1
|
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
|
2
|
Quinn TA, Kohl P. Cardiac Mechano-Electric Coupling: Acute Effects of Mechanical Stimulation on Heart Rate and Rhythm. Physiol Rev 2020; 101:37-92. [PMID: 32380895 DOI: 10.1152/physrev.00036.2019] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The heart is vital for biological function in almost all chordates, including humans. It beats continually throughout our life, supplying the body with oxygen and nutrients while removing waste products. If it stops, so does life. The heartbeat involves precise coordination of the activity of billions of individual cells, as well as their swift and well-coordinated adaption to changes in physiological demand. Much of the vital control of cardiac function occurs at the level of individual cardiac muscle cells, including acute beat-by-beat feedback from the local mechanical environment to electrical activity (as opposed to longer term changes in gene expression and functional or structural remodeling). This process is known as mechano-electric coupling (MEC). In the current review, we present evidence for, and implications of, MEC in health and disease in human; summarize our understanding of MEC effects gained from whole animal, organ, tissue, and cell studies; identify potential molecular mediators of MEC responses; and demonstrate the power of computational modeling in developing a more comprehensive understanding of ‟what makes the heart tick.ˮ.
Collapse
Affiliation(s)
- T Alexander Quinn
- Department of Physiology and Biophysics and School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg/Bad Krozingen, Medical Faculty of the University of Freiburg, Freiburg, Germany; and CIBSS-Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Peter Kohl
- Department of Physiology and Biophysics and School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg/Bad Krozingen, Medical Faculty of the University of Freiburg, Freiburg, Germany; and CIBSS-Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| |
Collapse
|
3
|
Hazim A, Belhamadia Y, Dubljevic S. Effects of mechano-electrical feedback on the onset of alternans: A computational study. CHAOS (WOODBURY, N.Y.) 2019; 29:063126. [PMID: 31266317 DOI: 10.1063/1.5095778] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 06/05/2019] [Indexed: 06/09/2023]
Abstract
Cardiac alternans is a heart rhythm instability that is associated with cardiac arrhythmias and may lead to sudden cardiac death. The onset of this instability, which is linked to period-doubling bifurcation and may be a route to chaos, is of particular interest. Mechano-electric feedback depicts the effects of tissue deformation on cardiac excitation. The main effect of mechano-electric feedback is delivered via the so-called stretch-activated ion channels and is caused by stretch-activated currents. Mechano-electric feedback, which is believed to have proarrhythmic and antiarrhythmic effects on cardiac electrophysiology, affects the action potential duration in a manner dependent on cycle length, but the mechanisms by which this occurs remain to be elucidated. In this study, a biophysically detailed electromechanical model of cardiac tissue is employed to show how a stretch-activated current can affect the action potential duration at cellular and tissue levels, illustrating its effects on the onset of alternans. Also, using a two-dimensional iterated map that incorporates stretch-activated current effects, we apply linear stability analysis to study the stability of the bifurcation. We show that alternans bifurcation can be prevented depending on the strength of the stretch-activated current.
Collapse
Affiliation(s)
- Azzam Hazim
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta T6G 2V2, Canada
| | - Youssef Belhamadia
- Department of Mathematics and Statistics, American University of Sharjah, Sharjah, United Arab Emirates
| | - Stevan Dubljevic
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada
| |
Collapse
|
4
|
Buccarello A, Azzarito M, Michoud F, Lacour SP, Kucera JP. Uniaxial strain of cultured mouse and rat cardiomyocyte strands slows conduction more when its axis is parallel to impulse propagation than when it is perpendicular. Acta Physiol (Oxf) 2018; 223:e13026. [PMID: 29282897 DOI: 10.1111/apha.13026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/14/2017] [Accepted: 12/21/2017] [Indexed: 11/28/2022]
Abstract
AIM Cardiac tissue deformation can modify tissue resistance, membrane capacitance and ion currents and hence cause arrhythmogenic slow conduction. Our aim was to investigate whether uniaxial strain causes different changes in conduction velocity (θ) when the principal strain axis is parallel vs perpendicular to impulse propagation. METHODS Cardiomyocyte strands were cultured on stretchable custom microelectrode arrays, and θ was determined during steady-state pacing. Uniaxial strain (5%) with principal axis parallel (orthodromic) or perpendicular (paradromic) to propagation was applied for 1 minute and controlled by imaging a grid of markers. The results were analysed in terms of cable theory. RESULTS Both types of strain induced immediate changes of θ upon application and release. In material coordinates, orthodromic strain decreased θ significantly more (P < .001) than paradromic strain (2.2 ± 0.5% vs 1.0 ± 0.2% in n = 8 mouse cardiomyocyte cultures, 2.3 ± 0.4% vs 0.9 ± 0.5% in n = 4 rat cardiomyocyte cultures, respectively). The larger effect of orthodromic strain can be explained by the increase in axial myoplasmic resistance, which is not altered by paradromic strain. Thus, changes in tissue resistance substantially contributed to the changes of θ during strain, in addition to other influences (eg stretch-activated channels). Besides these immediate effects, the application of strain also consistently initiated a slow progressive decrease in θ and a slow recovery of θ upon release. CONCLUSION Changes in cardiac conduction velocity caused by acute stretch do not only depend on the magnitude of strain but also on its orientation relative to impulse propagation. This dependence is due to different effects on tissue resistance.
