1
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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: 61] [Impact Index Per Article: 15.3] [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.
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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
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2
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Lee CT, Laughlin JG, Moody JB, Amaro RE, McCammon JA, Holst M, Rangamani P. An Open-Source Mesh Generation Platform for Biophysical Modeling Using Realistic Cellular Geometries. Biophys J 2020; 118:1003-1008. [PMID: 32032503 PMCID: PMC7063475 DOI: 10.1016/j.bpj.2019.11.3400] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 11/08/2019] [Accepted: 11/27/2019] [Indexed: 11/16/2022] Open
Abstract
Advances in imaging methods such as electron microscopy, tomography, and other modalities are enabling high-resolution reconstructions of cellular and organelle geometries. Such advances pave the way for using these geometries for biophysical and mathematical modeling once these data can be represented as a geometric mesh, which, when carefully conditioned, enables the discretization and solution of partial differential equations. In this work, we outline the steps for a naïve user to approach the Geometry-preserving Adaptive MeshER software version 2, a mesh generation code written in C++ designed to convert structural data sets to realistic geometric meshes while preserving the underlying shapes. We present two example cases: 1) mesh generation at the subcellular scale as informed by electron tomography and 2) meshing a protein with a structure from x-ray crystallography. We further demonstrate that the meshes generated by the Geometry-preserving Adaptive MeshER software are suitable for use with numerical methods. Together, this collection of libraries and tools simplifies the process of constructing realistic geometric meshes from structural biology data.
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Affiliation(s)
- Christopher T Lee
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California.
| | - Justin G Laughlin
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California
| | - John B Moody
- Department of Mathematics, University of California, San Diego, La Jolla, California
| | - Rommie E Amaro
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California
| | - J Andrew McCammon
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California
| | - Michael Holst
- Department of Mathematics, University of California, San Diego, La Jolla, California
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California.
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3
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Lee CT, Moody JB, Amaro RE, McCammon JA, Holst MJ. The Implementation of the Colored Abstract Simplicial Complex and its Application to Mesh Generation. ACM TRANSACTIONS ON MATHEMATICAL SOFTWARE. ASSOCIATION FOR COMPUTING MACHINERY 2019; 45:28. [PMID: 31474782 PMCID: PMC6716611 DOI: 10.1145/3321515] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 03/01/2019] [Indexed: 06/10/2023]
Abstract
We introduce CASC: a new, modern, and header-only C++ library which provides a data structure to represent arbitrary dimension abstract simplicial complexes (ASC) with user-defined classes stored directly on the simplices at each dimension. This is accomplished by using the latest C++ language features including variadic template parameters introduced in C++11 and automatic function return type deduction from C++14. Effectively CASC decouples the representation of the topology from the interactions of user data. We present the innovations and design principles of the data structure and related algorithms. This includes a metadata aware decimation algorithm which is general for collapsing simplices of any dimension. We also present an example application of this library to represent an orientable surface mesh.
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Affiliation(s)
- Christopher T Lee
- Department of Chemistry and Biochemistry, University of California San Diego
| | - John B Moody
- ViaSat, Inc. Carlsbad-Bldg 10-2063, 6155 El Camino Real, Carlsbad, CA 92009
| | - Rommie E Amaro
- Department of Chemistry and Biochemistry, University of California San Diego
| | - J Andrew McCammon
- Department of Chemistry and Biochemistry, University of California San Diego
| | - Michael J Holst
- Department of Mathematics, University of California San Diego
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4
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Wu Y. Research on feature point extraction and matching machine learning method based on light field imaging. Neural Comput Appl 2019. [DOI: 10.1007/s00521-018-3962-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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5
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Rajagopal V, Bass G, Ghosh S, Hunt H, Walker C, Hanssen E, Crampin E, Soeller C. Creating a Structurally Realistic Finite Element Geometric Model of a Cardiomyocyte to Study the Role of Cellular Architecture in Cardiomyocyte Systems Biology. J Vis Exp 2018. [PMID: 29733314 DOI: 10.3791/56817] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
With the advent of three-dimensional (3D) imaging technologies such as electron tomography, serial-block-face scanning electron microscopy and confocal microscopy, the scientific community has unprecedented access to large datasets at sub-micrometer resolution that characterize the architectural remodeling that accompanies changes in cardiomyocyte function in health and disease. However, these datasets have been under-utilized for investigating the role of cellular architecture remodeling in cardiomyocyte function. The purpose of this protocol is to outline how to create an accurate finite element model of a cardiomyocyte using high resolution electron microscopy and confocal microscopy images. A detailed and accurate model of cellular architecture has significant potential to provide new insights into cardiomyocyte biology, more than experiments alone can garner. The power of this method lies in its ability to computationally fuse information from two disparate imaging modalities of cardiomyocyte ultrastructure to develop one unified and detailed model of the cardiomyocyte. This protocol outlines steps to integrate electron tomography and confocal microscopy images of adult male Wistar (name for a specific breed of albino rat) rat cardiomyocytes to develop a half-sarcomere finite element model of the cardiomyocyte. The procedure generates a 3D finite element model that contains an accurate, high-resolution depiction (on the order of ~35 nm) of the distribution of mitochondria, myofibrils and ryanodine receptor clusters that release the necessary calcium for cardiomyocyte contraction from the sarcoplasmic reticular network (SR) into the myofibril and cytosolic compartment. The model generated here as an illustration does not incorporate details of the transverse-tubule architecture or the sarcoplasmic reticular network and is therefore a minimal model of the cardiomyocyte. Nevertheless, the model can already be applied in simulation-based investigations into the role of cell structure in calcium signaling and mitochondrial bioenergetics, which is illustrated and discussed using two case studies that are presented following the detailed protocol.
