101
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Bashirzadeh Y, Dumbali S, Qian S, Maruthamuthu V. Mechanical response of an epithelial island subject to uniaxial stretch on a hybrid silicone substrate. Cell Mol Bioeng 2019; 12:33-40. [PMID: 31105800 DOI: 10.1007/s12195-018-00560-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Introduction The mechanical response of large multi-cellular collectives to external stretch has remained largely unexplored, despite its relevance to normal function and to external challenges faced by some tissues. Here, we introduced a simple hybrid silicone substrate to enable external stretch while providing a physiologically relevant physical micro-environment for cells. Methods We micropatterned epithelial islands on the substrate using a stencil to allow for a circular island shape without restraining island edges. We then used traction force microscopy to determine the strain energy and the inter-cellular sheet tension within the island as a function of time after stretch. Results While the strain energy stored in the substrate for unstretched cell islands stayed constant over time, a uniaxial 10% stretch resulted in an abrupt increase, followed by sustained increase in the strain energy of the islands over tens of minutes, indicating slower dynamics than for single cells reported previously. The sheet tension at the island mid-line perpendicular to the stretch direction also more than doubled compared to unstretched islands. Interestingly, the sheet tension at the island mid-line parallel to the stretch direction also reached similar levels over tens of minutes indicating the tendency of the island to homogenize its internal stress. Conclusions We found that the sheet tension within large epithelial islands depends on its direction relative to that of the stretch initially, but not at longer times. We suggest that the hybrid silicone substrate provides for an accessible substrate for studying the mechanobiology of large epithelial cell islands.
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Affiliation(s)
- Yashar Bashirzadeh
- Mechanical & Aerospace Engineering, Old Dominion University, 4635 Hampton Blvd, 238e Kaufman, Norfolk, VA 23529 USA
| | - Sandeep Dumbali
- Mechanical & Aerospace Engineering, Old Dominion University, 4635 Hampton Blvd, 238e Kaufman, Norfolk, VA 23529 USA
| | - Shizhi Qian
- Mechanical & Aerospace Engineering, Old Dominion University, 4635 Hampton Blvd, 238e Kaufman, Norfolk, VA 23529 USA
| | - Venkat Maruthamuthu
- Mechanical & Aerospace Engineering, Old Dominion University, 4635 Hampton Blvd, 238e Kaufman, Norfolk, VA 23529 USA
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102
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Sasaki H, Hokugo A, Wang L, Morinaga K, Ngo JT, Okawa H, Nishimura I. Neuronal PAS Domain 2 (Npas2)-Deficient Fibroblasts Accelerate Skin Wound Healing and Dermal Collagen Reconstruction. Anat Rec (Hoboken) 2019; 303:1630-1641. [PMID: 30851151 DOI: 10.1002/ar.24109] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 12/11/2018] [Accepted: 12/17/2018] [Indexed: 01/17/2023]
Abstract
The circadian clock, which consists of endogenous self-sustained and cell-autonomous oscillations in mammalian cells, is known to regulate a wide range of peripheral tissues. The unique upregulation of a clock gene, neuronal PAS domain protein 2 (Npas2), observed along with fibroblast aging prompted us to investigate the role of Npas2 in the homeostasis of dermal structure using in vivo and in vitro wound healing models. Time-course healing of a full-thickness skin punched wound exhibited significantly faster wound closure in Npas2-/- mice than wild-type (WT) C57Bl/6J mice. Dorsal skin fibroblasts isolated from WT, Npas2+/-, and Npas2-/- mice exhibited consistent profiles of core clock gene expression except for Npas2 and Per2. In vitro behavioral characterizations of dermal fibroblasts revealed that Npas2-/- mutation was associated with increased proliferation, migration, and cell contraction measured by floating collagen gel contraction and single-cell force contraction assays. Npas2 knockout fibroblasts carrying sustained the high expression level of type XII and XIV FAICT collagens and synthesized dermis-like thick collagen fibers in vitro. Confocal laser scanning microscopy demonstrated the reconstruction of dermis-like collagen architecture in the wound healing area of Npas2-/- mice. This study indicates that the induced Npas2 expression in fibroblasts may interfere with skin homeostasis, wound healing, and dermal tissue reconstruction, providing a basis for novel therapeutic target and strategy. Anat Rec, 2019. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Hodaka Sasaki
- Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, California.,Department of Oral and Maxillofacial Implantology, Tokyo Dental College, Tokyo, Japan
| | - Akishige Hokugo
- Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, California.,Regenerative Bioengineering and Repair Laboratory, Division of Plastic and Reconstructive Surgery, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Lixin Wang
- Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, California.,Regenerative Bioengineering and Repair Laboratory, Division of Plastic and Reconstructive Surgery, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Kenzo Morinaga
- Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, California.,Department of Oral Rehabilitation, Section of Oral Implantology, Fukuoka Dental College, Fukuoka, Japan
| | - John T Ngo
- Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, California
| | - Hiroko Okawa
- Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, California.,Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry, Sendai, Japan
| | - Ichiro Nishimura
- Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, California
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103
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Pageon SV, Govendir MA, Kempe D, Biro M. Mechanoimmunology: molecular-scale forces govern immune cell functions. Mol Biol Cell 2019; 29:1919-1926. [PMID: 30088799 PMCID: PMC6232972 DOI: 10.1091/mbc.e18-02-0120] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Immune cell recognition of antigens is a pivotal process in initiating immune responses against injury, pathogens, and cancers. Breakthroughs over the past decade support a major role for mechanical forces in immune responses, laying the foundation for the emerging field of mechanoimmunology. In this Perspective, we discuss the mechanical forces acting at the level of ligand–receptor interactions and how they underpin receptor triggering, signal initiation, and immune cell activation. We also highlight the novel biophysical tools and advanced imaging techniques that have afforded us the recent progress in our understanding of the role of forces in immune cell functions.
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Affiliation(s)
- Sophie V Pageon
- EMBL Australia, Single Molecule Science Node, School of Medical Sciences, and
| | - Matt A Govendir
- EMBL Australia, Single Molecule Science Node, School of Medical Sciences, and
| | - Daryan Kempe
- EMBL Australia, Single Molecule Science Node, School of Medical Sciences, and
| | - Maté Biro
- EMBL Australia, Single Molecule Science Node, School of Medical Sciences, and.,ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney, NSW 2052, Australia
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104
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Sridharan Weaver S, Li Y, Foucard L, Majeed H, Bhaduri B, Levine AJ, Kilian KA, Popescu G. Simultaneous cell traction and growth measurements using light. JOURNAL OF BIOPHOTONICS 2019; 12:e201800182. [PMID: 30105846 PMCID: PMC7236521 DOI: 10.1002/jbio.201800182] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 07/27/2018] [Indexed: 05/12/2023]
Abstract
Characterizing the effects of force fields generated by cells on proliferation, migration and differentiation processes is challenging due to limited availability of nondestructive imaging modalities. Here, we integrate a new real-time traction stress imaging modality, Hilbert phase dynamometry (HPD), with spatial light interference microscopy (SLIM) for simultaneous monitoring of cell growth during differentiation processes. HPD uses holographic principles to extract displacement fields from chemically patterned fluorescent grid on deformable substrates. This is converted into forces by solving an elasticity inverse problem. Since HPD uses the epi-fluorescence channel of an inverted microscope, cellular behavior can be concurrently studied in transmission with SLIM. We studied the differentiation of mesenchymal stem cells (MSCs) and found that cells undergoing osteogenesis and adipogenesis exerted larger and more dynamic stresses than their precursors, with MSCs developing the smallest forces and growth rates. Thus, we develop a powerful means to study mechanotransduction during dynamic processes where the matrix provides context to guide cells toward a physiological or pathological outcome.
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Affiliation(s)
- Shamira Sridharan Weaver
- Quantitative Light Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Yanfen Li
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
- Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Louis Foucard
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California
| | - Hassaan Majeed
- Quantitative Light Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Basanta Bhaduri
- Quantitative Light Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Alex J Levine
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California
- Department of Physics & Astronomy, University of California, Los Angeles, California
- Department of Biomathematics, University of California, Los Angeles, California
| | - Kristopher A Kilian
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
- Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Gabriel Popescu
- Quantitative Light Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
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105
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Berman JD, Randeria M, Style RW, Xu Q, Nichols JR, Duncan AJ, Loewenberg M, Dufresne ER, Jensen KE. Singular dynamics in the failure of soft adhesive contacts. SOFT MATTER 2019; 15:1327-1334. [PMID: 30540331 DOI: 10.1039/c8sm02075b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We characterize the mechanical recovery of compliant silicone gels following adhesive contact failure. We establish broad, stable adhesive contacts between rigid microspheres and soft gels, then stretch the gels to large deformations by pulling quasi-statically on the contact. Eventually, the adhesive contact begins to fail, and ultimately slides to a final contact point on the bottom of the sphere. Immediately after detachment, the gel recoils quickly with a self-similar surface profile that evolves as a power law in time, suggesting that the adhesive detachment point is singular. The singular dynamics we observe are consistent with a relaxation process driven by surface stress and slowed by viscous flow through the porous, elastic network of the gel. Our results emphasize the importance of accounting for both the liquid and solid phases of gels in understanding their mechanics, especially under extreme deformation.
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Affiliation(s)
- Justin D Berman
- Department of Physics, Williams College, Williamstown, MA, USA.
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106
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Huang Y, Schell C, Huber TB, Şimşek AN, Hersch N, Merkel R, Gompper G, Sabass B. Traction force microscopy with optimized regularization and automated Bayesian parameter selection for comparing cells. Sci Rep 2019; 9:539. [PMID: 30679578 PMCID: PMC6345967 DOI: 10.1038/s41598-018-36896-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/27/2018] [Indexed: 12/12/2022] Open
Abstract
Adherent cells exert traction forces on to their environment which allows them to migrate, to maintain tissue integrity, and to form complex multicellular structures during developmental morphogenesis. Traction force microscopy (TFM) enables the measurement of traction forces on an elastic substrate and thereby provides quantitative information on cellular mechanics in a perturbation-free fashion. In TFM, traction is usually calculated via the solution of a linear system, which is complicated by undersampled input data, acquisition noise, and large condition numbers for some methods. Therefore, standard TFM algorithms either employ data filtering or regularization. However, these approaches require a manual selection of filter- or regularization parameters and consequently exhibit a substantial degree of subjectiveness. This shortcoming is particularly serious when cells in different conditions are to be compared because optimal noise suppression needs to be adapted for every situation, which invariably results in systematic errors. Here, we systematically test the performance of new methods from computer vision and Bayesian inference for solving the inverse problem in TFM. We compare two classical schemes, L1- and L2-regularization, with three previously untested schemes, namely Elastic Net regularization, Proximal Gradient Lasso, and Proximal Gradient Elastic Net. Overall, we find that Elastic Net regularization, which combines L1 and L2 regularization, outperforms all other methods with regard to accuracy of traction reconstruction. Next, we develop two methods, Bayesian L2 regularization and Advanced Bayesian L2 regularization, for automatic, optimal L2 regularization. Using artificial data and experimental data, we show that these methods enable robust reconstruction of traction without requiring a difficult selection of regularization parameters specifically for each data set. Thus, Bayesian methods can mitigate the considerable uncertainty inherent in comparing cellular tractions in different conditions.