Collapse
Affiliation(s)
- A. Buccarello
- Department of Physiology; University of Bern; Bern Switzerland
| | - M. Azzarito
- Department of Physiology; University of Bern; Bern Switzerland
| | - F. Michoud
- Bertarelli Foundation Chair in Neuroprosthetic Technology; Laboratory for Soft Bioelectronic Interfaces; Institute of Microengineering; Institute of Bioengineering; Centre for Neuroprosthetics; École Polytechnique Fédérale de Lausanne (EPFL); Geneva Switzerland
| | - S. P. Lacour
- Bertarelli Foundation Chair in Neuroprosthetic Technology; Laboratory for Soft Bioelectronic Interfaces; Institute of Microengineering; Institute of Bioengineering; Centre for Neuroprosthetics; École Polytechnique Fédérale de Lausanne (EPFL); Geneva Switzerland
| | - J. P. Kucera
- Department of Physiology; University of Bern; Bern Switzerland
| |
Collapse
|
5
|
Adding dimension to cellular mechanotransduction: Advances in biomedical engineering of multiaxial cell-stretch systems and their application to cardiovascular biomechanics and mechano-signaling. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017. [DOI: 10.1016/j.pbiomolbio.2017.06.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
|
6
|
Fleischman A, Vecchio C, Sunny Y, Bawiec CR, Lewin PA, Kresh JY, Kohut AR. Ultrasound-induced modulation of cardiac rhythm in neonatal rat ventricular cardiomyocytes. J Appl Physiol (1985) 2015; 118:1423-8. [PMID: 25858493 DOI: 10.1152/japplphysiol.00980.2014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 04/02/2015] [Indexed: 11/22/2022] Open
Abstract
Isolated neonatal rat ventricular cardiomyocytes were used to study the influence of ultrasound on the chronotropic response in a tissue culture model. The beat frequency of the cells, varying from 40 to 90 beats/min, was measured based upon the translocation of the nuclear membrane captured by a high-speed camera. Ultrasound pulses (frequency = 2.5 MHz) were delivered at 300-ms intervals [3.33 Hz pulse repetition frequency (PRF)], in turn corresponding to 200 pulses/min. The intensity of acoustic energy and pulse duration were made variable, 0.02-0.87 W/cm(2) and 1-5 ms, respectively. In 57 of 99 trials, there was a noted average increase in beat frequency of 25% with 8-s exposures to ultrasonic pulses. Applied ultrasound energy with a spatial peak time average acoustic intensity (Ispta) of 0.02 W/cm(2) and pulse duration of 1 ms effectively increased the contraction rate of cardiomyocytes (P < 0.05). Of the acoustic power tested, the lowest level of acoustic intensity and shortest pulse duration proved most effective at increasing the electrophysiological responsiveness and beat frequency of cardiomyocytes. Determining the optimal conditions for delivery of ultrasound will be essential to developing new models for understanding mechanoelectrical coupling (MEC) and understanding novel nonelectrical pacing modalities for clinical applications.
