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Dutta S, Muraganadan T, Vasudevan M. Evaluation of lamin A/C mechanotransduction under different surface topography in LMNA related muscular dystrophy. Cytoskeleton (Hoboken) 2024. [PMID: 39091017 DOI: 10.1002/cm.21895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 07/01/2024] [Accepted: 07/02/2024] [Indexed: 08/04/2024]
Abstract
Most of the single point mutations of the LMNA gene are associated with distinct muscular dystrophies, marked by heterogenous phenotypes but primarily the loss and symmetric weakness of skeletal muscle tissue. The molecular mechanism and phenotype-genotype relationships in these muscular dystrophies are poorly understood. An effort has been here to delineating the adaptation of mechanical inputs into biological response by mutant cells of lamin A associated muscular dystrophy. In this study, we implement engineered smooth and pattern surfaces of particular young modulus to mimic muscle physiological range. Using fluorescence and atomic force microscopy, we present distinct architecture of the actin filament along with abnormally distorted cell and nuclear shape in mutants, which showed a tendency to deviate from wild type cells. Topographic features of pattern surface antagonize the binding of the cell with it. Correspondingly, from the analysis of genome wide expression data in wild type and mutant cells, we report differential expression of the gene products of the structural components of cell adhesion as well as LINC (linkers of nucleoskeleton and cytoskeleton) protein complexes. This study also reveals mis expressed downstream signaling processes in mutant cells, which could potentially lead to onset of the disease upon the application of engineered materials to substitute the role of conventional cues in instilling cellular behaviors in muscular dystrophies. Collectively, these data support the notion that lamin A is essential for proper cellular mechanotransduction from extracellular environment to the genome and impairment of the muscle cell differentiation in the pathogenic mechanism for lamin A associated muscular dystrophy.
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Affiliation(s)
- Subarna Dutta
- Department of Biochemistry, University of Calcutta, Kolkata, West Bengal, India
- Theomics International Private Limited, Bengaluru, India
| | - T Muraganadan
- CSIR-Indian Institute of Chemical Biology, Kolkata, India
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2
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Choi Y, Morlino G, Toboso-Navasa A, Hopf R, Pramotton FM, Bigot A, Taddei A, Cesarovic N, Falk V, Mazza E, Giampietro C. A novel bistable device to study mechanosensitive cell responses to instantaneous stretch. BIOMATERIALS ADVANCES 2022; 141:213134. [PMID: 36191540 DOI: 10.1016/j.bioadv.2022.213134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 08/17/2022] [Accepted: 09/25/2022] [Indexed: 06/16/2023]
Abstract
The behavior of cells and tissues in vivo is determined by the integration of multiple biochemical and mechanical signals. Of the mechanical signals, stretch has been studied for decades and shown to contribute to pathophysiological processes. Several different stretch devices have been developed for in vitro investigations of cell stretch. In this work, we describe a new 3D-printed uniaxial stretching device for studying cell response to rapid deformation. The device is a bistable compliant mechanism holding two equilibrium states-an unstretched and stretched configuration-without the need of an external actuator. Furthermore, it allows multiple simultaneous measurements of different levels of stretch on a single substrate and is compatible with standard immunofluorescence imaging of fixed cells as well as live-cell imaging. To demonstrate the effectiveness of the device to stretch cells, a test case using aligned myotubes is presented. Leveraging material area changes associated with deformation of the substrate, changes in nuclei density provided evidence of affine deformation between cells and substrate. Furthermore, intranuclear deformations were also assessed and shown to deform non-affinely. As a proof-of-principle of the use of the device for mechanobiological studies, we uniaxially stretched aligned healthy and dystrophic myotubes that displayed different passive mechanical responses, consistent with previous literature in the field. We also identified a new feature in the mechanoresponse of dystrophic myotubes, which is of potential interest for identifying the diseased cells based on a quick mechanical readout. While some applications of the device for elucidating passive mechanical responses are demonstrated, the simplicity of the device allows it to be potentially used for other modes of deformation with little modifications.
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Affiliation(s)
- Young Choi
- Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland
| | | | | | - Raoul Hopf
- Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland; Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf 8600, Switzerland; Senecell AG, Zurich 8057, Switzerland
| | - Francesca Michela Pramotton
- Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland; Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf 8600, Switzerland
| | - Anne Bigot
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, F-75013 Paris, France
| | | | - Nikola Cesarovic
- Department of Health Sciences and Technology, ETH Zurich, Zurich 8092, Switzerland; Charité - Universitätsmedizin Berlin, Berlin 10117, Germany
| | - Volkmar Falk
- Department of Health Sciences and Technology, ETH Zurich, Zurich 8092, Switzerland; Charité - Universitätsmedizin Berlin, Berlin 10117, Germany
| | - Edoardo Mazza
- Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland; Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf 8600, Switzerland.
| | - Costanza Giampietro
- Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland; Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf 8600, Switzerland; Senecell AG, Zurich 8057, Switzerland.
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3
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Kourti D, Kanioura A, Chatzichristidi M, Beltsios KG, Kakabakos SE, Petrou PS. Photopatternable materials for guided cell adhesion and growth. Eur Polym J 2022. [DOI: 10.1016/j.eurpolymj.2021.110896] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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4
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George E, Jahan I, Barai A, Ganesan V, Sen S. High ligand density drives extensive spreading and motility on soft GelMA gels. Biomed Mater 2021; 16. [PMID: 34298538 DOI: 10.1088/1748-605x/ac177b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 07/23/2021] [Indexed: 12/18/2022]
Abstract
In comparison to synthetic hydrogels where ligand density and stiffness can be independently tuned, cell responses are expected to deviate on native biopolymer networks where ligand density and stiffness are coupled. Here we probe the tensional homeostasis of fibroblasts on methacrylated gelatin (GelMA) gels, which are widely used in tissue engineering applications. On 5%-15% GelMA gels which are very soft (10-100's of Pa's in stiffness), fibroblasts were found to spread extensively and assemble prominent stress fibers and focal adhesions. Probing of contractile mechanics using trypsin-induced detachment revealed adhesive drag, but not contractility, was sensitive to GelMA concentration. Contractility-altering drugs blebbistatin and nocodazole, which exhibited opposite effects on focal adhesion size, both led to reduction in adhesive drag and cell rounding. However, cell motility was impacted only in nocodazole-treated cells. Collectively, our experiments suggest that on soft GelMA gels, contractility-independent adhesion clustering mediated by high ligand density can drive cell spreading and motility.
