101
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Seriani R, de Souza CEC, Krempel PG, Frias DP, Matsuda M, Correia AT, Ferreira MZJ, Alencar AM, Negri EM, Saldiva PHN, Mauad T, Macchione M. Human bronchial epithelial cells exposed in vitro to diesel exhaust particles exhibit alterations in cell rheology and cytotoxicity associated with decrease in antioxidant defenses and imbalance in pro- and anti-apoptotic gene expression. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:9862-9870. [PMID: 26856867 DOI: 10.1007/s11356-016-6228-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 02/01/2016] [Indexed: 06/05/2023]
Abstract
Diesel exhaust particles (DEPs) from diesel engines produce adverse alterations in cells of the airways by activating intracellular signaling pathways and apoptotic gene overexpression, and also by influencing metabolism and cytoskeleton changes. This study used human bronchial epithelium cells (BEAS-2B) in culture and evaluates their exposure to DEPs (15ug/mL for 1 and 2 h) in order to determine changes to cell rheology (viscoelasticity) and gene expression of the enzymes involved in oxidative stress, apoptosis, and cytotoxicity. BEAS-2B cells exposed to DEPs were found to have a significant loss in stiffness, membrane stability, and mitochondrial activity. The genes involved in apoptosis [B cell lymphoma 2 (BCL-2 and caspase-3)] presented inversely proportional expressions (p = 0.05, p = 0.01, respectively), low expression of the genes involved in antioxidant responses [SOD1 (superoxide dismutase 1); SOD2 (superoxide dismutase 2), and GPx (glutathione peroxidase) (p = 0.01)], along with an increase in cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1) (p = 0.01). These results suggest that alterations in cell rheology and cytotoxicity could be associated with oxidative stress and imbalance between pro- and anti-apoptotic genes.
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Affiliation(s)
- Robson Seriani
- Laboratory of Experimental Air Pollution (LIM05), Department of Pathology, School of Medicine, University of São Paulo, Av. Dr. Arnaldo 455, 1°andar, sala 1150, Cerqueira César, São Paulo, SP, CEP:01246-903, Brazil.
- FAM - Faculdades das Américas, Rua Augusta, 1508, 3°andar, São Paulo, SP, 01304-001, Brazil.
| | - Claudia Emanuele Carvalho de Souza
- Laboratory of Chronopharmacology, Department of Physiology, Institute of Bioscience, University of São Paulo, Rua do Matão - travessa 14, Cidade Universitária, 05508900, São Paulo, SP, Brazil
| | - Paloma Gava Krempel
- Laboratory for Investigations in Ophthalmology (LIM-33), University of São Paulo Medical School São Paulo, Dr. Arnaldo 455, 5°andar, Cerqueira César, São Paulo, SP, CEP:01246-903, Brazil
| | - Daniela Perroni Frias
- Laboratory of Experimental Air Pollution (LIM05), Department of Pathology, School of Medicine, University of São Paulo, Av. Dr. Arnaldo 455, 1°andar, sala 1150, Cerqueira César, São Paulo, SP, CEP:01246-903, Brazil
| | - Monique Matsuda
- Laboratory for Investigations in Ophthalmology (LIM-33), University of São Paulo Medical School São Paulo, Dr. Arnaldo 455, 5°andar, Cerqueira César, São Paulo, SP, CEP:01246-903, Brazil
| | - Aristides Tadeu Correia
- Heart Institute (InCor), Department of Cardiopulmonology, University of São Paulo Medical School, Av. Dr. Enéas de Carvalho Aguiar, 44, Cerqueira Cesar, 05403-000, Sao Paulo, SP, Brazil
| | - Márcia Zotti Justo Ferreira
- Laboratory of Microrheology and Molecular Physiology, Institute of Physics, University of São Paulo, Rua do Matão, Travessa R Número 187, Cidade Universitária, 05508-090, Sao Paulo, SP, Brazil
| | - Adriano Mesquita Alencar
- Laboratory of Microrheology and Molecular Physiology, Institute of Physics, University of São Paulo, Rua do Matão, Travessa R Número 187, Cidade Universitária, 05508-090, Sao Paulo, SP, Brazil
| | - Elnara Marcia Negri
- Laboratory of Experimental Air Pollution (LIM05), Department of Pathology, School of Medicine, University of São Paulo, Av. Dr. Arnaldo 455, 1°andar, sala 1150, Cerqueira César, São Paulo, SP, CEP:01246-903, Brazil
| | - Paulo Hilário Nascimento Saldiva
- Laboratory of Experimental Air Pollution (LIM05), Department of Pathology, School of Medicine, University of São Paulo, Av. Dr. Arnaldo 455, 1°andar, sala 1150, Cerqueira César, São Paulo, SP, CEP:01246-903, Brazil
| | - Thais Mauad
- Laboratory of Experimental Air Pollution (LIM05), Department of Pathology, School of Medicine, University of São Paulo, Av. Dr. Arnaldo 455, 1°andar, sala 1150, Cerqueira César, São Paulo, SP, CEP:01246-903, Brazil
| | - Mariangela Macchione
- Laboratory of Experimental Air Pollution (LIM05), Department of Pathology, School of Medicine, University of São Paulo, Av. Dr. Arnaldo 455, 1°andar, sala 1150, Cerqueira César, São Paulo, SP, CEP:01246-903, Brazil
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102
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Atomic force microscopy indentation and inverse analysis for non-linear viscoelastic identification of breast cancer cells. Math Biosci 2016; 277:77-88. [PMID: 27107978 DOI: 10.1016/j.mbs.2016.03.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2016] [Revised: 03/27/2016] [Accepted: 03/31/2016] [Indexed: 12/20/2022]
Abstract
Breast cancer cells (MCF-7 and MCF-10A) are studied through indentation with spherical borosilicate glass particles in atomic force microscopy (AFM) contact mode in fluid. Their mechanical properties are obtained by analyzing the recorded reaction force-time response. The analysis is based on comparing experimental data with predictions from finite element (FE) simulation. Here, FE modeling is employed to simulate the AFM indentation experiment which is neither a displacement nor a force controlled test. This approach is expected to overcome many underlying problems of the widely used models such as Hertz contact model due to its capability to capture the contact behaviors between the spherical indentor and the cell, account for cell geometry, and incorporate with large strain theory. In this work, a non-linear viscoelastic (NLV) model in which the viscoelastic part is described by Prony series terms is used for the constitutive model of the cells. The time-dependent material parameters are extracted through an inverse analysis with the use of a surrogate model based on a Kriging estimator. The purpose is to automatically extract the NLV properties of the cells with a more efficient process compared to the iterative inverse technique that has been mostly applied in the literature. The method also allows the use of FE modeling in the analysis of a large amount of experimental data. The NLV parameters are compared between MCF-7 and MCF-10A and MCF-10A treated and untreated with the drug Cytochalasin D to examine the possibility of using relaxation properties as biomarkers for distinguishing these types of breast cancer cells. The comparisons indicate that malignant cells (MCF-7) are softer and exhibit more relaxation than benign cells (MCF-10A). Disrupting the cytoskeleton using the drug Cytochalasin D also results in a larger amount of relaxation in the cell's response. In addition, relaxation properties indicate larger differences as compared to the elastic moduli like instantaneous shear modulus. These results may be useful for disease diagnosing purposes.
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103
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Chaudhuri A, Chaudhuri D. Forced desorption of semiflexible polymers, adsorbed and driven by molecular motors. SOFT MATTER 2016; 12:2157-2165. [PMID: 26750537 DOI: 10.1039/c5sm02574e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We formulate and characterize a model to describe the dynamics of semiflexible polymers in the presence of activity due to motor proteins attached irreversibly to a substrate, and a transverse pulling force acting on one end of the filament. The stochastic binding-unbinding of the motor proteins and their ability to move along the polymer generate active forces. As the pulling force reaches a threshold value, the polymer eventually desorbs from the substrate. Performing underdamped Langevin dynamics simulation of the polymer, and with stochastic motor activity, we obtain desorption phase diagrams. The correlation time for fluctuations in the desorbed fraction increases as one approaches complete desorption, captured quantitatively by a power law spectral density. We present theoretical analysis of the phase diagram using mean field approximations in the weakly bending limit of the polymer and performing linear stability analysis. This predicts an increase in the desorption force with the polymer bending rigidity, active velocity and processivity of the motor proteins to capture the main features of the simulation results.
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Affiliation(s)
- Abhishek Chaudhuri
- Indian Institute of Science Education and Research Mohali, Knowledge City, Sector 81, SAS Nagar - 140306, Punjab, India.
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104
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Yoon AR, Stasinopoulos I, Kim JH, Yong HM, Kilic O, Wirtz D, Bhujwalla ZM, An SS. COX-2 dependent regulation of mechanotransduction in human breast cancer cells. Cancer Biol Ther 2016; 16:430-7. [PMID: 25701047 DOI: 10.1080/15384047.2014.1003004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
The ability of living cells to exert physical forces upon their surrounding is a necessary prerequisite for diverse biological processes, such as local cellular migrations in wound healing to metastatic-invasion of cancer. How forces are coopted in metastasis has remained unclear, however, because the mechanical interplay between cancer cells and the various stromal components has not been experimentally accessible. Current dogma implicates inflammation in these mechanical processes. Using Fourier transform traction microscopy, we measured the force-generating capacity of human breast cancer cells occupying a spectrum of invasiveness as well as basal and inducible COX-2 expression (MCF-7<SUM-149<MDA-MB-231). Compared with non-invasive MCF-7 and moderately-invasive SUM-149, poorly-differentiated MDA-MB-231 cells showed increased cellular dispersion on collagen matrix that was accompanied by emergent distribution of contractile stresses at the interface between the adherent cell and its substrate, defined herein as the traction field. In metastatic MDA-MB-231 cells, the local tractions were precisely tuned to the surrounding matrix rigidity in a physiologic range with the concomitant expression of mechanosensitive integrin β1. These discrete responses at the single-cell resolution were correlated with PGE2 secretion and were ablated by shRNA-mediated knockdown of COX-2. Both COX-2-silenced and COX-2-expressing cells expressed EP2 and EP4 receptors, but not EP1 and EP3. Exogenous addition of PGE2 increased cell tractions and stiffened the underlying cytoskeletal network. To our knowledge this is the first report linking the expression of COX-2 with mechanotransduction of human breast cancer cells, and the regulation of COX-2-PGE2-EP signaling with physical properties of the tumor microenvironment. Drug treatments aimed at reducing this mechanical interplay may have therapeutic potential in the treatment of breast cancer.