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Affiliation(s)
- Yunfei Huang
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems-2 and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Christoph Schell
- Institut für Klinische Pathologie, Universitätsklinikum Freiburg, D-79002, Freiburg, Germany.,Berta-Ottenstein Programme, Faculty of Medicine, University of Freiburg, Freiburg, D-79106, Germany
| | - Tobias B Huber
- Department of Medicine IV, Faculty of Medicine, Medical Center - University of Freiburg, Freiburg, Germany.,BIOSS Center for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, Freiburg, Germany.,III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Ahmet Nihat Şimşek
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems-2 and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Nils Hersch
- Biomechanics, Institute of Complex Systems-7, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Rudolf Merkel
- Biomechanics, Institute of Complex Systems-7, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems-2 and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Benedikt Sabass
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems-2 and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425, Juelich, Germany.
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107
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Banerjee S, Marchetti MC. Continuum Models of Collective Cell Migration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1146:45-66. [PMID: 31612453 DOI: 10.1007/978-3-030-17593-1_4] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Collective cell migration plays a central role in tissue development, morphogenesis, wound repair and cancer progression. With the growing realization that physical forces mediate cell motility in development and physiology, a key biological question is how cells integrate molecular activities for force generation on multicellular scales. In this review we discuss recent advances in modeling collective cell migration using quantitative tools and approaches rooted in soft matter physics. We focus on theoretical models of cell aggregates as continuous active media, where the feedback between mechanical forces and regulatory biochemistry gives rise to rich collective dynamical behavior. This class of models provides a powerful predictive framework for the physiological dynamics that underlies many developmental processes, where cells need to collectively migrate like a viscous fluid to reach a target region, and then stiffen to support mechanical stresses and maintain tissue cohesion.
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108
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Rosowski KA, Boltyanskiy R, Xiang Y, Van den Dries K, Schwartz MA, Dufresne ER. Vinculin and the mechanical response of adherent fibroblasts to matrix deformation. Sci Rep 2018; 8:17967. [PMID: 30568231 PMCID: PMC6299284 DOI: 10.1038/s41598-018-36272-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 11/14/2018] [Indexed: 12/21/2022] Open
Abstract
Cells respond to the mechanics of their environment. Mechanical cues include extracellular matrix (ECM) stiffness and deformation, which are primarily sensed through integrin-mediated adhesions. We investigated the impact of ECM deformation on cellular forces, measuring the time-evolution of traction forces of isolated mouse fibroblasts in response to stretch and release. Stretch triggered a marked increase of traction stresses and apparent stiffness. Expression of the focal adhesion protein vinculin not only increased baseline traction forces, but also increased dissipation of mechanical energy, which was correlated with the cells’ failure to recover baseline traction forces after release of stretch.
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Affiliation(s)
- Kathryn A Rosowski
- Department of Materials, ETH Zürich, 8093, Zürich, Switzerland.,Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Rostislav Boltyanskiy
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Yingjie Xiang
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Koen Van den Dries
- Cardiovascular Research Center and Department of Medicine (Cardiology), Yale University School of Medicine, New Haven, CT, 06511, USA.,Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Martin A Schwartz
- Cardiovascular Research Center and Department of Medicine (Cardiology), Yale University School of Medicine, New Haven, CT, 06511, USA.,Departments of Cell Biology and Biomedical Engineering, Yale University, New Haven, CT, 06511, USA
| | - Eric R Dufresne
- Department of Materials, ETH Zürich, 8093, Zürich, Switzerland. .,Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA.
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109
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Nier V, Peyret G, d'Alessandro J, Ishihara S, Ladoux B, Marcq P. Kalman Inversion Stress Microscopy. Biophys J 2018; 115:1808-1816. [PMID: 30301513 DOI: 10.1016/j.bpj.2018.09.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 08/29/2018] [Accepted: 09/12/2018] [Indexed: 10/28/2022] Open
Abstract
Although mechanical cues are crucial to tissue morphogenesis and development, the tissue mechanical stress field remains poorly characterized. Given traction force time-lapse movies, as obtained by traction force microscopy of in vitro cellular sheets, we show that the tissue stress field can be estimated by Kalman filtering. After validation using numerical data, we apply Kalman inversion stress microscopy to experimental data. We combine the inferred stress field with velocity and cell-shape measurements to quantify the rheology of epithelial cell monolayers in physiological conditions, found to be close to that of an elastic and active material.
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Affiliation(s)
- Vincent Nier
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Sorbonne Université, CNRS, Paris, France
| | - Grégoire Peyret
- Institut Jacques Monod, CNRS, Université Paris Diderot, Paris, France
| | | | - Shuji Ishihara
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Benoit Ladoux
- Institut Jacques Monod, CNRS, Université Paris Diderot, Paris, France; Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Philippe Marcq
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Sorbonne Université, CNRS, Paris, France.
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110
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Latorre E, Kale S, Casares L, Gómez-González M, Uroz M, Valon L, Nair RV, Garreta E, Montserrat N, Del Campo A, Ladoux B, Arroyo M, Trepat X. Active superelasticity in three-dimensional epithelia of controlled shape. Nature 2018; 563:203-208. [PMID: 30401836 DOI: 10.1038/s41586-018-0671-4] [Citation(s) in RCA: 140] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 10/08/2018] [Indexed: 01/13/2023]
Abstract
Fundamental biological processes are carried out by curved epithelial sheets that enclose a pressurized lumen. How these sheets develop and withstand three-dimensional deformations has remained unclear. Here we combine measurements of epithelial tension and shape with theoretical modelling to show that epithelial sheets are active superelastic materials. We produce arrays of epithelial domes with controlled geometry. Quantification of luminal pressure and epithelial tension reveals a tensional plateau over several-fold areal strains. These extreme strains in the tissue are accommodated by highly heterogeneous strains at a cellular level, in seeming contradiction to the measured tensional uniformity. This phenomenon is reminiscent of superelasticity, a behaviour that is generally attributed to microscopic material instabilities in metal alloys. We show that in epithelial cells this instability is triggered by a stretch-induced dilution of the actin cortex, and is rescued by the intermediate filament network. Our study reveals a type of mechanical behaviour-which we term active superelasticity-that enables epithelial sheets to sustain extreme stretching under constant tension.
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Affiliation(s)
- Ernest Latorre
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain.,LaCàN, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona, Spain
| | - Sohan Kale
- LaCàN, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona, Spain
| | - Laura Casares
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain
| | - Manuel Gómez-González
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain
| | - Marina Uroz
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain
| | - Léo Valon
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain
| | - Roshna V Nair
- INM-Leibniz Institut für Neue Materialien, Saarbrücken, Germany
| | - Elena Garreta
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain
| | - Nuria Montserrat
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain.,Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Barcelona, Spain
| | - Aránzazu Del Campo
- INM-Leibniz Institut für Neue Materialien, Saarbrücken, Germany.,Chemistry Department, Saarland University, Saarbrücken, Germany
| | - Benoit Ladoux
- CNRS UMR 7592, Institut Jacques Monod (IJM), Université Paris Diderot, Paris, France.,Mechanobiology Institute (MBI), National University of Singapore, Singapore, Singapore
| | - Marino Arroyo
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain. .,LaCàN, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona, Spain.
| | - Xavier Trepat
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute for Science and Technology (BIST), Barcelona, Spain. .,Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Barcelona, Spain. .,Unitat de Biofísica i Bioenginyeria, Universitat de Barcelona, Barcelona, Spain. .,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
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111
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Lee RM, Losert W. Dynamics phenotyping across length and time scales in collective cell migration. Semin Cell Dev Biol 2018; 93:69-76. [PMID: 31429407 DOI: 10.1016/j.semcdb.2018.10.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 10/25/2018] [Accepted: 10/25/2018] [Indexed: 11/29/2022]
Abstract
Processes in collective migration span many length and time scales. In this review, we focus on length scales ranging from tens of microns (single cells) to a few millimeters (cell clusters) and the motion of these cells and cell groups on time scales of minutes to hours. We focus on epithelial cell sheets and metrics of motion developed to measure migration phenotypes in this system. Comparisons between cell motion and fluid flows, facilitated by the popular image analysis technique particle image velocimetry, yield metrics that can be used to study migration across a range of length and time scales. Measuring collective cell migration across these scales provides a complex, quantitative phenotype useful for migration models, in particular those that compare and contrast collective cell migration to movement of particles near a transition to jamming. Contrasting the motion of epithelial cells and the jamming transition illustrates aspects of collective motion that can be attributed to the jammed character of cell clusters, and highlights aspects of collective behavior that likely involve active motility and cell-cell guidance. The application of multiple migration metrics, which span multiple scales of the system, thus allows us to link cell-scale signals and mechanics to collective behavior.
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Affiliation(s)
- Rachel M Lee
- University of Maryland School of Medicine, Baltimore, MD, 21201, USA; Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
| | - Wolfgang Losert
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA; Department of Physics, University of Maryland, College Park, MD, 20742, USA.
