1
|
Wagner R, Carré MJ, Perrault CM, Evans PC, Lewis R. Assessing friction and damage of cell monolayers on soft substrates in vitro. J R Soc Interface 2024; 21:20230696. [PMID: 38842440 DOI: 10.1098/rsif.2023.0696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 03/11/2024] [Indexed: 06/07/2024] Open
Abstract
In the area of surgical applications, understanding the interaction between medical device materials and tissue is important since this interaction may cause complications. The interaction often consists of a cell monolayer touching the medical device that can be mimicked in vitro. Prominent examples of this are contact lenses, where epithelial cells interact with the contact lens, or stents and catheters, which are in contact with endothelial cells. To investigate those interactions, in previous studies, expensive microtribometers were used to avoid pressures in the contact area far beyond physiologically relevant levels. Here, we aim to present a new methodology that is cost- and time-efficient, more accessible than those used previously and allows for the application of more realistic pressures, while permitting a quantification of the damage caused to the monolayer. For this, a soft polydimethylsiloxane is employed that better mimics the mechanical properties of blood vessels than materials used in other studies. Furthermore, a technique to account for misalignments within the experiment set-up is presented. This is carried out using the raw spatial and force data recorded by the tribometer and adjusting for misalignments. The methodology is demonstrated using an endothelial cell (human umbilical vein endothelial cells) monolayer.
Collapse
Affiliation(s)
- Rasmus Wagner
- Department of Mechanical Engineering, University of Sheffield , Sheffield S1 3JD, UK
| | - Matt J Carré
- Department of Mechanical Engineering, University of Sheffield , Sheffield S1 3JD, UK
| | - Cecile M Perrault
- Department of Mechanical Engineering, University of Sheffield , Sheffield S1 3JD, UK
- Eden Microfluidics , Paris 75012, France
| | - Paul C Evans
- Department of Infection, Immunity & Cardiovascular Disease, University of Sheffield , Sheffield S10 2RX, UK
| | - Roger Lewis
- Department of Mechanical Engineering, University of Sheffield , Sheffield S1 3JD, UK
| |
Collapse
|
2
|
Alonso A, Ebben A, Dabagh M. Impact of disturbed flow and arterial stiffening on mechanotransduction in endothelial cells. Biomech Model Mechanobiol 2023; 22:1919-1933. [PMID: 37709992 DOI: 10.1007/s10237-023-01743-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 07/05/2023] [Indexed: 09/16/2023]
Abstract
Disturbed flow promotes progression of atherosclerosis at particular regions of arteries where the recent studies show the arterial wall becomes stiffer. Objective of this study is to show how mechanotransduction in subcellular organelles of endothelial cells (ECs) will alter with changes in blood flow profiles applied on ECs surface and mechanical properties of arterial wall where ECs are attached to. We will examine the exposure of ECs to atherogenic flow profiles (disturbed flow) and non-atherogenic flow profiles (purely forward flow), while stiffness and viscoelasticity of arterial wall will change. A multicomponent model of endothelial cell monolayer was applied to quantify the response of subcellular organelles to the changes in their microenvironment. Our results show that arterial stiffening alters mechanotransduction in intra/inter-cellular organelles of ECs by slight increase in the transmitted stresses, particularly over central stress fibers (SFs). We also observed that degradation of glycocalyx and exposure to non-atherogenic flow profiles result in significantly higher stresses in subcellular organelles, while degradation of glycocalyx and exposure to atherogenic flow profiles result in dramatically lower stresses in the organelles. Moreover, we show that increasing the arterial wall viscoelasticity leads to slight increase in the stresses transmitted to subcellular organelles. FAs are particularly influenced with the changes in the arterial wall properties and viscoelasticity. Our study suggests that changes in viscoelasticity of arterial wall and degradation state of glycocalyx have to be considered along with arterial stiffening in designing more efficient treatment strategies for atherosclerosis. Our study provides insight into significant role of mechanotransduction in the localization of atherosclerosis by quantifying the role of ECs mechanosensors and suggests that mechanotransduction may play a key role in design of more efficient and precision therapeutics to slow down or block the progression of atherosclerosis.
