1
|
Rexius-Hall ML, Khalil NN, Escopete SS, Li X, Hu J, Yuan H, Parker SJ, McCain ML. A myocardial infarct border-zone-on-a-chip demonstrates distinct regulation of cardiac tissue function by an oxygen gradient. SCIENCE ADVANCES 2022; 8:eabn7097. [PMID: 36475790 PMCID: PMC9728975 DOI: 10.1126/sciadv.abn7097] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
After a myocardial infarction, the boundary between the injured, hypoxic tissue and the adjacent viable, normoxic tissue, known as the border zone, is characterized by an oxygen gradient. Yet, the impact of an oxygen gradient on cardiac tissue function is poorly understood, largely due to limitations of existing experimental models. Here, we engineered a microphysiological system to controllably expose engineered cardiac tissue to an oxygen gradient that mimics the border zone and measured the effects of the gradient on electromechanical function and the transcriptome. The gradient delayed calcium release, reuptake, and propagation; decreased diastolic and peak systolic stress; and increased expression of inflammatory cascades that are hallmarks of myocardial infarction. These changes were distinct from those observed in tissues exposed to uniform normoxia or hypoxia, demonstrating distinct regulation of cardiac tissue phenotypes by an oxygen gradient. Our border-zone-on-a-chip model advances functional and mechanistic insight into oxygen-dependent cardiac tissue pathophysiology.
Collapse
Affiliation(s)
- Megan L. Rexius-Hall
- Laboratory for Living Systems Engineering, Department of Biomedical Engineering, USC Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
| | - Natalie N. Khalil
- Laboratory for Living Systems Engineering, Department of Biomedical Engineering, USC Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
| | - Sean S. Escopete
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Xin Li
- Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Jiayi Hu
- Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Hongyan Yuan
- Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Sarah J. Parker
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Megan L. McCain
- Laboratory for Living Systems Engineering, Department of Biomedical Engineering, USC Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
- Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA
- Corresponding author.
| |
Collapse
|
2
|
Nayir S, Lacour SP, Kucera JP. Active force generation contributes to the complexity of spontaneous activity and to the response to stretch of murine cardiomyocyte cultures. J Physiol 2022; 600:3287-3312. [PMID: 35679256 PMCID: PMC9541716 DOI: 10.1113/jp283083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 06/01/2022] [Indexed: 11/17/2022] Open
Abstract
Abstract Cardiomyocyte cultures exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. In such preparations, beat rate variability exhibits features similar to those of heart rate variability in vivo. Mechanical deformations and forces feed back on the electrical properties of cardiomyocytes, but it is not fully elucidated how this mechano‐electrical interplay affects beating variability in such preparations. Using stretchable microelectrode arrays, we assessed the effects of the myosin inhibitor blebbistatin and the non‐selective stretch‐activated channel blocker streptomycin on beating variability and on the response of neonatal or fetal murine ventricular cell cultures against deformation. Spontaneous electrical activity was recorded without stretch and upon predefined deformation protocols (5% uniaxial and 2% equibiaxial strain, applied repeatedly for 1 min every 3 min). Without stretch, spontaneous activity originated from the edge of the preparations, and its site of origin switched frequently in a complex manner across the cultures. Blebbistatin did not change mean beat rate, but it decreased the spatial complexity of spontaneous activity. In contrast, streptomycin did not exert any manifest effects. During the deformation protocols, beat rate increased transiently upon stretch but, paradoxically, also upon release. Blebbistatin attenuated the response to stretch, whereas this response was not affected by streptomycin. Therefore, our data support the notion that in a spontaneously firing network of cardiomyocytes, active force generation, rather than stretch‐activated channels, is involved mechanistically in the complexity of the spatiotemporal patterns of spontaneous activity and in the stretch‐induced acceleration of beating.
![]() Key points Monolayer cultures of cardiac cells exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. Beating variability in these preparations recapitulates the power‐law behaviour of heart rate variability in vivo. However, the effects of mechano‐electrical feedback on beating variability are not yet fully understood. Using stretchable microelectrode arrays, we examined the effects of the contraction uncoupler blebbistatin and the non‐specific stretch‐activated channel blocker streptomycin on beating variability and on stretch‐induced changes of beat rate. Without stretch, blebbistatin decreased the spatial complexity of beating variability, whereas streptomycin had no effects. Both stretch and release increased beat rate transiently; blebbistatin attenuated the increase of beat rate upon stretch, whereas streptomycin had no effects. Active force generation contributes to the complexity of spatiotemporal patterns of beating variability and to the increase of beat rate upon mechanical deformation. Our study contributes to the understanding of how mechano‐electrical feedback influences heart rate variability.