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112
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Hanke J, Probst D, Zemel A, Schwarz US, Köster S. Dynamics of force generation by spreading platelets. SOFT MATTER 2018; 14:6571-6581. [PMID: 30052252 DOI: 10.1039/c8sm00895g] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In order to gain more insight into the role of human platelets for blood clot formation, here we investigate the dynamics of force generation by platelet spreading onto elastic substrates of variable stiffness. Despite their small size, platelets generate high and rapidly varying traction forces on their extracellular environment, which we reconstruct with adapted implementations of Fourier transform traction cytometry. We find that while the final spread area is reached within a few minutes, the build-up of forces typically takes 10-30 minutes. In addition, we identify two distinct behaviors of individual cells, namely oscillating and non-oscillating platelets. An eigenvalue analysis of the platelet dipole tensor reveals a small anisotropy of the exerted force, which is compatible with a random distribution of a few force transmitting centers, in agreement with the observed shapes and traction patterns. We find a correlation between the maximum force level a platelet reaches and its spread area, which we explain by a thin film model for the actively contracting cell. The model reveals a large internal stress of hundreds of kPa. Experimentally we do not find any statistically relevant relation between the force level reached and the substrate stiffness within the stiffness range from 19 to 83 kPa, which might be related to the high platelet activation level used in our study. In addition, our model suggests that due to the uniquely small thickness of platelets, their mechanosensitivity might be limited to a lower stiffness range.
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Affiliation(s)
- Jana Hanke
- Institute for X-Ray Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
| | - Dimitri Probst
- Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany. and BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - Assaf Zemel
- Institute of Dental Sciences and Fritz Haber Center for Molecular Dynamics, Hebrew University of Jerusalem, 91120, Israel
| | - Ulrich S Schwarz
- Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany. and BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - Sarah Köster
- Institute for X-Ray Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany. and German Center for Cardiovascular Research (DZHK), Partner Site Göttingen, Germany
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113
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Bashirzadeh Y, Chatterji S, Palmer D, Dumbali S, Qian S, Maruthamuthu V. Stiffness Measurement of Soft Silicone Substrates for Mechanobiology Studies Using a Widefield Fluorescence Microscope. J Vis Exp 2018. [PMID: 30035766 DOI: 10.3791/57797] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Soft tissues in the human body typically have stiffness in the kilopascal (kPa) range. Accordingly, silicone and hydrogel flexible substrates have been proven to be useful substrates for culturing cells in a physical microenvironment that partially mimics in vivo conditions. Here, we present a simple protocol for characterizing the Young's moduli of isotropic linear elastic substrates typically used for mechanobiology studies. The protocol consists of preparing a soft silicone substrate on a Petri dish or stiff silicone, coating the top surface of the silicone substrate with fluorescent beads, using a millimeter-scale sphere to indent the top surface (by gravity), imaging the fluorescent beads on the indented silicone surface using a fluorescence microscope, and analyzing the resultant images to calculate the Young's modulus of the silicone substrate. Coupling the substrate's top surface with a moduli extracellular matrix protein (in addition to the fluorescent beads) allows the silicone substrate to be readily used for cell plating and subsequent studies using traction force microscopy experiments. The use of stiff silicone, instead of a Petri dish, as the base of the soft silicone, enables the use of mechanobiology studies involving external stretch. A specific advantage of this protocol is that a widefield fluorescence microscope, which is commonly available in many labs, is the major equipment necessary for this procedure. We demonstrate this protocol by measuring the Young's modulus of soft silicone substrates of different elastic moduli.
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Affiliation(s)
- Yashar Bashirzadeh
- Department of Mechanical & Aerospace Engineering, Old Dominion University
| | | | - Dakota Palmer
- Department of Biological Sciences, Old Dominion University
| | - Sandeep Dumbali
- Department of Mechanical & Aerospace Engineering, Old Dominion University
| | - Shizhi Qian
- Department of Mechanical & Aerospace Engineering, Old Dominion University
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114
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Gahl TJ, Kunze A. Force-Mediating Magnetic Nanoparticles to Engineer Neuronal Cell Function. Front Neurosci 2018; 12:299. [PMID: 29867315 PMCID: PMC5962660 DOI: 10.3389/fnins.2018.00299] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 04/18/2018] [Indexed: 12/12/2022] Open
Abstract
Cellular processes like membrane deformation, cell migration, and transport of organelles are sensitive to mechanical forces. Technically, these cellular processes can be manipulated through operating forces at a spatial precision in the range of nanometers up to a few micrometers through chaperoning force-mediating nanoparticles in electrical, magnetic, or optical field gradients. But which force-mediating tool is more suitable to manipulate cell migration, and which, to manipulate cell signaling? We review here the differences in forces sensation to control and engineer cellular processes inside and outside the cell, with a special focus on neuronal cells. In addition, we discuss technical details and limitations of different force-mediating approaches and highlight recent advancements of nanomagnetics in cell organization, communication, signaling, and intracellular trafficking. Finally, we give suggestions about how force-mediating nanoparticles can be used to our advantage in next-generation neurotherapeutic devices.
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Affiliation(s)
| | - Anja Kunze
- Department of Electrical and Computer Engineering, Montana State University, Bozeman, MT, United States
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115
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Septiadi D, Crippa F, Moore TL, Rothen-Rutishauser B, Petri-Fink A. Nanoparticle-Cell Interaction: A Cell Mechanics Perspective. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1704463. [PMID: 29315860 DOI: 10.1002/adma.201704463] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 09/14/2017] [Indexed: 05/22/2023]
Abstract
Progress in the field of nanoparticles has enabled the rapid development of multiple products and technologies; however, some nanoparticles can pose both a threat to the environment and human health. To enable their safe implementation, a comprehensive knowledge of nanoparticles and their biological interactions is needed. In vitro and in vivo toxicity tests have been considered the gold standard to evaluate nanoparticle safety, but it is becoming necessary to understand the impact of nanosystems on cell mechanics. Here, the interaction between particles and cells, from the point of view of cell mechanics (i.e., bionanomechanics), is highlighted and put in perspective. Specifically, the ability of intracellular and extracellular nanoparticles to impair cell adhesion, cytoskeletal organization, stiffness, and migration are discussed. Furthermore, the development of cutting-edge, nanotechnology-driven tools based on the use of particles allowing the determination of cell mechanics is emphasized. These include traction force microscopy, colloidal probe atomic force microscopy, optical tweezers, magnetic manipulation, and particle tracking microrheology.
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Affiliation(s)
- Dedy Septiadi
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700, Fribourg, Switzerland
| | - Federica Crippa
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700, Fribourg, Switzerland
| | - Thomas Lee Moore
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700, Fribourg, Switzerland
| | | | - Alke Petri-Fink
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700, Fribourg, Switzerland
- Department of Chemistry, University of Fribourg, Chemin du Musée 9, 1700, Fribourg, Switzerland
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116
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117
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Bueno J, Bazilevs Y, Juanes R, Gomez H. Wettability control of droplet durotaxis. SOFT MATTER 2018; 14:1417-1426. [PMID: 29388999 DOI: 10.1039/c7sm01917c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Durotaxis refers to cell motion directed by stiffness gradients of an underlying substrate. Recent work has shown that droplets also move spontaneously along stiffness gradients through a process reminiscent of durotaxis. Wetting droplets, however, move toward softer substrates, an observation seemingly at odds with cell motion. Here, we extend our understanding of this phenomenon, and show that wettability of the substrate plays a critical role: while wetting droplets move in the direction of lower stiffness, nonwetting liquids reverse droplet durotaxis. Our numerical experiments also reveal that Laplace pressure can be used to determine the direction of motion of liquid slugs in confined environments. Our results suggest new ways of controlling droplet dynamics at small scales, which can open the door to enhanced bubble and droplet logic in microfluidic platforms.
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Affiliation(s)
- Jesus Bueno
- Departamento de Matemáticas. Universidade da Coruña. Campus de Elviña, 15192, A Coruña, Spain.
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118
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Jensen L, Neri E, Bassaneze V, De Almeida Oliveira NC, Dariolli R, Turaça LT, Levy D, Veronez D, Ferraz MSA, Alencar AM, Bydlowski SP, Cestari IA, Krieger JE. Integrated molecular, biochemical, and physiological assessment unravels key extraction method mediated influences on rat neonatal cardiomyocytes. J Cell Physiol 2018; 233:5420-5430. [PMID: 29219187 DOI: 10.1002/jcp.26380] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 12/04/2017] [Indexed: 12/29/2022]
Abstract
Neonatal cardiomyocytes are instrumental for disease modeling, but the effects of different cell extraction methods on basic cell biological processes remain poorly understood. We assessed the influence of two popular methods to extract rat neonatal cardiomyocytes, Pre-plating (PP), and Percoll (PC) on cell structure, metabolism, and function. Cardiomyocytes obtained from PP showed higher gene expression for troponins, titin, and potassium and sodium channels compared to PC. Also, PP cells displayed higher levels of troponin I protein. Cells obtained from PC displayed higher lactate dehydrogenase activity and lactate production than PP cells, indicating higher anaerobic metabolism after 8 days of culture. In contrast, reactive oxygen species levels were higher in PP cells as indicated by ethidium and hydroxyethidium production. Consistent with these data, protein nitration was higher in PP cells, as well as nitrite accumulation in cell medium. Moreover, PP cells showed higher global intracellular calcium under basal and 1 mM isoprenaline conditions. In a calcium-transient assessment under electrical stimulation (0.5 Hz), PP cells displayed higher calcium amplitude than cardiomyocytes obtained from PC and using a traction force microscope technique we observed that PP cardiomyocytes showed the highest relaxation. Collectively, we demonstrated that extraction methods influence parameters related to cell structure, metabolism, and function. Overall, PP derived cells are more active and mature than PC cells, displaying higher contractile function and generating more reactive oxygen species. On the other hand, PC derived cells display higher anaerobic metabolism, despite comparable high yields from both protocols.