Collapse
Affiliation(s)
| | - Christopher Vecchio
- School of Biomedical Engineering, Science & Health System, Drexel University, Philadelphia, Pennsylvania; and
| | - Youhan Sunny
- School of Biomedical Engineering, Science & Health System, Drexel University, Philadelphia, Pennsylvania; and
| | - Christopher R Bawiec
- School of Biomedical Engineering, Science & Health System, Drexel University, Philadelphia, Pennsylvania; and
| | - Peter A Lewin
- School of Biomedical Engineering, Science & Health System, Drexel University, Philadelphia, Pennsylvania; and
| | - J Yasha Kresh
- Department of Medicine, School of Medicine and School of Biomedical Engineering, Science & Health System, Drexel University, Philadelphia, Pennsylvania; and Department of Cardiothoracic Surgery, School of Medicine School of Medicine and Drexel University, Philadelphia, Pennsylvania
| | | |
Collapse
|
7
|
Living cardiac tissue slices: an organotypic pseudo two-dimensional model for cardiac biophysics research. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:314-27. [PMID: 25124067 DOI: 10.1016/j.pbiomolbio.2014.08.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 08/02/2014] [Indexed: 11/24/2022]
Abstract
Living cardiac tissue slices, a pseudo two-dimensional (2D) preparation, have received less attention than isolated single cells, cell cultures, or Langendorff-perfused hearts in cardiac biophysics research. This is, in part, due to difficulties associated with sectioning cardiac tissue to obtain live slices. With moderate complexity, native cell-types, and well-preserved cell-cell electrical and mechanical interconnections, cardiac tissue slices have several advantages for studying cardiac electrophysiology. The trans-membrane potential (Vm) has, thus far, mainly been explored using multi-electrode arrays. Here, we combine tissue slices with optical mapping to monitor Vm and intracellular Ca(2+) concentration ([Ca(2+)]i). This combination opens up the possibility of studying the effects of experimental interventions upon action potential (AP) and calcium transient (CaT) dynamics in 2D, and with relatively high spatio-temporal resolution. As an intervention, we conducted proof-of-principle application of stretch. Mechanical stimulation of cardiac preparations is well-established for membrane patches, single cells and whole heart preparations. For cardiac tissue slices, it is possible to apply stretch perpendicular or parallel to the dominant orientation of cells, while keeping the preparation in a constant focal plane for fluorescent imaging of in-slice functional dynamics. Slice-to-slice comparison furthermore allows one to assess transmural differences in ventricular tissue responses to mechanical challenges. We developed and tested application of axial stretch to cardiac tissue slices, using a manually-controlled stretching device, and recorded Vm and [Ca(2+)]i by optical mapping before, during, and after application of stretch. Living cardiac tissue slices, exposed to axial stretch, show an initial shortening in both AP and CaT duration upon stretch application, followed in most cases by a gradual prolongation of AP and CaT duration during stretch maintained for up to 50 min. After release of sustained stretch, AP duration (APD) and CaT duration reverted to shorter values. Living cardiac tissue slices are a promising experimental model for the study of cardiac mechano-electric interactions. The methodology described here can be refined to achieve more accurate control over stretch amplitude and timing (e.g. using a computer-controlled motorised stage, or by synchronising electrical and mechanical events) and through monitoring of regional tissue deformation (e.g. by adding motion tracking).
Collapse
|
8
|
Seo K, Inagaki M, Hidaka I, Fukano H, Sugimachi M, Hisada T, Nishimura S, Sugiura S. Relevance of cardiomyocyte mechano-electric coupling to stretch-induced arrhythmias: optical voltage/calcium measurement in mechanically stimulated cells, tissues and organs. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:129-39. [PMID: 25084395 DOI: 10.1016/j.pbiomolbio.2014.07.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 07/19/2014] [Indexed: 12/27/2022]
Abstract
Stretch-induced arrhythmias are multi-scale phenomena in which alterations in channel activities and/or calcium handling lead to the organ level derangement of the heart rhythm. To understand how cellular mechano-electric coupling (MEC) leads to stretch-induced arrhythmias at the organ level, we developed stretching devices and optical voltage/calcium measurement techniques optimized to each cardiac level. This review introduces these experimental techniques of (1) optical voltage measurement coupled with a carbon-fiber technique for single isolated cardiomyocytes, (2) optical voltage mapping combined with motion tracking technique for myocardial tissue/whole heart preparations and (3) real-time calcium imaging coupled with a laser optical trap technique for cardiomyocytes. Following the overview of each methodology, results are presented. We conclude that individual MEC in cardiomyocytes can be heterogeneous at the ventricular level, especially when moderate amplitude mechanical stretches are applied to the heart, and that this heterogeneous MEC can evoke focal excitation that develops into re-entrant arrhythmias.