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Affiliation(s)
- A-Rum Yoon
- a Environmental Health Science ; Johns Hopkins Bloomberg School of Public Health ; Baltimore , MD USA
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105
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Kurniawan NA, Chaudhuri PK, Lim CT. Mechanobiology of cell migration in the context of dynamic two-way cell-matrix interactions. J Biomech 2015; 49:1355-1368. [PMID: 26747513 DOI: 10.1016/j.jbiomech.2015.12.023] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 11/30/2015] [Accepted: 12/14/2015] [Indexed: 12/31/2022]
Abstract
Migration of cells is integral in various physiological processes in all facets of life. These range from embryonic development, morphogenesis, and wound healing, to disease pathology such as cancer metastasis. While cell migratory behavior has been traditionally studied using simple assays on culture dishes, in recent years it has been increasingly realized that the physical, mechanical, and chemical aspects of the matrix are key determinants of the migration mechanism. In this paper, we will describe the mechanobiological changes that accompany the dynamic cell-matrix interactions during cell migration. Furthermore, we will review what is to date known about how these changes feed back to the dynamics and biomechanical properties of the cell and the matrix. Elucidating the role of these intimate cell-matrix interactions will provide not only a better multi-scale understanding of cell motility in its physiological context, but also a more holistic perspective for designing approaches to regulate cell behavior.
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Affiliation(s)
- Nicholas A Kurniawan
- Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven, The Netherlands; Department of Systems Biophysics, FOM Institute AMOLF, Amsterdam, The Netherlands.
| | | | - Chwee Teck Lim
- Mechanobiology Institute, National University of Singapore, Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore.
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106
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Abstract
Vascular smooth muscle (VSM; see Table 1 for a list of abbreviations) is a heterogeneous biomaterial comprised of cells and extracellular matrix. By surrounding tubes of endothelial cells, VSM forms a regulated network, the vasculature, through which oxygenated blood supplies specialized organs, permitting the development of large multicellular organisms. VSM cells, the engine of the vasculature, house a set of regulated nanomotors that permit rapid stress-development, sustained stress-maintenance and vessel constriction. Viscoelastic materials within, surrounding and attached to VSM cells, comprised largely of polymeric proteins with complex mechanical characteristics, assist the engine with countering loads imposed by the heart pump, and with control of relengthening after constriction. The complexity of this smart material can be reduced by classical mechanical studies combined with circuit modeling using spring and dashpot elements. Evaluation of the mechanical characteristics of VSM requires a more complete understanding of the mechanics and regulation of its biochemical parts, and ultimately, an understanding of how these parts work together to form the machinery of the vascular tree. Current molecular studies provide detailed mechanical data about single polymeric molecules, revealing viscoelasticity and plasticity at the protein domain level, the unique biological slip-catch bond, and a regulated two-step actomyosin power stroke. At the tissue level, new insight into acutely dynamic stress-strain behavior reveals smooth muscle to exhibit adaptive plasticity. At its core, physiology aims to describe the complex interactions of molecular systems, clarifying structure-function relationships and regulation of biological machines. The intent of this review is to provide a comprehensive presentation of one biomachine, VSM.
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Affiliation(s)
- Paul H Ratz
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
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107
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Vincent R, Bazellières E, Pérez-González C, Uroz M, Serra-Picamal X, Trepat X. Active Tensile Modulus of an Epithelial Monolayer. PHYSICAL REVIEW LETTERS 2015; 115:248103. [PMID: 26705659 DOI: 10.1103/physrevlett.115.248103] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Indexed: 06/05/2023]
Abstract
A general trait of cell monolayers is their ability to exert contractile stresses on their surroundings. The scaling laws that link such contractile stresses with the size and geometry of constituent cells remain largely unknown. In this Letter, we show that the active tension of an epithelial monolayer scales linearly with the size of the constituent cells, a surprisingly simple relationship. The slope of this relationship defines an active tensile modulus, which depends on the concentration of myosin and spans more than 2 orders of magnitude across cell types and molecular perturbations.
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Affiliation(s)
- Romaric Vincent
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
| | - Elsa Bazellières
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
| | | | - Marina Uroz
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
| | | | - Xavier Trepat
- Institut Català de Recerca i Estudis Avançats (ICREA), Barcelona 08028, Spain and Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
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108
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Chen ZY, Wang PW, Shieh DB, Chiu KY, Liou YM. Involvement of gelsolin in TGF-beta 1 induced epithelial to mesenchymal transition in breast cancer cells. J Biomed Sci 2015; 22:90. [PMID: 26482896 PMCID: PMC4615330 DOI: 10.1186/s12929-015-0197-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 09/29/2015] [Indexed: 11/21/2022] Open
Abstract
Background Increasing evidence suggests that transforming growth factor-beta 1 (TGF-β1) triggers epithelial to mesenchymal transition (EMT) and facilitates breast cancer stem cell differentiation. Gelsolin (GSN) is a ubiquitous actin filament-severing protein. However, the relationship between the expression level of GSN and the TGF-β signaling for EMT progression in breast cancer cells is not clear. Results TGF-β1 acted on MDA-MB231 breast cancer cells by decreasing cell proliferation, changing cell morphology to a fibroblast-like shape, increasing expressions for CD44 and GSN, and increasing EMT expression and cell migration/invasion. Study with GSN overexpression (GSN op) in both MDA-MB231 and MCF-7 cells demonstrated that increased GSN expression resulted in alterations of cell proliferation and cell cycle progression, modification of the actin filament assembly associated with altering cell surface elasticity and cell detachment in these breast cancer cells. In addition, increased cell migration was found in GSN op MDA-MB231 cells. Studies with GSN op and silencing by small interfering RNA verified that GSN could modulate the expression of vimentin. Sorted by flow cytometry, TGF-β1 increased subpopulation of CD44+/CD22- cells increasing their expressions for GSN, Nanog, Sox2, Oct4, N-cadherin, and vimentin but decreasing the E-cadherin expression. Methylation specific PCR analysis revealed that TGF-β1 decreased 50 % methylation but increased 3-fold unmethylation on the GSN promoter in CD44+/CD22- cells. Two DNA methyltransferases, DNMT1and DNMT3B were also inhibited by TGF-β1. Conclusions TGF-β1 induced epigenetic modification of GSN could alter the EMT process in breast cancer cells.
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Affiliation(s)
- Zhi-Yuan Chen
- Department of Life Sciences, National Chung-Hsing University, Taichung, 40227, Taiwan.
| | - Pei-Wen Wang
- Institute of Basic Medical Sciences, National Cheng Kung University, Tainan, 701, Taiwan.
| | - Dar-Bin Shieh
- Institute of Basic Medical Sciences, National Cheng Kung University, Tainan, 701, Taiwan. .,Institute of Oral Medicine, National Cheng Kung University, Tainan, 701, Taiwan.
| | - Kuan-Ying Chiu
- Department of Life Sciences, National Chung-Hsing University, Taichung, 40227, Taiwan.
| | - Ying-Ming Liou
- Department of Life Sciences, National Chung-Hsing University, Taichung, 40227, Taiwan. .,Rong Hsing Research Center for Translational Medicine, National Chung Hsing University, Taichung, 40227, Taiwan.
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109
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Cell Volume Fluctuations in MDCK Monolayers. Biophys J 2015; 108:247-50. [PMID: 25606673 DOI: 10.1016/j.bpj.2014.11.1856] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 11/07/2014] [Accepted: 11/14/2014] [Indexed: 12/13/2022] Open
Abstract
Cells moving collectively in tissues constitute a form of active matter, in which collective motion depends strongly on driven fluctuations at the single-cell scale. Fluctuations in cell area and number density are often seen in monolayers, yet their role in collective migration is not known. Here we study density fluctuations at the single- and multicell level, finding that single-cell volumes oscillate with a timescale of 4 h and an amplitude of 20%; the timescale and amplitude are found to depend on cytoskeletal activity. At the multicellular scale, density fluctuations violate the central limit theorem, highlighting the role of nonequilibrium driving forces in multicellular density fluctuations.
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110
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Kuo YC, Chang TH, Hsu WT, Zhou J, Lee HH, Hui-Chun Ho J, Chien S, Lee OKS, Kuang-Sheng O. Oscillatory shear stress mediates directional reorganization of actin cytoskeleton and alters differentiation propensity of mesenchymal stem cells. Stem Cells 2015; 33:429-42. [PMID: 25302937 DOI: 10.1002/stem.1860] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 07/17/2014] [Accepted: 07/23/2014] [Indexed: 01/06/2023]
Abstract
Shear stress stimuli differentially regulate cellular functions based on the pattern, magnitude as well as duration of the flow. Shear stress can modify intracellular kinase activities and cytoskeleton reorganization to result in changes of cell behavior. Mesenchymal stem cells (MSCs) are mechano-sensitive cells, but little is known about the effects of oscillatory shear stress (OS). In this study, we demonstrate that OS of 0.5 ± 4 dyn/cm(2) induces directional reorganization of F-actin to mediate the fate choice of MSCs through the regulation of β-catenin. We also found that intercellular junction molecules are the predominant mechanosensors of OS in MSCs to deliver the signals that result in directional rearrangement of F-actin, as well as the increase of phosphorylated β-catenin (pβ-catenin) after 30 minutes of OS stimulation. Depolymerization of F-actin and increase in pβ-catenin also lead to the upregulation of Wnt inhibitory factors sclerostin and dickkopf-1. Inhibition of β-catenin/Wnt signaling pathway is accompanied by the upregulation of sex determining region Y-box2 and NANOG to control self-renewal. In conclusion, the reorganization of actin cytoskeleton and increase in β-catenin phosphorylation triggered by OS regulate the expression of pluripotency genes via the β-catenin/Wnt signaling pathway to differentially direct fate choices of MSCs at different time points. Results from this study have provided new information regarding how MSCs respond to mechanical cues from their microenvironment in a time-dependent fashion, and such biophysical stimuli could be administered to guide the fate and differentiation of stem cells in addition to conventional biochemical approaches.