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Affiliation(s)
- Vijay Rajagopal
- Cell Structure and Mechanobiology Group, University of Melbourne; Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne; Department of Biomedical Engineering, University of Melbourne;
| | - Gregory Bass
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne; Department of Biomedical Engineering, University of Melbourne
| | - Shouryadipta Ghosh
- Cell Structure and Mechanobiology Group, University of Melbourne; Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne; Department of Biomedical Engineering, University of Melbourne
| | - Hilary Hunt
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne; School of Mathematics and Statistics, Faculty of Science, University of Melbourne
| | - Cameron Walker
- Department of Engineering Science, University of Auckland
| | - Eric Hanssen
- Advanced Microscopy Facility, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne
| | - Edmund Crampin
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne; Department of Biomedical Engineering, University of Melbourne; School of Mathematics and Statistics, Faculty of Science, University of Melbourne; ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, University of Melbourne; School of Medicine, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne
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6
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Ali RA, Mehdi AM, Rothnagel R, Hamilton NA, Gerle C, Landsberg MJ, Hankamer B. RAZA: A Rapid 3D z-crossings algorithm to segment electron tomograms and extract organelles and macromolecules. J Struct Biol 2017; 200:73-86. [PMID: 29032142 DOI: 10.1016/j.jsb.2017.10.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 10/06/2017] [Accepted: 10/09/2017] [Indexed: 11/30/2022]
Abstract
Resolving the 3D architecture of cells to atomic resolution is one of the most ambitious challenges of cellular and structural biology. Central to this process is the ability to automate tomogram segmentation to identify sub-cellular components, facilitate molecular docking and annotate detected objects with associated metadata. Here we demonstrate that RAZA (Rapid 3D z-crossings algorithm) provides a robust, accurate, intuitive, fast, and generally applicable segmentation algorithm capable of detecting organelles, membranes, macromolecular assemblies and extrinsic membrane protein domains. RAZA defines each continuous contour within a tomogram as a discrete object and extracts a set of 3D structural fingerprints (major, middle and minor axes, surface area and volume), enabling selective, semi-automated segmentation and object extraction. RAZA takes advantage of the fact that the underlying algorithm is a true 3D edge detector, allowing the axes of a detected object to be defined, independent of its random orientation within a cellular tomogram. The selectivity of object segmentation and extraction can be controlled by specifying a user-defined detection tolerance threshold for each fingerprint parameter, within which segmented objects must fall and/or by altering the number of search parameters, to define morphologically similar structures. We demonstrate the capability of RAZA to selectively extract subgroups of organelles (mitochondria) and macromolecular assemblies (ribosomes) from cellular tomograms. Furthermore, the ability of RAZA to define objects and their contours, provides a basis for molecular docking and rapid tomogram annotation.
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Affiliation(s)
- Rubbiya A Ali
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Ahmed M Mehdi
- Translational Research Institute, University of Queensland Diamantina Institute, Brisbane, QLD, Australia; Department of Electrical Engineering, University of Engineering and Technology, Lahore, Punjab, Pakistan
| | - Rosalba Rothnagel
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Nicholas A Hamilton
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Christoph Gerle
- Picobiology Institute, Department of Life Science, Graduate School of Life Science, University of Hyogo, Kamigori, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi, Japan
| | - Michael J Landsberg
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia; School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
| | - Ben Hankamer
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia.