Collapse
Affiliation(s)
- Kinya Seo
- Division of Cardiology, Department of Medicine, The Johns Hopkins Medical Institutions, Baltimore, MD 21205, USA.
| | - Masashi Inagaki
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center Research Institute, Osaka 565-0873, Japan.
| | - Ichiro Hidaka
- Division of Physical and Health Education, Graduate School of Education, The University of Tokyo, Tokyo 113-0033, Japan.
| | - Hana Fukano
- Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan.
| | - Masaru Sugimachi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center Research Institute, Osaka 565-0873, Japan.
| | - Toshiaki Hisada
- Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan.
| | - Satoshi Nishimura
- Research Division of Cell and Molecular Medicine, Center for Molecular Medicine, Jichi Medical University, Tochigi 329-0498, Japan; Department of Cardiovascular Medicine, Translational Systems Biology and Medicine Initiative, The University of Tokyo, Tokyo 113-8655, Japan.
| | - Seiryo Sugiura
- Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan.
| |
Collapse
|
9
|
Abstract
Current concepts of mechanosensation are general and applicable to almost every cell type. However, striated muscle cells are distinguished by their ability to generate strong forces via actin/myosin interaction, and this process is fine-tuned for optimum contractility. This aspect, unique for actively contracting cells, may be defined as "sensing of the magnitude and dynamics of contractility," as opposed to the well-known concepts of the "perception of extracellular mechanical stimuli." The acto/myosin interaction, by producing changes in ATP, ADP, Pi, and force on a millisecond timescale, may be regarded as a novel and previously unappreciated mechanosensory mechanism. In addition, sarcomeric mechanosensory structures, such as the Z-disc, are directly linked to autophagy, survival, and cell death-related pathways. One emerging example is telethonin and its ability to interfere with p53 metabolism and hence apoptosis (mechanoptosis). In this article, we introduce contractility per se as an important mechanosensory mechanism, and we differentiate extracellular from intracellular mechanosensory effects.
Collapse
Affiliation(s)
- Ralph Knöll
- Heart Science Section, National Heart & Lung Institute, Imperial College, London W12 0NN, UK.
| | | |
Collapse
|
10
|
The zebrafish as a novel animal model to study the molecular mechanisms of mechano-electrical feedback in the heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:154-65. [PMID: 22835662 DOI: 10.1016/j.pbiomolbio.2012.07.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 07/16/2012] [Indexed: 02/07/2023]
Abstract
Altered mechanical loading of the heart leads to hypertrophy, decompensated heart failure and fatal arrhythmias. However, the molecular mechanisms that link mechanical and electrical dysfunction remain poorly understood. Growing evidence suggest that ventricular electrical remodeling (VER) is a process that can be induced by altered mechanical stress, creating persistent electrophysiological changes that predispose the heart to life-threatening arrhythmias. While VER is clearly a physiological property of the human heart, as evidenced by "T wave memory", it is also thought to occur in a variety of pathological states associated with altered ventricular activation such as bundle branch block, myocardial infarction, and cardiac pacing. Animal models that are currently being used for investigating stretch-induced VER have significant limitations. The zebrafish has recently emerged as an attractive animal model for studying cardiovascular disease and could overcome some of these limitations. Owing to its extensively sequenced genome, high conservation of gene function, and the comprehensive genetic resources that are available in this model, the zebrafish may provide new insights into the molecular mechanisms that drive detrimental electrical remodeling in response to stretch. Here, we have established a zebrafish model to study mechano-electrical feedback in the heart, which combines efficient genetic manipulation with high-precision stretch and high-resolution electrophysiology. In this model, only 90 min of ventricular stretch caused VER and recapitulated key features of VER found previously in the mammalian heart. Our data suggest that the zebrafish model is a powerful platform for investigating the molecular mechanisms underlying mechano-electrical feedback and VER in the heart.
Collapse
|
11
|
Dabiri BE, Lee H, Parker KK. A potential role for integrin signaling in mechanoelectrical feedback. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:196-203. [PMID: 22819851 DOI: 10.1016/j.pbiomolbio.2012.07.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 07/11/2012] [Indexed: 01/20/2023]
Abstract
Certain forms of heart disease involve gross morphological changes to the myocardium that alter its hemodynamic loading conditions. These changes can ultimately lead to the increased deposition of extracellular matrix (ECM) proteins, such as collagen and fibronectin, which together work to pathologically alter the myocardium's bulk tissue mechanics. In addition to changing the mechanical properties of the heart, this maladaptive remodeling gives rise to changes in myocardium electrical conductivity and synchrony since the tissue's mechanical properties are intimately tied to its electrical characteristics. This phenomenon, called mechanoelectrical coupling (MEC), can render individuals affected by heart disease arrhythmogenic and susceptible to Sudden Cardiac Death (SCD). The underlying mechanisms of MEC have been attributed to various processes, including the action of stretch activated channels and changes in troponin C-Ca(2+) binding affinity. However, changes in the heart post infarction or due to congenital myopathies are also accompanied by shifts in the expression of various molecular components of cardiomyocytes, including the mechanosensitive family of integrin proteins. As transmembrane proteins, integrins mechanically couple the ECM with the intracellular cytoskeleton and have been implicated in mediating ion homeostasis in various cell types, including neurons and smooth muscle. Given evidence of altered integrin expression in the setting of heart disease coupled with the associated increased risk for arrhythmia, we argue in this review that integrin signaling contributes to MEC. In light of the significant mortality associated with arrhythmia and SCD, close examination of all culpable mechanisms, including integrin-mediated MEC, is necessary.
