic or nonischemic according to a predefined ischemic threshold of at least 25% increment in peak systolic velocity (PSV)from baseline to maximal stress. CFR was measured as the ratio of peak/baseline of maximal diastolic velocity in the distal LAD.

Results: PSV increased both during placebo and adenosine infusions from baseline to maximal stress. However, in the ischemic walls, the PSV increased only during adenosine infusion, whereas no differences were observed in the nonischemic walls. There were no differences in blood pressure, heart rate, or regional CFR during placebo or adenosine infusion.

Conclusion: Low-dose adenosine infusion improves regional LV systolic function in the ischemic walls, without any effect on CFR, suggesting that the observed improvement may be because of ischemic preconditioning.
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http://dx.doi.org/10.1097/mca.0b013e32832ac5c1DOI Listing
August 2009

A novel stenting technique for coronary artery bifurcation stenosis.

Catheter Cardiovasc Interv 2009 Jun;73(7):903-9

Department of Cardiology, Karolinska Institute at Karolinska University Hospital, Stockholm, Sweden.

A novel stenting technique, using one stent strategy, designed to treat type Medina 1,0,0 coronary bifurcation lesions, is described. The atherosclerotic plaque burden in this category of bifurcation lesions is located in the proximal segment of the main branch (MB) of a coronary bifurcation in which the side branch has a sharp angulation (T- or reverse-shaped) relative to the MB. The advantages of this technique are the accurate placement of the stent tailored to cover solely the bifurcation lesion, shoving the plaque burden away from the side branch ostium during stent expansion and the ability to maintain guide wire access in the branch at highest risk of occlusion obviating the need for more cumbersome and time consuming percutaneous coronary intervention procedure.
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http://dx.doi.org/10.1002/ccd.22031DOI Listing
June 2009

Relationship of plasma erythropoietin to long-term outcome in acute coronary syndrome.

Int J Cardiol 2010 Aug 9;143(2):165-70. Epub 2009 Mar 9.

Department of Medicine H7, Section of Cardiology, Huddinge, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.

Background: Erythropoietin has been related to adverse prognosis in patients with heart failure, but it is unknown whether it adds prognostic information in acute coronary syndrome.

Methods: Plasma erythropoietin was measured on admission with enzyme-linked immunosorbent assay in 627 patients. Patients were divided into three groups depending on their erythropoietin level and followed for myocardial infarction (MI) (median 6 months) and mortality (median 39 months). Cox regression models were used to evaluate erythropoietin compared to clinical variables; age, gender, diabetes, smoking, prior MI, heart failure, hypertension and revascularization. In a second Cox regression model, laboratory markers were assessed; hemoglobin, estimated glomerular filtration rate (eGFR), C-reactive protein (CRP), cardiac troponin T (cTnT) and N-terminal pro-brain-natriuretic peptide (NT-proBNP).

Results: Patients with the highest erythropoietin level (>8.8 mU/mL, n=205) had a 47% increased mortality (HR 1.47, 95% CI 1.04-2.06, p=0.028) when adjusted for clinical variables. Compared to laboratory risk markers, erythropoietin added prognostic information (HR 1.59, 95% CI 1.05-2.38, p=0.027) when adjusted for hemoglobin, eGFR and CRP. Erythropoietin (HR 1.21, 95% CI 0.79-1.86, p=0.387) was no longer significantly associated with mortality when cTnT and NT-proBNP were added. Erythropoietin was not related to the risk of future MI (HR 1.24, 95% CI 0.65-2.33, p=0.513).

Conclusion: Elevated erythropoietin level was associated with increased mortality in patients admitted with possible ACS when adjusted for clinical variables, or for kidney function and hemoglobin. However, erythropoietin does not add prognostic information when markers of myocardial necrosis and dysfunction are available in ACS.
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http://dx.doi.org/10.1016/j.ijcard.2009.02.003DOI Listing
August 2010

Gene transfer to mouse heart and skeletal muscles using a minicircle expressing human vascular endothelial growth factor.