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Affiliation(s)
- Leonardo Jensen
- Laboratory of Genetics and Molecular Cardiology/LIM 13, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Elida Neri
- Laboratory of Genetics and Molecular Cardiology/LIM 13, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Vinicius Bassaneze
- Laboratory of Genetics and Molecular Cardiology/LIM 13, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Nathalia C De Almeida Oliveira
- Laboratory of Genetics and Molecular Cardiology/LIM 13, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Rafael Dariolli
- Laboratory of Genetics and Molecular Cardiology/LIM 13, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Lauro T Turaça
- Laboratory of Genetics and Molecular Cardiology/LIM 13, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Débora Levy
- Laboratory of Genetics and Molecular Hematology/LIM 31, Clinics Hospital (HC), University of São Paulo Medical School, São Paulo, Brazil
| | - Douglas Veronez
- Bioengineering Division, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Mariana S A Ferraz
- Laboratory of Microrheology and Molecular Physiology, Institute of Physics, University of São Paulo, São Paulo, Brazil
| | - Adriano M Alencar
- Laboratory of Microrheology and Molecular Physiology, Institute of Physics, University of São Paulo, São Paulo, Brazil
| | - Sérgio P Bydlowski
- Laboratory of Genetics and Molecular Hematology/LIM 31, Clinics Hospital (HC), University of São Paulo Medical School, São Paulo, Brazil
| | - Idágene A Cestari
- Bioengineering Division, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - José Eduardo Krieger
- Laboratory of Genetics and Molecular Cardiology/LIM 13, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
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119
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Zhang Y, Feng J, Heizler SI, Levine H. Hindrances to precise recovery of cellular forces in fibrous biopolymer networks. Phys Biol 2018; 15:026001. [PMID: 29231177 DOI: 10.1088/1478-3975/aaa107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
How cells move through the three-dimensional extracellular matrix (ECM) is of increasing interest in attempts to understand important biological processes such as cancer metastasis. Just as in motion on flat surfaces, it is expected that experimental measurements of cell-generated forces will provide valuable information for uncovering the mechanisms of cell migration. However, the recovery of forces in fibrous biopolymer networks may suffer from large errors. Here, within the framework of lattice-based models, we explore possible issues in force recovery by solving the inverse problem: how can one determine the forces cells exert to their surroundings from the deformation of the ECM? Our results indicate that irregular cell traction patterns, the uncertainty of local fiber stiffness, the non-affine nature of ECM deformations and inadequate knowledge of network topology will all prevent the precise force determination. At the end, we discuss possible ways of overcoming these difficulties.
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Affiliation(s)
- Yunsong Zhang
- Department of Physics & Astronomy and Center for Theoretical Biological Physics, Rice University, Houston TX, 77030, United States of America
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120
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Dittmann J, Dietzel A, Böl M. Mechanical characterisation of oocytes - The influence of sample geometry on parameter identification. J Mech Behav Biomed Mater 2018; 77:764-775. [DOI: 10.1016/j.jmbbm.2017.07.037] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 07/07/2017] [Accepted: 07/25/2017] [Indexed: 01/24/2023]
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121
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Strömblad S, Lock JG. Using Systems Microscopy to Understand the Emergence of Cell Migration from Cell Organization. Methods Mol Biol 2018; 1749:119-134. [PMID: 29525994 DOI: 10.1007/978-1-4939-7701-7_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cell migration is a dynamic process that emerges from fine-tuned networks coordinated in three-dimensional space, spanning molecular, subcellular, and cellular scales, and over multiple temporal scales, from milliseconds to days. Understanding how cell migration arises from this complexity requires data collection and analyses that quantitatively integrate these spatial and temporal scales. To meet this need, we have combined quantitative live and fixed cell fluorescence microscopy, customized image analysis tools, multivariate statistical methods, and mathematical modeling. Collectively, this constitutes the systems microscopy strategy that we have applied to dissect how cells organize themselves to migrate. In this overview, we highlight key principles, concepts, and components of our systems microscopy methodology, and exemplify what we have learnt so far and where this approach may lead.
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Affiliation(s)
- Staffan Strömblad
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
| | - John G Lock
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney, Australia
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122
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Vig DK, Hamby AE, Wolgemuth CW. Cellular Contraction Can Drive Rapid Epithelial Flows. Biophys J 2017; 113:1613-1622. [PMID: 28978451 DOI: 10.1016/j.bpj.2017.08.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 08/01/2017] [Accepted: 08/07/2017] [Indexed: 01/18/2023] Open
Abstract
Single, isolated epithelial cells move randomly; however, during wound healing, organism development, cancer metastasis, and many other multicellular phenomena, motile cells group into a collective and migrate persistently in a directed manner. Recent work has examined the physics and biochemistry that coordinates the motions of these groups of cells. Of late, two mechanisms have been touted as being crucial to the physics of these systems: leader cells and jamming. However, the actual importance of these to collective migration remains circumstantial. Fundamentally, collective behavior must arise from the actions of individual cells. Here, we show how biophysical activity of an isolated cell impacts collective dynamics in epithelial layers. Although many reports suggest that wound closure rates depend on isolated cell speed and/or leader cells, we find that these correlations are not universally true, nor do collective dynamics follow the trends suggested by models for jamming. Instead, our experimental data, when coupled with a mathematical model for collective migration, shows that intracellular contractile stress, isolated cell speed, and adhesion all play a substantial role in influencing epithelial dynamics, and that alterations in contraction and/or substrate adhesion can cause confluent epithelial monolayers to exhibit an increase in motility, a feature reminiscent of cancer metastasis. These results directly question the validity of wound-healing assays as a general means for measuring cell migration, and provide further insight into the salient physics of collective migration.
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Affiliation(s)
- Dhruv K Vig
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona
| | - Alex E Hamby
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona
| | - Charles W Wolgemuth
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona; Department of Physics, University of Arizona, Tucson, Arizona.
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123
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Chiou K, Collins EMS. Why we need mechanics to understand animal regeneration. Dev Biol 2017; 433:155-165. [PMID: 29179947 DOI: 10.1016/j.ydbio.2017.09.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 08/31/2017] [Accepted: 09/17/2017] [Indexed: 12/19/2022]
Abstract
Mechanical forces are an important contributor to cell fate specification and cell migration during embryonic development in animals. Similarities between embryogenesis and regeneration, particularly with regards to pattern formation and large-scale tissue movements, suggest similarly important roles for physical forces during regeneration. While the influence of the mechanical environment on stem cell differentiation in vitro is being actively exploited in the fields of tissue engineering and regenerative medicine, comparatively little is known about the role of stresses and strains acting during animal regeneration. In this review, we summarize published work on the role of physical principles and mechanical forces in animal regeneration. Novel experimental techniques aimed at addressing the role of mechanics in embryogenesis have greatly enhanced our understanding at scales from the subcellular to the macroscopic - we believe the time is ripe for the field of regeneration to similarly leverage the tools of the mechanobiological research community.
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Affiliation(s)
- Kevin Chiou
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Eva-Maria S Collins
- Physics Department, UC San Diego, La Jolla, CA 92093, USA; Section of Cell&Developmental Biology, UC San Diego, La Jolla, CA 92093, USA.
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124
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Park SJ, Bostwick JB, De Andrade V, Je JH. Self-spreading of the wetting ridge during stick-slip on a viscoelastic surface. SOFT MATTER 2017; 13:8331-8336. [PMID: 29058731 DOI: 10.1039/c7sm01408b] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Dynamic wetting behaviors on soft solids are important to interpret complex biological processes from cell-substrate interactions. Despite intensive research studies over the past half-century, the underlying mechanisms of spreading behaviors are not clearly understood. The most interesting feature of wetting on soft matter is the formation of a "wetting ridge", a surface deformation by a competition between elasticity and capillarity. Dynamics of the wetting ridge formed at the three-phase contact line underlies the dynamic wetting behaviors, but remains largely unexplored mostly due to limitations in indirect observation. Here, we directly visualize wetting ridge dynamics during continuous- and stick-slip motions on a viscoelastic surface using X-ray microscopy. Strikingly, we discover that the ridge spreads spontaneously during stick and triggers contact line depinning (stick-to-slip transition) by changing the ridge geometry which weakens the contact line pinning. Finally, we clarify 'viscoelastic-braking', 'stick-slipping', and 'stick-breaking' spreading behaviors through the ridge dynamics. In stick-breaking, no ridge-spreading occurs and contact line pinning (hysteresis) is enhanced by cusp-bending while preserving a microscopic equilibrium at the ridge tip. We have furthered the understanding of spreading behaviors on soft solids and demonstrated the value of X-ray microscopy in elucidating various dynamic wetting behaviors on soft solids as well as puzzling biological issues.
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Affiliation(s)
- S J Park
- X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang 37673, South Korea.
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125
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Chang F. Forces that shape fission yeast cells. Mol Biol Cell 2017; 28:1819-1824. [PMID: 28684607 PMCID: PMC5541833 DOI: 10.1091/mbc.e16-09-0671] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 04/18/2017] [Accepted: 04/18/2017] [Indexed: 11/11/2022] Open
Abstract
One of the major challenges of modern cell biology is to understand how cells are assembled from nanoscale components into micrometer-scale entities with a specific size and shape. Here I describe how our quest to understand the morphogenesis of the fission yeast Schizosaccharomyces pombe drove us to investigate cellular mechanics. These studies build on the view that cell shape arises from the physical properties of an elastic cell wall inflated by internal turgor pressure. Consideration of cellular mechanics provides new insights into not only mechanisms responsible for cell-shape determination and growth, but also cellular processes such as cytokinesis and endocytosis. Studies in yeast can help to illuminate approaches and mechanisms to study the mechanobiology of the cell surface in other cell types, including animal cells.
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Affiliation(s)
- Fred Chang
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143
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126
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Das A, Monteiro M, Barai A, Kumar S, Sen S. MMP proteolytic activity regulates cancer invasiveness by modulating integrins. Sci Rep 2017; 7:14219. [PMID: 29079818 PMCID: PMC5660204 DOI: 10.1038/s41598-017-14340-w] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 10/10/2017] [Indexed: 12/20/2022] Open
Abstract
Cancer invasion through dense extracellular matrices (ECMs) is mediated by matrix metalloproteinases (MMPs) which degrade the ECM thereby creating paths for migration. However, how this degradation influences the phenotype of cancer cells is not fully clear. Here we address this question by probing the function of MMPs in regulating biophysical properties of cancer cells relevant to invasion. We show that MMP catalytic activity regulates cell spreading, motility, contractility and cortical stiffness by stabilizing integrins at the membrane and activating focal adhesion kinase. Interestingly, cell rounding and cell softening on stiff gels induced by MMP inhibition is attenuated on MMP pre-conditioned surfaces. Together, our results suggest that MMP catalytic activity regulates invasiveness of cancer cells by modulating integrins.
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Affiliation(s)
- Alakesh Das
- Department of Biosciences & Bioengineering, IIT Bombay, Mumbai, 400 076, India
| | - Melissa Monteiro
- Department of Biosciences & Bioengineering, IIT Bombay, Mumbai, 400 076, India
| | - Amlan Barai
- Department of Biosciences & Bioengineering, IIT Bombay, Mumbai, 400 076, India
| | - Sandeep Kumar
- Department of Biosciences & Bioengineering, IIT Bombay, Mumbai, 400 076, India
| | - Shamik Sen
- Department of Biosciences & Bioengineering, IIT Bombay, Mumbai, 400 076, India.