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Affiliation(s)
- Yi-Chun Kuo
- Stem Cell Research Center, National Yang-Ming University, Taipei, Taiwan, Republic of China; Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China
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111
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Fusco S, Panzetta V, Embrione V, Netti PA. Crosstalk between focal adhesions and material mechanical properties governs cell mechanics and functions. Acta Biomater 2015; 23:63-71. [PMID: 26004223 DOI: 10.1016/j.actbio.2015.05.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 04/28/2015] [Accepted: 05/10/2015] [Indexed: 12/31/2022]
Abstract
Mechanical properties of materials strongly influence cell fate and functions. Focal adhesions are involved in the extremely important processes of mechanosensing and mechanotransduction. To address the relationship between the mechanical properties of cell substrates, focal adhesion/cytoskeleton assembly and cell functions, we investigated the behavior of NIH/3T3 cells over a wide range of stiffness (3-1000kPa) using two of the most common synthetic polymers for cell cultures: polyacrylamide and polydimethylsiloxane. An overlapping stiffness region was created between them to compare focal adhesion characteristics and cell functions, taking into account their different time-dependent behavior. Indeed, from a rheological point of view, polyacrylamide behaves like a strong gel (elastically), whereas polydimethylsiloxane like a viscoelastic solid. First, focal adhesion characteristics and dynamics were addressed in terms of material stiffness, then cell spreading area, migration rate and cell mechanical properties were correlated with focal adhesion size and assembly. Focal adhesion size was found to increase in the whole range of stiffness and to be in agreement in the overlapping rigidity region for the investigated materials. Cell mechanics directly correlated with focal adhesion lengths, whereas migration rate followed an inverse correlation. Cell spreading correlated with the substrate stiffness on polyacrylamide hydrogel, while no specific trend was found on polydimethylsiloxane. Substrate mechanics can be considered as a key physical cue that regulates focal adhesion assembly, which in turn governs important cellular properties and functions.
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112
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Ueda M, Sasa SI. Replica Symmetry Breaking in Trajectories of a Driven Brownian Particle. PHYSICAL REVIEW LETTERS 2015; 115:080605. [PMID: 26340175 DOI: 10.1103/physrevlett.115.080605] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Indexed: 06/05/2023]
Abstract
We study a Brownian particle passively driven by a field obeying the noisy Burgers' equation. We demonstrate that the system exhibits replica symmetry breaking in the path ensemble with the initial position of the particle being fixed. The key step of the proof is that the path ensemble with a modified boundary condition can be exactly mapped onto the canonical ensemble of directed polymers.
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Affiliation(s)
- Masahiko Ueda
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Shin-ichi Sasa
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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113
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De Rossi MC, De Rossi ME, Sued M, Rodríguez D, Bruno L, Levi V. Asymmetries in kinesin-2 and cytoplasmic dynein contributions to melanosome transport. FEBS Lett 2015; 589:2763-8. [DOI: 10.1016/j.febslet.2015.07.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 07/17/2015] [Accepted: 07/20/2015] [Indexed: 10/23/2022]
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114
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Plaza GR, Uyeda TQP, Mirzaei Z, Simmons CA. Study of the influence of actin-binding proteins using linear analyses of cell deformability. SOFT MATTER 2015; 11:5435-5446. [PMID: 26059185 DOI: 10.1039/c5sm00125k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The actin cytoskeleton plays a key role in the deformability of the cell and in mechanosensing. Here we analyze the contributions of three major actin cross-linking proteins, myosin II, α-actinin and filamin, to cell deformability, by using micropipette aspiration of Dictyostelium cells. We examine the applicability of three simple mechanical models: for small deformation, linear viscoelasticity and drop of liquid with a tense cortex; and for large deformation, a Newtonian viscous fluid. For these models, we have derived linearized equations and we provide a novel, straightforward methodology to analyze the experiments. This methodology allowed us to differentiate the effects of the cross-linking proteins in the different regimes of deformation. Our results confirm some previous observations and suggest important relations between the molecular characteristics of the actin-binding proteins and the cell behavior: the effect of myosin is explained in terms of the relation between the lifetime of the bond to actin and the resistive force; the presence of α-actinin obstructs the deformation of the cytoskeleton, presumably mainly due to the higher molecular stiffness and to the lower dissociation rate constants; and filamin contributes critically to the global connectivity of the network, possibly by rapidly turning over cross-links during the remodeling of the cytoskeletal network, thanks to the higher rate constants, flexibility and larger size. The results suggest a sophisticated relationship between the expression levels of actin-binding proteins, deformability and mechanosensing.
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Affiliation(s)
- Gustavo R Plaza
- Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain.
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115
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Lee CF. Thermal breakage of a semiflexible polymer: breakage profile and rate. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:275101. [PMID: 26061714 DOI: 10.1088/0953-8984/27/27/275101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Understanding fluctuation-induced breakages in polymers has important implications for basic and applied sciences. Here I present for the first time an analytical treatment of the thermal breakage problem of a semi-flexible polymer model that is asymptotically exact in the low temperature and high friction limits. Specifically, I provide analytical expressions for the breakage propensity and rate, and discuss the generalities of the results and their relevance to biopolymers. This work is fundamental to our understanding of the kinetics of living polymerisation.
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Affiliation(s)
- Chiu Fan Lee
- Department of Bioengineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
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116
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Sha B, Gao W, Cui X, Wang L, Xu F. The potential health challenges of TiO2nanomaterials. J Appl Toxicol 2015; 35:1086-101. [DOI: 10.1002/jat.3193] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Revised: 05/10/2015] [Accepted: 05/10/2015] [Indexed: 01/09/2023]
Affiliation(s)
- Baoyong Sha
- School of Basic Medical Science; Xi'an Medical University; Xi'an 710021 China
- Bioinspired Engineering & Biomechanics Center (BEBC); Xi'an Jiaotong University; Xi'an 710049 China
| | - Wei Gao
- Department of Anesthesiology; the First Affiliated Hospital of Xi'an Jiaotong University Health Science Center; Xi'an 710061 China
| | - Xingye Cui
- Bioinspired Engineering & Biomechanics Center (BEBC); Xi'an Jiaotong University; Xi'an 710049 China
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology; Xi'an Jiaotong University; Xi'an 710049 China
| | - Lin Wang
- Bioinspired Engineering & Biomechanics Center (BEBC); Xi'an Jiaotong University; Xi'an 710049 China
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology; Xi'an Jiaotong University; Xi'an 710049 China
| | - Feng Xu
- Bioinspired Engineering & Biomechanics Center (BEBC); Xi'an Jiaotong University; Xi'an 710049 China
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology; Xi'an Jiaotong University; Xi'an 710049 China
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117
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Ben-Isaac E, Fodor É, Visco P, van Wijland F, Gov NS. Modeling the dynamics of a tracer particle in an elastic active gel. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:012716. [PMID: 26274211 DOI: 10.1103/physreve.92.012716] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Indexed: 06/04/2023]
Abstract
The internal dynamics of active gels both in artificial (in vitro) model systems and inside the cytoskeleton of living cells has been extensively studied with experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct nonthermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures," and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments and provide physical interpretation of existing observations, as well as predictions for future studies.
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Affiliation(s)
- E Ben-Isaac
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - É Fodor
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
| | - P Visco
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
| | - F van Wijland
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
| | - Nir S Gov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
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118
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Metzner C, Mark C, Steinwachs J, Lautscham L, Stadler F, Fabry B. Superstatistical analysis and modelling of heterogeneous random walks. Nat Commun 2015; 6:7516. [PMID: 26108639 PMCID: PMC4491834 DOI: 10.1038/ncomms8516] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 05/16/2015] [Indexed: 01/21/2023] Open
Abstract
Stochastic time series are ubiquitous in nature. In particular, random walks with time-varying statistical properties are found in many scientific disciplines. Here we present a superstatistical approach to analyse and model such heterogeneous random walks. The time-dependent statistical parameters can be extracted from measured random walk trajectories with a Bayesian method of sequential inference. The distributions and correlations of these parameters reveal subtle features of the random process that are not captured by conventional measures, such as the mean-squared displacement or the step width distribution. We apply our new approach to migration trajectories of tumour cells in two and three dimensions, and demonstrate the superior ability of the superstatistical method to discriminate cell migration strategies in different environments. Finally, we show how the resulting insights can be used to design simple and meaningful models of the underlying random processes. Conventional methods to quantify the migratory behaviour of cells assume that underlying parameters are constant. Mark et al. apply a superstatistical approach to extract time-dependent parameters of motile cells, and demonstrate an enhanced ability to distinguish between different migration strategies.
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Affiliation(s)
- Claus Metzner
- Department of Physics, Biophysics Group, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen 91052, Germany
| | - Christoph Mark
- Department of Physics, Biophysics Group, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen 91052, Germany
| | - Julian Steinwachs
- Department of Physics, Biophysics Group, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen 91052, Germany
| | - Lena Lautscham
- Department of Physics, Biophysics Group, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen 91052, Germany
| | - Franz Stadler
- Department of Physics, Biophysics Group, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen 91052, Germany
| | - Ben Fabry
- Department of Physics, Biophysics Group, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen 91052, Germany
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119
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Fiocco D, Foffi G, Sastry S. Memory effects in schematic models of glasses subjected to oscillatory deformation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:194130. [PMID: 25923880 DOI: 10.1088/0953-8984/27/19/194130] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We consider two schematic models of glasses subjected to oscillatory shear deformation, motivated by the observations, in computer simulations of a model glass, of a nonequilibrium transition from a localized to a diffusive regime as the shear amplitude is increased, and of persistent memory effects in the localized regime. The first of these schematic models is the NK model, a spin model with disordered multi-spin interactions previously studied as a model for sheared amorphous solids. The second model, a transition matrix model, is an abstract formulation of the manner in which occupancy of local energy minima evolves under oscillatory deformation cycles. In both of these models, we find a behavior similar to that of an atomic model glass studied earlier. We discuss possible further extensions of the approaches outlined.