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Affiliation(s)
- Edna George
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Iffat Jahan
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Amlan Barai
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Vignesh Ganesan
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Shamik Sen
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
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5
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Abstract
Hagfish slime is a unique predator defence material containing a network of long fibrous threads each ∼10 cm in length. Hagfish release the threads in a condensed coiled state known as skeins (∼100 µm), which must unravel within a fraction of a second to thwart a predator attack. Here we consider the hypothesis that viscous hydrodynamics can be responsible for this rapid unravelling, as opposed to chemical reaction kinetics alone. Our main conclusion is that, under reasonable physiological conditions, unravelling due to viscous drag can occur within a few hundred milliseconds, and is accelerated if the skein is pinned at a surface such as the mouth of a predator. We model a single skein unspooling as the fibre peels away due to viscous drag. We capture essential features by considering simplified cases of physiologically relevant flows and one-dimensional scenarios where the fibre is aligned with streamlines in either uniform or uniaxial extensional flow. The peeling resistance is modelled with a power-law dependence on peeling velocity. A dimensionless ratio of viscous drag to peeling resistance appears in the dynamical equations and determines the unraveling time scale. Our modelling approach is general and can be refined with future experimental measurements of peel strength for skein unravelling. It provides key insights into the unravelling process, offers potential answers to lingering questions about slime formation from threads and mucous vesicles, and will aid the growing interest in engineering similar bioinspired material systems.
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Affiliation(s)
- Gaurav Chaudhary
- 1 Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign , Urbana, IL , USA
| | - Randy H Ewoldt
- 1 Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign , Urbana, IL , USA
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6
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Lev R, Seliktar D. Hydrogel biomaterials and their therapeutic potential for muscle injuries and muscular dystrophies. J R Soc Interface 2018; 15:20170380. [PMID: 29343633 PMCID: PMC5805959 DOI: 10.1098/rsif.2017.0380] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 12/18/2017] [Indexed: 12/23/2022] Open
Abstract
Muscular diseases such as muscular dystrophies and muscle injuries constitute a large group of ailments that manifest as muscle weakness, atrophy or fibrosis. Although cell therapy is a promising treatment option, the delivery and retention of cells in the muscle is difficult and prevents sustained regeneration needed for adequate functional improvements. Various types of biomaterials with different physical and chemical properties have been developed to improve the delivery of cells and/or growth factors for treating muscle injuries. Hydrogels are a family of materials with distinct advantages for use as cell delivery systems in muscle injuries and ailments, including their mild processing conditions, their similarities to natural tissue extracellular matrix, and their ability to be delivered with less invasive approaches. Moreover, hydrogels can be made to completely degrade in the body, leaving behind their biological payload in a process that can enhance the therapeutic process. For these reasons, hydrogels have shown great potential as cell delivery matrices. This paper reviews a few of the hydrogel systems currently being applied together with cell therapy and/or growth factor delivery to promote the therapeutic repair of muscle injuries and muscle wasting diseases such as muscular dystrophies.
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Affiliation(s)
- Rachel Lev
- Faculty of Biomedical Engineering, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel
| | - Dror Seliktar
- Faculty of Biomedical Engineering, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel
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7
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Winklbauer R. Cell adhesion strength from cortical tension - an integration of concepts. J Cell Sci 2016; 128:3687-93. [PMID: 26471994 DOI: 10.1242/jcs.174623] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Morphogenetic mechanisms such as cell movement or tissue separation depend on cell attachment and detachment processes, which involve adhesion receptors as well as the cortical cytoskeleton. The interplay between the two components is of stunning complexity. Most strikingly, the binding energy of adhesion molecules is usually too small for substantial cell-cell attachment, pointing to a main deficit in our present understanding of adhesion. In this Opinion article, I integrate recent findings and conceptual advances in the field into a coherent framework for cell adhesion. I argue that active cortical tension is best viewed as an integral part of adhesion, and propose on this basis a non-arbitrary measure of adhesion strength - the tissue surface tension of cell aggregates. This concept of adhesion integrates heterogeneous molecular inputs into a single mechanical property and simplifies the analysis of attachment-detachment processes. It draws attention to the enormous variation of adhesion strengths among tissues, whose origin and function is little understood.
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Affiliation(s)
- Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada
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8
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Fuhrmann A, Engler AJ. The cytoskeleton regulates cell attachment strength. Biophys J 2016; 109:57-65. [PMID: 26153702 DOI: 10.1016/j.bpj.2015.06.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 05/19/2015] [Accepted: 06/03/2015] [Indexed: 11/25/2022] Open
Abstract
Quantitative information about adhesion strength is a fundamental part of our understanding of cell-extracellular matrix (ECM) interactions. Adhesion assays should measure integrin-ECM bond strength, but reports now suggest that cell components remain behind after exposure to acute force for radial shear assays in the presence of divalent cations that increase integrin-ECM affinity. Here, we show that focal adhesion proteins FAK, paxillin, and vinculin but not the cytoskeletal protein actin remain behind after shear-induced detachment of HT1080 fibrosarcoma cells. Cytoskeletal stabilization increased attachment strength by eightfold, whereas cross-linking integrins to the substrate only caused a 1.5-fold increase. Reducing temperature-only during shear application-also increased attachment strength eightfold, with detachment again occurring between focal adhesion proteins and actin. Detachment at the focal adhesion-cytoskeleton interface was also observed in mouse and human fibroblasts and was ligand-independent, highlighting the ubiquity of this mode of detachment in the presence of divalent cations. These data show that the cytoskeleton and its dynamic coupling to focal adhesions are critically important for cell adhesion in niche with divalent cations.
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Affiliation(s)
- Alexander Fuhrmann
- Department of Bioengineering, University of California, San Diego, La Jolla, California
| | - Adam J Engler
- Department of Bioengineering, University of California, San Diego, La Jolla, California; Sanford Consortium for Regenerative Medicine, La Jolla, California.
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9
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Stoppel WL, Kaplan DL, Black LD. Electrical and mechanical stimulation of cardiac cells and tissue constructs. Adv Drug Deliv Rev 2016; 96:135-55. [PMID: 26232525 DOI: 10.1016/j.addr.2015.07.009] [Citation(s) in RCA: 157] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 07/16/2015] [Accepted: 07/25/2015] [Indexed: 12/19/2022]
Abstract
The field of cardiac tissue engineering has made significant strides over the last few decades, highlighted by the development of human cell derived constructs that have shown increasing functional maturity over time, particularly using bioreactor systems to stimulate the constructs. However, the functionality of these tissues is still unable to match that of native cardiac tissue and many of the stem-cell derived cardiomyocytes display an immature, fetal like phenotype. In this review, we seek to elucidate the biological underpinnings of both mechanical and electrical signaling, as identified via studies related to cardiac development and those related to an evaluation of cardiac disease progression. Next, we review the different types of bioreactors developed to individually deliver electrical and mechanical stimulation to cardiomyocytes in vitro in both two and three-dimensional tissue platforms. Reactors and culture conditions that promote functional cardiomyogenesis in vitro are also highlighted. We then cover the more recent work in the development of bioreactors that combine electrical and mechanical stimulation in order to mimic the complex signaling environment present in vivo. We conclude by offering our impressions on the important next steps for physiologically relevant mechanical and electrical stimulation of cardiac cells and engineered tissue in vitro.