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127
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Desai S, Barai A, Bukhari AB, De A, Sen S. α-Actinin-4 confers radioresistance coupled invasiveness in breast cancer cells through AKT pathway. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1865:196-208. [PMID: 29055790 DOI: 10.1016/j.bbamcr.2017.10.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 10/09/2017] [Accepted: 10/13/2017] [Indexed: 12/18/2022]
Abstract
Acquired radioresistance accompanied with increased metastatic potential is a major hurdle in effective radiotherapy of breast cancers. However, the nature of their inter-dependence and the underlying mechanism remains largely intangible. By employing radioresistant (RR) cell lines, we herein demonstrate that MCF-7 RR cells display phenotypic and molecular alterations evocative of epithelial to mesenchymal transition (EMT) with increased traction forces and membrane ruffling culminating in boosted invasiveness. We then show that these changes can be attributed to overexpression of alpha-actinin-4 (ACTN4), with ACTN4 knockdown near-completely abrogating both radioresistance and EMT-associated changes. We further found that in MCF-7 RR cells, ACTN4 mediates the observed effects by activating AKT, and downstream AKT/GSK3β signalling. Though ACTN4 plays a similar role in mediating radioresistance and invasiveness in MDA-MB-231 RR cells, co-immunoprecipitation studies reveal that these changes are effected through increased association with AKT and not by overexpression of AKT. Taken together, our study identifies ACTN4/AKT/GSK3β as a novel pathway regulating radioresistance coupled invasion which can be further explored to improve the radiotherapeutic gain.
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Affiliation(s)
- Sejal Desai
- Biosciences and Bioengineering Department, IIT Bombay, Mumbai, India
| | - Amlan Barai
- Biosciences and Bioengineering Department, IIT Bombay, Mumbai, India
| | | | - Abhijit De
- ACTREC, Tata Memorial Centre, Kharghar, Navi Mumbai, India.
| | - Shamik Sen
- Biosciences and Bioengineering Department, IIT Bombay, Mumbai, India.
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128
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Abstract
Asexual freshwater planarians reproduce by tearing themselves into two pieces by a process called binary fission. The resulting head and tail pieces regenerate within about a week, forming two new worms. Understanding this process of ripping oneself into two parts poses a challenging biomechanical problem. Because planarians stop "doing it" at the slightest disturbance, this remained a centuries-old puzzle. We focus on Dugesia japonica fission and show that it proceeds in three stages: a local constriction ("waist formation"), pulsation-which increases waist longitudinal stresses-and transverse rupture. We developed a linear mechanical model with a planarian represented by a thin shell. The model fully captures the pulsation dynamics leading to rupture and reproduces empirical time scales and stresses. It asserts that fission execution is a mechanical process. Furthermore, we show that the location of waist formation, and thus fission, is determined by physical constraints. Together, our results demonstrate that where and how a planarian rips itself apart during asexual reproduction can be fully explained through biomechanics.
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129
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Xu Q, Jensen KE, Boltyanskiy R, Sarfati R, Style RW, Dufresne ER. Direct measurement of strain-dependent solid surface stress. Nat Commun 2017; 8:555. [PMID: 28916752 PMCID: PMC5601460 DOI: 10.1038/s41467-017-00636-y] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 07/14/2017] [Indexed: 11/09/2022] Open
Abstract
Surface stress, also known as surface tension, is a fundamental material property of any interface. However, measurements of solid surface stress in traditional engineering materials, such as metals and oxides, have proven to be very challenging. Consequently, our understanding relies heavily on untested theories, especially regarding the strain dependence of this property. Here, we take advantage of the high compliance and large elastic deformability of a soft polymer gel to directly measure solid surface stress as a function of strain. As anticipated by theoretical work for metals, we find that the surface stress depends on the strain via a surface modulus. Remarkably, the surface modulus of our soft gels is many times larger than the zero-strain surface tension. This suggests that surface stresses can play a dominant role in solid mechanics at larger length scales than previously anticipated.Solid surface stress is a fundamental property of solid interfaces. Here authors measure the solid surface stress of a gel, and show its dependence on surface strain through a surface modulus.
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Affiliation(s)
- Qin Xu
- Department of Materials, ETH Zürich, 8093, Zürich, Switzerland.,Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Katharine E Jensen
- Department of Materials, ETH Zürich, 8093, Zürich, Switzerland.,Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Rostislav Boltyanskiy
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Raphaël Sarfati
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Robert W Style
- Department of Materials, ETH Zürich, 8093, Zürich, Switzerland. .,Mathematical Institute, University of Oxford, Oxford, OX1 3LB, UK.
| | - Eric R Dufresne
- Department of Materials, ETH Zürich, 8093, Zürich, Switzerland. .,Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA.
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130
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Liu Y, Rogel N, Harada K, Jarett L, Maiorana CH, German GK, Mahler GJ, Doiron AL. Nanoparticle size-specific actin rearrangement and barrier dysfunction of endothelial cells. Nanotoxicology 2017; 11:846-856. [PMID: 28885066 DOI: 10.1080/17435390.2017.1371349] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In this work, we evaluated the impact of gold nanoparticles on endothelial cell behavior and function beyond the influence on cell viability. Five types of gold nanoparticles were studied: 5 nm and 20 nm bare gold nanoparticles, 5 nm and 20 nm gold nanoparticles with biocompatible polyethylene glycol (PEG) coating and 60 nm bare gold nanoparticles. We found that all tested gold nanoparticles did not affect cell viability significantly and reduced the reactive oxygen species (ROS) level in endothelial cells. Only 20 nm bare gold nanoparticles caused an over 50% increase in endothelial barrier permeability and slow recovery of barrier function was observed after the gold nanoparticles were removed. This impairment in endothelial barrier function was caused by unbalanced forces between intracellular tensions and paracellular forces, actin microfilament rearrangement, which occurred through a Rho/ROCK kinase-dependent pathway and broke the force balance between intracellular tensions and paracellular forces. The size-specific effect of gold nanoparticles on endothelial cells may have important implications regarding the behavior of nanoparticles in the biological system and provide valuable guidance in nanomaterial design and biomedical applications.
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Affiliation(s)
- Yizhong Liu
- a Department of Biomedical Engineering , Binghamton University , Binghamton , NY, USA
| | - Noga Rogel
- b Department of Neuroscience , Binghamton University , Binghamton , NY, USA
| | - Kei Harada
- a Department of Biomedical Engineering , Binghamton University , Binghamton , NY, USA
| | - Leigha Jarett
- a Department of Biomedical Engineering , Binghamton University , Binghamton , NY, USA
| | | | - Guy K German
- a Department of Biomedical Engineering , Binghamton University , Binghamton , NY, USA
| | - Gretchen J Mahler
- a Department of Biomedical Engineering , Binghamton University , Binghamton , NY, USA
| | - Amber L Doiron
- a Department of Biomedical Engineering , Binghamton University , Binghamton , NY, USA
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131
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Localized stress fluctuations drive shear thickening in dense suspensions. Proc Natl Acad Sci U S A 2017; 114:8740-8745. [PMID: 28765373 DOI: 10.1073/pnas.1703871114] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dense particulate suspensions exhibit a dramatic increase in average viscosity above a critical, material-dependent shear stress. This thickening changes from continuous to discontinuous as the concentration is increased. Using direct measurements of spatially resolved surface stresses in the continuous thickening regime, we report the existence of clearly defined dynamic localized regions of substantially increased stress that appear intermittently at stresses above the critical stress. With increasing applied stress, these regions occupy an increasing fraction of the system, and the increase accounts quantitatively for the observed shear thickening. The regions represent high-viscosity fluid phases, with a size determined by the distance between the shearing surfaces and a viscosity that is nearly independent of shear rate but that increases rapidly with concentration. Thus, we find that continuous shear thickening arises from increasingly frequent localized discontinuous transitions between distinct fluid phases with widely differing viscosities.
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132
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Leggett SE, Khoo AS, Wong IY. Multicellular tumor invasion and plasticity in biomimetic materials. Biomater Sci 2017; 5:1460-1479. [PMID: 28530743 PMCID: PMC5531215 DOI: 10.1039/c7bm00272f] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cancer cell invasion through the extracellular matrix is associated with metastatic spread and therapeutic resistance. In carcinomas, the detachment and dissemination of individual cells has been associated with an epithelial-mesenchymal transition, but tumors can also invade using collective, multicellular phenotypes. This malignant tumor progression is also associated with alignment and stiffening of the surrounding extracellular matrix. Historically, tumor invasion has been investigated using 2D monolayer culture, small animal models or patient histology. These assays have been complemented by the use of natural biomaterials such as reconstituted basement membrane and collagen I. More recently, engineered materials with well-defined physical, chemical and biomolecular properties have enabled more controlled microenvironments. In this review, we highlight recent developments in multicellular tumor invasion based on microfabricated structures or hydrogels. We emphasize the role of interfacial geometries, biomaterial stiffness, matrix remodeling, and co-culture models. Finally, we discuss future directions for the field, particularly integration with precision measurements of biomaterial properties and single cell heterogeneity, standardization and scale-up of these platforms, as well as integration with patient-derived samples.
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Affiliation(s)
- Susan E Leggett
- School of Engineering, Center for Biomedical Engineering, Brown University, Providence, RI 02912, USA. and Pathobiology Graduate Program, Brown University, Providence, RI 02912, USA
| | - Amanda S Khoo
- School of Engineering, Center for Biomedical Engineering, Brown University, Providence, RI 02912, USA.
| | - Ian Y Wong
- School of Engineering, Center for Biomedical Engineering, Brown University, Providence, RI 02912, USA. and Pathobiology Graduate Program, Brown University, Providence, RI 02912, USA
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133
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Coppola S, Carnevale I, Danen EHJ, Peters GJ, Schmidt T, Assaraf YG, Giovannetti E. A mechanopharmacology approach to overcome chemoresistance in pancreatic cancer. Drug Resist Updat 2017; 31:43-51. [PMID: 28867243 DOI: 10.1016/j.drup.2017.07.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 07/19/2017] [Indexed: 02/07/2023]
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is a highly chemoresistant malignancy. This chemoresistant phenotype has been historically associated with genetic factors. Major biomedical research efforts were concentrated that resulted in the identification of subtypes characterized by specific genetic lesions and gene expression signatures that suggest important biological differences. However, to date, these distinct differences could not be exploited for therapeutic interventions. Apart from these genetic factors, desmoplasia and tumor microenvironment have been recognized as key contributors to PDAC chemoresistance. However, while several strategies targeting tumor-stroma have been explored including drugs against members of the Hedgehog family, they failed to meet the expectations in the clinical setting. These unsatisfactory clinical results suggest that, an important link between genetics and the influence of tumor microenvironment on PDAC chemoresistance remains to be elucidated. In this respect, mechanobiology is an emerging multidisciplinary field that encompasses cell and developmental biology as well as biophysics and bioengineering. Herein we provide a comprehensive overview of the key players in pancreatic cancer chemoresistance from the perspective of mechanobiology, and discuss novel experimental avenues such as elastic micropillar arrays that could provide fresh insights for the development of mechanobiology-targeted therapeutic approaches (know as mechanopharmacology) to overcome anticancer drug resistance in pancreatic cancer.