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Affiliation(s)
- Davide Fiocco
- Institute of Theoretical Physics (ITP), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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120
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Smelser AM, Macosko JC, O'Dell AP, Smyre S, Bonin K, Holzwarth G. Mechanical properties of normal versus cancerous breast cells. Biomech Model Mechanobiol 2015; 14:1335-47. [PMID: 25929519 DOI: 10.1007/s10237-015-0677-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Accepted: 04/04/2015] [Indexed: 12/21/2022]
Abstract
A cell's mechanical properties are important in determining its adhesion, migration, and response to the mechanical properties of its microenvironment and may help explain behavioral differences between normal and cancerous cells. Using fluorescently labeled peroxisomes as microrheological probes, the interior mechanical properties of normal breast cells were compared to a metastatic breast cell line, MDA-MB-231. To estimate the mechanical properties of cell cytoplasms from the motions of their peroxisomes, it was necessary to reduce the contribution of active cytoskeletal motions to peroxisome motion. This was done by treating the cells with blebbistatin, to inhibit myosin II, or with sodium azide and 2-deoxy-D-glucose, to reduce intracellular ATP. Using either treatment, the peroxisomes exhibited normal diffusion or subdiffusion, and their mean squared displacements (MSDs) showed that the MDA-MB-231 cells were significantly softer than normal cells. For these two cell types, peroxisome MSDs in treated and untreated cells converged at high frequencies, indicating that cytoskeletal structure was not altered by the drug treatment. The MSDs from ATP-depleted cells were analyzed by the generalized Stokes-Einstein relation to estimate the interior viscoelastic modulus G* and its components, the elastic shear modulus G' and viscous shear modulus G", at angular frequencies between 0.126 and 628 rad/s. These moduli are the material coefficients that enter into stress-strain relations and relaxation times in quantitative mechanical models such as the poroelastic model of the interior regions of cancerous and non-cancerous cells.
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Affiliation(s)
- Amanda M Smelser
- Department of Biochemistry and Molecular Biology, Wake Forest University School of Medicine, Winston-Salem, NC, 27157, USA
| | - Jed C Macosko
- Department of Biochemistry and Molecular Biology, Wake Forest University School of Medicine, Winston-Salem, NC, 27157, USA
- Department of Physics, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - Adam P O'Dell
- Department of Physics, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - Scott Smyre
- Department of Physics, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - Keith Bonin
- Department of Physics, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - George Holzwarth
- Department of Physics, Wake Forest University, Winston-Salem, NC, 27109, USA.
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121
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Shu R, Sun W, Liu X, Tong Z. Temperature dependence of aging kinetics of hectorite clay suspensions. J Colloid Interface Sci 2015; 444:132-40. [PMID: 25594804 DOI: 10.1016/j.jcis.2014.12.073] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 12/11/2014] [Accepted: 12/20/2014] [Indexed: 10/24/2022]
Abstract
The aging of salt-free hectorite suspensions with different concentrations (c(L)=2.9, 3.2 and 3.5 wt%) stored for 2 days or 4 days was studied by rheology at different temperatures. The evolution of storage and loss moduli G' and G″ during aging followed aging time-temperature superposition. The temperature dependence of the shift factor a(T), which reflected the aging kinetics, was interpreted by the reaction-limited colloidal aggregation (RLCA) mechanism with counterion condensation in calculating the double-layer interaction of the charged clay particles. Temperature dependence of the plateau modulus and yield stress of the suspension aged for 800 s was modeled with the soft glassy rheology (SGR) theory. The estimated noise temperature x indicated that the sample aged at higher temperature corresponded to a deeper quench in the nonergodic state. Under larger amplitude of oscillatory shear, the suspension exhibited a strain rate-frequency superposition (SRFS). The shearing eliminated the effects of aging and heating.
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Affiliation(s)
- Ruiwen Shu
- Research Institute of Materials Science and State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China
| | - Weixiang Sun
- Research Institute of Materials Science and State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China.
| | - Xinxing Liu
- Research Institute of Materials Science and State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China
| | - Zhen Tong
- Research Institute of Materials Science and State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China.
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122
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Maneshi MM, Sachs F, Hua SZ. A Threshold Shear Force for Calcium Influx in an Astrocyte Model of Traumatic Brain Injury. J Neurotrauma 2015; 32:1020-9. [PMID: 25442327 DOI: 10.1089/neu.2014.3677] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Traumatic brain injury (TBI) refers to brain damage resulting from external mechanical force, such as a blast or crash. Our current understanding of TBI is derived mainly from in vivo studies that show measurable biological effects on neurons sampled after TBI. Little is known about the early responses of brain cells during stimuli and which features of the stimulus are most critical to cell injury. We generated defined shear stress in a microfluidic chamber using a fast pressure servo and examined the intracellular Ca(2+) levels in cultured adult astrocytes. Shear stress increased intracellular Ca(2+) depending on the magnitude, duration, and rise time of the stimulus. Square pulses with a fast rise time (∼2 ms) caused transient increases in intracellular Ca(2+), but when the rise time was extended to 20 ms, the response was much less. The threshold for a response is a matrix of multiple parameters. Cells can integrate the effect of shear force from repeated challenges: A pulse train of 10 narrow pulses (11.5 dyn/cm(2) and 10 ms wide) resulted in a 4-fold increase in Ca(2+) relative to a single pulse of the same amplitude 100 ms wide. The Ca(2+) increase was eliminated in Ca(2+)-free media, but was observed after depleting the intracellular Ca(2+) stores with thapsigargin suggesting the need for a Ca(2+) influx. The Ca(2+) influx was inhibited by extracellular Gd(3+), a nonspecific inhibitor of mechanosensitive ion channels, but it was not affected by the more specific inhibitor, GsMTx4. The voltage-gated channel blockers, nifedipine, diltiazem, and verapamil, were also ineffective. The data show that the mechanically induced Ca(2+) influx commonly associated with neuron models for TBI is also present in astrocytes, and there is a viscoelastic/plastic coupling of shear stress to the Ca(2+) influx. The site of Ca(2+) influx has yet to be determined.
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Affiliation(s)
| | - Frederick Sachs
- 2 Department of Physiology and Biophysics, SUNY-Buffalo , Buffalo, New York
| | - Susan Z Hua
- 1 Department of Mechanical and Aerospace Engineering, SUNY-Buffalo , Buffalo, New York.,2 Department of Physiology and Biophysics, SUNY-Buffalo , Buffalo, New York
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123
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Enriched inorganic compounds in diesel exhaust particles induce mitogen-activated protein kinase activation, cytoskeleton instability, and cytotoxicity in human bronchial epithelial cells. ACTA ACUST UNITED AC 2015; 67:323-9. [PMID: 25769681 DOI: 10.1016/j.etp.2015.02.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 02/20/2015] [Indexed: 11/23/2022]
Abstract
This study assessed the effects of the diesel exhaust particles on ERK and JNK MAPKs activation, cell rheology (viscoelasticity), and cytotoxicity in bronchial epithelial airway cells (BEAS-2B). Crude DEP and DEP after extraction with hexane (DEP/HEX) were utilized. The partial reduction of some DEP/HEX organics increased the biodisponibility of many metallic elements. JNK and ERK were activated simultaneously by crude DEP with no alterations in viscoelasticity of the cells. Mitochondrial activity, however, revealed a decrease through the MTT assay. DEP/HEX treatment increased viscoelasticity and cytotoxicity (membrane damage), and also activated JNK. Our data suggest that the greater bioavailability of metals could be involved in JNK activation and, consequently, in the reduction of fiber coherence and increase in the viscoelasticity and cytotoxicity of BEAS cells. The adverse findings detected after exposure to crude DEP and to DEP/HEX reflect the toxic potential of diesel compounds. Considering the fact that the cells of the respiratory epithelium are the first line of defense between the body and the environment, our data contribute to a better understanding of the pathways leading to respiratory cell injury and provide evidence for the onset of or worsening of respiratory diseases caused by inorganic compounds present in DEP.
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124
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Haase K, Pelling AE. Investigating cell mechanics with atomic force microscopy. J R Soc Interface 2015; 12:20140970. [PMID: 25589563 PMCID: PMC4345470 DOI: 10.1098/rsif.2014.0970] [Citation(s) in RCA: 216] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 12/18/2014] [Indexed: 12/12/2022] Open
Abstract
Transmission of mechanical force is crucial for normal cell development and functioning. However, the process of mechanotransduction cannot be studied in isolation from cell mechanics. Thus, in order to understand how cells 'feel', we must first understand how they deform and recover from physical perturbations. Owing to its versatility, atomic force microscopy (AFM) has become a popular tool to study intrinsic cellular mechanical properties. Used to directly manipulate and examine whole and subcellular reactions, AFM allows for top-down and reconstitutive approaches to mechanical characterization. These studies show that the responses of cells and their components are complex, and largely depend on the magnitude and time scale of loading. In this review, we generally describe the mechanotransductive process through discussion of well-known mechanosensors. We then focus on discussion of recent examples where AFM is used to specifically probe the elastic and inelastic responses of single cells undergoing deformation. We present a brief overview of classical and current models often used to characterize observed cellular phenomena in response to force. Both simple mechanistic models and complex nonlinear models have been used to describe the observed cellular behaviours, however a unifying description of cell mechanics has not yet been resolved.