Collapse
Affiliation(s)
- Seyma Nayir
- Department of Physiology, University of Bern, Bern, Switzerland
| | | | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
| |
Collapse
|
3
|
Podgurskaya AD, Slotvitsky MM, Tsvelaya VA, Frolova SR, Romanova SG, Balashov VA, Agladze KI. Cyclophosphamide arrhythmogenicitytesting using human-induced pluripotent stem cell-derived cardiomyocytes. Sci Rep 2021; 11:2336. [PMID: 33504826 PMCID: PMC7841168 DOI: 10.1038/s41598-020-79085-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 12/04/2020] [Indexed: 11/09/2022] Open
Abstract
Cyclophosphamide (CP) is an anticancer drug, an alkylating agent. Cardiotoxicity of CP is associated with one of its metabolites, acrolein, and clinical cardiotoxicity manifestations are described for cases of taking CP in high doses. Nevertheless, modern arrhythmogenicity prediction assays in vitro include evaluation of beat rhythm and rate as well as suppression of cardiac late markers after acute exposure to CP, but not its metabolites. The mechanism of CP side effects when taken at low doses (i.e., < 100 mg/kg), especially at the cellular level, remains unclear. In this study conduction properties and cytoskeleton structure of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) obtained from a healthy donor under CP were evaluated. Arrhythmogenicity testing including characterization of 3 values: conduction velocity, maximum capture rate (MCR) measurements and number of occasions of re-entry on a standard linear obstacle was conducted and revealed MCR decrease of 25% ± 7% under CP. Also, conductivity area reduced by 34 ± 15%. No effect of CP on voltage-gated ion channels was found. Conduction changes (MCR and conductivity area decrease) are caused by exposure time-dependent alpha-actinin disruption detected both in hiPSC-CMs and neonatal ventricular cardiomyocytes in vitro. Deviation from the external stimulus frequency and appearance of non-conductive areas in cardiac tissue under CP is potentially arrhythmogenic and could develop arrhythmic effects in vivo.
Collapse
Affiliation(s)
- A D Podgurskaya
- Moscow Institute of Physics and Technology (National Research University), Dolgoprudny, Moscow Region, 141701, Russian Federation
| | - M M Slotvitsky
- Moscow Institute of Physics and Technology (National Research University), Dolgoprudny, Moscow Region, 141701, Russian Federation
| | - V A Tsvelaya
- Moscow Institute of Physics and Technology (National Research University), Dolgoprudny, Moscow Region, 141701, Russian Federation
| | - S R Frolova
- Moscow Institute of Physics and Technology (National Research University), Dolgoprudny, Moscow Region, 141701, Russian Federation
| | - S G Romanova
- Moscow Institute of Physics and Technology (National Research University), Dolgoprudny, Moscow Region, 141701, Russian Federation
| | - V A Balashov
- Moscow Institute of Physics and Technology (National Research University), Dolgoprudny, Moscow Region, 141701, Russian Federation
| | - K I Agladze
- Moscow Institute of Physics and Technology (National Research University), Dolgoprudny, Moscow Region, 141701, Russian Federation.
- M.F. Vladimirsky Moscow Regional Clinical Research Institute, Moscow, 129110, Russian Federation.