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10
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Krishnan R, Park JA, Seow CY, Lee PVS, Stewart AG. Cellular Biomechanics in Drug Screening and Evaluation: Mechanopharmacology. Trends Pharmacol Sci 2015; 37:87-100. [PMID: 26651416 DOI: 10.1016/j.tips.2015.10.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 10/12/2015] [Accepted: 10/23/2015] [Indexed: 12/14/2022]
Abstract
The study of mechanobiology is now widespread. The impact of cell and tissue mechanics on cellular responses is well appreciated. However, knowledge of the impact of cell and tissue mechanics on pharmacological responsiveness, and its application to drug screening and mechanistic investigations, have been very limited in scope. We emphasize the need for a heightened awareness of the important bidirectional influence of drugs and biomechanics in all living systems. We propose that the term 'mechanopharmacology' be applied to approaches that employ in vitro systems, biomechanically appropriate to the relevant (patho)physiology, to identify new drugs and drug targets. This article describes the models and techniques that are being developed to transform drug screening and evaluation, ranging from a 2D environment to the dynamic 3D environment of the target expressed in the disease of interest.
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Affiliation(s)
- Ramaswamy Krishnan
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Jin-Ah Park
- Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Chun Y Seow
- Center for Heart Lung Innovation, St Pauls Hospital, University of British Columbia, Vancouver, Canada
| | - Peter V-S Lee
- Department of Mechanical Engineering, University of Melbourne, Melbourne, Australia
| | - Alastair G Stewart
- Lung Health Research Centre, Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, Australia.
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11
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Chan KLS, Khankhel AH, Thompson RL, Coisman BJ, Wong KHK, Truslow JG, Tien J. Crosslinking of collagen scaffolds promotes blood and lymphatic vascular stability. J Biomed Mater Res A 2013; 102:3186-3195. [PMID: 24151175 DOI: 10.1002/jbm.a.34990] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 09/11/2013] [Accepted: 10/02/2013] [Indexed: 11/09/2022]
Abstract
The low stiffness of reconstituted collagen hydrogels has limited their use as scaffolds for engineering implantable tissues. Although chemical crosslinking has been used to stiffen collagen and protect it against enzymatic degradation in vivo, it remains unclear how crosslinking alters the vascularization of collagen hydrogels. In this study, we examine how the crosslinking agents genipin and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide alter vascular stability and function in microfluidic type I collagen gels in vitro. Under moderate perfusion (∼10 dyn/cm(2) shear stress), tubes of blood endothelial cells (ECs) exhibited indistinguishable stability and barrier function in untreated and crosslinked scaffolds. Surprisingly, under low perfusion (∼5 dyn/cm(2) shear stress) or nearly zero transmural pressure, microvessels in crosslinked scaffolds remained stable, while those in untreated gels rapidly delaminated and became poorly perfused. Similarly, tubes of lymphatic ECs under intermittent flow were more stable in crosslinked gels than in untreated ones. These effects correlated well with the degree of mechanical stiffening, as predicted by analysis of fracture energies at the cell-scaffold interface. This work demonstrates that crosslinking of collagen scaffolds does not hinder normal EC physiology; instead, crosslinked scaffolds promote vascular stability. Thus, routine crosslinking of scaffolds may assist in vascularization of engineered tissues.
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Affiliation(s)
- Kelvin L S Chan
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215
| | - Aimal H Khankhel
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215
| | - Rebecca L Thompson
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215
| | - Brent J Coisman
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215
| | - Keith H K Wong
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215
| | - James G Truslow
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215
| | - Joe Tien
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215.,Division of Materials Science and Engineering, Boston University, 15 St. Mary's Street, Brookline, MA 02446
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12
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Yoshikawa HY, Kawano T, Matsuda T, Kidoaki S, Tanaka M. Morphology and Adhesion Strength of Myoblast Cells on Photocurable Gelatin under Native and Non-native Micromechanical Environments. J Phys Chem B 2013; 117:4081-8. [DOI: 10.1021/jp4008224] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hiroshi Y. Yoshikawa
- Physical Chemistry of Biosystems,
Institute of Physical Chemistry, University of Heidelberg, Heidelberg 69120, Germany
- Department of Chemistry, Saitama University, Saitama 338-8570, Japan
| | - Takahito Kawano
- Division of Biomolecular Chemistry,
Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Takehisa Matsuda
- Genome Biotechnology Laboratory, Kanazawa Institute of Technology, Ishikawa 924-0838,
Japan
| | - Satoru Kidoaki
- Division of Biomolecular Chemistry,
Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Motomu Tanaka
- Physical Chemistry of Biosystems,
Institute of Physical Chemistry, University of Heidelberg, Heidelberg 69120, Germany
- Institute for Integrated
Cell-Material
Sciences (WPI iCeMS), Kyoto University,
606-8501, Kyoto, Japan
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13
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Shim J, Grosberg A, Nawroth JC, Parker KK, Bertoldi K. Modeling of cardiac muscle thin films: pre-stretch, passive and active behavior. J Biomech 2012; 45:832-41. [PMID: 22236531 DOI: 10.1016/j.jbiomech.2011.11.024] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2011] [Indexed: 10/14/2022]
Abstract
Recent progress in tissue engineering has made it possible to build contractile bio-hybrid materials that undergo conformational changes by growing a layer of cardiac muscle on elastic polymeric membranes. Further development of such muscular thin films for building actuators and powering devices requires exploring several design parameters, which include the alignment of the cardiac myocytes and the thickness/Young's modulus of elastomeric film. To more efficiently explore these design parameters, we propose a 3-D phenomenological constitutive model, which accounts for both the passive deformation including pre-stretch and the active behavior of the cardiomyocytes. The proposed 3-D constitutive model is implemented within a finite element framework, and can be used to improve the current design of bio-hybrid thin films and help developing bio-hybrid constructs capable of complex conformational changes.
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Affiliation(s)
- Jongmin Shim
- School of Engineering and Applied Science, Harvard University, Cambridge, MA, United States.
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14
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Saidi N, Kouki S, Mehri I, Ben Rejeb A, Belila A, Hassen A, Ouzari H. Biofilm and Siderophore Effects on Secondary Waste Water Disinfection. Curr Microbiol 2011; 63:337-40. [DOI: 10.1007/s00284-011-9983-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Accepted: 07/04/2011] [Indexed: 01/14/2023]
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15
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Upregulation of paxillin and focal adhesion signaling follows Dystroglycan Complex deletions and promotes a hypertensive state of differentiation. Eur J Cell Biol 2011; 90:249-60. [PMID: 20663583 DOI: 10.1016/j.ejcb.2010.06.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 05/27/2010] [Accepted: 06/23/2010] [Indexed: 02/06/2023] Open
Abstract
Anchorage to matrix is mediated for many cells not only by integrin-based focal adhesions but also by a parallel assembly of integral and peripheral membrane proteins known as the Dystroglycan Complex. Deficiencies in either dystrophin (mdx mice) or γ-sarcoglycan (γSG(-/-) mice) components of the Dystroglycan Complex lead to upregulation of numerous focal adhesion proteins, and the phosphoprotein paxillin proves to be among the most prominent. In mdx muscle, paxillin-Y31 and Y118 are both hyper-phosphorylated as are key sites in focal adhesion kinase (FAK) and the stretch-stimulatable pro-survival MAPK pathway, whereas γSG(-/-) muscle exhibits more erratic hyper-phosphorylation. In cultured myotubes, cell tension generated by myosin-II appears required for localization of paxillin to adhesions while vinculin appears more stably integrated. Overexpression of wild-type (WT) paxillin has no obvious effect on focal adhesion density or the physical strength of adhesion, but WT and a Y118F mutant promote contractile sarcomere formation whereas a Y31F mutant shows no effect, implicating Y31 in striation. Self-peeling of cells as well as Atomic Force Microscopy (AFM) probing of cells with or without myosin-II inhibition indicate an increase in cell tension within paxillin-overexpressing cells. However, prednisolone, a first-line glucocorticoid for muscular dystrophies, decreases cell tension without affecting paxillin at adhesions, suggesting a non-linear relationship between paxillin and cell tension. Hypertension that results from upregulation of integrin adhesions is thus a natural and treatable outcome of Dystroglycan Complex down-regulation.