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Affiliation(s)
- Kristina Haase
- Department of Physics, Centre for Interdisciplinary NanoPhysics, MacDonald Hall, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada
| | - Andrew E Pelling
- Department of Physics, Centre for Interdisciplinary NanoPhysics, MacDonald Hall, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada Department of Biology, Gendron Hall, 30 Marie Curie, University of Ottawa, Ottawa, Ontario, Canada Institute for Science Society and Policy, Desmarais Building, 55 Laurier Ave. East, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
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125
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Mathai JC, Zhou EH, Yu W, Kim JH, Zhou G, Liao Y, Sun TT, Fredberg JJ, Zeidel ML. Hypercompliant apical membranes of bladder umbrella cells. Biophys J 2015; 107:1273-9. [PMID: 25229135 DOI: 10.1016/j.bpj.2014.07.047] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 07/14/2014] [Accepted: 07/22/2014] [Indexed: 12/14/2022] Open
Abstract
Urinary bladder undergoes dramatic volume changes during filling and voiding cycles. In the bladder the luminal surface of terminally differentiated urothelial umbrella cells is almost completely covered by plaques. These plaques (500 to 1000 nm) are made of a family of proteins called uroplakins that are known to form a tight barrier to prevent leakage of water and solutes. Electron micrographs from previous studies show these plaques to be interconnected by hinge regions to form structures that appear rigid, but these same structures must accommodate large changes in cell shape during voiding and filling cycles. To resolve this paradox, we measured the stiffness of the intact, living urothelial apical membrane and found it to be highly deformable, even more so than the red blood cell membrane. The intermediate cells underlying the umbrella cells do not have uroplakins but their membranes are an order of magnitude stiffer. Using uroplakin knockout mouse models we show that cell compliance is conferred by uroplakins. This hypercompliance may be essential for the maintenance of barrier function under dramatic cell deformation during filling and voiding of the bladder.
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Affiliation(s)
- John C Mathai
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
| | - Enhua H Zhou
- Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts
| | - Weiqun Yu
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Jae Hun Kim
- Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts
| | - Ge Zhou
- Department of Cell Biology, New York University, New York, New York
| | - Yi Liao
- Department of Cell Biology, New York University, New York, New York
| | - Tung-Tien Sun
- Department of Cell Biology, New York University, New York, New York
| | - Jeffrey J Fredberg
- Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts
| | - Mark L Zeidel
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
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126
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Abstract
We review studies that quantify newly discovered forces from single enzymatic reactions. These forces arise from the conversion of chemical energy to kinetic energy, which can be harnessed to direct diffusion of the enzyme up a concentration gradient of substrate, a novel phenomenon of molecular chemotaxis. When immobilized, enzymes can move fluid around them and perform directional pumping in microfluidic chambers. Because of the extensive array of enzymes in biological cells, we also develop three new hypotheses: that enzymatic self diffusion can assist in organizing signaling pathways in cells, can assist in pumping of fluid in cells, and can impose biologically significant forces on organelles, which will be manifested as stochastic motion not explained by thermal forces or myosin II. Such mechanochemical phenomena open up new directions in research in mechanobiology in which all enzymes, in addition to their primary function as catalysts for reactions, may have secondary functions as initiators of mechanosensitive transduction pathways.
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Affiliation(s)
- Peter J Butler
- Department of Biomedical Engineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA
| | - Krishna K Dey
- Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, USA
| | - Ayusman Sen
- Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, USA
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127
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Lan B, Norris BA, Liu JCY, Paré PD, Seow CY, Deng L. Development and maintenance of force and stiffness in airway smooth muscle. Can J Physiol Pharmacol 2014; 93:163-9. [PMID: 25615545 DOI: 10.1139/cjpp-2014-0404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Airway smooth muscle (ASM) plays a central role in the excessive narrowing of the airway that characterizes the primary functional impairment in asthma. This phenomenon is known as airway hyper-responsiveness (AHR). Emerging evidence suggests that the development and maintenance of ASM force involves dynamic reorganization of the subcellular filament network in both the cytoskeleton and the contractile apparatus. In this review, evidence is presented to support the view that regulation of ASM contraction extends beyond the classical actomyosin interaction and involves processes within the cytoskeleton and at the interfaces between the cytoskeleton, the contractile apparatus, and the extracellular matrix. These processes are initiated when the muscle is activated, and collectively they cause the cytoskeleton and the contractile apparatus to undergo structural transformation, resulting in a more connected and solid state that allows force generated by the contractile apparatus to be transmitted to the extracellular domain. Solidification of the cytoskeleton also serves to stiffen the muscle and hence the airway. Oscillatory strain from tidal breathing and deep inspiration is believed to be the counter balance that prevents hypercontraction and stiffening of ASM in vivo. Dysregulation of this balance could lead to AHR seen in asthma.
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Affiliation(s)
- Bo Lan
- Bioengineering College, Chongqing University, Chongqing, China., Centre for Heart and Lung Innovation, St Paul's Hospital and University of British Columbia, 1081 Burrard Street, Vancouver, BC V6Z 1Y6, Canada
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128
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Shoham N, Girshovitz P, Katzengold R, Shaked NT, Benayahu D, Gefen A. Adipocyte stiffness increases with accumulation of lipid droplets. Biophys J 2014; 106:1421-31. [PMID: 24655518 DOI: 10.1016/j.bpj.2014.01.045] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 01/24/2014] [Accepted: 01/29/2014] [Indexed: 11/17/2022] Open
Abstract
Adipogenesis and increase in fat tissue mass are mechanosensitive processes and hence should be influenced by the mechanical properties of adipocytes. We evaluated subcellular effective stiffnesses of adipocytes using atomic force microscopy (AFM) and interferometric phase microscopy (IPM), and we verified the empirical results using finite element (FE) simulations. In the AFM studies, we found that the mean ratio of stiffnesses of the lipid droplets (LDs) over the nucleus was 0.83 ± 0.14, from which we further evaluated the ratios of LDs over cytoplasm stiffness, as being in the range of 2.5 to 8.3. These stiffness ratios, indicating that LDs are stiffer than cytoplasm, were verified by means of FE modeling, which simulated the AFM experiments, and provided good agreement between empirical and model-predicted structural behavior. In the IPM studies, we found that LDs mechanically distort their intracellular environment, which again indicated that LDs are mechanically stiffer than the surrounding cytoplasm. Combining these empirical and simulation data together, we provide in this study evidence that adipocytes stiffen with differentiation as a result of accumulation of LDs. Our results are relevant to research of adipose-related diseases, particularly overweight and obesity, from a mechanobiology and cellular mechanics perspectives.
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Affiliation(s)
- Naama Shoham
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Pinhas Girshovitz
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Rona Katzengold
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Natan T Shaked
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dafna Benayahu
- Department of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Amit Gefen
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel.
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129
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Maloney JM, Van Vliet KJ. Chemoenvironmental modulators of fluidity in the suspended biological cell. SOFT MATTER 2014; 10:8031-8042. [PMID: 25160132 DOI: 10.1039/c4sm00743c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Biological cells can be characterized as "soft matter" with mechanical characteristics potentially modulated by external cues such as pharmaceutical dosage or fever temperature. Further, quantifying the effects of chemical and physical stimuli on a cell's mechanical response informs models of living cells as complex materials. Here, we investigate the mechanical behavior of single biological cells in terms of fluidity, or mechanical hysteresivity normalized to the extremes of an elastic solid or a viscous liquid. This parameter, which complements stiffness when describing whole-cell viscoelastic response, can be determined for a suspended cell within subsecond times. Questions remain, however, about the origin of fluidity as a conserved parameter across timescales, the physical interpretation of its magnitude, and its potential use for high-throughput sorting and separation of interesting cells by mechanical means. Therefore, we exposed suspended CH27 lymphoma cells to various chemoenvironmental conditions--temperature, pharmacological agents, pH, and osmolarity--and measured cell fluidity with a non-contact technique to extend familiarity with suspended-cell mechanics in the context of both soft-matter physics and mechanical flow cytometry development. The actin-cytoskeleton-disassembling drug latrunculin exacted a large effect on mechanical behavior, amenable to dose-dependence analysis of coupled changes in fluidity and stiffness. Fluidity was minimally affected by pH changes from 6.5 to 8.5, but strongly modulated by osmotic challenge to the cell, where the range spanned halfway from solid to liquid behavior. Together, these results support the interpretation of fluidity as a reciprocal friction within the actin cytoskeleton, with implications both for cytoskeletal models and for expectations when separating interesting cell subpopulations by mechanical means in the suspended state.
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Affiliation(s)
- John M Maloney
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
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130
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Bonakdar N, Schilling A, Spörrer M, Lennert P, Mainka A, Winter L, Walko G, Wiche G, Fabry B, Goldmann WH. Determining the mechanical properties of plectin in mouse myoblasts and keratinocytes. Exp Cell Res 2014; 331:331-7. [PMID: 25447312 PMCID: PMC4325136 DOI: 10.1016/j.yexcr.2014.10.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/30/2014] [Accepted: 10/02/2014] [Indexed: 11/21/2022]
Abstract
Plectin is the prototype of an intermediate filament (IF)-based cytolinker protein. It affects cells mechanically by interlinking and anchoring cytoskeletal filaments and acts as scaffolding and docking platform for signaling proteins to control cytoskeleton dynamics. The most common disease caused by mutations in the human plectin gene, epidermolysis bullosa simplex with muscular dystrophy (EBS-MD), is characterized by severe skin blistering and progressive muscular dystrophy. Therefore, we compared the biomechanical properties and the response to mechanical stress of murine plectin-deficient myoblasts and keratinocytes with wild-type cells. Using a cell stretching device, plectin-deficient myoblasts exhibited lower mechanical vulnerability upon external stress compared to wild-type cells, which we attributed to lower cellular pre-stress. Contrary to myoblasts, wild-type and plectin-deficient keratinocytes showed no significant differences. In magnetic tweezer measurements using fibronectin-coated paramagnetic beads, the stiffness of keratinocytes was higher than of myoblasts. Interestingly, cell stiffness, adhesion strength, and cytoskeletal dynamics were strikingly altered in plectin-deficient compared to wild-type myoblasts, whereas smaller differences were observed between plectin-deficient and wild-type keratinocytes, indicating that plectin might be more important for stabilizing cytoskeletal structures in myoblasts than in keratinocytes. Traction forces strongly correlated with the stiffness of plectin-deficient and wild-type myoblasts and keratinocytes. Contrary to that cell motility was comparable in plectin-deficient and wild-type myoblasts, but was significantly increased in plectin-deficient compared to wild-type keratinocytes. Thus, we postulate that the lack of plectin has divergent implications on biomechanical properties depending on the respective cell type. The intermediate filament-associated protein plectin has divergent biomechanical implications depending on cell/tissue type. In plectin−/− myoblasts, cell vulnerability, stiffness, strain and binding strength are lower than in wild-type cells. Plectin−/− keratinocytes exhibit higher cell stiffness, binding strength, strain and velocity than wild-type cells.