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Affiliation(s)
- Stefano Coppola
- Physics of Life Processes, Huygens-Kamerlingh Onnes Laboratory, Leiden University, Leiden, The Netherlands
| | - Ilaria Carnevale
- Department of Medical Oncology, VU University Medical Center Amsterdam, Amsterdam, The Netherlands; Cancer Pharmacology Lab, AIRC Start-Up Unit, University Hospital of Pisa, Pisa, Italy
| | - Erik H J Danen
- Division of Toxicology, LACDR, Leiden University, Leiden, The Netherlands
| | - Godefridus J Peters
- Department of Medical Oncology, VU University Medical Center Amsterdam, Amsterdam, The Netherlands
| | - Thomas Schmidt
- Physics of Life Processes, Huygens-Kamerlingh Onnes Laboratory, Leiden University, Leiden, The Netherlands
| | - Yehuda G Assaraf
- The Fred Wyszkowski Cancer Research Laboratory, Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Elisa Giovannetti
- Department of Medical Oncology, VU University Medical Center Amsterdam, Amsterdam, The Netherlands; Cancer Pharmacology Lab, AIRC Start-Up Unit, University Hospital of Pisa, Pisa, Italy; Institute for Nanoscience and Nanotechnologies, CNR-Nano, Pisa.
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134
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Bachir AI, Horwitz AR, Nelson WJ, Bianchini JM. Actin-Based Adhesion Modules Mediate Cell Interactions with the Extracellular Matrix and Neighboring Cells. Cold Spring Harb Perspect Biol 2017; 9:9/7/a023234. [PMID: 28679638 DOI: 10.1101/cshperspect.a023234] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Cell adhesions link cells to the extracellular matrix (ECM) and to each other and depend on interactions with the actin cytoskeleton. Both cell-ECM and cell-cell adhesion sites contain discrete, yet overlapping, functional modules. These modules establish physical associations with the actin cytoskeleton, locally modulate actin organization and dynamics, and trigger intracellular signaling pathways. Interplay between these modules generates distinct actin architectures that underlie different stages, types, and functions of cell-ECM and cell-cell adhesions. Actomyosin contractility is required to generate mature, stable adhesions, as well as to sense and translate the mechanical properties of the cellular environment into changes in cell organization and behavior. Here, we review the organization and function of different adhesion modules and how they interact with the actin cytoskeleton. We highlight the molecular mechanisms of mechanotransduction in adhesions and how adhesion molecules mediate cross talk between cell-ECM and cell-cell adhesion sites.
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Affiliation(s)
- Alexia I Bachir
- Protein and Cell Analysis, Biosciences Division, Thermo Fisher Scientific, Eugene, Oregon 97402
| | - Alan Rick Horwitz
- Protein and Cell Analysis, Biosciences Division, Thermo Fisher Scientific, Eugene, Oregon 97402
| | - W James Nelson
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22903
| | - Julie M Bianchini
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22903
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135
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136
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Lee P, Wolgemuth CW. Physical Mechanisms of Cancer in the Transition to Metastasis. Biophys J 2017; 111:256-66. [PMID: 27410752 DOI: 10.1016/j.bpj.2016.05.046] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 05/20/2016] [Accepted: 05/31/2016] [Indexed: 10/21/2022] Open
Abstract
Whether a tumor is metastatic is one of the most significant factors that influence the prognosis for a cancer patient. The transition from a nonmetastatic tumor to a metastatic one is accompanied by a number of genetic and proteomic changes within the tumor cells. These protein-level changes conspire to produce behavioral changes in the cells: cells that had been relatively stationary begin to move, often as a group. In this study we ask the question of what cell-level biophysical changes are sufficient to initiate evasion away from an otherwise static tumor. We use a mathematical model developed to describe the biophysics of epithelial tissue to explore this problem. The model is first validated against in vitro wound healing experiments with cancer cell lines. Then we simulate the behavior of a group of mutated cells within a sea of healthy tissue. We find that moderate increases in adhesion between the cell and extracellular matrix (ECM) accompanied by a decrease in cell-cell adhesion and/or Rho family of small GTPase activation can cause a group of cells to break free from a tumor and spontaneously migrate. This result may explain why some metastatic cells have been observed to upregulate integrin, downregulate cadherin, and activate Rho family signaling.
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Affiliation(s)
- Pilhwa Lee
- Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
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137
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Schierbaum N, Rheinlaender J, Schäffer TE. Viscoelastic properties of normal and cancerous human breast cells are affected differently by contact to adjacent cells. Acta Biomater 2017; 55:239-248. [PMID: 28396292 DOI: 10.1016/j.actbio.2017.04.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 03/14/2017] [Accepted: 04/05/2017] [Indexed: 01/07/2023]
Abstract
Malignant transformation drastically alters the mechanical properties of the cell and its response to the surrounding cellular environment. We studied the influence of the physical contact between adjacent cells in an epithelial monolayer on the viscoelastic behavior of normal MCF10A, non-invasive cancerous MCF7, and invasive cancerous MDA-MB-231 human breast cells. Using an atomic force microscopy (AFM) imaging technique termed force clamp force mapping (FCFM) to record images of the viscoelastic material properties, we found that normal MCF10A cells are stiffer and have a lower fluidity at confluent than at sparse density. Contrarily, cancerous MCF7 and MDA-MB-231 cells do not stiffen and do not decrease their fluidity when progressing from sparse to confluent density. The behavior of normal MCF10A cells appears to be governed by the formation of stable cell-cell contacts, because their disruption with a calcium-chelator (EGTA) causes the stiffness and fluidity values to return to those at sparse density. In contrast, EGTA-treatment of MCF7 and MDA-MB-231 cells does not change their viscoelastic properties. Confocal fluorescence microscopy showed that the change of the viscoelastic behavior in MCF10A cells when going from sparse to confluent density is accompanied by a remodeling of the actin cytoskeleton into thick stress fiber bundles, while in MCF7 and MDA-MB-231 cells the actin cytoskeleton is only composed of thin and short fibers, regardless of cell density. While the observed behavior of normal MCF10A cells might be crucial for providing mechanical stability and thus in turn integrity of the epithelial monolayer, the dysregulation of this behavior in cancerous MCF7 and MDA-MB-231 cells is possibly a central aspect of cancer progression in the epithelium. STATEMENT OF SIGNIFICANCE We measured the viscoelastic properties of normal and cancerous human breast epithelial cells in different states of confluency using atomic force microscopy. We found that confluent normal cells are stiffer and have lower fluidity than sparse normal cells, which appears to be governed by the formation of cell-cell contacts. Contrarily, confluent cancer cells do not stiffen and not have a decreased fluidity compared to sparse cancer cells and their viscoelastic properties are independent of cell-cell contact formation. While the observed behavior of normal cells appears to be crucial for providing the mechanical stability and therefore the integrity of the epithelial monolayer, the dysregulation of this behavior in cancer cells might be a central aspect of early stage cancer progression and metastasis in the epithelium.
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Affiliation(s)
- Nicolas Schierbaum
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Johannes Rheinlaender
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Tilman E Schäffer
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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138
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Smith Q, Chan XY, Carmo AM, Trempel M, Saunders M, Gerecht S. Compliant substratum guides endothelial commitment from human pluripotent stem cells. SCIENCE ADVANCES 2017; 3:e1602883. [PMID: 28580421 PMCID: PMC5451190 DOI: 10.1126/sciadv.1602883] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 04/10/2017] [Indexed: 05/24/2023]
Abstract
The role of mechanical regulation in driving human induced pluripotent stem cell (hiPSC) differentiation has been minimally explored. Although endothelial cell (EC) fate from hiPSCs has been demonstrated using small molecules to drive mesoderm induction, the effects of substrate stiffness with regard to EC differentiation efficiency have yet to be elucidated. We hypothesized that substrate compliance can modulate mesoderm differentiation kinetics from hiPSCs and affect downstream EC commitment. To this end, we used polydimethylsiloxane (PDMS)-a transparent, biocompatible elastomeric material-as a substrate to study EC commitment of hiPSCs using a stepwise differentiation scheme. Using physiologically stiff (1.7 MPa) and soft (3 kPa) PDMS substrates, compared to polystyrene plates (3 GPa), we demonstrate that mechanical priming during mesoderm induction activates the Yes-associated protein and drives Wnt/β-catenin signaling. When mesoderm differentiation was induced on compliant PDMS substrates in both serum and serum-free E6 medium, mesodermal genetic signatures (T, KDR, MESP-1, GATA-2, and SNAIL-1) were enhanced. Furthermore, examination of EC fate following stiffness priming revealed that compliant substrates robustly improve EC commitment through VECad, CD31, vWF, and eNOS marker expression. Overall, we show that substrate compliance guides EC fate by enhancing mesoderm induction through Wnt activation without the addition of small molecules. These findings are the first to show that the mechanical context of the differentiation niche can be as potent as chemical cues in driving EC identity from hiPSCs.