| |
Collapse
|
4
|
Wei N, Tolkacheva EG. Interplay between ephaptic coupling and complex geometry of border zone during acute myocardial ischemia: Effect on arrhythmogeneity. CHAOS (WOODBURY, N.Y.) 2020; 30:033111. [PMID: 32237767 DOI: 10.1063/1.5134447] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 02/12/2020] [Indexed: 06/11/2023]
Abstract
Acute myocardial ischemia is an imbalance between myocardial blood supply and demand, which is caused by the cessation of blood flow within the heart resulting from an obstruction in one of the major coronary arteries. A severe blockage may result in a region of nonperfused tissue known as ischemic core (IC). As a result, a border zone (BZ) between perfused and nonperfused regions is created due to differences in blood and oxygen supplies. Recent experimental findings reveal a complex "finger-like" geometry in BZ; however, its effect on arrhythmogenicity is not clear. Ephaptic coupling, which relies on the intercalated disk between cell ends, has been suggested to play an active role in mediating intercellular electrical communication when gap junctions are impaired. In this paper, we explored the interplay between ephaptic coupling and the geometry of BZ on action potential propagation across the ischemic region. Our study shows that ephaptic coupling can greatly suppress the occurrence of a conduction block, which points to its beneficial effect. The beneficial effect of ephaptic coupling is more evident in BZ with the "finger-like" geometry. In addition, the complex geometry of BZ, i.e., more frequent, deeper, and wider "fingers," promotes the conduction through the ischemic region. In contrast, the larger size of IC impedes the cardiac conduction across the ischemic region. Our results also show that ephaptic coupling promotes the impact of the complex geometry of BZ on signal propagation; however, it inhibits the impact of IC size.
Collapse
Affiliation(s)
- Ning Wei
- Department of Mathematics, Purdue University, West Lafayette, Indiana 47907, USA
| | - Elena G Tolkacheva
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| |
Collapse
|
5
|
de Bakker JM. Electrogram recording and analyzing techniques to optimize selection of target sites for ablation of cardiac arrhythmias. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2019; 42:1503-1516. [PMID: 31609005 PMCID: PMC6916598 DOI: 10.1111/pace.13817] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 10/03/2019] [Accepted: 10/09/2019] [Indexed: 12/27/2022]
Abstract
The extracellular electrogram is caused by transmembrane currents that flow into extracellular space during propagation of the electrical impulse. Electrograms are usually recorded in unipolar or bipolar mode that have different characteristics, but provide complementary information. Both recording modes have specific advantages, but also suffer from disadvantages. Techniques to circumvent some of the weaknesses are reviewed. The origin of remote and fractionated deflections and their relation with electrode characteristics are discussed. Epicardial and endocardial sites of origin and breakthrough sites as well as the effect of fatty tissue on extracellular electrograms are presented. Induction of tachycardia to assess the arrhythmogenic area is not always possible because of hemodynamic instability of the patient. Techniques to assess sites with high reentry vulnerability without induction of arrhythmias are outlined such as activation‐repolarization mapping and decremental stimulation. Pitfalls of substrate mapping and techniques to avoid them as omnipolar mapping and characterization of complex electrograms by entropy are presented. Technical aspects that influence electrogram morphology as electrode size, filtering, contact force, and catheter position are delineated. Data from the various publications suggest that a combination of unipolar and bipolar electrogram analysis techniques is helpful to optimize determination of target sites for ablation.
Collapse
Affiliation(s)
- Jacques Mt de Bakker
- Heart Center, Department of Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands
| |
Collapse
|
6
|
Imboden M, de Coulon E, Poulin A, Dellenbach C, Rosset S, Shea H, Rohr S. High-speed mechano-active multielectrode array for investigating rapid stretch effects on cardiac tissue. Nat Commun 2019; 10:834. [PMID: 30783104 PMCID: PMC6381132 DOI: 10.1038/s41467-019-08757-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 01/24/2019] [Indexed: 11/25/2022] Open
Abstract
Systematic investigations of the effects of mechano-electric coupling (MEC) on cellular cardiac electrophysiology lack experimental systems suitable to subject tissues to in-vivo like strain patterns while simultaneously reporting changes in electrical activation. Here, we describe a self-contained motor-less device (mechano-active multielectrode-array, MaMEA) that permits the assessment of impulse conduction along bioengineered strands of cardiac tissue in response to dynamic strain cycles. The device is based on polydimethylsiloxane (PDMS) cell culture substrates patterned with dielectric actuators (DEAs) and compliant gold ion-implanted extracellular electrodes. The DEAs induce uniaxial stretch and compression in defined regions of the PDMS substrate at selectable amplitudes and with rates up to 18 s−1. Conduction along cardiomyocyte strands was found to depend linearly on static strain according to cable theory while, unexpectedly, being completely independent on strain rates. Parallel operation of multiple MaMEAs provides for systematic high-throughput investigations of MEC during spatially patterned mechanical perturbations mimicking in-vivo conditions. While strain is known to affect cardiac electrophysiology, experimental systems to interrogate the effect of rapid strain cycles on cardiac tissue are lacking. Here the authors introduce a multielectrode array that can induce rapid dynamic strain cycles on cardiomyocyte strands and see effects of strain amplitude but not strain rate on impulse conduction.