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Affiliation(s)
- Navid Bonakdar
- Department of Physics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
| | - Achim Schilling
- Department of Physics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
| | - Marina Spörrer
- Department of Physics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
| | - Pablo Lennert
- Department of Physics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
| | - Astrid Mainka
- Department of Physics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
| | - Lilli Winter
- Department of Molecular Cell Biology, Max F. Perutz Laboratories, University of Vienna, Austria
| | - Gernot Walko
- Department of Molecular Cell Biology, Max F. Perutz Laboratories, University of Vienna, Austria
| | - Gerhard Wiche
- Department of Molecular Cell Biology, Max F. Perutz Laboratories, University of Vienna, Austria
| | - Ben Fabry
- Department of Physics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
| | - Wolfgang H Goldmann
- Department of Physics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany.
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131
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Fodor É, Kanazawa K, Hayakawa H, Visco P, van Wijland F. Energetics of active fluctuations in living cells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:042724. [PMID: 25375540 DOI: 10.1103/physreve.90.042724] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Indexed: 06/04/2023]
Abstract
The nonequilibrium activity taking place in a living cell can be monitored with a tracer embedded in the medium. While microrheology experiments based on optical manipulation of such probes have become increasingly standard, we put forward a number of experiments with alternative protocols that, we claim, will provide insight into the energetics of active fluctuations. These are based on either performing thermodynamiclike cycles in control-parameter space or determining response to external perturbations of the confining trap beyond simple translation. We illustrate our proposals on an active itinerant Brownian oscillator modeling the dynamics of a probe embedded in a living medium.
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Affiliation(s)
- É Fodor
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
| | - K Kanazawa
- Yukawa Institute for Theoretical Physics, Kyoto University, Kitashirakawa-oiwake cho, Sakyo-ku, Kyoto 606-8502, Japan
| | - H Hayakawa
- Yukawa Institute for Theoretical Physics, Kyoto University, Kitashirakawa-oiwake cho, Sakyo-ku, Kyoto 606-8502, Japan
| | - P Visco
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
| | - F van Wijland
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
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132
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Mankin R, Laas K, Lumi N, Rekker A. Cage effect for the velocity correlation functions of a Brownian particle in viscoelastic shear flows. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:042127. [PMID: 25375458 DOI: 10.1103/physreve.90.042127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Indexed: 06/04/2023]
Abstract
The long-time limit behavior of velocity correlation functions (VCFs) for an underdamped Brownian particle in an oscillatory viscoelastic shear flow is investigated using the generalized Langevin equation with a power-law memory kernel. The influence of a fluctuating environment is modeled by an additive external fractional Gaussian noise. The exact expressions of the correlation functions of the fluctuating components of velocity for the Brownian particle in the shear plane have been calculated. Also, the particle's angular momentum is found. It is shown that in a certain region of the system parameters an interplay of the shear flow, memory effects, and external noise can induce a bounded long-time behavior of the VCFs, even in the shear flow direction, where in the case of internal noise the velocity process is subdiffusive, i.e., unbounded in time. Moreover, we find resonant behavior of the VCFs and the angular momentum versus the shear oscillation frequency, implying that they can be efficiently excited by oscillatory shear. The role of the initial positional distribution of particles is also discussed.
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Affiliation(s)
- Romi Mankin
- Institute of Mathematics and Natural Sciences, Tallinn University, 29 Narva Road, 10120 Tallinn, Estonia
| | - Katrin Laas
- Institute of Mathematics and Natural Sciences, Tallinn University, 29 Narva Road, 10120 Tallinn, Estonia
| | - Neeme Lumi
- Institute of Mathematics and Natural Sciences, Tallinn University, 29 Narva Road, 10120 Tallinn, Estonia
| | - Astrid Rekker
- Institute of Mathematics and Natural Sciences, Tallinn University, 29 Narva Road, 10120 Tallinn, Estonia
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133
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Kim JJ, Yin B, Christudass CS, Terada N, Rajagopalan K, Fabry B, Lee DY, Shiraishi T, Getzenberg RH, Veltri RW, An SS, Mooney SM. Acquisition of paclitaxel resistance is associated with a more aggressive and invasive phenotype in prostate cancer. J Cell Biochem 2014. [PMID: 23192682 DOI: 10.1002/jcb.24464] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Drug resistance is a major limitation to the successful treatment of advanced prostate cancer (PCa). Patients who have metastatic, castration-resistant PCa (mCRPC) are treated with chemotherapeutics. However, these standard therapy modalities culminate in the development of resistance. We established paclitaxel resistance in a classic, androgen-insensitive mCRPC cell line (DU145) and, using a suite of molecular and biophysical methods, characterized the structural and functional changes in vitro and in vivo that are associated with the development of drug resistance. After acquiring paclitaxel-resistance, cells exhibited an abnormal nuclear morphology with extensive chromosomal content, an increase in stiffness, and faster cytoskeletal remodeling dynamics. Compared with the parental DU145, paclitaxel-resistant (DU145-TxR) cells became highly invasive and motile in vitro, exercised greater cell traction forces, and formed larger and rapidly growing tumors in mouse xenografts. Furthermore, DU145-TxR cells showed a discrete loss of keratins but a distinct gain of ZEB1, Vimentin and Snail, suggesting an epithelial-to-mesenchymal transition. These findings demonstrate, for the first time, that paclitaxel resistance in PCa is associated with a trans-differentiation of epithelial cell machinery that enables more aggressive and invasive phenotype and portend new strategies for developing novel biomarkers and effective treatment modalities for PCa patients.
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Affiliation(s)
- John J Kim
- Department of Urology, James Buchanan Brady Urological Institute, Baltimore, Maryland 21287, USA
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134
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Moeendarbary E, Harris AR. Cell mechanics: principles, practices, and prospects. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2014; 6:371-88. [PMID: 25269160 PMCID: PMC4309479 DOI: 10.1002/wsbm.1275] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cells generate and sustain mechanical forces within their environment as part of their normal physiology. They are active materials that can detect mechanical stimulation by the activation of mechanosensitive signaling pathways, and respond to physical cues through cytoskeletal re-organization and force generation. Genetic mutations and pathogens that disrupt the cytoskeletal architecture can result in changes to cell mechanical properties such as elasticity, adhesiveness, and viscosity. On the other hand, perturbations to the mechanical environment can affect cell behavior. These transformations are often a hallmark and symptom of a variety of pathologies. Consequently, there are now a myriad of experimental techniques and theoretical models adapted from soft matter physics and mechanical engineering to characterize cell mechanical properties. Interdisciplinary research combining modern molecular biology with advanced cell mechanical characterization techniques now paves the way for furthering our fundamental understanding of cell mechanics and its role in development, physiology, and disease. We describe a generalized outline for measuring cell mechanical properties including loading protocols, tools, and data interpretation.We summarize recent advances in the field and explain how cell biomechanics research can be adopted by physicists, engineers, biologists, and clinicians alike.
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Affiliation(s)
- Emad Moeendarbary
- Department of Physiology, Development and Neuroscience, University of CambridgeCambridge, UK
- Hughes Hall, University of CambridgeCambridge, UK
| | - Andrew R Harris
- Department of Bioengineering, University of California BerkeleyBerkeley, CA, USA
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135
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Guo M, Ehrlicher AJ, Jensen MH, Renz M, Moore JR, Goldman RD, Lippincott-Schwartz J, Mackintosh FC, Weitz DA. Probing the stochastic, motor-driven properties of the cytoplasm using force spectrum microscopy. Cell 2014; 158:822-832. [PMID: 25126787 PMCID: PMC4183065 DOI: 10.1016/j.cell.2014.06.051] [Citation(s) in RCA: 323] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 04/28/2014] [Accepted: 06/29/2014] [Indexed: 01/17/2023]
Abstract
Molecular motors in cells typically produce highly directed motion; however, the aggregate, incoherent effect of all active processes also creates randomly fluctuating forces, which drive diffusive-like, nonthermal motion. Here, we introduce force-spectrum-microscopy (FSM) to directly quantify random forces within the cytoplasm of cells and thereby probe stochastic motor activity. This technique combines measurements of the random motion of probe particles with independent micromechanical measurements of the cytoplasm to quantify the spectrum of force fluctuations. Using FSM, we show that force fluctuations substantially enhance intracellular movement of small and large components. The fluctuations are three times larger in malignant cells than in their benign counterparts. We further demonstrate that vimentin acts globally to anchor organelles against randomly fluctuating forces in the cytoplasm, with no effect on their magnitude. Thus, FSM has broad applications for understanding the cytoplasm and its intracellular processes in relation to cell physiology in healthy and diseased states.
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Affiliation(s)
- Ming Guo
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Allen J Ehrlicher
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Beth Israel Deaconess Medical Center, Boston, MA 02115, USA
| | - Mikkel H Jensen
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Department of Physiology and Biophysics, Boston University, Boston, MA 02118, USA
| | - Malte Renz
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jeffrey R Moore
- Department of Physiology and Biophysics, Boston University, Boston, MA 02118, USA
| | - Robert D Goldman
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Jennifer Lippincott-Schwartz
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | | | - David A Weitz
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Department of Physics, Harvard University, Cambridge, MA 02138, USA.
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136
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Patrício P, Almeida PL, Portela R, Sobral RG, Grilo IR, Cidade T, Leal CR. Living bacteria rheology: population growth, aggregation patterns, and collective behavior under different shear flows. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:022720. [PMID: 25215771 DOI: 10.1103/physreve.90.022720] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Indexed: 06/03/2023]
Abstract
The activity of growing living bacteria was investigated using real-time and in situ rheology-in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus-strain COL and its isogenic cell wall autolysis mutant, RUSAL9-were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage.