Collapse
Affiliation(s)
- Borna E Dabiri
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, 29 Oxford St, Pierce Hall 321, Cambridge, MA 02138, USA
| | | | | |
Collapse
|
12
|
Abstract
One of the most important components of mechanoelectric coupling is stretch-activated channels, sarcolemmal channels that open upon mechanical stimuli. Uncovering the mechanisms by which stretch-activated channels contribute to ventricular arrhythmogenesis under a variety of pathologic conditions is hampered by the lack of experimental methodologies that can record the 3-dimensional electromechanical activity simultaneously at high spatiotemporal resolution. Computer modeling provides such an opportunity. The goal of this review is to illustrate the utility of sophisticated, physiologically realistic, whole heart computer simulations in determining the role of mechanoelectric coupling in ventricular arrhythmogenesis. We first present the various ways by which stretch-activated channels have been modeled and demonstrate how these channels affect cardiac electrophysiologic properties. Next, we use an electrophysiologic model of the rabbit ventricles to understand how so-called commotio cordis, the mechanical impact to the precordial region of the heart, can initiate ventricular tachycardia via the recruitment of stretch-activated channels. Using the same model, we also provide mechanistic insight into the termination of arrhythmias by precordial thump under normal and globally ischemic conditions. Lastly, we use a novel anatomically realistic dynamic 3-dimensional coupled electromechanical model of the rabbit ventricles to gain insight into the role of electromechanical dysfunction in arrhythmogenesis during acute regional ischemia.
Collapse
|
13
|
Nishimura S, Seo K, Nagasaki M, Hosoya Y, Yamashita H, Fujita H, Nagai R, Sugiura S. Responses of single-ventricular myocytes to dynamic axial stretching. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:282-97. [DOI: 10.1016/j.pbiomolbio.2008.02.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
14
|
Masé M, Glass L, Ravelli F. A model for mechano-electrical feedback effects on atrial flutter interval variability. Bull Math Biol 2008; 70:1326-47. [PMID: 18347877 DOI: 10.1007/s11538-008-9301-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 12/18/2007] [Indexed: 11/29/2022]
Abstract
Atrial flutter is a supraventricular arrhythmia, based on a reentrant mechanism mainly confined to the right atrium. Although atrial flutter is considered a regular rhythm, the atrial flutter interval (i.e., the time interval between consecutive atrial activation times) presents a spontaneous beat-to-beat variability, which has been suggested to be related to ventricular contraction and respiration by mechano-electrical feedback. This paper introduces a model to predict atrial activity during atrial flutter, based on the assumption that atrial flutter variability is related to the phase of the reentrant activity in the ventricular and respiratory cycles. Thus, atrial intervals are given as a superimposition of phase-dependent ventricular and respiratory modulations. The model includes a simplified atrioventricular (AV) branch with constant refractoriness and conduction times, which allows the prediction of ventricular activations in a closed-loop with atrial activations. Model predictions are quantitatively compared with real activation series recorded in 12 patients with atrial flutter. The model predicts the time course of both atrial and ventricular time series with a high beat-to-beat agreement, reproducing 96+/-8% and 86+/-21% of atrial and ventricular variability, respectively. The model also predicts the existence of phase-locking of atrial flutter intervals during periodic ventricular pacing and such results are observed in patients. These results constitute evidence in favor of mechano-electrical feedback as a major source of cycle length variability during atrial flutter.