Collapse
Affiliation(s)
- Matthias Imboden
- Soft Transducers Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland. .,Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland.
| | - Etienne de Coulon
- Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland
| | - Alexandre Poulin
- Soft Transducers Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Christian Dellenbach
- Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland
| | - Samuel Rosset
- Soft Transducers Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Herbert Shea
- Soft Transducers Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Stephan Rohr
- Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland.
| |
Collapse
|
7
|
Zhang P, Xu J, Hu W, Yu D, Bai X. Effects of Pinocembrin Pretreatment on Connexin 43 (Cx43) Protein Expression After Rat Myocardial Ischemia-Reperfusion and Cardiac Arrhythmia. Med Sci Monit 2018; 24:5008-5014. [PMID: 30022020 PMCID: PMC6063136 DOI: 10.12659/msm.909162] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Background Cardiac infarction frequently leads to arrhythmia and ischemia/reperfusion (I/R) aggravates cardiac injury. Pinocembrin can resist cerebral ischemia and decrease cardiac infarction area. This study thus generated a rat myocardial I/R model to assess the effect on ventricular rhythm and expression of gap junction connexin (Cx43). Material/Methods Male SD rats were randomly assigned into sham, model, and pinocembrin (30 mg/kg) pretreatment groups (N=15 each). The I/R model was generated by ligation of the left anterior descending coronary artery for 30 min. The pinocembrin group received intravenous injection 10 min before surgery. Heart rate (HR), mean artery pressure (MAP), rate pressure product (RPP), and arrhythmia were observed at 10 min before ischemia, 30 min after ischemia, and at 30, 60, and 120 min after reperfusion. ELISA was used to assess serum CK-MB and cTnI levels. Na+-K+ATPase and Ca+-Mg2+ATPase levels were quantified by spectrometry, followed by HE staining, IHC approach for Cx43 expression, and Western blot for Kir2.1 protein expression. Results Model rats had significantly lower HR, MAP, and RPP than in the sham group, and the pinocembrin pretreatment group had higher serum indexes. Arrhythmia index, CK-MB, and cTnI were higher in the model and pinocembrin groups, while Na+-K+ATPase, Ca+-Mg2+ATPase, Cx43, and Kir2.1 proteins were lower (p<0.05). Conclusions Pinocembrin alleviated ventricular arrhythmia in I/R rats via enhancing Na+-K+ATPase and Ca+-Mg2+ATPase activity and upregulating Cx43 and Kir2.1 protein expression.
Collapse
Affiliation(s)
- Peng Zhang
- Department of Cardiology, Minhang Hospital, Zhongshan Hospital, Fudan University, Shanghai, China (mainland)
| | - Jin Xu
- Department of Anesthesiology, Shanghai East Hospital, Tongji University, Shanghai, China (mainland)
| | - Wei Hu
- Department of Cardiology, Minhang Hospital, Zhongshan Hospital, Fudan University, Shanghai, China (mainland)
| | - Dong Yu
- Department of Cardiology, Minhang Hospital, Zhongshan Hospital, Fudan University, Shanghai, China (mainland)
| | - Xiaolu Bai
- Department of Cardiology, Minhang Hospital, Zhongshan Hospital, Fudan University, Shanghai, China (mainland)
| |
Collapse
|
8
|
Arroyo PA, Alonso S, Weber Dos Santos R. Discretization-dependent model for weakly connected excitable media. Phys Rev E 2018; 97:032214. [PMID: 29776138 DOI: 10.1103/physreve.97.032214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Indexed: 06/08/2023]
Abstract
Pattern formation has been widely observed in extended chemical and biological processes. Although the biochemical systems are highly heterogeneous, homogenized continuum approaches formed by partial differential equations have been employed frequently. Such approaches are usually justified by the difference of scales between the heterogeneities and the characteristic spatial size of the patterns. Under different conditions, for example, under weak coupling, discrete models are more adequate. However, discrete models may be less manageable, for instance, in terms of numerical implementation and mesh generation, than the associated continuum models. Here we study a model to approach discreteness which permits the computer implementation on general unstructured meshes. The model is cast as a partial differential equation but with a parameter that depends not only on heterogeneities sizes, as in the case of quasicontinuum models, but also on the discretization mesh. Therefore, we refer to it as a discretization-dependent model. We validate the approach in a generic excitable media that simulates three different phenomena: the propagation of action membrane potential in cardiac tissue, in myelinated axons of neurons, and concentration waves in chemical microemulsions.