J Cardiovasc Pharmacol 2009 Jan;53(1):18-23

Vecura, Clinical Research Center, Karolinska University Hospital Huddinge, Stockholm, Sweden.

Background: : Gene transfer to heart muscle is a promising modality to treat ischemic heart disease. However, current vectors are inefficient and need to be improved. A novel vector system that shows great promise is the minicircle (MC) vector being smaller than conventional plasmid vectors and devoid of bacterial sequences.

Aims: : To study gene transfer of MC DNA, expressing the human vascular endothelial growth factor (hVEGF), to mouse heart and skeletal muscles and to compare it with one of the efficient plasmids used in cardiovascular trials, the phVEGF165 containing the same expression cassette as the MC.

Results: : The MC and the phVEGF165 plasmid show similar expression patterns both in vitro and in mouse heart and skeletal muscle studies in vivo on molar basis (equal expression in heart 24 hours, 0.9 fold lower expression from MC in heart and 1.9 fold higher in skeletal muscle at 7 days), whereas on weight basis the MC construct was more efficient in skeletal muscle (5.6 fold higher expression, P < 0.05), and at least as efficient in heart (1.6 fold higher expression).

Conclusions: : The gene expression is similar in the 2 vector systems, so the smaller size and the fact that the MC construct is devoid of bacterial sequences and antibiotics resistance gene make the MC vector an attractive alternative for nonviral gene therapy.
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http://dx.doi.org/10.1097/FJC.0b013e318194234eDOI Listing
January 2009

[Improved diagnostics yield better and better treatment].

Lakartidningen 2008 Oct 22-28;105(43):3022-3

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November 2008

Refractory angina pectoris carries a favourable prognosis: a three-year follow-up of 150 patients.

Scand Cardiovasc J 2008 Oct;42(5):291-4

Department of Cardiology, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden.

Objective: To investigate the three-year prognosis in refractory angina pectoris.

Patients: Two hundred and forty three patients were screened at six European university hospitals for a gene therapy trial. In 150 patients refractory angina pectoris could be confirmed. Vital status was assessed after a mean of 33 months.

Results: At baseline, mean age was 63+/-9 years and mean LVEF was 52+/-12%. In 61% there was a history of myocardial infarction and 83% had previously been revascularised. Mortality was 5.5% at one year and 13.5% at three years. New revascularisation options were found in 9.5% of the 243 screened patients at baseline coronary angiography. Additionally, in 6% of the trial patients the protocol-specified angiogram after three months revealed new significant stenosis, which was treated by percutaneous intervention.

Conclusions: Annual mortality in refractory angina pectoris seems higher than in stable angina pectoris in general, but substantially lower than after myocardial infarction. The "refractoriness" of these patients should be re-evaluated regularly, as new revascularisation options often occur.
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http://dx.doi.org/10.1080/14017430802084997DOI Listing
October 2008

Modulation of ephrinB2 leads to increased angiogenesis in ischemic myocardium and endothelial cell proliferation.

Biochem Biophys Res Commun 2008 Aug 20;373(3):355-9. Epub 2008 Jun 20.

Department of Cardiology, Karolinska University Hospital, Karolinska Institute, S141 86 Stockholm, Sweden.

Eph/ephrin signaling is pivotal in prenatal angiogenesis while its potential role in postnatal angiogenesis largely remains to be explored. Therefore its putative angiogenic and therapeutic effects were explored in endothelium and in myocardial ischemia. In culture of human aortic endothelial cells the fusion protein ephrinB2-Fc induced cell proliferation (p<0.0005) and in the murine aortic ring model ephrinB2-Fc induced increased sprouting (p<0.05). Myocardial infarction was induced by ligation of the left anterior descending artery in mouse. During the following 2 weeks mRNA of the receptor/ligand pair EphB4/ephrinB2 was expressed dichotomously (p<0.05) and other Eph/ephrin pairs were expressed to a lesser degree. Twenty-four hours after intraperitoneal administration of ephrinB2-Fc it was detected in abundance throughout the myocardium along capillaries, showing signs of increased mitosis. After 4 weeks the capillary density was increased 28% in the periinfarcted area (p<0.05) to a level not different from healthy regions of the heart where no change was observed. These results implicate that EphB4/ephrinB2 is an important signaling pathway in ischemic heart disease and its modulation may induce therapeutic angiogenesis.
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http://dx.doi.org/10.1016/j.bbrc.2008.06.036DOI Listing
August 2008

Costimulation blockade induces tolerance to HESC transplanted to the testis and induces regulatory T-cells to HESC transplanted into the heart.