Collapse
Affiliation(s)
- Michela Masé
- Department of Physics, University of Trento, via Sommarive, 14, 38050, Povo, Trento, Italy.
| | | | | |
Collapse
|
15
|
McNary TG, Sohn K, Taccardi B, Sachse FB. Experimental and computational studies of strain-conduction velocity relationships in cardiac tissue. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:383-400. [PMID: 18406453 DOI: 10.1016/j.pbiomolbio.2008.02.023] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Velocity of electrical conduction in cardiac tissue is a function of mechanical strain. Although strain-modulated velocity is a well established finding in experimental cardiology, its underlying mechanisms are not well understood. In this work, we summarized potential factors contributing to strain-velocity relationships and reviewed related experimental and computational studies. We presented results from our experimental studies on rabbit papillary muscle, which supported a biphasic relationship of strain and velocity under uni-axial straining conditions. In the low strain range, the strain-velocity relationship was positive. Conduction velocity peaked with 0.59 m/s at 100% strain corresponding to maximal force development. In the high strain range, the relationship was negative. Conduction was reversibly blocked at 118+/-1.8% strain. Reversible block occurred also in the presence of streptomycin. Furthermore, our studies revealed a moderate hysteresis of conduction velocity, which was reduced by streptomycin. We reconstructed several features of the strain-velocity relationship in a computational study with a myocyte strand. The modeling included strain-modulation of intracellular conductivity and stretch-activated cation non-selective ion channels. The computational study supported our hypotheses, that the positive strain-velocity relationship at low strain is caused by strain-modulation of intracellular conductivity and the negative relationship at high strain results from activity of stretch-activated channels. Conduction block was not reconstructed in our computational studies. We concluded this work by sketching a hypothesis for strain-modulation of conduction and conduction block in papillary muscle. We suggest that this hypothesis can also explain uni-axially measured strain-conduction velocity relationships in other types of cardiac tissue, but apparently necessitates adjustments to reconstruct pressure or volume related changes of velocity in atria and ventricles.
Collapse
Affiliation(s)
- T G McNary
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA
| | | | | | | |
Collapse
|
16
|
Zhang Y, Sekar RB, McCulloch AD, Tung L. Cell cultures as models of cardiac mechanoelectric feedback. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:367-82. [PMID: 18384846 DOI: 10.1016/j.pbiomolbio.2008.02.017] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Although stretch-activated currents have been extensively studied in isolated cells and intact heart in the context of mechanoelectric feedback (MEF) in the heart, quantitative data regarding other mechanical parameters such as pressure, shear, bending, etc, are still lacking at the multicellular level. Cultured cardiac cell monolayers have been used increasingly in the past decade as an in vitro model for the studies of fundamental mechanisms that underlie normal and pathological electrophysiology at the tissue level. Optical mapping makes possible multisite recording and analysis of action potentials and wavefront propagation, suitable for monitoring the electrophysiological activity of the cardiac cell monolayer under a wide variety of controlled mechanical conditions. In this paper, we review methodologies that have been developed or could be used to mechanically perturb cell monolayers, and present some new results on the acute effects of pressure, shear stress and anisotropic strain on cultured neonatal rat ventricular myocyte (NRVM) monolayers.
Collapse
Affiliation(s)
- Yibing Zhang
- Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21205, USA
| | | | | | | |
Collapse
|
17
|
Belmonte S, Morad M. 'Pressure-flow'-triggered intracellular Ca2+ transients in rat cardiac myocytes: possible mechanisms and role of mitochondria. J Physiol 2008; 586:1379-97. [PMID: 18187469 DOI: 10.1113/jphysiol.2007.149294] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cardiac myocytes, in the intact heart, are exposed to shear/fluid forces during each cardiac cycle. Here we describe a novel Ca(2+) signalling pathway, generated by 'pressurized flows' (PFs) of solutions, resulting in the activation of slowly developing ( approximately 300 ms) Ca(2+) transients lasting approximately 1700 ms at room temperature. Though subsequent PFs (applied some 10-30 s later) produced much smaller or undetectable responses, such transients could be reactivated following caffeine- or KCl-induced Ca(2+) releases, suggesting that a small, but replenishable, Ca(2+) pool serves as the source for their activation. PF-triggered Ca(2+) transients could be activated in Ca(2+)-free solutions or in solutions that block voltage-gated Ca(2+) channels, stretch-activated channels (SACs), or the Na(+)-Ca(2+) exchanger (NCX), using Cd(2+), Gd(3+), or Ni(2+), respectively. PF-triggered Ca(2+) transients were significantly smaller in quiescent than in electrically paced myocytes. Paced Ca(2+) transients activated at the peak of PF-triggered Ca(2+) transients were not significantly smaller than those produced normally, suggesting functionally separate Ca(2+) pools for paced and PF-triggered transients. Suppression of nitric oxide (NO) or IP(3) signalling pathways did not alter the PF-triggered Ca(2+) transients. On the other hand, mitochondrial metabolic uncoupler FCCP, in the presence of oligomycin (to prevent ATP depletion), reversibly suppressed PF-triggered Ca(2+) transients, as did the mitochondrial Ca(2+) uniporter (mCU) blocker, Ru360. Reducing agent DTT and reactive oxygen species (ROS) scavenger tempol, as well as mitochondrial NCX (mNCX) blocker CGP-37157, inhibited PF-triggered Ca(2+) transients. In rhod-2 AM-loaded and permeabilized cells, confocal imaging of mitochondrial Ca(2+) showed a transient increase in Ca(2+) on caffeine exposure and a decrease in mitochondrial Ca(2+) on application of PF pulses of solution. These signals were strongly suppressed by either Na(+)-free or CGP-37157-containing solutions, implicating mNCX in mediating the Ca(2+) release process. We conclude that subjecting rat cardiac myocytes to pressurized flow pulses of solutions triggers the release of Ca(2+) from a store that appears to access mitochondrial Ca(2+).