Collapse
Affiliation(s)
- Andrea Alonso
- Department of Biomedical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI, 53211, USA
| | - Alessandra Ebben
- Department of Biomedical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI, 53211, USA
| | - Mahsa Dabagh
- Department of Biomedical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI, 53211, USA.
| |
Collapse
|
3
|
Sajid N. Topography and mechanical measurements of primary Schwann cells and neuronal cells with atomic force microscope for understanding and controlling nerve growth. Micron 2023; 167:103427. [PMID: 36805164 DOI: 10.1016/j.micron.2023.103427] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 01/27/2023] [Accepted: 02/03/2023] [Indexed: 02/16/2023]
Abstract
Peripheral nerve injuries require a piece of substantial information for a satisfactory treatment. The prior peripheral nerve injury knowledge, can improve nerve repair, and its growth at molecular and cellular level. In this study, we employed an atomic force microscope (AFM) to investigate the topography and mechanical properties of the primary Schwann cells and neuronal cells. Tapping mode images and contact points force-volume maps provide the cells topography. Two different probes were used to acquire the micro and nanomechanical properties of the primary Schwann cells, NG-108-15 neuronal cells, and growth cones. Moreover, the sharp probe was only used to investigate neurites nanomechanics. A significant difference in the elastic moduli found between primary Schwann cells, and neuronal cells, with both probes, with consistent results. The elastic moduli of the growth cones were found higher, than the neuronal cells and primary Schwann cells, with both probes. Furthermore, the modulus variations were also found between neurites. These results have significant implications for a better understanding of the peripheral nerve system (PNS) in terms of defining the optimal pattern surface and nerve guidance conduits.
Collapse
Affiliation(s)
- Nusrat Sajid
- Department of Physics, COMSATS University Islamabad, Lahore Campus, Lahore 54000, Pakistan.
| |
Collapse
|
4
|
Ebben A, Dabagh M. Mechanotransduction in Endothelial Cells in Vicinity of Cancer Cells. Cell Mol Bioeng 2022; 15:313-330. [DOI: 10.1007/s12195-022-00728-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 06/14/2022] [Indexed: 11/30/2022] Open
|
5
|
In silico stress fibre content affects peak strain in cytoplasm and nucleus but not in the membrane for uniaxial substrate stretch. Med Biol Eng Comput 2021; 59:1933-1944. [PMID: 34392447 DOI: 10.1007/s11517-021-02393-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 06/13/2021] [Indexed: 10/20/2022]
Abstract
Existing in silico models for single cell mechanics feature limited representations of cytoskeletal structures that contribute substantially to the mechanics of a cell. We propose a micromechanical hierarchical approach to capture the mechanical contribution of actin stress fibres. For a cell-specific fibroblast geometry with membrane, cytoplasm and nucleus, the Mori-Tanaka homogenization method was employed to describe cytoplasmic inhomogeneities and constitutive contribution of actin stress fibres. The homogenization was implemented in a finite element model of the fibroblast attached to a substrate through focal adhesions. Strain in cell membrane, cytoplasm and nucleus due to uniaxial substrate stretch was assessed for different stress fibre volume fractions and different elastic modulus of the substrate. A considerable decrease of the peak strain with increasing stress fibre content was observed in cytoplasm and nucleus but not the membrane, whereas the peak strain in cytoplasm, nucleus and membrane increased for increasing elastic modulus of the substrate. Finite element mesh of reconstructed human fibroblast and intracellular strain distribution in cell subjected to substrate stretch.