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Affiliation(s)
- Quinton Smith
- Department of Chemical and Biomolecular Engineering and Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Xin Yi Chan
- Department of Chemical and Biomolecular Engineering and Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Ana Maria Carmo
- Department of Chemical and Biomolecular Engineering and Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Michelle Trempel
- Department of Chemical and Biomolecular Engineering and Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Michael Saunders
- Department of Chemical and Biomolecular Engineering and Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Sharon Gerecht
- Department of Chemical and Biomolecular Engineering and Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
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139
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Nerger BA, Siedlik MJ, Nelson CM. Microfabricated tissues for investigating traction forces involved in cell migration and tissue morphogenesis. Cell Mol Life Sci 2017; 74:1819-1834. [PMID: 28008471 PMCID: PMC5391279 DOI: 10.1007/s00018-016-2439-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 12/02/2016] [Accepted: 12/08/2016] [Indexed: 01/09/2023]
Abstract
Cell-generated forces drive an array of biological processes ranging from wound healing to tumor metastasis. Whereas experimental techniques such as traction force microscopy are capable of quantifying traction forces in multidimensional systems, the physical mechanisms by which these forces induce changes in tissue form remain to be elucidated. Understanding these mechanisms will ultimately require techniques that are capable of quantifying traction forces with high precision and accuracy in vivo or in systems that recapitulate in vivo conditions, such as microfabricated tissues and engineered substrata. To that end, here we review the fundamentals of traction forces, their quantification, and the use of microfabricated tissues designed to study these forces during cell migration and tissue morphogenesis. We emphasize the differences between traction forces in two- and three-dimensional systems, and highlight recently developed techniques for quantifying traction forces.
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Affiliation(s)
- Bryan A Nerger
- Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ, 08544, USA
| | - Michael J Siedlik
- Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ, 08544, USA
| | - Celeste M Nelson
- Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ, 08544, USA.
- Department of Molecular Biology, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ, 08544, USA.
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140
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Sonn-Segev A, Bernheim-Groswasser A, Roichman Y. Dynamics in steady state in vitro acto-myosin networks. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:163002. [PMID: 28234236 DOI: 10.1088/1361-648x/aa62ca] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
It is well known that many biochemical processes in the cell such as gene regulation, growth signals and activation of ion channels, rely on mechanical stimuli. However, the mechanism by which mechanical signals propagate through cells is not as well understood. In this review we focus on stress propagation in a minimal model for cell elasticity, actomyosin networks, which are comprised of a sub-family of cytoskeleton proteins. After giving an overview of th actomyosin network components, structure and evolution we review stress propagation in these materials as measured through the correlated motion of tracer beads. We also discuss the possibility to extract structural features of these networks from the same experiments. We show that stress transmission through these networks has two pathways, a quickly dissipative one through the bulk, and a long ranged weakly dissipative one through the pre-stressed actin network.
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Affiliation(s)
- Adar Sonn-Segev
- Raymond & Beverly Sackler School of Chemistry, Tel Aviv University, Tel Aviv 6997801, Israel
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141
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Šmít D, Fouquet C, Pincet F, Zapotocky M, Trembleau A. Axon tension regulates fasciculation/defasciculation through the control of axon shaft zippering. eLife 2017; 6:19907. [PMID: 28422009 PMCID: PMC5478281 DOI: 10.7554/elife.19907] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 04/04/2017] [Indexed: 01/16/2023] Open
Abstract
While axon fasciculation plays a key role in the development of neural networks, very little is known about its dynamics and the underlying biophysical mechanisms. In a model system composed of neurons grown ex vivo from explants of embryonic mouse olfactory epithelia, we observed that axons dynamically interact with each other through their shafts, leading to zippering and unzippering behavior that regulates their fasciculation. Taking advantage of this new preparation suitable for studying such interactions, we carried out a detailed biophysical analysis of zippering, occurring either spontaneously or induced by micromanipulations and pharmacological treatments. We show that zippering arises from the competition of axon-axon adhesion and mechanical tension in the axons, and provide the first quantification of the force of axon-axon adhesion. Furthermore, we introduce a biophysical model of the zippering dynamics, and we quantitatively relate the individual zipper properties to global characteristics of the developing axon network. Our study uncovers a new role of mechanical tension in neural development: the regulation of axon fasciculation.
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Affiliation(s)
- Daniel Šmít
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Coralie Fouquet
- Neuroscience Paris Seine - Institute of Biology Paris Seine, Sorbonne Université, UPMC Univ Paris 06, INSERM, CNRS, Paris, France
| | - Frédéric Pincet
- Laboratoire de Physique Statistique, Ecole Normale Superieure, PSL Research University, Paris, France
| | - Martin Zapotocky
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Alain Trembleau
- Neuroscience Paris Seine - Institute of Biology Paris Seine, Sorbonne Université, UPMC Univ Paris 06, INSERM, CNRS, Paris, France
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142
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Boltyanskiy R, Merrill JW, Dufresne ER. Tracking particles with large displacements using energy minimization. SOFT MATTER 2017; 13:2201-2206. [PMID: 28243646 DOI: 10.1039/c6sm02011a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We describe a method to track particles undergoing large displacements. Starting with a list of particle positions sampled at different time points, we assign particle identities by minimizing the sum across all particles of the trace of the square of the strain tensor. This method of tracking corresponds to minimizing the stored energy in an elastic solid or the dissipated energy in a viscous fluid. Our energy-minimizing approach extends the advantages of particle tracking to situations where particle imaging velocimetry and digital imaging correlation are typically required. This approach is much more reliable than the standard squared-displacement minimizing approach for spatially-correlated displacements that are larger than the typical interparticle spacing. Thus, it is suitable for particles embedded in a material undergoing large deformations. On the other hand, squared-displacement minimization is more effective for particles undergoing uncorrelated random motion. In the ESI, we include a flexible MATLAB particle tracker that implements either approach with a robust optimal assignment algorithm. This implementation returns an estimation of the strain tensor for each particle, in addition to its identification.
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Affiliation(s)
| | | | - Eric R Dufresne
- Department of Materials, ETH Zürich, 8092 Zürich, CH, Switzerland.
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143
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Barson MSJ, Peddibhotla P, Ovartchaiyapong P, Ganesan K, Taylor RL, Gebert M, Mielens Z, Koslowski B, Simpson DA, McGuinness LP, McCallum J, Prawer S, Onoda S, Ohshima T, Bleszynski Jayich AC, Jelezko F, Manson NB, Doherty MW. Nanomechanical Sensing Using Spins in Diamond. NANO LETTERS 2017; 17:1496-1503. [PMID: 28146361 DOI: 10.1021/acs.nanolett.6b04544] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Nanomechanical sensors and quantum nanosensors are two rapidly developing technologies that have diverse interdisciplinary applications in biological and chemical analysis and microscopy. For example, nanomechanical sensors based upon nanoelectromechanical systems (NEMS) have demonstrated chip-scale mass spectrometry capable of detecting single macromolecules, such as proteins. Quantum nanosensors based upon electron spins of negatively charged nitrogen-vacancy (NV) centers in diamond have demonstrated diverse modes of nanometrology, including single molecule magnetic resonance spectroscopy. Here, we report the first step toward combining these two complementary technologies in the form of diamond nanomechanical structures containing NV centers. We establish the principles for nanomechanical sensing using such nanospin-mechanical sensors (NSMS) and assess their potential for mass spectrometry and force microscopy. We predict that NSMS are able to provide unprecedented AC force images of cellular biomechanics and to not only detect the mass of a single macromolecule but also image its distribution. When combined with the other nanometrology modes of the NV center, NSMS potentially offer unparalleled analytical power at the nanoscale.
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Affiliation(s)
- Michael S J Barson
- Laser Physics Centre, Research School of Physics and Engineering, Australian National University , Canberra, ACT 0200, Australia
| | | | - Preeti Ovartchaiyapong
- Department of Physics, University of California Santa Barbara , Santa Barbara, California 93106, United States
| | - Kumaravelu Ganesan
- School of Physics, University of Melbourne , Melbourne, Victoria 3010, Australia
| | - Richard L Taylor
- Laser Physics Centre, Research School of Physics and Engineering, Australian National University , Canberra, ACT 0200, Australia
| | - Matthew Gebert
- Laser Physics Centre, Research School of Physics and Engineering, Australian National University , Canberra, ACT 0200, Australia
| | - Zoe Mielens
- Laser Physics Centre, Research School of Physics and Engineering, Australian National University , Canberra, ACT 0200, Australia
| | - Berndt Koslowski
- Institut für Festkörperphysik, Universität Ulm , D-89081 Ulm, Germany
| | - David A Simpson
- School of Physics, University of Melbourne , Melbourne, Victoria 3010, Australia
| | - Liam P McGuinness
- Institut für Quantenoptik, Universität Ulm , D-89081 Ulm, Germany
- School of Physics, University of Melbourne , Melbourne, Victoria 3010, Australia
| | - Jeffrey McCallum
- School of Physics, University of Melbourne , Melbourne, Victoria 3010, Australia
| | - Steven Prawer
- School of Physics, University of Melbourne , Melbourne, Victoria 3010, Australia
| | - Shinobu Onoda
- National Institutes for Quantum and Radiological Science and Technology (QST) , 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
| | - Takeshi Ohshima
- National Institutes for Quantum and Radiological Science and Technology (QST) , 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
| | - Ania C Bleszynski Jayich
- Department of Physics, University of California Santa Barbara , Santa Barbara, California 93106, United States
| | - Fedor Jelezko
- Institut für Quantenoptik, Universität Ulm , D-89081 Ulm, Germany
| | - Neil B Manson
- Laser Physics Centre, Research School of Physics and Engineering, Australian National University , Canberra, ACT 0200, Australia
| | - Marcus W Doherty
- Laser Physics Centre, Research School of Physics and Engineering, Australian National University , Canberra, ACT 0200, Australia
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144
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Kennedy KM, Bhaw-Luximon A, Jhurry D. Cell-matrix mechanical interaction in electrospun polymeric scaffolds for tissue engineering: Implications for scaffold design and performance. Acta Biomater 2017; 50:41-55. [PMID: 28011142 DOI: 10.1016/j.actbio.2016.12.034] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 11/10/2016] [Accepted: 12/15/2016] [Indexed: 12/24/2022]
Abstract
Engineered scaffolds produced by electrospinning of biodegradable polymers offer a 3D, nanofibrous environment with controllable structural, chemical, and mechanical properties that mimic the extracellular matrix of native tissues and have shown promise for a number of tissue engineering applications. The microscale mechanical interactions between cells and electrospun matrices drive cell behaviors including migration and differentiation that are critical to promote tissue regeneration. Recent developments in understanding these mechanical interactions in electrospun environments are reviewed, with emphasis on how fiber geometry and polymer structure impact on the local mechanical properties of scaffolds, how altering the micromechanics cues cell behaviors, and how, in turn, cellular and extrinsic forces exerted on the matrix mechanically remodel an electrospun scaffold throughout tissue development. Techniques used to measure and visualize these mechanical interactions are described. We provide a critical outlook on technological gaps that must be overcome to advance the ability to design, assess, and manipulate the mechanical environment in electrospun scaffolds toward constructs that may be successfully applied in tissue engineering and regenerative medicine. STATEMENT OF SIGNIFICANCE Tissue engineering requires design of scaffolds that interact with cells to promote tissue development. Electrospinning is a promising technique for fabricating fibrous, biomimetic scaffolds. Effects of electrospun matrix microstructure and biochemical properties on cell behavior have been extensively reviewed previously; here, we consider cell-matrix interaction from a mechanical perspective. Micromechanical properties as a driver of cell behavior has been well established in planar substrates, but more recently, many studies have provided new insights into mechanical interaction in fibrillar, electrospun environments. This review provides readers with an overview of how electrospun scaffold mechanics and cell behavior work in a dynamic feedback loop to drive tissue development, and discusses opportunities for improved design of mechanical environments that are conducive to tissue development.