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16
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Yoshikawa HY, Rossetti FF, Kaufmann S, Kaindl T, Madsen J, Engel U, Lewis AL, Armes SP, Tanaka M. Quantitative evaluation of mechanosensing of cells on dynamically tunable hydrogels. J Am Chem Soc 2011; 133:1367-74. [PMID: 21218794 DOI: 10.1021/ja1060615] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thin hydrogel films based on an ABA triblock copolymer gelator [where A is pH-sensitive poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) and B is biocompatible poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC)] were used as a stimulus-responsive substrate that allows fine adjustment of the mechanical environment experienced by mouse myoblast cells. The hydrogel film elasticity could be reversibly modulated by a factor of 40 via careful pH adjustment without adversely affecting cell viability. Myoblast cells exhibited pronounced stress fiber formation and flattening on increasing the hydrogel elasticity. As a new tool to evaluate the strength of cell adhesion, we combined a picosecond laser with an inverted microscope and utilized the strong shock wave created by the laser pulse to determine the critical pressure required for cell detachment. Furthermore, we demonstrate that an abrupt jump in the hydrogel elasticity can be utilized to monitor how cells adapt their morphology to changes in their mechanical environment.
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Affiliation(s)
- Hiroshi Y Yoshikawa
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, D69120 Heidelberg, Germany
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17
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Théry M. Micropatterning as a tool to decipher cell morphogenesis and functions. J Cell Sci 2010; 123:4201-13. [DOI: 10.1242/jcs.075150] [Citation(s) in RCA: 530] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In situ, cells are highly sensitive to geometrical and mechanical constraints from their microenvironment. These parameters are, however, uncontrolled under classic culture conditions, which are thus highly artefactual. Micro-engineering techniques provide tools to modify the chemical properties of cell culture substrates at sub-cellular scales. These can be used to restrict the location and shape of the substrate regions, in which cells can attach, so-called micropatterns. Recent progress in micropatterning techniques has enabled the control of most of the crucial parameters of the cell microenvironment. Engineered micropatterns can provide a micrometer-scale, soft, 3-dimensional, complex and dynamic microenvironment for individual cells or for multi-cellular arrangements. Although artificial, micropatterned substrates allow the reconstitution of physiological in situ conditions for controlled in vitro cell culture and have been used to reveal fundamental cell morphogenetic processes as highlighted in this review. By manipulating micropattern shapes, cells were shown to precisely adapt their cytoskeleton architecture to the geometry of their microenvironment. Remodelling of actin and microtubule networks participates in the adaptation of the entire cell polarity with respect to external constraints. These modifications further impact cell migration, growth and differentiation.
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Affiliation(s)
- Manuel Théry
- Laboratoire de Physiologie Cellulaire et Végétale, iRTSV, CEA/CNRS/UJF/INRA, 17 Rue des Martyrs, 38054, Grenoble, France
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18
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Christ KV, Williamson KB, Masters KS, Turner KT. Measurement of single-cell adhesion strength using a microfluidic assay. Biomed Microdevices 2010; 12:443-55. [PMID: 20213215 DOI: 10.1007/s10544-010-9401-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Despite the importance of cell adhesion in numerous physiological, pathological, and biomaterial-related responses, our understanding of adhesion strength at the cell-substrate interface and its relationship to cell function remains incomplete. One reason for this deficit is a lack of accessible experimental approaches that quantify adhesion strength at the single-cell level and facilitate large numbers of tests. The current work describes the design, fabrication, and use of a microfluidic-based method for single-cell adhesion strength measurements. By applying a monotonically increasing flow rate in a microfluidic channel in combination with video microscopy, the adhesion strength of individual NIH3T3 fibroblasts cultured for 24 h on various surfaces was measured. The small height of the channel allows high shear stresses to be generated under laminar conditions, allowing strength measurements on well-spread, strongly adhered cells that cannot be characterized in most conventional assays. This assay was used to quantify the relationship between morphological characteristics and adhesion strength for individual well-spread cells. Cell adhesion strength was found to be positively correlated with both cell area and circularity. Computational fluid dynamics (CFD) analysis was performed to examine the role of cell geometry in determining the actual stress applied to the cell. Use of this method to examine adhesion at the single-cell level allows the detachment of strongly-adhered cells under a highly-controllable, uniform loading to be directly observed and will enable the characterization of biological events and relationships that cannot currently be achieved using existing methods.
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Affiliation(s)
- Kevin V Christ
- Materials Science Program, University of Wisconsin, Madison, WI 53706, USA
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Zemel A, Rehfeldt F, Brown AEX, Discher DE, Safran SA. Optimal matrix rigidity for stress fiber polarization in stem cells. NATURE PHYSICS 2010; 6:468-473. [PMID: 20563235 PMCID: PMC2885792 DOI: 10.1038/nphys1613] [Citation(s) in RCA: 233] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The shape and differentiation of human mesenchymal stem cells is especially sensitive to the rigidity of their environment; the physical mechanisms involved are unknown. A theoretical model and experiments demonstrate here that the polarization/alignment of stress-fibers within stem cells is a non-monotonic function of matrix rigidity. We treat the cell as an active elastic inclusion in a surrounding matrix whose polarizability, unlike dead matter, depends on the feedback of cellular forces that develop in response to matrix stresses. The theory correctly predicts the monotonic increase of the cellular forces with the matrix rigidity and the alignment of stress-fibers parallel to the long axis of cells. We show that the anisotropy of this alignment depends non-monotonically on matrix rigidity and demonstrate it experimentally by quantifying the orientational distribution of stress-fibers in stem cells. These findings offer a first physical insight for the dependence of stem cell differentiation on tissue elasticity.