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7
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Cárdenes R, Zhang C, Klementieva O, Werner S, Guttmann P, Pratsch C, Cladera J, Bijnens BH. 3D membrane segmentation and quantification of intact thick cells using cryo soft X-ray transmission microscopy: A pilot study. PLoS One 2017; 12:e0174324. [PMID: 28376110 PMCID: PMC5380311 DOI: 10.1371/journal.pone.0174324] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 03/07/2017] [Indexed: 12/28/2022] Open
Abstract
Structural analysis of biological membranes is important for understanding cell and sub-cellular organelle function as well as their interaction with the surrounding environment. Imaging of whole cells in three dimension at high spatial resolution remains a significant challenge, particularly for thick cells. Cryo-transmission soft X-ray microscopy (cryo-TXM) has recently gained popularity to image, in 3D, intact thick cells (∼10μm) with details of sub-cellular architecture and organization in near-native state. This paper reports a new tool to segment and quantify structural changes of biological membranes in 3D from cryo-TXM images by tracking an initial 2D contour along the third axis of the microscope, through a multi-scale ridge detection followed by an active contours-based model, with a subsequent refinement along the other two axes. A quantitative metric that assesses the grayscale profiles perpendicular to the membrane surfaces is introduced and shown to be linearly related to the membrane thickness. Our methodology has been validated on synthetic phantoms using realistic microscope properties and structure dimensions, as well as on real cryo-TXM data. Results demonstrate the validity of our algorithms for cryo-TXM data analysis.
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Affiliation(s)
| | - Chong Zhang
- Physense, Universitat Pompeu Fabra, Barcelona, Spain
| | - Oxana Klementieva
- Institute of Neuropathology, IDIBELL-University Hospital Bellvitge, L’Hospitalet de Llobregat, Spain
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Stephan Werner
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institute Soft Matters and Functional Materials, Electron Storage Ring BESSY II, Berlin, Germany
| | - Peter Guttmann
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institute Soft Matters and Functional Materials, Electron Storage Ring BESSY II, Berlin, Germany
| | - Christoph Pratsch
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institute Soft Matters and Functional Materials, Electron Storage Ring BESSY II, Berlin, Germany
| | - Josep Cladera
- Biophysics Unit & Centre of Studies in Biophysics, Dept. of Biochemistry & Molecular Biology, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Bart H. Bijnens
- Physense, Universitat Pompeu Fabra, Barcelona, Spain
- ICREA, Barcelona, Spain
- * E-mail:
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8
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Sulkin MS, Yang F, Holzem KM, Van Leer B, Bugge C, Laughner JI, Green K, Efimov IR. Nanoscale three-dimensional imaging of the human myocyte. J Struct Biol 2014; 188:55-60. [PMID: 25160725 DOI: 10.1016/j.jsb.2014.08.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 08/08/2014] [Accepted: 08/18/2014] [Indexed: 11/28/2022]
Abstract
The ventricular human myocyte is spatially organized for optimal ATP and Ca(2+) delivery to sarcomeric myosin and ionic pumps during every excitation-contraction cycle. Comprehension of three-dimensional geometry of the tightly packed ultrastructure has been derived from discontinuous two-dimensional images, but has never been precisely reconstructed or analyzed in human myocardium. Using a focused ion beam scanning electron microscope, we created nanoscale resolution serial images to quantify the three-dimensional ultrastructure of a human left ventricular myocyte. Transverse tubules (t-tubule), lipid droplets, A-bands, and mitochondria occupy 1.8, 1.9, 10.8, and 27.9% of the myocyte volume, respectively. The complex t-tubule system has a small tortuosity (1.04±0.01), and is composed of long transverse segments with diameters of 317±24nm and short branches. Our data indicates that lipid droplets located well beneath the sarcolemma are proximal to t-tubules, where 59% (13 of 22) of lipid droplet centroids are within 0.50μm of a t-tubule. This spatial association could have an important implication in the development and treatment of heart failure because it connects two independently known pathophysiological alterations, a substrate switch from fatty acids to glucose and t-tubular derangement.
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Affiliation(s)
- Matthew S Sulkin
- Department of Biomedical Engineering, Washington University in St. Louis, MO, USA
| | - Fei Yang
- Department of Radiation Oncology, School of Medicine, Washington University in St. Louis, MO, USA
| | - Katherine M Holzem
- Department of Biomedical Engineering, Washington University in St. Louis, MO, USA
| | | | | | - Jacob I Laughner
- Department of Biomedical Engineering, Washington University in St. Louis, MO, USA
| | - Karen Green
- Department of Pathology and Immunology, School of Medicine, Washington University in St. Louis, MO, USA
| | - Igor R Efimov
- Department of Biomedical Engineering, Washington University in St. Louis, MO, USA.
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9
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Hake J, Kekenes-Huskey PM, McCulloch AD. Computational modeling of subcellular transport and signaling. Curr Opin Struct Biol 2014; 25:92-7. [PMID: 24509246 PMCID: PMC4040296 DOI: 10.1016/j.sbi.2014.01.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 01/07/2014] [Indexed: 11/19/2022]
Abstract
Numerous signaling processes in the cell are controlled in microdomains that are defined by cellular structures ranging from nm to μm in size. Recent improvements in microscopy enable the resolution and reconstruction of these micro domains, while new computational methods provide the means to elucidate their functional roles. Collectively these tools allow for a biophysical understanding of the cellular environment and its pathological progression in disease. Here we review recent advancements in microscopy, and subcellular modeling on the basis of reconstructed geometries, with a special focus on signaling microdomains that are important for the excitation contraction coupling in cardiac myocytes.
