Publications by authors named "Elif Levent"

6 Publications

  • Page 1 of 1

Inhibition of Prolyl-Hydroxylase Domain Enzymes Protects From Reoxygenation Injury in Engineered Human Myocardium.

Circulation 2020 Oct 26;142(17):1694-1696. Epub 2020 Oct 26.

Institute of Pharmacology and Toxicology, University Medical Center Göttingen, Germany (E.L., C.N., L.C.Z., W-H.Z., M.T.).

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http://dx.doi.org/10.1161/CIRCULATIONAHA.119.044471DOI Listing
October 2020

Optogenetic Monitoring of the Glutathione Redox State in Engineered Human Myocardium.

Front Physiol 2019 4;10:272. Epub 2019 Apr 4.

Institute of Pharmacology & Toxicology, University Medical Center Göttingen, Göttingen, Germany.

Redox signaling affects all aspects of cardiac function and homeostasis. With the development of genetically encoded fluorescent redox sensors, novel tools for the optogenetic investigation of redox signaling have emerged. Here, we sought to develop a human heart muscle model for in-tissue imaging of redox alterations. For this, we made use of (1) the genetically-encoded Grx1-roGFP2 sensor, which reports changes in cellular glutathione redox status (GSH/GSSG), (2) human embryonic stem cells (HES2), and (3) the engineered heart muscle (EHM) technology. We first generated HES2 lines expressing Grx1-roGFP2 in cytosol or mitochondria compartments by TALEN-guided genomic integration. Grx1-roGFP2 sensor localization and function was verified by fluorescence imaging. Grx1-roGFP2 HES2 were then subjected to directed differentiation to obtain high purity cardiomyocyte populations. Despite being able to report glutathione redox potential from cytosol and mitochondria, we observed dysfunctional sarcomerogenesis in Grx1-roGFP2 expressing cardiomyocytes. Conversely, lentiviral transduction of Grx1-roGFP2 in already differentiated HES2-cardiomyocytes and human foreskin fibroblast was possible, without compromising cell function as determined in EHM from defined Grx1-roGFP2-expressing cardiomyocyte and fibroblast populations. Finally, cell-type specific GSH/GSSG imaging was demonstrated in EHM. Collectively, our observations suggests a crucial role for redox signaling in cardiomyocyte differentiation and provide a solution as to how this apparent limitation can be overcome to enable cell-type specific GSH/GSSG imaging in a human heart muscle context.
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http://dx.doi.org/10.3389/fphys.2019.00272DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6460052PMC
April 2019

Defined Engineered Human Myocardium With Advanced Maturation for Applications in Heart Failure Modeling and Repair.

Circulation 2017 May 6;135(19):1832-1847. Epub 2017 Feb 6.

From Institute of Pharmacology and Toxicology, University Medical Center Göttingen, Germany (M.T., J.E.H., P.B., S.S., T.M., M.-L.C.L., E.L., F.R., S.Z., E. Wettwer, W.-H.Z.); German Center for Cardiovascular Research (DZHK), partner site Göttingen, Germany (M.T., J.E.H., P.B., S.S., T.M., M.-L.C.L., E.L., F.R., S.Z., E. Wingender, W.A.L., W.-H.Z.); Institute of Bioinformatics, University Medical Center Göttingen, Germany (S.Z., E. Wingender); Stanford Cardiovascular Institute (J.R., M.W., J.D.G., J.C.W.) and Department of Radiology (J.D.G., J.C.W.), Molecular Imaging Program, Stanford University School of Medicine, CA; The Sohnis Laboratory for Cardiac Electrophysiology and Regenerative Medicine, Technion-Israel Institute of Technology, Haifa (I.K., L.G.); Institute of Pharmacology and Toxicology, Technical University Dresden, Germany (E. Wettwer, U.R.); University Medical Center Utrecht and Hubrecht Institute, The Netherlands (P.D., L.W.v.L.); Leiden University Medical Center, The Netherlands (M.J.G.); Clinic for Cardiology and Pneumology, University Medical Center Göttingen, Germany (S.K., K.T., G.H., W.A.L.); Center for Applied Technology, Beckman Research Institute, City of Hope, Duarte, CA (L.A.C.); Department of Cardiovascular Physiology, Institute of Physiology, Ruhr University Bochum, Bochum, Germany (A.U., W.A.L.); New Laura and Isaac Perlmutter Cancer Center at New York University Langone (T.A., B.N.); and McEwen Centre for Regenerative Medicine, Toronto, Canada (G.K.). The current address for Dr Hudson is Laboratory for Cardiac Regeneration, School of Biomedical Sciences, The University of Queensland, Australia.

Background: Advancing structural and functional maturation of stem cell-derived cardiomyocytes remains a key challenge for applications in disease modeling, drug screening, and heart repair. Here, we sought to advance cardiomyocyte maturation in engineered human myocardium (EHM) toward an adult phenotype under defined conditions.

Methods: We systematically investigated cell composition, matrix, and media conditions to generate EHM from embryonic and induced pluripotent stem cell-derived cardiomyocytes and fibroblasts with organotypic functionality under serum-free conditions. We used morphological, functional, and transcriptome analyses to benchmark maturation of EHM.

Results: EHM demonstrated important structural and functional properties of postnatal myocardium, including: (1) rod-shaped cardiomyocytes with M bands assembled as a functional syncytium; (2) systolic twitch forces at a similar level as observed in bona fide postnatal myocardium; (3) a positive force-frequency response; (4) inotropic responses to β-adrenergic stimulation mediated via canonical β- and β-adrenoceptor signaling pathways; and (5) evidence for advanced molecular maturation by transcriptome profiling. EHM responded to chronic catecholamine toxicity with contractile dysfunction, cardiomyocyte hypertrophy, cardiomyocyte death, and N-terminal pro B-type natriuretic peptide release; all are classical hallmarks of heart failure. In addition, we demonstrate the scalability of EHM according to anticipated clinical demands for cardiac repair.