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Affiliation(s)
- A Zemel
- Institute of Dental Sciences, Faculty of Dental Medicine, and the Fritz Haber Center for Molecular Dynamics, the Hebrew University-Hadassah Medical Center, Jerusalem, 91120, Israel
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Chirasatitsin S, Engler AJ. Detecting cell-adhesive sites in extracellular matrix using force spectroscopy mapping. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:194102. [PMID: 21152375 PMCID: PMC2997741 DOI: 10.1088/0953-8984/22/19/194102] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
The cell microenvironment is composed of extracellular matrix (ECM), which contains specific binding sites that allow the cell to adhere to its surroundings. Cells employ focal adhesion proteins, which must be able to resist a variety of forces to bind to ECM. Current techniques for detecting the spatial arrangement of these adhesions, however, have limited resolution and those that detect adhesive forces lack sufficient spatial characterization or resolution. Using a unique application of force spectroscopy, we demonstrate here the ability to determine local changes in the adhesive property of a fibronectin substrate down to the resolution of the fibronectin antibody-functionalized tip diameter, ~20 nm. To verify the detection capabilities of force spectroscopy mapping (FSM), changes in loading rate and temperature were used to alter the bond dynamics and change the adhesion force. Microcontact printing was also used to pattern fluorescein isothiocyanate-conjugated fibronectin in order to mimic the discontinuous adhesion domains of native ECM. Fluorescent detection was used to identify the pattern while FSM was used to map cell adhesion sites in registry with the initial fluorescent image. The results show that FSM can be used to detect the adhesion domains at high resolution and may subsequently be applied to native ECM with randomly distributed cell adhesion sites.
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Affiliation(s)
- Somyot Chirasatitsin
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
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21
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Zemel A, Rehfeldt F, Brown AEX, Discher DE, Safran SA. Cell shape, spreading symmetry and the polarization of stress-fibers in cells. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:194110. [PMID: 20458358 PMCID: PMC2865697 DOI: 10.1088/0953-8984/22/19/194110] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The active regulation of cellular forces during cell adhesion plays an important role in the determination of cell size, shape and internal structure. While on flat, homogeneous and isotropic substrates some cells spread isotropically, others spread anisotropically and assume elongated structures. In addition, in their native environment as well as in vitro experiments, the cell shape and spreading asymmetry can be modulated by the local distribution of adhesive molecules and topography of the environment. We present a simple elastic model, and experiments on stem cells to explain the variation of cell size with the matrix rigidity. In addition, we predict the experimental consequences of two mechanisms of acto-myosin polarization and focus here on the effect of the cell spreading asymmetry on the regulation of the stress-fiber alignment in the cytoskeleton. We show that when cell spreading is sufficiently asymmetric the alignment of acto-myosin forces in the cell increases monotonically with the matrix rigidity; however, in general this alignment is non-monotonic as shown previously. These results highlight the importance of the symmetry characteristics of cell spreading in the regulation of cytoskeleton structure and suggest a mechanism by which different cell types may acquire different morphologies and internal structures in different mechanical environments.
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Affiliation(s)
- A Zemel
- Institute of Dental Sciences, Faculty of Dental Medicine, Hebrew University-Hadassah Medical Center, Jerusalem, Israel
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22
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Ahmed WW, Wolfram T, Goldyn AM, Bruellhoff K, Rioja BA, Möller M, Spatz JP, Saif TA, Groll J, Kemkemer R. Myoblast morphology and organization on biochemically micro-patterned hydrogel coatings under cyclic mechanical strain. Biomaterials 2010; 31:250-8. [DOI: 10.1016/j.biomaterials.2009.09.047] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 09/11/2009] [Indexed: 10/20/2022]
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Abstract
Recent discoveries have established that mechanical properties of the cellular environment such as its rigidity, geometry, and external stresses play an important role in determining the cellular function and fate. Mechanical properties have been shown to influence cell shape and orientation, regulate cell proliferation and differentiation, and even govern the development and organization of tissues. In recent years, many theoretical and experimental investigations have been carried out to elucidate the mechanisms and consequences of the mechanosensitivity of cells. In this review, we discuss recent theoretical concepts and approaches that explain and predict cell mechanosensitivity. We focus on the interplay of active and passive processes that govern cell-cell and cell-matrix interactions and discuss the role of this interplay in the processes of cell adhesion, regulation of cytoskeleton mechanics and the response of cells to applied mechanical stresses.
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Affiliation(s)
- Rumi De
- Indian institute of Science Education and Research, Kolkata, Mohanpur 741252, Nadia, West Bengal, India
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Cai N, Wong CC, Tan SCW, Chan V, Liao K. Temporal effect of functional blocking of beta1 integrin on cell adhesion strength under serum depletion. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:10939-10947. [PMID: 19735145 DOI: 10.1021/la901527x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Cell adhesion is generally concomitant to the formation of focal adhesion. Although it is well-known that focal adhesion plays an important role in the functional regulations of anchorage dependent cells, previous experimental studies have not provided quantitative description of the relation between focal adhesion and biophysical responses of cells. Furthermore, there is lack of knowledge on the importance of the beta1 integrin subunit to the dynamic responses of cells during initial cell seeding. In this study, we attempt to bridge the quantitative connection between focal adhesion density and cell-substrate interactions and evaluate the influence on functional blocking of beta1 integrin on adhesion strength. Total internal reflection fluorescence microscopy (TIRFM), fluorescence microscopy, and phase contrast microscopy was employed to study the time-dependent evolvement of vinculin pattern, distribution of actin filament, and morphological change, respectively, during 4 h of culture for porcine esophageal fibroblasts (non-blocked and beta1-blocked) on a fibronectin-coated surface. Micropipet aspiration technique was used to study the change of mechanotransduction through the determination of adhesion force and strength. It is shown in our experimental results that spread area, adhesion force, and adhesion strength increases over time on the two types of cells. Throughout the culture period, the two key mechanotransduction parameters of non-blocked cells is higher than those of beta1-blocked cells. Interestingly, adhesion strength initially ascends, then begins to diminish at a critical time point, and finally resumes increasing linearly against the increase of focal adhesion density. This variation as mentioned above can be explained by peeling and fracture models based on the dissimilar vinculin pattern of cells after being cultured for different time periods. Moreover, the averaged focal adhesion strength and non-focal adhesion strength of beta1-blocked cells are significantly less than those of non-blocked of cells. The weaker adhesion strength on beta(1)-blocked cells is directly caused by lower focal and non-focal adhesion strength, as well as by smaller focal adhesion density.