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Affiliation(s)
- Johan Hake
- Center for Biomedical Computing, Simula Research Laboratory, P.O. Box 134, 1325 Lysaker, Norway.
| | | | - Andrew D McCulloch
- Department of Bioengineering and Medicine, University of California San Diego, CA, USA
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10
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Ferrantini C, Crocini C, Coppini R, Vanzi F, Tesi C, Cerbai E, Poggesi C, Pavone FS, Sacconi L. The transverse-axial tubular system of cardiomyocytes. Cell Mol Life Sci 2013; 70:4695-710. [PMID: 23846763 PMCID: PMC11113601 DOI: 10.1007/s00018-013-1410-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 06/03/2013] [Accepted: 06/13/2013] [Indexed: 10/26/2022]
Abstract
A characteristic histological feature of striated muscle cells is the presence of deep invaginations of the plasma membrane (sarcolemma), most commonly referred to as T-tubules or the transverse-axial tubular system (TATS). TATS mediates the rapid spread of the electrical signal (action potential) to the cell core triggering Ca(2+) release from the sarcoplasmic reticulum, ultimately inducing myofilament contraction (excitation-contraction coupling). T-tubules, first described in vertebrate skeletal muscle cells, have also been recognized for a long time in mammalian cardiac ventricular myocytes, with a structure and a function that in recent years have been shown to be far more complex and pivotal for cardiac function than initially thought. Renewed interest in T-tubule function stems from the loss and disorganization of T-tubules found in a number of pathological conditions including human heart failure (HF) and dilated and hypertrophic cardiomyopathies, as well as in animal models of HF, chronic ischemia and atrial fibrillation. Disease-related remodeling of the TATS leads to asynchronous and inhomogeneous Ca(2+)-release, due to the presence of orphan ryanodine receptors that have lost their coupling with the dihydropyridine receptors and are either not activated or activated with a delay. Here, we review the physiology of the TATS, focusing first on the relationship between function and structure, and then describing T-tubular remodeling and its reversal in disease settings and following effective therapeutic approaches.
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Affiliation(s)
- C. Ferrantini
- Division of Physiology, Department of Clinical and Experimental Medicine, University of Florence, Florence, Italy
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
| | - C. Crocini
- European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, Sesto Fiorentino, Italy
| | - R. Coppini
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
- Division of Pharmacology, Department “NeuroFarBa”, University of Florence, Florence, Italy
| | - F. Vanzi
- European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, Sesto Fiorentino, Italy
- Department of Biology, University of Florence, Florence, Italy
| | - C. Tesi
- Division of Physiology, Department of Clinical and Experimental Medicine, University of Florence, Florence, Italy
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
| | - E. Cerbai
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
- Division of Pharmacology, Department “NeuroFarBa”, University of Florence, Florence, Italy
| | - C. Poggesi
- Division of Physiology, Department of Clinical and Experimental Medicine, University of Florence, Florence, Italy
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
| | - F. S. Pavone
- European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, Italy
- National Institute of Optics (INO), National Research Council (CNR), Florence, Italy
| | - L. Sacconi
- European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, Sesto Fiorentino, Italy
- National Institute of Optics (INO), National Research Council (CNR), Florence, Italy
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11
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Feng X, Xia K, Chen Z, Tong Y, Wei GW. Multiscale geometric modeling of macromolecules II: Lagrangian representation. J Comput Chem 2013; 34:2100-20. [PMID: 23813599 PMCID: PMC3760017 DOI: 10.1002/jcc.23364] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 05/10/2013] [Accepted: 05/26/2013] [Indexed: 12/16/2022]
Abstract
Geometric modeling of biomolecules plays an essential role in the conceptualization of biolmolecular structure, function, dynamics, and transport. Qualitatively, geometric modeling offers a basis for molecular visualization, which is crucial for the understanding of molecular structure and interactions. Quantitatively, geometric modeling bridges the gap between molecular information, such as that from X-ray, NMR, and cryo-electron microscopy, and theoretical/mathematical models, such as molecular dynamics, the Poisson-Boltzmann equation, and the Nernst-Planck equation. In this work, we present a family of variational multiscale geometric models for macromolecular systems. Our models are able to combine multiresolution geometric modeling with multiscale electrostatic modeling in a unified variational framework. We discuss a suite of techniques for molecular surface generation, molecular surface meshing, molecular volumetric meshing, and the estimation of Hadwiger's functionals. Emphasis is given to the multiresolution representations of biomolecules and the associated multiscale electrostatic analyses as well as multiresolution curvature characterizations. The resulting fine resolution representations of a biomolecular system enable the detailed analysis of solvent-solute interaction, and ion channel dynamics, whereas our coarse resolution representations highlight the compatibility of protein-ligand bindings and possibility of protein-protein interactions.