Collapse
Affiliation(s)
- Pedro André Arroyo
- Graduate Program in Computational Modeling, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil
- Department of Physics, Universitat Politècnica de Catalunya, Barcelona, Spain
| | - Sergio Alonso
- Graduate Program in Computational Modeling, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil
- Department of Physics, Universitat Politècnica de Catalunya, Barcelona, Spain
| | - Rodrigo Weber Dos Santos
- Graduate Program in Computational Modeling, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil
| |
Collapse
|
9
|
Kucera JP, Rohr S, Kleber AG. Microstructure, Cell-to-Cell Coupling, and Ion Currents as Determinants of Electrical Propagation and Arrhythmogenesis. Circ Arrhythm Electrophysiol 2017; 10:CIRCEP.117.004665. [DOI: 10.1161/circep.117.004665] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 07/17/2017] [Indexed: 11/16/2022]
Affiliation(s)
- Jan P. Kucera
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| | - Stephan Rohr
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| | - Andre G. Kleber
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| |
Collapse
|
10
|
Kudryashova N, Tsvelaya V, Agladze K, Panfilov A. Virtual cardiac monolayers for electrical wave propagation. Sci Rep 2017; 7:7887. [PMID: 28801548 PMCID: PMC5554264 DOI: 10.1038/s41598-017-07653-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 06/28/2017] [Indexed: 11/08/2022] Open
Abstract
The complex structure of cardiac tissue is considered to be one of the main determinants of an arrhythmogenic substrate. This study is aimed at developing the first mathematical model to describe the formation of cardiac tissue, using a joint in silico-in vitro approach. First, we performed experiments under various conditions to carefully characterise the morphology of cardiac tissue in a culture of neonatal rat ventricular cells. We considered two cell types, namely, cardiomyocytes and fibroblasts. Next, we proposed a mathematical model, based on the Glazier-Graner-Hogeweg model, which is widely used in tissue growth studies. The resultant tissue morphology was coupled to the detailed electrophysiological Korhonen-Majumder model for neonatal rat ventricular cardiomyocytes, in order to study wave propagation. The simulated waves had the same anisotropy ratio and wavefront complexity as those in the experiment. Thus, we conclude that our approach allows us to reproduce the morphological and physiological properties of cardiac tissue.
Collapse
Affiliation(s)
- Nina Kudryashova
- Department of Physics and Astronomy, Gent University, Gent, 9000, Belgium
- Laboratory of Biophysics of Excitable Systems, Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Moscow Region, Russia
| | - Valeriya Tsvelaya
- Laboratory of Biophysics of Excitable Systems, Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Moscow Region, Russia
| | - Konstantin Agladze
- Laboratory of Biophysics of Excitable Systems, Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Moscow Region, Russia.
| | - Alexander Panfilov
- Department of Physics and Astronomy, Gent University, Gent, 9000, Belgium.