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145
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Muhamed I, Chowdhury F, Maruthamuthu V. Biophysical Tools to Study Cellular Mechanotransduction. Bioengineering (Basel) 2017; 4:E12. [PMID: 28952491 PMCID: PMC5590431 DOI: 10.3390/bioengineering4010012] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 01/30/2017] [Accepted: 02/02/2017] [Indexed: 01/25/2023] Open
Abstract
The cell membrane is the interface that volumetrically isolates cellular components from the cell's environment. Proteins embedded within and on the membrane have varied biological functions: reception of external biochemical signals, as membrane channels, amplification and regulation of chemical signals through secondary messenger molecules, controlled exocytosis, endocytosis, phagocytosis, organized recruitment and sequestration of cytosolic complex proteins, cell division processes, organization of the cytoskeleton and more. The membrane's bioelectrical role is enabled by the physiologically controlled release and accumulation of electrochemical potential modulating molecules across the membrane through specialized ion channels (e.g., Na⁺, Ca2+, K⁺ channels). The membrane's biomechanical functions include sensing external forces and/or the rigidity of the external environment through force transmission, specific conformational changes and/or signaling through mechanoreceptors (e.g., platelet endothelial cell adhesion molecule (PECAM), vascular endothelial (VE)-cadherin, epithelial (E)-cadherin, integrin) embedded in the membrane. Certain mechanical stimulations through specific receptor complexes induce electrical and/or chemical impulses in cells and propagate across cells and tissues. These biomechanical sensory and biochemical responses have profound implications in normal physiology and disease. Here, we discuss the tools that facilitate the understanding of mechanosensitive adhesion receptors. This article is structured to provide a broad biochemical and mechanobiology background to introduce a freshman mechano-biologist to the field of mechanotransduction, with deeper study enabled by many of the references cited herein.
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Affiliation(s)
- Ismaeel Muhamed
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Raleigh, NC 27695, USA.
| | - Farhan Chowdhury
- Department of Mechanical Engineering and Energy Processes, Southern Illinois University Carbondale, Carbondale, IL 62901, USA.
| | - Venkat Maruthamuthu
- Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, VA 23529, USA.
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146
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Gross W, Kress H. Simultaneous measurement of the Young's modulus and the Poisson ratio of thin elastic layers. SOFT MATTER 2017; 13:1048-1055. [PMID: 28094390 DOI: 10.1039/c6sm02470j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The behavior of cells and tissue is greatly influenced by the mechanical properties of their environment. For studies on the interactions between cells and soft matrices, especially those applying traction force microscopy the characterization of the mechanical properties of thin substrate layers is essential. Various techniques to measure the elastic modulus are available. Methods to accurately measure the Poisson ratio of such substrates are rare and often imply either a combination of multiple techniques or additional equipment which is not needed for the actual biological studies. Here we describe a novel technique to measure both parameters, the Youngs's modulus and the Poisson ratio in a single experiment. The technique requires only a standard inverted epifluorescence microscope. As a model system, we chose cross-linked polyacrylamide and poly-N-isopropylacrylamide hydrogels which are known to obey Hooke's law. We place millimeter-sized steel spheres on the substrates which indent the surface. The data are evaluated using a previously published model which takes finite thickness effects of the substrate layer into account. We demonstrate experimentally for the first time that the application of the model allows the simultaneous determination of both the Young's modulus and the Poisson ratio. Since the method is easy to adapt and comes without the need of special equipment, we envision the technique to become a standard tool for the characterization of substrates for a wide range of investigations of cell and tissue behavior in various mechanical environments as well as other samples, including biological materials.
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Affiliation(s)
- Wolfgang Gross
- Department of Physics, University of Bayreuth, Bayreuth, Germany.
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147
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High-resolution traction force microscopy on small focal adhesions - improved accuracy through optimal marker distribution and optical flow tracking. Sci Rep 2017; 7:41633. [PMID: 28164999 PMCID: PMC5292691 DOI: 10.1038/srep41633] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 12/22/2016] [Indexed: 12/04/2022] Open
Abstract
The accurate determination of cellular forces using Traction Force Microscopy at increasingly small focal attachments to the extracellular environment presents an important yet substantial technical challenge. In these measurements, uncertainty regarding accuracy is prominent since experimental calibration frameworks at this size scale are fraught with errors – denying a gold standard against which accuracy of TFM methods can be judged. Therefore, we have developed a simulation platform for generating synthetic traction images that can be used as a benchmark to quantify the influence of critical experimental parameters and the associated errors. Using this approach, we show that TFM accuracy can be improved >35% compared to the standard approach by placing fluorescent beads as densely and closely as possible to the site of applied traction. Moreover, we use the platform to test tracking algorithms based on optical flow that measure deformation directly at the beads and show that these can dramatically outperform classical particle image velocimetry algorithms in terms of noise sensitivity and error. We then report how optimized experimental and numerical strategy can improve traction map accuracy, and further provide the best available benchmark to date for defining practical limits to TFM accuracy as a function of focal adhesion size.
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148
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Wilen L. Acoustic resonance spectroscopy of soft solids. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2017; 141:956. [PMID: 28253639 DOI: 10.1121/1.4976058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
An acoustic resonance apparatus for probing mechanical properties of materials with soft to moderate hardness (elastic modulus <5 GPa) is described. The technique employs stereo phono-needle transducers suitable for measurements in the range from 40 Hz to 40 kHz which are very weakly perturbing to the sample and have polarized excitation and detection. Identification of the normal modes is facilitated by the polarization information, and the technique is applicable to materials ranging from soft elastomers to hard plastics. The experimental setup is described in detail, and the utility of the technique is showcased in three example applications.
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Affiliation(s)
- Larry Wilen
- Department of Mechanical Engineering and Center for Engineering Innovation and Design, School of Engineering and Applied Sciences, Yale University, New Haven, Connecticut 06510, USA
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149
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Shimomura S, Matsuno H, Sanada K, Tanaka K. Cell adhesion on glassy scaffolds with a different mechanical response. J Mater Chem B 2017; 5:714-719. [PMID: 32263839 DOI: 10.1039/c6tb02617f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
L929 mouse fibroblast cells were cultured on bilayer films composed of a glassy poly(methyl methacrylate) (PMMA) on a rubbery polyisoprene. When the thickness of the upper PMMA film fell short of a threshold value of 50 nm, the adhesion of fibroblasts on it was remarkably suppressed. A possible explanation is that the surface of a bilayer with an ultrathin PMMA layer apparently becomes softer due to the manifestation of a mechanical response from the rubbery layer underneath. Finite element analysis shows that the shear stress at the bilayer surface induced by traction force of the attached cells is dependent on the PMMA thickness, similar to the cell adhesion behavior. These results make it clear that fibroblasts can sense the surface stiffness of polymers with a modulus even on the order of MPa.
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150
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Álvarez-González B, Zhang S, Gómez-González M, Meili R, Firtel RA, Lasheras JC, Del Álamo JC. Two-Layer Elastographic 3-D Traction Force Microscopy. Sci Rep 2017; 7:39315. [PMID: 28074837 PMCID: PMC5225457 DOI: 10.1038/srep39315] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 11/15/2016] [Indexed: 01/16/2023] Open
Abstract
Cellular traction force microscopy (TFM) requires knowledge of the mechanical properties of the substratum where the cells adhere to calculate cell-generated forces from measurements of substratum deformation. Polymer-based hydrogels are broadly used for TFM due to their linearly elastic behavior in the range of measured deformations. However, the calculated stresses, particularly their spatial patterns, can be highly sensitive to the substratum's Poisson's ratio. We present two-layer elastographic TFM (2LETFM), a method that allows for simultaneously measuring the Poisson's ratio of the substratum while also determining the cell-generated forces. The new method exploits the analytical solution of the elastostatic equation and deformation measurements from two layers of the substratum. We perform an in silico analysis of 2LETFM concluding that this technique is robust with respect to TFM experimental parameters, and remains accurate even for noisy measurement data. We also provide experimental proof of principle of 2LETFM by simultaneously measuring the stresses exerted by migrating Physarum amoeboae on the surface of polyacrylamide substrata, and the Poisson's ratio of the substrata. The 2LETFM method could be generalized to concurrently determine the mechanical properties and cell-generated forces in more physiologically relevant extracellular environments, opening new possibilities to study cell-matrix interactions.
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Affiliation(s)
- Begoña Álvarez-González
- Division of Cell and Developmental Biology, University of California, San Diego.,Department of Mechanical and Aerospace Engineeing, University of California, San Diego
| | - Shun Zhang
- Department of Mechanical and Aerospace Engineeing, University of California, San Diego
| | - Manuel Gómez-González
- Department of Mechanical and Aerospace Engineeing, University of California, San Diego
| | - Ruedi Meili
- Division of Cell and Developmental Biology, University of California, San Diego.,Department of Mechanical and Aerospace Engineeing, University of California, San Diego
| | - Richard A Firtel
- Division of Cell and Developmental Biology, University of California, San Diego
| | - Juan C Lasheras
- Department of Mechanical and Aerospace Engineeing, University of California, San Diego.,Department of Bioengineering, University of California, San Diego.,Center for Medical Devices and Instrumentation, Institute for Engineering in Medicine, University of California, San Diego
| | - Juan C Del Álamo
- Department of Mechanical and Aerospace Engineeing, University of California, San Diego.,Center for Medical Devices and Instrumentation, Institute for Engineering in Medicine, University of California, San Diego
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