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Affiliation(s)
- Xin Feng
- Department of Computer Science and Engineering Michigan State University, MI 48824, USA
| | - Kelin Xia
- Department of Mathematics Michigan State University, MI 48824, USA
| | - Zhan Chen
- Department of Mathematics Michigan State University, MI 48824, USA
| | - Yiying Tong
- Department of Computer Science and Engineering Michigan State University, MI 48824, USA
| | - Guo-Wei Wei
- Department of Mathematics Michigan State University, MI 48824, USA
- Department of Biochemistry and Molecular Biology Michigan State University, MI 48824, USA
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12
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Sorensen AB, Søndergaard MT, Overgaard MT. Calmodulin in a Heartbeat. FEBS J 2013; 280:5511-32. [DOI: 10.1111/febs.12337] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 04/28/2013] [Accepted: 05/07/2013] [Indexed: 01/16/2023]
Affiliation(s)
- Anders B. Sorensen
- Department of Biotechnology, Chemistry and Environmental Engineering; Aalborg University; Denmark
| | - Mads T. Søndergaard
- Department of Biotechnology, Chemistry and Environmental Engineering; Aalborg University; Denmark
| | - Michael T. Overgaard
- Department of Biotechnology, Chemistry and Environmental Engineering; Aalborg University; Denmark
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13
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Feng X, Xia K, Tong Y, Wei GW. Geometric modeling of subcellular structures, organelles, and multiprotein complexes. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2012; 28:1198-223. [PMID: 23212797 PMCID: PMC3568658 DOI: 10.1002/cnm.2532] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 10/16/2012] [Accepted: 11/02/2012] [Indexed: 05/11/2023]
Abstract
Recently, the structure, function, stability, and dynamics of subcellular structures, organelles, and multiprotein complexes have emerged as a leading interest in structural biology. Geometric modeling not only provides visualizations of shapes for large biomolecular complexes but also fills the gap between structural information and theoretical modeling, and enables the understanding of function, stability, and dynamics. This paper introduces a suite of computational tools for volumetric data processing, information extraction, surface mesh rendering, geometric measurement, and curvature estimation of biomolecular complexes. Particular emphasis is given to the modeling of cryo-electron microscopy data. Lagrangian-triangle meshes are employed for the surface presentation. On the basis of this representation, algorithms are developed for surface area and surface-enclosed volume calculation, and curvature estimation. Methods for volumetric meshing have also been presented. Because the technological development in computer science and mathematics has led to multiple choices at each stage of the geometric modeling, we discuss the rationales in the design and selection of various algorithms. Analytical models are designed to test the computational accuracy and convergence of proposed algorithms. Finally, we select a set of six cryo-electron microscopy data representing typical subcellular complexes to demonstrate the efficacy of the proposed algorithms in handling biomolecular surfaces and explore their capability of geometric characterization of binding targets. This paper offers a comprehensive protocol for the geometric modeling of subcellular structures, organelles, and multiprotein complexes.
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Affiliation(s)
- Xin Feng
- Department of Computer Science and Engineering, Michigan State University, MI 48824, USA
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14
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Das T, Hoshijima M. Adding a new dimension to cardiac nano-architecture using electron microscopy: coupling membrane excitation to calcium signaling. J Mol Cell Cardiol 2012. [PMID: 23201225 DOI: 10.1016/j.yjmcc.2012.11.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Advances in microscopic imaging technologies and associated computational methods now allow descriptions of cellular anatomy to go beyond 2-dimensions, revealing new micro-domain dynamics at unprecedented resolutions. In cardiomyocytes, electron microscopy (EM) first described junctional membrane complexes between the sarcolemma and sarcoplasmic reticulum over a half-century ago. Since then, 3-dimensional EM technologies such as electron tomography have become successful in determining the realistic nano-geometry of membrane junctions (dyads and peripheral junctions) and associated structures such as transverse tubules (T-tubules, aka. T-system). Concomitantly, super-resolution light microscopy has gone beyond the diffraction-limit to determine the distribution of molecules, such as ryanodine receptors, with 10(-8) meter (10nm) order accuracy. This review provides the current structural perspective and functional interpretation of membrane junction complexes, which are the central machinery controlling cardiac excitation-contraction coupling via calcium signaling.