Collapse
Affiliation(s)
- Stephen Belmonte
- Department of Pharmacology, Georgetown University, Washington, DC 20007, USA
| | | |
Collapse
|
18
|
Sachse FB, Hunter GAM, Weiss DL, Seemann G. A Framework for Modeling of Mechano-Electrical Feedback Mechanisms of Cardiac Myocytes and Tissues. ACTA ACUST UNITED AC 2007; 2007:160-3. [DOI: 10.1109/iembs.2007.4352247] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
19
|
Kohl P, Bollensdorff C, Garny A. Effects of mechanosensitive ion channels on ventricular electrophysiology: experimental and theoretical models. Exp Physiol 2006; 91:307-21. [PMID: 16407474 DOI: 10.1113/expphysiol.2005.031062] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The heart is an electrically driven mechanical pump, somewhat like an electric motor. Interestingly, like an electric motor in 'dynamo mode', the heart can also convert mechanical stimuli into electrical signals. This feedback from cardiac mechanics to electrical activity involves mechanosensitive ion channels, whose properties and pathophysiological relevance are reviewed in the context of experimental and theoretical modelling of ventricular beat-by-beat electromechanical function.
Collapse
Affiliation(s)
- Peter Kohl
- The Cardiac Mechano-Electric Feedback Group, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.
| | | | | |
Collapse
|
20
|
Kong CR, Bursac N, Tung L. Mechanoelectrical excitation by fluid jets in monolayers of cultured cardiac myocytes. J Appl Physiol (1985) 2005; 98:2328-36; discussion 2320. [PMID: 15731396 DOI: 10.1152/japplphysiol.01084.2004] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the prevailing view of mechanoelectric feedback (MEF) in the heart is in terms of longitudinal cell stretch, other mechanical forces are considerable during the cardiac cycle, including intramyocardial pressure and shear stress. Their contribution to MEF is largely unknown. In this study, mechanical stimuli in the form of localized fluid jet pulses were applied to neonatal rat ventricular cells cultured as confluent monolayers. Such pulses result in pressure and shear stresses (but not longitudinal stretch) in the monolayer at the point of impingement. The goal was to determine whether these mechanical stimuli can trigger excitation, initiate a propagated wave, and induce reentry. Cells were stained with the voltage-sensitive dye RH237, and multi-site optical mapping was used to record the spread of electrical activity in isotropic and anisotropic monolayers. Pulses (10 ms) with velocities ranging from 0.3 to 1.8 m/s were applied from a 0.4-mm diameter nozzle located 1 mm above the cell monolayer. Fluid jet pulses resulted in circular wavefronts that propagated radially from the stimulus site. The likelihood for mechanical stimulation was quantified as an average stimulus success rate (ASSR). ASSR increased with jet amplitude and time waited between stimuli and decreased with the application of gadolinium and streptomycin, blockers of stretch-activated channels, but not with nifedipine, a blocker of the L-type Ca channel. Absence of cellular injury was confirmed by smooth propagation maps and propidium iodide stains. In rare instances, the mechanical pulse resulted in the induction of reentrant activity. We conclude that mechanical stimuli other than stretch can evoke action potentials, propagated activity, and reentrant arrhythmia in two-dimensional sheets of cardiac cells.