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Affiliation(s)
- Ning Cai
- School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 639798
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25
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Shimizu K, Fujita H, Nagamori E. Micropatterning of single myotubes on a thermoresponsive culture surface using elastic stencil membranes for single-cell analysis. J Biosci Bioeng 2009; 109:174-8. [PMID: 20129103 DOI: 10.1016/j.jbiosc.2009.07.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 07/16/2009] [Accepted: 07/28/2009] [Indexed: 12/24/2022]
Abstract
We have developed a micropatterning procedure for single myotubes and demonstrated recovery of patterned myotubes without the use of methods that might cause damage to the cells. Since skeletal muscle is a highly ordered tissue mainly composed of myotubes, analysis of single myotubes is one of the promising approaches for studying the various diseases related to skeletal muscle tissues. However, the analysis of single myotubes is quite complicated because of the difficulty in distinguishing individual myotubes differentiated on a normal cell culture surface. In the present study, thin polydimethylsiloxane (PDMS) membranes, which have rectangular holes (30, 50, 100, and 200 microm in width; 500, 750, and 1000 microm in length) through them, were fabricated by using a photolithography technique and used for single myotube micropatterning. A bovine serum albumin-coated (BSA-coated) stencil membrane was placed on a cell culture surface and C2C12 myoblasts were seeded on it. Since the cells could not attach to the surface of the stencil membrane, the cell proliferated and differentiated into myotubes in the hole areas specifically. By peeling off the membrane, a micropattern of myotubes was obtained. It was revealed that the optimum width of rectangular holes for a micropattern of single myotubes was between 30 to 50 microm. Furthermore, by placing a membrane on a thermoresponsive culture surface, recovery of the micropatterned myotubes was possible by lowering the temperature. This method involving the stencil membranes and a thermoresponsive culture surface is useful for analyzing subcellular or single myotubes.
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Affiliation(s)
- Kazunori Shimizu
- Toyota Central R&D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi, Japan
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26
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Fu G, Milburn C, Mwenifumbo S, Cao Y, Oparinde G, Adeoye M, Therialt C, Beye A, Soboyejo W. Shear assay measurements of cell adhesion on biomaterials surfaces. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2009. [DOI: 10.1016/j.msec.2008.10.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Engler AJ, Chan M, Boettiger D, Schwarzbauer JE. A novel mode of cell detachment from fibrillar fibronectin matrix under shear. J Cell Sci 2009; 122:1647-53. [PMID: 19401337 DOI: 10.1242/jcs.040824] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells within tissues are surrounded by fibrillar extracellular matrix (ECM) that supports cell adhesion via integrin receptors. The strength of cell interactions with fibrillar matrix and the effects of force on these interactions have not been quantified. To this end, we used a spinning disc device to apply radially increasing shear to human HT1080 fibrosarcoma cells attached to a cell-derived fibrillar fibronectin (FN) matrix. The shear required to detach 50% of HT1080 cells was eight times greater on a FN-coated, rigid glass substrate than on fibrillar FN matrix. Covalent crosslinking of the FN matrix increased its stiffness tenfold and produced a modest increase in shear detachment force for these cells. On FN-coated surfaces, cells detach by releasing interactions between alpha5beta1 integrin and FN. By contrast, cell detachment from fibrillar matrix occurred through a novel mechanism of fibril breakage, which left holes in the matrix visible by fluorescence microscopy. These results show that cells require less force to detach from fibrillar matrix than from FN adsorbed on glass and that detachment occurs through breaking fibrils instead of by release of integrin-matrix bonds. Thus, ECM fibril breakage is another molecular feature to consider when understanding cell and tissue homeostasis.
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Affiliation(s)
- Adam J Engler
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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28
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Li B, Lin M, Tang Y, Wang B, Wang JHC. A novel functional assessment of the differentiation of micropatterned muscle cells. J Biomech 2008; 41:3349-53. [PMID: 19007933 DOI: 10.1016/j.jbiomech.2008.09.025] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2008] [Revised: 09/25/2008] [Accepted: 09/26/2008] [Indexed: 11/20/2022]
Abstract
Duchenne muscular dystrophy (DMD) is a lethal disease characterized by rapid, progressive atrophy of muscle tissues. Timely screening of therapeutic interventions is necessary for the development of effective treatment approaches for DMD. We have developed an in vitro model using a combination of micropatterning of C2C12 skeletal muscle cells and cell traction force microscopy (CTFM). In this model, C2C12 cells were micropatterned on a highly elongated adhesive island such that the cells assumed a shape typical of a myotube. During differentiation, these cells gradually fused together and began expressing dystrophin, a structural protein of myotubes, meanwhile, their contractile forces, represented by cell traction forces, continually increased until the myotubes reached maturation. In addition, the high-degree alignment of cells favored myotube differentiation and dystrophin expression. Since the fundamental structural unit of muscle tissue is myofiber, which is responsible for muscle contraction, such a technology that can directly quantify the contractile forces of the myotube, a precursor of myofiber, may constitute a fast and efficient screening approach for DMD therapies.
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Affiliation(s)
- Bin Li
- MechanoBiology Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 210 Lothrop Street, BST, E1640, Pittsburgh, PA 15213, USA
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29
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Srividya N, Muralidharan S. Determination of the Line Tension of Giant Vesicles from Pore-Closing Dynamics. J Phys Chem B 2008; 112:7147-52. [DOI: 10.1021/jp7119203] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Narayanan Srividya
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164
| | - Subra Muralidharan
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164
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30
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Kasza KE, Rowat AC, Liu J, Angelini TE, Brangwynne CP, Koenderink GH, Weitz DA. The cell as a material. Curr Opin Cell Biol 2007; 19:101-7. [PMID: 17174543 DOI: 10.1016/j.ceb.2006.12.002] [Citation(s) in RCA: 263] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Accepted: 12/07/2006] [Indexed: 01/16/2023]
Abstract
To elucidate the dynamic and functional role of a cell within the tissue it belongs to, it is essential to understand its material properties. The cell is a viscoelastic material with highly unusual properties. Measurements of the mechanical behavior of cells are beginning to probe the contribution of constituent components to cell mechanics. Reconstituted cytoskeletal protein networks have been shown to mimic many aspects of the mechanical properties of cells, providing new insight into the origin of cellular behavior. These networks are highly nonlinear, with an elastic modulus that depends sensitively on applied stress. Theories can account for some of the measured properties, but a complete model remains elusive.
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Affiliation(s)
- Karen E Kasza
- Department of Physics & DEAS, Harvard University, Cambridge, MA 02138, USA
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31
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Abstract
Integrin-mediated adhesion is based on the binding of integrins to immobilized ligands either in the extracellular matrix or on the surface of adjacent cells. The strength of adhesion is determined primarily by the number of adhesive bonds that form. Integrins have also been described as signaling receptors. Like adhesion, signals from integrins receptors can depend on the number of integrins that are bound to substrate attached ligands. The common methods for measuring cell adhesion are only capable of measuring initial interactions because the multivalent nature of adhesive bonds when the cell is considered as a unit, these assays reach plateau levels. To measure adhesive integrin-ligand bonds, a spinning disc device is described in which the mean cell detachment force is proportional to the number of adhesive bonds. Particularly as the field has moved from identification of integrins and their ligands into the analysis of adhesion and its relationship to cell signaling, it is important to shift to assays that relate the extracellular binding to the intracellular signals. Specific plans, methods, and analytic strategies are provided to apply this technology to current problems in integrin biology. At present, this is the only published approach that will provide good measures of the number of adhesive bonds that can be generally applied.