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Affiliation(s)
- Tapaswini Das
- The Center for Research in Biological Systems, University of California San Diego, La Jolla, CA 92093, USA
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15
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Lee YS, Liu OZ, Sobie EA. Decoding myocardial Ca²⁺ signals across multiple spatial scales: a role for sensitivity analysis. J Mol Cell Cardiol 2012; 58:92-9. [PMID: 23026728 DOI: 10.1016/j.yjmcc.2012.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 09/20/2012] [Indexed: 11/28/2022]
Abstract
Numerous studies have employed mathematical modeling to quantitatively understand release of Ca(2+) from the sarcoplasmic reticulum (SR) in the heart. Models have been used to investigate physiologically important phenomena such as triggering of SR Ca(2+) release by Ca(2+) entry across the cell membrane and spontaneous leak of Ca(2+) from the SR in quiescent heart cells. In this review we summarize studies that have modeled myocardial Ca(2+) at different spatial scales: the sub-cellular level, the cellular level, and the multicellular level. We discuss each category of models from the standpoint of parameter sensitivity analysis, a common simulation procedure that can generate quantitative, comprehensive predictions about how changes in conditions influence model output. We propose that this is a useful perspective for conceptualizing models, in part because a sensitivity analysis requires the investigator to define the relevant parameters and model outputs. This procedure therefore helps to illustrate the capabilities and limitations of each model. We further suggest that in future studies, sensitivity analyses will aid in simplifying complex models and in suggesting experiments to differentiate between competing models built with different assumptions. We conclude with a discussion of unresolved questions that are likely to be addressed over the next several years.
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Affiliation(s)
- Young-Seon Lee
- Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY, USA
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16
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Hake J, Edwards AG, Yu Z, Kekenes-Huskey PM, Michailova AP, McCammon JA, Holst MJ, Hoshijima M, McCulloch AD. Modelling cardiac calcium sparks in a three-dimensional reconstruction of a calcium release unit. J Physiol 2012; 590:4403-22. [PMID: 22495592 DOI: 10.1113/jphysiol.2012.227926] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Triggered release of Ca2+ from an individual sarcoplasmic reticulum (SR) Ca(2+) release unit (CRU) is the fundamental event of cardiac excitation–contraction coupling, and spontaneous release events (sparks) are the major contributor to diastolic Ca(2+) leak in cardiomyocytes. Previous model studies have predicted that the duration and magnitude of the spark is determined by the local CRU geometry, as well as the localization and density of Ca(2+) handling proteins. We have created a detailed computational model of a CRU, and developed novel tools to generate the computational geometry from electron tomographic images. Ca(2+) diffusion was modelled within the SR and the cytosol to examine the effects of localization and density of the Na(+)/Ca(2+) exchanger, sarco/endoplasmic reticulum Ca(2+)-ATPase 2 (SERCA), and calsequestrin on spark dynamics. We reconcile previous model predictions of approximately 90% local Ca(2+) depletion in junctional SR, with experimental reports of about 40%. This analysis supports the hypothesis that dye kinetics and optical averaging effects can have a significant impact on measures of spark dynamics. Our model also predicts that distributing calsequestrin within non-junctional Z-disc SR compartments, in addition to the junctional compartment, prolongs spark release time as reported by Fluo5. By pumping Ca(2+) back into the SR during a release, SERCA is able to prolong a Ca(2+) spark, and this may contribute to SERCA-dependent changes in Ca(2+) wave speed. Finally, we show that including the Na(+)/Ca(2+) exchanger inside the dyadic cleft does not alter local [Ca(2+)] during a spark.
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Affiliation(s)
- Johan Hake
- Department of Bioengineering, University of California San Diego, CA, USA.
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17
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Wang J, Yu Z. Quality Mesh Smoothing via Local Surface Fitting and Optimum Projection. GRAPHICAL MODELS 2011; 73:127-139. [PMID: 21686314 PMCID: PMC3113477 DOI: 10.1016/j.gmod.2011.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The smoothness and angle quality of a surface mesh are two important indicators of the "goodness" of the mesh for downstream applications such as visualization and numerical simulation. We present in this paper a novel surface mesh processing method not only to reduce mesh noise but to improve angle quality as well. Our approach is based on the local surface fitting around each vertex using the least square minimization technique. The new position of the vertex is obtained by finding the maximum inscribed circle (MIC) of the surrounding polygon and projecting the circle's center onto the analytically fitted surface. The procedure above repeats until the maximal vertex displacement is less than a pre-defined threshold. The mesh smoothness is improved by a combined idea of surface fitting and projection, while the angle quality is achieved by utilizing the MIC-based projection scheme. Results on a variety of geometric mesh models have demonstrated the effectiveness of our method.
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Affiliation(s)
- Jun Wang
- Department of Computer Science, University of Wisconsin-Milwaukee, 3200 N. Cramer St., Milwaukee, WI 53211, USA
| | - Zeyun Yu
- Department of Computer Science, University of Wisconsin-Milwaukee, 3200 N. Cramer St., Milwaukee, WI 53211, USA
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18
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Yu Z, Yao G, Hoshijima M, Michailova A, Holst M. Multiscale modeling of calcium dynamics in ventricular myocytes with realistic transverse tubules. IEEE Trans Biomed Eng 2011; 58:2947-51. [PMID: 21632291 DOI: 10.1109/tbme.2011.2158316] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Spatial-temporal Ca(2+) dynamics due to Ca(2+) release, buffering, and reuptaking plays a central role in studying excitation-contraction (E-C) coupling in both normal and diseased cardiac myocytes. In this paper, we employ two numerical methods, namely, the meshless method and the finite element method, to model such Ca(2+) behaviors by solving a nonlinear system of reaction-diffusion partial differential equations at two scales. In particular, a subcellular model containing several realistic transverse tubules (or t-tubules) is investigated and assumed to reside at different locations relative to the cell membrane. To this end, the Ca(2+) concentration calculated from the whole-cell modeling is adopted as part of the boundary constraint in the subcellular model. The preliminary simulations show that Ca(2+) concentration changes in ventricular myocytes are mainly influenced by calcium release from t-tubules.