| |
Collapse
|
11
|
Reentry and Ectopic Pacemakers Emerge in a Three-Dimensional Model for a Slab of Cardiac Tissue with Diffuse Microfibrosis near the Percolation Threshold. PLoS One 2016; 11:e0166972. [PMID: 27875591 PMCID: PMC5119821 DOI: 10.1371/journal.pone.0166972] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 11/07/2016] [Indexed: 02/07/2023] Open
Abstract
Arrhythmias in cardiac tissue are generally associated with irregular electrical wave propagation in the heart. Cardiac tissue is formed by a discrete cell network, which is often heterogeneous. Recently, it was shown in simulations of two-dimensional (2D) discrete models of cardiac tissue that a wave crossing a fibrotic, heterogeneous region may produce reentry and transient or persistent ectopic activity provided the fraction of conducting connections is just above the percolation threshold. Here, we investigate the occurrence of these phenomena in three-dimensions by simulations of a discrete model representing a thin slab of cardiac tissue. This is motivated (i) by the necessity to study the relevance and properties of the percolation-related mechanism for the emergence of microreentries in three dimensions and (ii) by the fact that atrial tissue is quite thin in comparison with ventricular tissue. Here, we simplify the model by neglecting details of tissue anatomy, e. g. geometries of atria or ventricles and the anisotropy in the conductivity. Hence, our modeling study is confined to the investigation of the effect of the tissue thickness as well as to the comparison of the dynamics of electrical excitation in a 2D layer with the one in a 3D slab. Our results indicate a strong and non-trivial effect of the thickness even for thin tissue slabs on the probability of microreentries and ectopic beat generation. The strong correlation of the occurrence of microreentry with the percolation threshold reported earlier in 2D layers persists in 3D slabs. Finally, a qualitative agreement of 3D simulated electrograms in the fibrotic region with the experimentally observed complex fractional atrial electrograms (CFAE) as well as strong difference between simulated electrograms in 2D and 3D were found for the cases where reentry and ectopic activity were triggered by the micro-fibrotic region.
Collapse
|
12
|
Jousset F, Maguy A, Rohr S, Kucera JP. Myofibroblasts Electrotonically Coupled to Cardiomyocytes Alter Conduction: Insights at the Cellular Level from a Detailed In silico Tissue Structure Model. Front Physiol 2016; 7:496. [PMID: 27833567 PMCID: PMC5081362 DOI: 10.3389/fphys.2016.00496] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 10/11/2016] [Indexed: 01/05/2023] Open
Abstract
Fibrotic myocardial remodeling is typically accompanied by the appearance of myofibroblasts (MFBs). In vitro, MFBs were shown to slow conduction and precipitate ectopic activity following gap junctional coupling to cardiomyocytes (CMCs). To gain further mechanistic insights into this arrhythmogenic MFB-CMC crosstalk, we performed numerical simulations in cell-based high-resolution two-dimensional tissue models that replicated experimental conditions. Cell dimensions were determined using confocal microscopy of single and co-cultured neonatal rat ventricular CMCs and MFBs. Conduction was investigated as a function of MFB density in three distinct cellular tissue architectures: CMC strands with endogenous MFBs, CMC strands with coating MFBs of two different sizes, and CMC strands with MFB inserts. Simulations were performed to identify individual contributions of heterocellular gap junctional coupling and of the specific electrical phenotype of MFBs. With increasing MFB density, both endogenous and coating MFBs slowed conduction. At MFB densities of 5-30%, conduction slowing was most pronounced in strands with endogenous MFBs due to the MFB-dependent increase in axial resistance. At MFB densities >40%, very slow conduction and spontaneous activity was primarily due to MFB-induced CMC depolarization. Coating MFBs caused non-uniformities of resting membrane potential, which were more prominent with large than with small MFBs. In simulations of MFB inserts connecting two CMC strands, conduction delays increased with increasing insert lengths and block appeared for inserts >1.2 mm. Thus, electrophysiological properties of engineered CMC-MFB co-cultures depend on MFB density, MFB size and their specific positioning in respect to CMCs. These factors may influence conduction characteristics in the heterocellular myocardium.