Stem Cells 2008 Jul 8;26(7):1850-7. Epub 2008 May 8.

Department of Molecular Medicine and Surgery, Division of Cardiothoracic Surgery and Anaesthesiology, Karolinska University Hospital, S-171 76, Stockholm, Sweden.

In order to study the ability of costimulation blockade to induce tolerance to human embryonic stem cells (HESC), severe combined immunodeficient (SCID), and immunocompetent C57BL/6 mice treated with costimulation blockade received intratesticular and intramyocardial HESC transplants. All SCID mice with intratesticular HESC transplants developed teratoma. When SCID mice were transplanted intramyocardially, only two of five mice developed teratoma-like tumors. C57BL/6 mice transplanted intratesticularly and treated with costimulation blockade all developed teratoma and were surrounded by CD4(+)CD25(+)Foxp3(+) T-cells, while isotype control treated recipients rejected their grafts. Most C57BL/6 mice transplanted intramyocardially and treated with costimulation blockade demonstrated lymphocytic infiltrates 1 month after transplantation, whereas one maintained its graft. Isolation of regulatory T-cells from intramyocardial transplanted recipients treated with costimulation blockade demonstrated specificity toward undifferentiated HESC and down-regulated naive T-cell activation toward HESC. These results demonstrate that costimulation blockade is sufficiently robust to induce tolerance to HESC in the immune-privileged environment of the testis. HESC specific regulatory T-cells developed to HESC transplanted to the heart and the success of transplantation was similar to that seen in SCID mice.
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http://dx.doi.org/10.1634/stemcells.2008.0111DOI Listing
July 2008

Therapeutic angiogenesis gains a leg to stand on.

Mol Ther 2008 May;16(5):808-10

Karolinska Institute, Department of Cardiology, Karolinska University Hospital, Stockholm, Sweden.

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http://dx.doi.org/10.1038/mt.2008.65DOI Listing
May 2008

Erythropoietin has an antiapoptotic effect after myocardial infarction and stimulates in vitro aortic ring sprouting.

Biochem Biophys Res Commun 2008 Jun 14;371(1):75-8. Epub 2008 Apr 14.

Department of Cardiology, M52 Karolinska University Hospital, S14186 Stockholm, Sweden.

Aims were to explore if darbepoietin-alpha in mouse can induce angiogenesis and if moderate doses after myocardial infarction stimulates periinfarct capillary and arteriolar densities, cell proliferation, and apoptosis. Myocardial infarction was induced by ligation of LAD. Mouse aortic rings (0.8mm) were cultured in matrigel and the angiogenic sprouting was studied after addition of darbepoietin-alpha with and without VEGF-165. After 12 days the hemoglobin concentration was 25% higher in the darbepoietin-alpha treated mice than in the control group. No difference in capillary densities in the periinfarct or noninfarcted areas was seen with darbepoietin-alpha. Cell proliferation was about 10 times higher in the periinfarct area than in the noninfarcted wall. Darbepoietin-alpha treatment led to a decrease of cell proliferation (BrdU, (p<0.02)) and apoptosis (TUNEL, p<0.005) with about 30% in the periinfarct area. Darbepoietin-alpha and VEGF-165 both independently induced sprouting from aortic rings. The results suggest that darbepoietin-alpha can induce angiogenesis but that moderate doses after myocardial infarction are not angiogenic but antiapoptotic.
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http://dx.doi.org/10.1016/j.bbrc.2008.04.025DOI Listing
June 2008