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Affiliation(s)
- David Boettiger
- Department of Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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32
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Milan JL, Wendling-Mansuy S, Jean M, Chabrand P. Divided medium-based model for analyzing the dynamic reorganization of the cytoskeleton during cell deformation. Biomech Model Mechanobiol 2006; 6:373-90. [PMID: 17063370 DOI: 10.1007/s10237-006-0057-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Accepted: 09/07/2006] [Indexed: 10/24/2022]
Abstract
Cell deformability and mechanical responses of living cells depend closely on the dynamic changes in the structural architecture of the cytoskeleton (CSK). To describe the dynamic reorganization and the heterogeneity of the prestressed multi-modular CSK, we developed a two-dimensional model for the CSK which was taken to be a system of tension and compression interactions between the nodes in a divided medium. The model gives the dynamic reorganization of the CSK consisting of fast changes in connectivity between nodes during medium deformation and the resulting mechanical behavior is consistent with the strain-hardening and prestress-induced stiffening observed in cells in vitro. In addition, the interaction force networks which occur and balance to each other in the model can serve to identify the main CSK substructures: cortex, stress fibers, intermediate filaments, microfilaments, microtubules and focal adhesions. Removing any of these substructures results in a loss of integrity in the model and a decrease in the prestress and stiffness, and suggests that the CSK substructures are highly interdependent. The present model may therefore provide a useful tool for understanding the cellular processes involving CSK reorganization, such as mechanotransduction, migration and adhesion processes.
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Affiliation(s)
- J L Milan
- CNRS-USR 2164 Laboratoire d'Aérodynamique et de Biomécanique du Mouvement, Parc Scientifique et Technologique de Luminy, 13288, Marseille Cedex 9, France
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33
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Féréol S, Fodil R, Labat B, Galiacy S, Laurent VM, Louis B, Isabey D, Planus E. Sensitivity of alveolar macrophages to substrate mechanical and adhesive properties. ACTA ACUST UNITED AC 2006; 63:321-40. [PMID: 16634082 DOI: 10.1002/cm.20130] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In order to understand the sensitivity of alveolar macrophages (AMs) to substrate properties, we have developed a new model of macrophages cultured on substrates of increasing Young's modulus: (i) a monolayer of alveolar epithelial cells representing the supple (approximately 0.1 kPa) physiological substrate, (ii) polyacrylamide gels with two concentrations of bis-acrylamide representing low and high intermediate stiffness (respectively 40 kPa and 160 kPa) and, (iii) a highly rigid surface of plastic or glass (respectively 3 MPa and 70 MPa), the two latter being or not functionalized with type I-collagen. The macrophage response was studied through their shape (characterized by 3D-reconstructions of F-actin structure) and their cytoskeletal stiffness (estimated by transient twisting of magnetic RGD-coated beads and corrected for actual bead immersion). Macrophage shape dramatically changed from rounded to flattened as substrate stiffness increased from soft ((i) and (ii)) to rigid (iii) substrates, indicating a net sensitivity of alveolar macrophages to substrate stiffness but without generating F-actin stress fibers. Macrophage stiffness was also increased by large substrate stiffness increase but this increase was not due to an increase in internal tension assessed by the negligible effect of a F-actin depolymerizing drug (cytochalasine D) on bead twisting. The mechanical sensitivity of AMs could be partly explained by an idealized numerical model describing how low cell height enhances the substrate-stiffness-dependence of the apparent (measured) AM stiffness. Altogether, these results suggest that macrophages are able to probe their physical environment but the mechanosensitive mechanism behind appears quite different from tissue cells, since it occurs at no significant cell-scale prestress, shape changes through minimal actin remodeling and finally an AMs stiffness not affected by the loss in F-actin integrity.
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Affiliation(s)
- Sophie Féréol
- Inserm UMR 651, Fonctions Cellulaires et Moléculaires de l'Appareil Respiratoire et des Vaisseaux, Equipe Biomécanique Cellulaire et Respiratoire et Université Paris XII, Faculté de Médecine, Institut Supérieur des Biosciences de Paris, Créteil, France
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Abstract
Gas exchange, the primary function of the lung, can come about only with the application of physical forces on the macroscale and their transmission to the scale of small airway, small blood vessel, and alveolus, where they serve to distend and stabilize structures that would otherwise collapse. The pathway for force transmission then continues down to the level of cell, nucleus, and molecule; moreover, to lesser or greater degrees most cell types that are resident in the lung have the ability to generate contractile forces. At these smallest scales, physical forces serve to distend the cytoskeleton, drive cytoskeletal remodeling, expose cryptic binding domains, and ultimately modulate reaction rates and gene expression. Importantly, evidence has now accumulated suggesting that multiscale phenomena span these scales and govern integrative lung behavior.
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Affiliation(s)
- Jeffrey J Fredberg
- Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
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35
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Tsang PH, Li G, Brun YV, Freund LB, Tang JX. Adhesion of single bacterial cells in the micronewton range. Proc Natl Acad Sci U S A 2006; 103:5764-8. [PMID: 16585522 PMCID: PMC1458647 DOI: 10.1073/pnas.0601705103] [Citation(s) in RCA: 181] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The adhesion of bacteria to surfaces plays critical roles in the environment, disease, and industry. In aquatic environments, Caulobacter crescentus is one of the first colonizers of submerged surfaces. Using a micromanipulation technique, we measured the adhesion force of single C. crescentus cells attached to borosilicate substrates through their adhesive holdfast. The detachment forces measured for 14 cells ranged over 0.11 to 2.26 microN, averaging 0.59 +/- 0.62 microN. Based on the calculation of stress distribution with the finite element analysis method (dividing an object into small grids and calculating relevant parameters for all of the elements), the adhesion strength between the holdfast and the substrate is >68 N/mm(2) in the central region of contact. To our knowledge, this strength of adhesion is the strongest ever measured for biological adhesives.
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Affiliation(s)
| | | | - Yves V. Brun
- Department of Biology, Indiana University, Bloomington, IN 47405
| | - L. Ben Freund
- Division of Engineering, Brown University, Providence, RI 02912; and
- To whom correspondence should be addressed. E-mail:
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Tourovskaia A, Figueroa-Masot X, Folch A. Long-term microfluidic cultures of myotube microarrays for high-throughput focal stimulation. Nat Protoc 2006; 1:1092-104. [PMID: 17406389 PMCID: PMC4393750 DOI: 10.1038/nprot.2006.123] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have developed a microfluidic cell culture method that allows for the formation of linear isolated myotubes organized in a parallel microarray. Attachment and spreading of cells are confined within microtracks of cell-adherent proteins separated by a protein-repellent coating. Signaling molecules or other molecules of interest can be focally delivered to the myotubes using heterogeneous microfluidic streams. We have used the method to focally deliver agrin (a molecule implicated as a postsynaptic organizer), which leads to localized acetylcholine receptor clustering. These techniques can be modified to accommodate other cell types and can be adapted to virtually any bioactive molecule such as signaling factors or drugs. This protocol features two major techniques that can be utilized simultaneously or independently to (i) micropattern cells using surface chemical modification and (ii) use a microfluidic platform for culturing and focal stimulation of cells with molecules of interest. Device design, fabrication and assembly can be completed in 3 days.