Conclusions: We provide proof-of-concept for a universally applicable technology for the engineering of macroscale human myocardium for disease modeling and heart repair from embryonic and induced pluripotent stem cell-derived cardiomyocytes under defined, serum-free conditions.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.116.024145DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5501412PMC
May 2017

Pre- and post-conditional inhibition of prolyl-4-hydroxylase domain enzymes protects the heart from an ischemic insult.

Pflugers Arch 2015 Oct 13;467(10):2141-9. Epub 2015 Jan 13.

Institute of Cardiovascular Physiology, University Medical Center, Georg-August-University Göttingen, Humboldtallee 23, 37073, Göttingen, Germany.

Several genetically modified mouse models implicated that prolyl-4-hydroxylase domain (PHD) enzymes are critical mediators for protecting tissues from an ischemic insult including myocardial infarction by affecting the stability and activation of hypoxia-inducible factor (HIF)-1 and HIF-2. Thus, the current efforts to develop small-molecule PHD inhibitors open a new therapeutic option for myocardial tissue protection during ischemia. Therefore, we aimed to investigate the applicability and efficacy of pharmacological HIFα stabilization by a small-molecule PHD inhibitor in the heart. We tested for protective effects in the acute phase of myocardial infarction after pre- or post-conditional application of the inhibitor. Application of the specific PHD inhibitor 2-(1-chloro-4-hydroxyisoquinoline-3-carboxamido) acetate (ICA) resulted in HIF-1α and HIF-2α accumulation in heart muscle cells in vitro and in vivo. The rapid and robust responsiveness of cardiac tissue towards ICA was further confirmed by induction of the known HIF target genes heme oxygenase-1 and PHD3. Pre- and post-conditional treatment of mice undergoing myocardial infarction resulted in a significantly smaller infarct size. Tissue protection from ischemia after pre- or post-conditional ICA treatment demonstrates that there is a therapeutic time window for the application of the PHD inhibitor (PHI) post-myocardial infarction, which might be exploited for acute medical interventions.
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http://dx.doi.org/10.1007/s00424-014-1667-zDOI Listing
October 2015

miR-133a enhances the protective capacity of cardiac progenitors cells after myocardial infarction.

Stem Cell Reports 2014 Dec 20;3(6):1029-42. Epub 2014 Nov 20.

Immunology and Oncology Department, National Center for Biotechnology, CSIC, 28049 Madrid, Spain; Department of Cardiovascular Development and Repair, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III, 28029 Madrid, Spain. Electronic address:

miR-133a and miR-1 are known as muscle-specific microRNAs that are involved in cardiac development and pathophysiology. We have shown that both miR-1 and miR-133a are early and progressively upregulated during in vitro cardiac differentiation of adult cardiac progenitor cells (CPCs), but only miR-133a expression was enhanced under in vitro oxidative stress. miR-1 was demonstrated to favor differentiation of CPCs, whereas miR-133a overexpression protected CPCs against cell death, targeting, among others, the proapoptotic genes Bim and Bmf. miR-133a-CPCs clearly improved cardiac function in a rat myocardial infarction model by reducing fibrosis and hypertrophy and increasing vascularization and cardiomyocyte proliferation. The beneficial effects of miR-133a-CPCs seem to correlate with the upregulated expression of several relevant paracrine factors and the plausible cooperative secretion of miR-133a via exosomal transport. Finally, an in vitro heart muscle model confirmed the antiapoptotic effects of miR-133a-CPCs, favoring the structuration and contractile functionality of the artificial tissue.
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http://dx.doi.org/10.1016/j.stemcr.2014.10.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4264058PMC
December 2014

Lights on for HIF-1α: genetically enhanced mouse cardiomyocytes for heart tissue imaging.

Cell Physiol Biochem 2014 30;34(2):455-62. Epub 2014 Jul 30.

Institute of Cardiovascular Physiology, Georg-August-University Göttingen, Göttingen, Germany.

Background/aims: The hypoxia inducible factor-1 (HIF-1) is a suitable marker for tissue oxygenation. We intended to develop cardiomyocytes (CMs) expressing the oxygen-dependent degradation domain of HIF-1α fused to the firefly luciferase (ODD-Luc) followed by proof-of-concept for its applicability in the assessment of heart muscle oxygenation.

Methods And Results: We first generated embryonic stem cell (ESC) lines (ODD-Luc ESCs) from a Tg ROSA26 ODD-Luc/+ mouse. Subsequent CMs selection was facilitated by stable integration of an antibiotic resistance expressed under the control of the αMHC promoter. ODD-Luc ESCs showed a strong Luc-signal within 1 h of hypoxia (1% oxygen), which coincided with endogenous HIF-1α. Engineered heart muscle (EHM) constructed with ODD-Luc CMs confirmed the utility of the model to sense hypoxia, and monitor reoxygenation also in a multicellular heart muscle model. Pharmacologically induced inotropy/chronotropy under isoprenaline resulted in enhanced Luc-signal suggesting enhanced oxygen consumption, leading to notable myocardial hypoxia.

Conclusions: ODD-Luc-CMs can be used to monitor dynamic changes of cardiomyocyte oxygenation in living heart muscle samples. We provide proof-of-concept for pharmacologically induced myocardial interventions and envision applications of the developed model in drug screens and fundamental studies of ischemia/reperfusion injury.
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http://dx.doi.org/10.1159/000363014DOI Listing
April 2015