Collapse
Affiliation(s)
- Florian Jousset
- Department of Physiology, University of Bern Bern, Switzerland
| | - Ange Maguy
- Department of Physiology, University of Bern Bern, Switzerland
| | - Stephan Rohr
- Department of Physiology, University of Bern Bern, Switzerland
| | - Jan P Kucera
- Department of Physiology, University of Bern Bern, Switzerland
| |
Collapse
|
13
|
Wei N, Mori Y, Tolkacheva EG. The dual effect of ephaptic coupling on cardiac conduction with heterogeneous expression of connexin 43. J Theor Biol 2016; 397:103-14. [PMID: 26968493 DOI: 10.1016/j.jtbi.2016.02.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/25/2016] [Accepted: 02/19/2016] [Indexed: 11/30/2022]
Abstract
Decreased and heterogeneous expression of connexin 43 (Cx43) are common features in animal heart failure models. Ephpatic coupling, which relies on the presence of junctional cleft space between the ends of adjacent cells, has been suggested to play a more active role in mediating intercellular electrical communication when gap junctions are reduced. To better understand the interplay of Cx43 expression and ephaptic coupling on cardiac conduction during heart failure, we performed numerical simulations on our model when Cx43 expression is reduced and heterogeneous. Under severely reduced Cx43 expression, we identified three new phenomena in the presence of ephaptic coupling: alternating conduction, in which ephaptic and gap junction-mediated mechanisms alternate; instability of planar fronts; and small amplitude action potential (SAP), which has a smaller potential amplitude than the normal action potential. In the presence of heterogeneous Cx43 expression, ephaptic coupling can either prevent or promote conduction block (CB) depending on the Cx43 knockout (Cx43KO) content. When Cx43KO content is relatively high, ephaptic coupling reduces the probabilities of CB. However, ephaptic coupling promotes CB when Cx43KO and wild type cells are mixed in roughly equal proportion, which can be attributed to an increase in current-to-load mismatch.
Collapse
Affiliation(s)
- Ning Wei
- School of Mathematics, University of Minnesota, 206 Church St. SE, Minneapolis, MN 55455, United States
| | - Yoichiro Mori
- School of Mathematics, University of Minnesota, 206 Church St. SE, Minneapolis, MN 55455, United States
| | - Elena G Tolkacheva
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, 6-128 Nils Hasselmo Hall, Minneapolis, MN 55455, United States.
| |
Collapse
|
14
|
Kucera JP, Prudat Y, Marcu IC, Azzarito M, Ullrich ND. Slow conduction in mixed cultured strands of primary ventricular cells and stem cell-derived cardiomyocytes. Front Cell Dev Biol 2015; 3:58. [PMID: 26442264 PMCID: PMC4585316 DOI: 10.3389/fcell.2015.00058] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 09/09/2015] [Indexed: 11/30/2022] Open
Abstract
Modern concepts for the treatment of myocardial diseases focus on novel cell therapeutic strategies involving stem cell-derived cardiomyocytes (SCMs). However, functional integration of SCMs requires similar electrophysiological properties as primary cardiomyocytes (PCMs) and the ability to establish intercellular connections with host myocytes in order to contribute to the electrical and mechanical activity of the heart. The aim of this project was to investigate the properties of cardiac conduction in a co-culture approach using SCMs and PCMs in cultured cell strands. Murine embryonic SCMs were pooled with fetal ventricular cells and seeded in predefined proportions on microelectrode arrays to form patterned strands of mixed cells. Conduction velocity (CV) was measured during steady state pacing. SCM excitability was estimated from action potentials measured in single cells using the patch clamp technique. Experiments were complemented with computer simulations of conduction using a detailed model of cellular architecture in mixed cell strands. CV was significantly lower in strands composed purely of SCMs (5.5 ± 1.5 cm/s, n = 11) as compared to PCMs (34.9 ± 2.9 cm/s, n = 21) at similar refractoriness (100% SCMs: 122 ± 25 ms, n = 9; 100% PCMs: 139 ± 67 ms, n = 14). In mixed strands combining both cell types, CV was higher than in pure SCMs strands, but always lower than in 100% PCM strands. Computer simulations demonstrated that both intercellular coupling and electrical excitability limit CV. These data provide evidence that in cultures of murine ventricular cardiomyocytes, SCMs cannot restore CV to control levels resulting in slow conduction, which may lead to reentry circuits and arrhythmias.