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Affiliation(s)
- P Patrício
- ISEL, Rua Conselheiro Emídio Navarro 1, P-1959-007 Lisboa, Portugal and CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal
| | - P L Almeida
- ISEL, Rua Conselheiro Emídio Navarro 1, P-1959-007 Lisboa, Portugal and CENIMAT/I3N, Faculdade Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - R Portela
- Centro de Recursos Microbiológicos, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - R G Sobral
- Centro de Recursos Microbiológicos, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - I R Grilo
- Laboratório de Genética Molecular, ITQB, Universidade Nova de Lisboa, 2780 Oeiras, Portugal
| | - T Cidade
- CENIMAT/I3N, Faculdade Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal and Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - C R Leal
- ISEL, Rua Conselheiro Emídio Navarro 1, P-1959-007 Lisboa, Portugal and CENIMAT/I3N, Faculdade Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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137
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Noble PB, Pascoe CD, Lan B, Ito S, Kistemaker LEM, Tatler AL, Pera T, Brook BS, Gosens R, West AR. Airway smooth muscle in asthma: linking contraction and mechanotransduction to disease pathogenesis and remodelling. Pulm Pharmacol Ther 2014; 29:96-107. [PMID: 25062835 DOI: 10.1016/j.pupt.2014.07.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Revised: 07/12/2014] [Accepted: 07/15/2014] [Indexed: 02/07/2023]
Abstract
Asthma is an obstructive airway disease, with a heterogeneous and multifactorial pathogenesis. Although generally considered to be a disease principally driven by chronic inflammation, it is becoming increasingly recognised that the immune component of the pathology poorly correlates with the clinical symptoms of asthma, thus highlighting a potentially central role for non-immune cells. In this context airway smooth muscle (ASM) may be a key player, as it comprises a significant proportion of the airway wall and is the ultimate effector of acute airway narrowing. Historically, the contribution of ASM to asthma pathogenesis has been contentious, yet emerging evidence suggests that ASM contractile activation imparts chronic effects that extend well beyond the temporary effects of bronchoconstriction. In this review article we describe the effects that ASM contraction, in combination with cellular mechanotransduction and novel contraction-inflammation synergies, contribute to asthma pathogenesis. Specific emphasis will be placed on the effects that ASM contraction exerts on the mechanical properties of the airway wall, as well as novel mechanisms by which ASM contraction may contribute to more established features of asthma such as airway wall remodelling.
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Affiliation(s)
- Peter B Noble
- School of Anatomy, Physiology and Human Biology, University of Western Australia, WA, Australia
| | - Chris D Pascoe
- Center for Heart Lung Innovation, University of British Columbia, BC, Canada
| | - Bo Lan
- Center for Heart Lung Innovation, University of British Columbia, BC, Canada; Bioengineering College, Chongqing University, Chongqing, China
| | - Satoru Ito
- Department of Respiratory Medicine, Nagoya University, Aichi, Japan
| | - Loes E M Kistemaker
- Department of Molecular Pharmacology, University of Groningen, The Netherlands
| | - Amanda L Tatler
- Division of Respiratory Medicine, University of Nottingham, United Kingdom
| | - Tonio Pera
- Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA, USA
| | - Bindi S Brook
- School of Mathematical Sciences, University of Nottingham, United Kingdom
| | - Reinoud Gosens
- Department of Molecular Pharmacology, University of Groningen, The Netherlands
| | - Adrian R West
- Department of Physiology, University of Manitoba, MB, Canada; Biology of Breathing, Manitoba Institute of Child Health, MB, Canada.
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138
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Bonakdar N, Schilling A, Lennert P, Spörrer M, Gerum RC, Alonso JL, Goldmann WH. Measuring mechanical properties in cells: three easy methods for biologists. Cell Biol Int 2014; 38:1227-32. [PMID: 24803101 DOI: 10.1002/cbin.10303] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 04/14/2014] [Indexed: 11/08/2022]
Affiliation(s)
- Navid Bonakdar
- Department of Physics, Biophysics, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
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139
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Bouzat S. Influence of molecular motors on the motion of particles in viscoelastic media. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:062707. [PMID: 25019814 DOI: 10.1103/physreve.89.062707] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Indexed: 06/03/2023]
Abstract
We study theoretically and by numerical simulations the motion of particles driven by molecular motors in a viscoelastic medium representing the cell cytoplasm. For this, we consider a generalized Langevin equation coupled to a stochastic stepping dynamics for the motors that takes into account the action of each motor separately. In the absence of motors, the model produces subdiffusive motion of particles characterized by a power-law scaling of the mean square displacement versus the lag time as t^{α}, with 0<α<1, similar to that observed in cells. Our results show how the action of the motors can induce a transition to a superdiffusive regime at large lag times with the characteristics of those found in experiments reported in the literature. We also show that at small lag times, the motors can act as static crosslinkers that slow down the natural subdiffusive transport. An analysis of previously reported experimental data in the relevant time scales provides evidence of this phenomenon. Finally, we study the effect of a harmonic potential representing an optical trap, and we show a way to approach to a macroscopic description of the active transport in cells. This last point stresses the relevance of the molecular motors for generating not only directed motion to specific targets, but also fast diffusivelike random motion.
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Affiliation(s)
- Sebastián Bouzat
- Consejo Nacional de Investigaciones Científicas y Técnicas, Centro Atómico Bariloche (CNEA), (8400) Bariloche, Río Negro, Argentina
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140
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Maloney JM, Lehnhardt E, Long AF, Van Vliet KJ. Mechanical fluidity of fully suspended biological cells. Biophys J 2014; 105:1767-77. [PMID: 24138852 DOI: 10.1016/j.bpj.2013.08.040] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 08/01/2013] [Accepted: 08/26/2013] [Indexed: 11/16/2022] Open
Abstract
Mechanical characteristics of single biological cells are used to identify and possibly leverage interesting differences among cells or cell populations. Fluidity-hysteresivity normalized to the extremes of an elastic solid or a viscous liquid-can be extracted from, and compared among, multiple rheological measurements of cells: creep compliance versus time, complex modulus versus frequency, and phase lag versus frequency. With multiple strategies available for acquisition of this nondimensional property, fluidity may serve as a useful and robust parameter for distinguishing cell populations, and for understanding the physical origins of deformability in soft matter. Here, for three disparate eukaryotic cell types deformed in the suspended state via optical stretching, we examine the dependence of fluidity on chemical and environmental influences at a timescale of ∼1 s. We find that fluidity estimates are consistent in the time and frequency domains under a structural damping (power-law or fractional-derivative) model, but not under an equivalent-complexity, lumped-component (spring-dashpot) model; the latter predicts spurious time constants. Although fluidity is suppressed by chemical cross-linking, we find that ATP depletion in the cell does not measurably alter the parameter, and we thus conclude that active ATP-driven events are not a crucial enabler of fluidity during linear viscoelastic deformation of a suspended cell. Finally, by using the capacity of optical stretching to produce near-instantaneous increases in cell temperature, we establish that fluidity increases with temperature-now measured in a fully suspended, sortable cell without the complicating factor of cell-substratum adhesion.
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Affiliation(s)
- John M Maloney
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
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141
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Cai P, Mizutani Y, Tsuchiya M, Maloney JM, Fabry B, Van Vliet KJ, Okajima T. Quantifying cell-to-cell variation in power-law rheology. Biophys J 2014; 105:1093-102. [PMID: 24010652 DOI: 10.1016/j.bpj.2013.07.035] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 06/15/2013] [Accepted: 07/12/2013] [Indexed: 11/17/2022] Open
Abstract
Among individual cells of the same source and type, the complex shear modulus G(∗) exhibits a large log-normal distribution that is the result of spatial, temporal, and intrinsic variations. Such large distributions complicate the statistical evaluation of pharmacological treatments and the comparison of different cell states. However, little is known about the characteristic features of cell-to-cell variation. In this study, we investigated how this variation depends on the spatial location within the cell and on the actin filament cytoskeleton, the organization of which strongly influences cell mechanics. By mechanically probing fibroblasts arranged on a microarray, via atomic force microscopy, we observed that the standard deviation σ of G(∗) was significantly reduced among cells in which actin filaments were depolymerized. The parameter σ also exhibited a subcellular spatial dependence. Based on our findings regarding the frequency dependence of σ of the storage modulus G('), we proposed two types of cell-to-cell variation in G(') that arise from the purely elastic and the frequency-dependent components in terms of the soft glassy rheology model of cell deformability. We concluded that the latter inherent cell-to-cell variation can be reduced greatly by disrupting actin networks, by probing at locations within the cell nucleus boundaries distant from the cell center, and by measuring at high loading frequencies.
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Affiliation(s)
- PingGen Cai
- Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Japan
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142
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Ingber DE, Wang N, Stamenović D. Tensegrity, cellular biophysics, and the mechanics of living systems. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2014; 77:046603. [PMID: 24695087 PMCID: PMC4112545 DOI: 10.1088/0034-4885/77/4/046603] [Citation(s) in RCA: 227] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The recent convergence between physics and biology has led many physicists to enter the fields of cell and developmental biology. One of the most exciting areas of interest has been the emerging field of mechanobiology that centers on how cells control their mechanical properties, and how physical forces regulate cellular biochemical responses, a process that is known as mechanotransduction. In this article, we review the central role that tensegrity (tensional integrity) architecture, which depends on tensile prestress for its mechanical stability, plays in biology. We describe how tensional prestress is a critical governor of cell mechanics and function, and how use of tensegrity by cells contributes to mechanotransduction. Theoretical tensegrity models are also described that predict both quantitative and qualitative behaviors of living cells, and these theoretical descriptions are placed in context of other physical models of the cell. In addition, we describe how tensegrity is used at multiple size scales in the hierarchy of life—from individual molecules to whole living organisms—to both stabilize three-dimensional form and to channel forces from the macroscale to the nanoscale, thereby facilitating mechanochemical conversion at the molecular level.
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Affiliation(s)
- Donald E. Ingber
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Harvard Medical School, Harvard School of Engineering and Applied Sciences, and Boston Children’s Hospital, 3 Blackfan Circle, CLSB5, Boston, MA 02115
| | - Ning Wang
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 W. Green St, Urbana, IL 61801
| | - Dimitrije Stamenović
- Department of Biomedical Engineering, and Division of Material Science and Engineering, College of Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215
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143
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Head DA, Ikebe E, Nakamasu A, Zhang P, Villaruz LG, Kinoshita S, Ando S, Mizuno D. High-frequency affine mechanics and nonaffine relaxation in a model cytoskeleton. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:042711. [PMID: 24827282 DOI: 10.1103/physreve.89.042711] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Indexed: 06/03/2023]
Abstract
The cytoskeleton is a network of crosslinked, semiflexible filaments, and it has been suggested that it has properties of a glassy state. Here we employ optical-trap-based microrheology to apply forces to a model cytoskeleton and measure the high-bandwidth response at an anterior point. Simulating the highly nonlinear and anisotropic stress-strain propagation assuming affinity, we found that theoretical predictions for the quasistatic response of semiflexible polymers are only realized at high frequencies inaccessible to conventional rheometers. We give a theoretical basis for determining the frequency when both affinity and quasistaticity are valid, and we discuss with experimental evidence that the relaxations at lower frequencies can be characterized by the experimentally obtained nonaffinity parameter.