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Affiliation(s)
- Zeyun Yu
- Department of Computer Science, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA.
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19
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SynapticDB, effective web-based management and sharing of data from serial section electron microscopy. Neuroinformatics 2010; 9:39-57. [PMID: 21181305 PMCID: PMC3063557 DOI: 10.1007/s12021-010-9088-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Serial section electron microscopy (ssEM) is rapidly expanding as a primary tool to investigate synaptic circuitry and plasticity. The ultrastructural images collected through ssEM are content rich and their comprehensive analysis is beyond the capacity of an individual laboratory. Hence, sharing ultrastructural data is becoming crucial to visualize, analyze, and discover the structural basis of synaptic circuitry and function in the brain. We devised a web-based management system called SynapticDB (http://synapses.clm.utexas.edu/synapticdb/) that catalogues, extracts, analyzes, and shares experimental data from ssEM. The management strategy involves a library with check-in, checkout and experimental tracking mechanisms. We developed a series of spreadsheet templates (MS Excel, Open Office spreadsheet, etc) that guide users in methods of data collection, structural identification, and quantitative analysis through ssEM. SynapticDB provides flexible access to complete templates, or to individual columns with instructional headers that can be selected to create user-defined templates. New templates can also be generated and uploaded. Research progress is tracked via experimental note management and dynamic PDF forms that allow new investigators to follow standard protocols and experienced researchers to expand the range of data collected and shared. The combined use of templates and tracking notes ensures that the supporting experimental information is populated into the database and associated with the appropriate ssEM images and analyses. We anticipate that SynapticDB will serve future meta-analyses towards new discoveries about the composition and circuitry of neurons and glia, and new understanding about structural plasticity during development, behavior, learning, memory, and neuropathology.
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20
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Control of Ca2+ release by action potential configuration in normal and failing murine cardiomyocytes. Biophys J 2010; 99:1377-86. [PMID: 20816049 DOI: 10.1016/j.bpj.2010.06.055] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 05/13/2010] [Accepted: 06/14/2010] [Indexed: 01/15/2023] Open
Abstract
Cardiomyocytes from failing hearts exhibit spatially nonuniform or dyssynchronous sarcoplasmic reticulum (SR) Ca(2+) release. We investigated the contribution of action potential (AP) prolongation in mice with congestive heart failure (CHF) after myocardial infarction. AP recordings from CHF and control myocytes were included in a computational model of the dyad, which predicted more dyssynchronous ryanodine receptor opening during stimulation with the CHF AP. This prediction was confirmed in cardiomyocyte experiments, when cells were alternately stimulated by control and CHF AP voltage-clamp waveforms. However, when a train of like APs was used as the voltage stimulus, the control and CHF AP produced a similar Ca(2+) release pattern. In this steady-state condition, greater integrated Ca(2+) entry during the CHF AP lead to increased SR Ca(2+) content. A resulting increase in ryanodine receptor sensitivity synchronized SR Ca(2+) release in the mathematical model, thus offsetting the desynchronizing effects of reduced driving force for Ca(2+) entry. A modest nondyssynchronous prolongation of Ca(2+) release was nevertheless observed during the steady-state CHF AP, which contributed to increased time-to-peak measurements for Ca(2+) transients in failing cells. Thus, dyssynchronous Ca(2+) release in failing mouse myocytes does not result from electrical remodeling, but rather other alterations such as T-tubule reorganization.