Collapse
Affiliation(s)
- Chae-Ryon Kong
- Dept. of Biomedical Engineering, The Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA
| | | | | |
Collapse
|
21
|
Kohl P, Ravens U. Cardiac mechano-electric feedback: past, present, and prospect. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2003; 82:3-9. [PMID: 12732264 DOI: 10.1016/s0079-6107(03)00022-1] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Mechanical effects on heart rhythm have been known to the clinical community for well over a century, and documented cases include both arrhythmogenic and pro-rhythmic consequences of mechanical stimulation. The intracardiac pathway that leads from changes in the cardiac mechanical environment to altered electrical activity is referred to as mechano-electric feedback (MEF). Fundamental research into the mechanisms underlying cardiac MEF is 'engineering-intensive', and much of the current insight would have been impossible without the introduction of novel techniques for the study of isolated cardiac cells. Clinical and basic research into MEF have developed over different time scales, often uninformed of each other, and utilizing disparate concepts and terminology. Bridging the gap between the two domains is not straightforward, as physicians and scientists tend to publish in different journals and attend different meetings. There is, however, a growing interest in 're-uniting' the clinic and basic MEF research, as witnessed by an increasing number of dedicated journal issues and international meetings, including events hosted by major European and American professional organisations such as the ESC and NASPE. Last year alone saw an international workshop on Cardiac MEF & Arrhythmias at Oxford, as well as dedicated sessions at NASPE's 23rd annual meeting in San Diego, CardioStim 2002 in Nice, and the UK Physiological Society meeting in Leeds. This volume of Progress in Biophysics and Molecular Biology incorporates clinical and basic science results, and it is fitting that its publication coincides with a special session on cardiac MEF at the 2003 meeting of NASPE.
Collapse
|
22
|
Martinac B, Kloda A. Evolutionary origins of mechanosensitive ion channels. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2003; 82:11-24. [PMID: 12732265 DOI: 10.1016/s0079-6107(03)00002-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
According to the recent revision, the universal phylogenetic tree is composed of three domains: Eukarya (eukaryotes), Bacteria (eubacteria) and Archaea (archaebacteria). Mechanosensitive (MS) ion channels have been documented in cells belonging to all three domains suggesting their very early appearance during evolution of life on Earth. The channels show great diversity in conductance, selectivity and voltage dependence, while sharing the property of being gated by mechanical stimuli exerted on cell membranes. In prokaryotes, MS channels were first documented in Bacteria followed by their discovery in Archaea. The finding of MS channels in archaeal cells helped to recognize and establish the evolutionary relationship between bacterial and archaeal MS channels and to show that this relationship extends to eukaryotic Fungi (Schizosaccharomyces pombe) and Plants (Arabidopsis thaliana). Similar to their bacterial and archaeal homologues, MS channels in eukaryotic cell-walled Fungi and Plants may serve in protecting the cellular plasma membrane from excessive dilation and rupture that may occur during osmotic stress. This review summarizes briefly some of the recent developments in the MS channel research field that may ultimately lead to elucidation of the biophysical and evolutionary principles underlying the mechanosensory transduction in living cells.
Collapse
Affiliation(s)
- Boris Martinac
- Department of Pharmacology, QEII Medical Center, The University of Western Australia, WA 6009, Crawley, Australia.
| | | |
Collapse
|
23
|
Isenberg G, Kazanski V, Kondratev D, Gallitelli MF, Kiseleva I, Kamkin A. Differential effects of stretch and compression on membrane currents and [Na+]c in ventricular myocytes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2003; 82:43-56. [PMID: 12732267 DOI: 10.1016/s0079-6107(03)00004-x] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Mechano-electrical feedback was studied in the single ventricular myocytes. A small fraction (approximately 10%) of the cell surface could be stretched or compressed by a glass stylus. Stretch depolarised, shortened the action potential and induced extra systoles. Stretch activated non-selective cation currents (I(ns)) showed a linear voltage dependence, a reversal potential of 0 mV, a pure cation selectivity, and were blocked by 8 microM Gd(3+) or 30 microM streptomycin. Stretch reduced Ca(2+) and K(+) (I(K)) currents. Local compression of broadwise attached cells activated I(K) but not I(ns). Cytochalasin D or colchicin, thought to disrupt the cytoskeleton, suppressed the mechanosensitivity of I(ns) and I(K). During stretch, the cytosolic sodium concentration increased with spatial heterogeneities, local hotspots with [Na(+)](c)>24 mM appeared close to surface membrane and t-tubules (pseudoratiometric imaging using Sodium Green fluorescence). Electronprobe microanalysis confirmed this result and indicated that stretch increased total sodium [Na] in cell compartments such as mitochondria, nuclear envelope and nucleus. Our results obtained by local stretch differ from those obtained by end-to-end stretch (literature). We speculate that channels may be activated not only by axial but also by shear stress, and, that stretch can activate channels outside the deformed sarcomeres via second messenger.
Collapse
Affiliation(s)
- Gerrit Isenberg
- Department of Physiology, Martin-Luther-Universität, Magdeburgerstrasse 6, 06097, Halle, Germany.
| | | | | | | | | | | |
Collapse
|