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Affiliation(s)
- David A Head
- School of Computing, Leeds University, Leeds LS2 9JT, United Kingdom
| | - Emi Ikebe
- Department of Physics, Faculty of Exact Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Akiko Nakamasu
- Department of Physics, Faculty of Exact Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Peijuan Zhang
- Department of Physics, Faculty of Exact Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Lara Gay Villaruz
- Department of Physics, Faculty of Exact Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Suguru Kinoshita
- Department of Physics, Faculty of Exact Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Shoji Ando
- Faculty of Biotechnology and Life Science, Sojo University, Kumamoto 860-0082, Japan
| | - Daisuke Mizuno
- Department of Physics, Faculty of Exact Sciences, Kyushu University, Fukuoka 812-8581, Japan
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144
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Pritchard RH, Huang YYS, Terentjev EM. Mechanics of biological networks: from the cell cytoskeleton to connective tissue. SOFT MATTER 2014; 10:1864-84. [PMID: 24652375 DOI: 10.1039/c3sm52769g] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
From the cell cytoskeleton to connective tissues, fibrous networks are ubiquitous in metazoan life as the key promoters of mechanical strength, support and integrity. In recent decades, the application of physics to biological systems has made substantial strides in elucidating the striking mechanical phenomena observed in such networks, explaining strain stiffening, power law rheology and cytoskeletal fluidisation - all key to the biological function of individual cells and tissues. In this review we focus on the current progress in the field, with a primer into the basic physics of individual filaments and the networks they form. This is followed by a discussion of biological networks in the context of a broad spread of recent in vitro and in vivo experiments.
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Affiliation(s)
- Robyn H Pritchard
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
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145
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Sadati M, Nourhani A, Fredberg JJ, Qazvini NT. Glass-like dynamics in the cell and in cellular collectives. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2014; 6:137-49. [PMID: 24431332 PMCID: PMC4000035 DOI: 10.1002/wsbm.1258] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2013] [Revised: 10/21/2013] [Accepted: 12/02/2013] [Indexed: 01/19/2023]
Abstract
Prominent fluctuations, heterogeneity, and cooperativity dominate the dynamics of the cytoskeleton as well as the dynamics of the cellular collective. Such systems are out of equilibrium, disordered, and remain poorly understood. To explain these findings, we consider a unifying mechanistic rubric that imagines these systems as comprising phases of soft condensed matter in proximity to a glass or jamming transition, with associated transitions between solid-like versus liquid-like phases. At the scale of the cytoskeleton, data suggest that intermittent dynamics, kinetic arrest, and dynamic heterogeneity represent mesoscale features of glassy protein-protein interactions that link underlying biochemical events to integrative cellular behaviors such as crawling, contraction, and remodeling. At the scale of the multicellular collective, jamming has the potential to unify diverse biological factors that previously had been considered mostly as acting separately and independently. Although a quantitative relationship between intra- and intercellular dynamics is still lacking, glassy dynamics and jamming offer insights linking the mechanobiology of cell to human physiology and pathophysiology.
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Affiliation(s)
- Monirosadat Sadati
- School of Public Health, Harvard University, Boston, MA 02115, United States
| | - Amir Nourhani
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, United States
| | - Jeffrey J. Fredberg
- School of Public Health, Harvard University, Boston, MA 02115, United States
| | - Nader Taheri Qazvini
- School of Public Health, Harvard University, Boston, MA 02115, United States, School of Chemistry, College of Science, University of Tehran, Tehran, Iran
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146
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Lautscham LA, Lin CY, Auernheimer V, Naumann CA, Goldmann WH, Fabry B. Biomembrane-mimicking lipid bilayer system as a mechanically tunable cell substrate. Biomaterials 2014; 35:3198-207. [PMID: 24439398 PMCID: PMC4026006 DOI: 10.1016/j.biomaterials.2013.12.091] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 12/22/2013] [Indexed: 11/26/2022]
Abstract
Cell behavior such as cell adhesion, spreading, and contraction critically depends on the elastic properties of the extracellular matrix. It is not known, however, how cells respond to viscoelastic or plastic material properties that more closely resemble the mechanical environment cells encounter in the body. In this report, we employ viscoelastic and plastic biomembrane-mimicking cell substrates. The compliance of the substrates can be tuned by increasing the number of polymer-tethered bilayers. This leaves the density and conformation of adhesive ligands on the top bilayer unaltered. We then observe the response of fibroblasts to these property changes. For comparison, we also study the cells on soft polyacrylamide and hard glass surfaces. Cell morphology, motility, cell stiffness, contractile forces and adhesive contact size all decrease on more compliant matrices but are less sensitive to changes in matrix dissipative properties. These data suggest that cells are able to feel and respond predominantly to the effective matrix compliance, which arises as a combination of substrate and adhesive ligand mechanical properties.
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Affiliation(s)
- Lena A Lautscham
- Department of Biophysics, University of Erlangen-Nuremberg, Erlangen 91052, Germany.
| | - Corey Y Lin
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University, Indianapolis 46202, USA
| | - Vera Auernheimer
- Department of Biophysics, University of Erlangen-Nuremberg, Erlangen 91052, Germany
| | - Christoph A Naumann
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University, Indianapolis 46202, USA
| | - Wolfgang H Goldmann
- Department of Biophysics, University of Erlangen-Nuremberg, Erlangen 91052, Germany
| | - Ben Fabry
- Department of Biophysics, University of Erlangen-Nuremberg, Erlangen 91052, Germany
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147
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Head DA, Briels WJ, Gompper G. Nonequilibrium structure and dynamics in a microscopic model of thin-film active gels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:032705. [PMID: 24730872 DOI: 10.1103/physreve.89.032705] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Indexed: 06/03/2023]
Abstract
In the presence of adenosine triphosphate, molecular motors generate active force dipoles that drive suspensions of protein filaments far from thermodynamic equilibrium, leading to exotic dynamics and pattern formation. Microscopic modeling can help to quantify the relationship between individual motors plus filaments to organization and dynamics on molecular and supramolecular length scales. Here, we present results of extensive numerical simulations of active gels where the motors and filaments are confined between two infinite parallel plates. Thermal fluctuations and excluded-volume interactions between filaments are included. A systematic variation of rates for motor motion, attachment, and detachment, including a differential detachment rate from filament ends, reveals a range of nonequilibrium behavior. Strong motor binding produces structured filament aggregates that we refer to as asters, bundles, or layers, whose stability depends on motor speed and differential end detachment. The gross features of the dependence of the observed structures on the motor rate and the filament concentration can be captured by a simple one-filament model. Loosely bound aggregates exhibit superdiffusive mass transport, where filament translocation scales with lag time with nonunique exponents that depend on motor kinetics. An empirical data collapse of filament speed as a function of motor speed and end detachment is found, suggesting a dimensional reduction of the relevant parameter space. We conclude by discussing the perspectives of microscopic modeling in the field of active gels.
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Affiliation(s)
- D A Head
- School of Computing, Leeds University, Leeds LS2 9JT, United Kingdom
| | - W J Briels
- Computational Biophysics, University of Twente, 7500 AE Enschede, The Netherlands
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
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148
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Takahashi R, Ichikawa S, Subagyo A, Sueoka K, Okajima T. Atomic force microscopy measurements of mechanical properties of single cells patterned by microcontact printing. Adv Robot 2014. [DOI: 10.1080/01691864.2013.876933] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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149
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Coughlin MF, Fredberg JJ. Changes in cytoskeletal dynamics and nonlinear rheology with metastatic ability in cancer cell lines. Phys Biol 2013; 10:065001. [PMID: 24304722 DOI: 10.1088/1478-3975/10/6/065001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Metastatic outcome is impacted by the biophysical state of the primary tumor cell. To determine if changes in cancer cell biophysical properties facilitate metastasis, we quantified cytoskeletal biophysics in well-characterized human skin, bladder, prostate and kidney cell line pairs that differ in metastatic ability. Using magnetic twisting cytometry with optical detection, cytoskeletal dynamics was observed through spontaneous motion of surface bound marker beads and nonlinear rheology was characterized through large amplitude forced oscillations of probe beads. Measurements of cytoskeletal dynamics and nonlinear rheology differed between strongly and weakly metastatic cells. However, no set of biophysical parameters changed systematically with metastatic ability across all cell lines. Compared to their weakly metastatic counterparts, the strongly metastatic kidney cancer cells exhibited both increased cytoskeletal dynamics and stiffness at large deformation which are thought to facilitate the process of vascular invasion.
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150
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Joo C, de Boer JF. Field-based dynamic light scattering microscopy: theory and numerical analysis. APPLIED OPTICS 2013; 52:7618-28. [PMID: 24216666 DOI: 10.1364/ao.52.007618] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We present a theoretical framework for field-based dynamic light scattering microscopy based on a spectral-domain optical coherence phase microscopy (SD-OCPM) platform. SD-OCPM is an interferometric microscope capable of quantitative measurement of amplitude and phase of scattered light with high phase stability. Field-based dynamic light scattering (F-DLS) analysis allows for direct evaluation of complex-valued field autocorrelation function and measurement of localized diffusive and directional dynamic properties of biological and material samples with high spatial resolution. In order to gain insight into the information provided by F-DLS microscopy, theoretical and numerical analyses are performed to evaluate the effect of numerical aperture of the imaging optics. We demonstrate that sharp focusing of fields affects the measured diffusive and transport velocity, which leads to smaller values for the dynamic properties in the sample. An approach for accurately determining the dynamic properties of the samples is discussed.
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