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Hoshijima M, Hayashi T, Jeon YE, Fu Z, Gu Y, Dalton ND, Ellisman MH, Xiao X, Powell FL, Ross J. Delta-sarcoglycan gene therapy halts progression of cardiac dysfunction, improves respiratory failure, and prolongs life in myopathic hamsters. Circ Heart Fail 2010; 4:89-97. [PMID: 21036890 DOI: 10.1161/circheartfailure.110.957258] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND The BIO14.6 hamster provides a useful model of hereditary cardiomyopathies and muscular dystrophy. Previous δ-sarcoglycan (δSG) gene therapy (GT) studies were limited to neonatal and young adult animals and prevented the development of cardiac and skeletal muscle dysfunction. GT of a pseudophosphorylated mutant of phospholamban (S16EPLN) moderately alleviated the progression of cardiomyopathy. METHODS AND RESULTS We treated 4-month-old BIO14.6 hamsters with established cardiac and skeletal muscle diseases intravenously with a serotype-9 adeno-associated viral vector carrying δSG alone or in combination with S16EPLN. Before treatment at age 14 weeks, the left ventricular fractional shortening by echocardiography was 31.3% versus 45.8% in normal hamsters. In a randomized trial, GT halted progression of left ventricular dilation and left ventricular dysfunction. Also, respiratory function improved. Addition of S16EPLN had no significant additional effects. δSG-GT prevented severe degeneration of the transverse tubular system in cardiomyocytes (electron tomography) and restored distribution of dystrophin and caveolin-3. All placebo-treated hamsters, except animals removed for the hemodynamic study, died with heart failure between 34 and 67 weeks of age. In the GT group, signs of cardiac and respiratory failure did not develop, and animals lived for 92 weeks or longer, an age comparable to that reported in normal hamsters. CONCLUSION GT was highly effective in BIO14.6 hamsters even when given in late-stage disease, a finding that may carry implications for the future treatment of hereditary cardiac and muscle diseases in humans.
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Affiliation(s)
- Masahiko Hoshijima
- Center for Research in Biological Systems, the Department of Medicine, National Center for Microscopy and Imaging Research, University of California-San Diego, La Jolla, CA, USA.
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22
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Cheng Y, Yu Z, Hoshijima M, Holst MJ, McCulloch AD, McCammon JA, Michailova AP. Numerical analysis of Ca2+ signaling in rat ventricular myocytes with realistic transverse-axial tubular geometry and inhibited sarcoplasmic reticulum. PLoS Comput Biol 2010; 6:e1000972. [PMID: 21060856 PMCID: PMC2965743 DOI: 10.1371/journal.pcbi.1000972] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 09/23/2010] [Indexed: 12/21/2022] Open
Abstract
The t-tubules of mammalian ventricular myocytes are invaginations of the cell membrane that occur at each Z-line. These invaginations branch within the cell to form a complex network that allows rapid propagation of the electrical signal, and hence synchronous rise of intracellular calcium (Ca2+). To investigate how the t-tubule microanatomy and the distribution of membrane Ca2+ flux affect cardiac excitation-contraction coupling we developed a 3-D continuum model of Ca2+ signaling, buffering and diffusion in rat ventricular myocytes. The transverse-axial t-tubule geometry was derived from light microscopy structural data. To solve the nonlinear reaction-diffusion system we extended SMOL software tool (http://mccammon.ucsd.edu/smol/). The analysis suggests that the quantitative understanding of the Ca2+ signaling requires more accurate knowledge of the t-tubule ultra-structure and Ca2+ flux distribution along the sarcolemma. The results reveal the important role for mobile and stationary Ca2+ buffers, including the Ca2+ indicator dye. In agreement with experiment, in the presence of fluorescence dye and inhibited sarcoplasmic reticulum, the lack of detectible differences in the depolarization-evoked Ca2+ transients was found when the Ca2+ flux was heterogeneously distributed along the sarcolemma. In the absence of fluorescence dye, strongly non-uniform Ca2+ signals are predicted. Even at modest elevation of Ca2+, reached during Ca2+ influx, large and steep Ca2+ gradients are found in the narrow sub-sarcolemmal space. The model predicts that the branched t-tubule structure and changes in the normal Ca2+ flux density along the cell membrane support initiation and propagation of Ca2+ waves in rat myocytes. In cardiac muscle cells, calcium (Ca2+) is best known for its role in contraction activation. A remarkable amount of quantitative data on cardiac cell structure, ion-transporting protein distributions and intracellular Ca2+ dynamics has been accumulated. Various alterations in the protein distributions or cell ultra-structure are now recognized to be the primary mechanisms of cardiac dysfunction in a diverse range of common pathologies including cardiac arrhythmias and hypertrophy. Using a 3-D computational model, incorporating more realistic transverse-axial t-tubule geometry and considering geometric irregularities and inhomogeneities in the distribution of ion-transporting proteins, we analyze several important spatial and temporal features of Ca2+ signaling in rat ventricular myocytes. This study demonstrates that the computational models could serve as powerful tools for prediction and analyses of how the Ca2+ dynamics and cardiac excitation-contraction coupling are regulated under normal conditions or certain pathologies. The use of computational and mathematical approaches will help also to better understand aspects of cell functions that are not currently amenable to experimental investigation.
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Affiliation(s)
- Yuhui Cheng
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Zeyun Yu
- Department of Computer Science, University of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Masahiko Hoshijima
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Michael J. Holst
- Department of Mathematics, University of California San Diego, La Jolla, California, United States of America
| | - Andrew D. McCulloch
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - J. Andrew McCammon
- Department of Chemistry and Biochemistry, Department of Pharmacology, University of California San Diego, La Jolla, California, United States of America
- Howard Hughes Medical Institute, University of California San Diego, La Jolla, California, United States of America
| | - Anushka P. Michailova
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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