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Affiliation(s)
- Anna Tourovskaia
- Department of Bioengineering, University of Washington, Box 355061, Seattle, Washington 98195-2255, USA
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Griffin MA, Feng H, Tewari M, Acosta P, Kawana M, Sweeney HL, Discher DE. gamma-Sarcoglycan deficiency increases cell contractility, apoptosis and MAPK pathway activation but does not affect adhesion. J Cell Sci 2005; 118:1405-16. [PMID: 15769854 DOI: 10.1242/jcs.01717] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The functions of gamma-sarcoglycan (gammaSG) in normal myotubes are largely unknown, however gammaSG is known to assemble into a key membrane complex with dystroglycan and its deficiency is one known cause of limb-girdle muscular dystrophy. Previous findings of apoptosis from gammaSG-deficient mice are extended here to cell culture where apoptosis is seen to increase more than tenfold in gammaSG-deficient myotubes compared with normal cells. The deficient myotubes also exhibit an increased contractile prestress that results in greater shortening and widening when the cells are either lightly detached or self-detached. However, micropipette-forced peeling of single myotubes revealed no significant difference in cell adhesion. Consistent with a more contractile phenotype, acto-myosin striations were more prominent in gammaSG-deficient myotubes than in normal cells. An initial phosphoscreen of more than 12 signaling proteins revealed a number of differences between normal and gammaSG(-/-) muscle, both before and after stretching. MAPK-pathway proteins displayed the largest changes in activation, although significant phosphorylation also appeared for other proteins linked to hypertension. We conclude that gammaSG normally moderates contractile prestress in skeletal muscle, and we propose a role for gammaSG in membrane-based signaling of the effects of prestress and sarcomerogenesis.
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Affiliation(s)
- Maureen A Griffin
- Pennsylvania Muscle Institute, University of Pennsylvania Medical Center, D-700 Richards Building, 3700 Hamilton Walk, Philadelphia, PA 19104-6083, USA
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Griffin MA, Sen S, Sweeney HL, Discher DE. Adhesion-contractile balance in myocyte differentiation. J Cell Sci 2004; 117:5855-63. [PMID: 15522893 DOI: 10.1242/jcs.01496] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tissue cells generally pull on their matrix attachments and balance a quasi-static contractility against adequate adhesion, but any correlation with and/or influence on phenotype are not yet understood. Here, we begin to demonstrate how differentiation state couples to actomyosin-based contractility through adhesion and substrate compliance. Myotubes are differentiated from myoblasts on collagen-patterned coverslips that allow linear fusion but prevent classic myotube branching. Post-fusion, myotubes adhere to the micro-strips but lock into a stress fiber-rich state and do not differentiate significantly further. In contrast, myotubes grown on top of such cells do progress through differentiation, exhibiting actomyosin striations within one week. A compliant adhesion to these lower cells is suggested to couple to contractility and accommodate the reorganization needed for upper cell striation. Contractility is assessed in these adherent cells by mechanically detaching one end of the myotubes. All myotubes, whether striated or not, shorten with an exponential decay. The cell-on-cell myotubes relax more, which implies a greater contractile stress. The non-muscle myosin II inhibitor blebbistatin inhibits relaxation for either case. Myotubes in culture are thus clearly prestressed by myosin II, and this contractility couples to substrate compliance and ultimately influences actomyosin striation.
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Affiliation(s)
- Maureen A Griffin
- Biophysical Engineering Laboratory, 112 Towne Building, and Pennsylvania Muscle Institute, University of Pennsylvania, D-700 Richards Building, 3700 Hamilton Walk, Philadelphia, PA 19104, USA
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Byfield FJ, Aranda-Espinoza H, Romanenko VG, Rothblat GH, Levitan I. Cholesterol depletion increases membrane stiffness of aortic endothelial cells. Biophys J 2004; 87:3336-43. [PMID: 15347591 PMCID: PMC1304801 DOI: 10.1529/biophysj.104.040634] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2004] [Accepted: 08/23/2004] [Indexed: 11/18/2022] Open
Abstract
This study has investigated the effect of cellular cholesterol on membrane deformability of bovine aortic endothelial cells. Cellular cholesterol content was depleted by exposing the cells to methyl-beta-cyclodextrin or enriched by exposing the cells to methyl-beta-cyclodextrin saturated with cholesterol. Control cells were treated with methyl-beta-cyclodextrin-cholesterol at a molar ratio that had no effect on the level of cellular cholesterol. Mechanical properties of the cells with different cholesterol contents were compared by measuring the degree of membrane deformation in response to a step in negative pressure applied to the membrane by a micropipette. The experiments were performed on substrate-attached cells that maintained normal morphology. The data were analyzed using a standard linear elastic half-space model to calculate Young elastic modulus. Our observations show that, in contrast to the known effect of cholesterol on membrane stiffness of lipid bilayers, cholesterol depletion of bovine aortic endothelial cells resulted in a significant decrease in membrane deformability and a corresponding increase in the value of the elastic coefficient of the membrane, indicating that cholesterol-depleted cells are stiffer than control cells. Repleting the cells with cholesterol reversed the effect. An increase in cellular cholesterol to a level higher than that of normal cells, however, had no effect on the elastic properties of bovine aortic endothelial cells. We also show that although cholesterol depletion had no apparent effect on the intensity of F-actin-specific fluorescence, disrupting F-actin with latrunculin A abrogated the stiffening effect. We suggest that cholesterol depletion increases the stiffness of the membrane by altering the properties of the submembrane F-actin and/or its attachment to the membrane.
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Affiliation(s)
- Fitzroy J Byfield
- Institute for Medicine and Engineering, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Engler AJ, Griffin MA, Sen S, Bönnemann CG, Sweeney HL, Discher DE. Myotubes differentiate optimally on substrates with tissue-like stiffness: pathological implications for soft or stiff microenvironments. ACTA ACUST UNITED AC 2004; 166:877-87. [PMID: 15364962 PMCID: PMC2172122 DOI: 10.1083/jcb.200405004] [Citation(s) in RCA: 1172] [Impact Index Per Article: 58.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Contractile myocytes provide a test of the hypothesis that cells sense their mechanical as well as molecular microenvironment, altering expression, organization, and/or morphology accordingly. Here, myoblasts were cultured on collagen strips attached to glass or polymer gels of varied elasticity. Subsequent fusion into myotubes occurs independent of substrate flexibility. However, myosin/actin striations emerge later only on gels with stiffness typical of normal muscle (passive Young's modulus, E approximately 12 kPa). On glass and much softer or stiffer gels, including gels emulating stiff dystrophic muscle, cells do not striate. In addition, myotubes grown on top of a compliant bottom layer of glass-attached myotubes (but not softer fibroblasts) will striate, whereas the bottom cells will only assemble stress fibers and vinculin-rich adhesions. Unlike sarcomere formation, adhesion strength increases monotonically versus substrate stiffness with strongest adhesion on glass. These findings have major implications for in vivo introduction of stem cells into diseased or damaged striated muscle of altered mechanical composition.
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Affiliation(s)
- Adam J Engler
- School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
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