Collapse
Affiliation(s)
- Jan P Kucera
- Department of Physiology, University of Bern Bern, Switzerland
| | - Yann Prudat
- Department of Physiology, University of Bern Bern, Switzerland
| | - Irene C Marcu
- Department of Physiology, University of Bern Bern, Switzerland ; Department of Physiology and Pathophysiology, Heidelberg University Heidelberg, Germany
| | | | - Nina D Ullrich
- Department of Physiology and Pathophysiology, Heidelberg University Heidelberg, Germany
| |
Collapse
|
15
|
Marcu IC, Illaste A, Heuking P, Jaconi ME, Ullrich ND. Functional Characterization and Comparison of Intercellular Communication in Stem Cell-Derived Cardiomyocytes. Stem Cells 2015; 33:2208-18. [PMID: 25968594 DOI: 10.1002/stem.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 03/08/2015] [Indexed: 02/05/2023]
Abstract
One novel treatment strategy for the diseased heart focuses on the use of pluripotent stem cell-derived cardiomyocytes (SC-CMs) to overcome the heart's innate deficiency for self-repair. However, targeted application of SC-CMs requires in-depth characterization of their true cardiogenic potential in terms of excitability and intercellular coupling at cellular level and in multicellular preparations. In this study, we elucidated the electrical characteristics of single SC-CMs and intercellular coupling quality of cell pairs, and concomitantly compared them with well-characterized murine native neonatal and immortalized HL-1 cardiomyocytes. Firstly, we investigated the electrical properties and Ca(2+) signaling mechanisms specific to cardiac contraction in single SC-CMs. Despite heterogeneity of the new cardiac cell population, their electrophysiological activity and Ca(2+) handling were similar to native cells. Secondly, we investigated the capability of paired SC-CMs to form an adequate subunit of a functional syncytium and analyzed gap junctions and signal transmission by dye transfer in cell pairs. We discovered significantly diminished coupling in SC-CMs compared with native cells, which could not be enhanced by a coculture approach combining SC-CMs and primary CMs. Moreover, quantitative and structural analysis of gap junctions presented significantly reduced connexin expression levels compared with native CMs. Strong dependence of intercellular coupling on gap junction density was further confirmed by computational simulations. These novel findings demonstrate that despite the cardiogenic electrophysiological profile, SC-CMs present significant limitations in intercellular communication. Inadequate coupling may severely impair functional integration and signal transmission, which needs to be carefully considered for the prospective use of SC-CMs in cardiac repair. Stem Cells 2015;33:2208-2218.
Collapse
Affiliation(s)
- Irene C Marcu
- Department of Physiology, University of Bern, Bern, Switzerland.,Department of Physiology and Pathophysiology, University of Heidelberg, Heidelberg, Germany
| | - Ardo Illaste
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Pernilla Heuking
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland
| | - Marisa E Jaconi
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland
| | - Nina D Ullrich
- Department of Physiology, University of Bern, Bern, Switzerland.,Department of Physiology and Pathophysiology, University of Heidelberg, Heidelberg, Germany
| |
Collapse
|
16
|
Kleber AG, Saffitz JE. Role of the intercalated disc in cardiac propagation and arrhythmogenesis. Front Physiol 2014; 5:404. [PMID: 25368581 PMCID: PMC4201087 DOI: 10.3389/fphys.2014.00404] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 09/30/2014] [Indexed: 01/28/2023] Open
Abstract
This review article discusses mechanisms underlying impulse propagation in cardiac muscle with specific emphasis on the role of the cardiac cell-to-cell junction, called the “intercalated disc.”The first part of this review deals with the role of gap junction channels, formed by connexin proteins, as a determinant of impulse propagation. It is shown that, depending on the underlying structure of the cellular network, decreasing the conductance of gap junction channels (so-called “electrical uncoupling”) may either only slow, or additionally stabilize propagation and reverse unidirectional propagation block to bidirectional propagation. This is because the safety factor for propagation increases with decreasing intercellular electrical conductance. The role of heterogeneous connexin expression, which may be present in disease states, is also discussed. The hypothesis that so-called ephaptic impulse transmission plays a role in heart and can substitute for electrical coupling has been revived recently. Whereas ephaptic transmission can be demonstrated in theoretical simulations, direct experimental evidence has not yet been presented. The second part of this review deals with the interaction of three protein complexes at the intercalated disc: (1) desmosomal and adherens junction proteins, (2) ion channel proteins, and (3) gap junction channels consisting of connexins. Recent work has revealed multiple interactions between these three protein complexes which occur, at least in part, at the level of protein trafficking. Such interactions are likely to play an important role in the pathogenesis of arrhythmogenic cardiomyopathy, and may reveal new therapeutic concepts and targets.
Collapse
Affiliation(s)
- Andre G Kleber
- Department of Pathology, Beth Israel Medical Center, Harvard Medical School Boston, MA, USA
| | - Jeffrey E Saffitz
- Department of Pathology, Beth Israel Medical Center, Harvard Medical School Boston, MA, USA
| |
Collapse
|