Collapse
|
6
|
Grexa I, Fekete T, Molnár J, Molnár K, Vizsnyiczai G, Ormos P, Kelemen L. Single-Cell Elasticity Measurement with an Optically Actuated Microrobot. MICROMACHINES 2020; 11:mi11090882. [PMID: 32972024 PMCID: PMC7570390 DOI: 10.3390/mi11090882] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 09/15/2020] [Accepted: 09/20/2020] [Indexed: 02/07/2023]
Abstract
A cell elasticity measurement method is introduced that uses polymer microtools actuated by holographic optical tweezers. The microtools were prepared with two-photon polymerization. Their shape enables the approach of the cells in any lateral direction. In the presented case, endothelial cells grown on vertical polymer walls were probed by the tools in a lateral direction. The use of specially shaped microtools prevents the target cells from photodamage that may arise during optical trapping. The position of the tools was recorded simply with video microscopy and analyzed with image processing methods. We critically compare the resulting Young’s modulus values to those in the literature obtained by other methods. The application of optical tweezers extends the force range available for cell indentations measurements down to the fN regime. Our approach demonstrates a feasible alternative to the usual vertical indentation experiments.
Collapse
Affiliation(s)
- István Grexa
- Biological Research Centre, Temesvári krt. 62, 6726 Szeged, Hungary; (I.G.); (T.F.); (J.M.); (K.M.); (G.V.); (P.O.)
- Doctoral School of Interdisciplinary Medicine, University of Szeged, Korányi fasor 10, 6720 Szeged, Hungary
| | - Tamás Fekete
- Biological Research Centre, Temesvári krt. 62, 6726 Szeged, Hungary; (I.G.); (T.F.); (J.M.); (K.M.); (G.V.); (P.O.)
- Doctoral School of Multidisciplinary Medicine, Dóm tér 9, Hungary University of Szeged, 6720 Szeged, Hungary
| | - Judit Molnár
- Biological Research Centre, Temesvári krt. 62, 6726 Szeged, Hungary; (I.G.); (T.F.); (J.M.); (K.M.); (G.V.); (P.O.)
| | - Kinga Molnár
- Biological Research Centre, Temesvári krt. 62, 6726 Szeged, Hungary; (I.G.); (T.F.); (J.M.); (K.M.); (G.V.); (P.O.)
- Doctoral School of Theoretical Medicine, University of Szeged, Korányi fasor 10, 6720 Szeged, Hungary
| | - Gaszton Vizsnyiczai
- Biological Research Centre, Temesvári krt. 62, 6726 Szeged, Hungary; (I.G.); (T.F.); (J.M.); (K.M.); (G.V.); (P.O.)
| | - Pál Ormos
- Biological Research Centre, Temesvári krt. 62, 6726 Szeged, Hungary; (I.G.); (T.F.); (J.M.); (K.M.); (G.V.); (P.O.)
| | - Lóránd Kelemen
- Biological Research Centre, Temesvári krt. 62, 6726 Szeged, Hungary; (I.G.); (T.F.); (J.M.); (K.M.); (G.V.); (P.O.)
- Correspondence: ; Tel.: +36-62-599-600 (ext. 419)
| |
Collapse
|
7
|
Wang P, Geng C, Pan L, Liu B. A carbon nanocoil-based flexible tip for a live cell study of mechanotransduction and electro-physiological characteristics. J Mater Chem B 2020; 8:1405-1410. [PMID: 31971204 DOI: 10.1039/c9tb02564b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The responses of living cells to external mechanical and electrical stimulation play important roles in regulating their biological functions and behaviors, and the response mechanisms have attracted great attention. Global stimulation on cells is generally used in traditional methods, but it is insufficient to investigate the mechanism of a dynamic physiological response at the subcellular level. At present, there is still lack of a low-cost and easy-operated method to apply local mechanical force and electrical stimulation on living cells. In this study, an individual carbon nanocoil (CNC) is used as a microscale noninvasive tool for local stimulation on a single cell, and a living cell imaging technology, fluorescence resonance energy transfer (FRET), is adopted to determine the responses of cells. After demonstrating that CNCs have low cytotoxicity to be applied in the biological field, an individual CNC is used as a needle tip to apply local mechanical force on a single osteosarcoma cell, which is transfected with a Src FRET biosensor to explore the mechano-physiological response. A spatially increasing and polarized Src protein activation is observed on the stimulated cell. Moreover, a single CNC is also used as an electrode to exert periodic local electrical stimulation. Osteosarcoma cells transfected with calcium-FRET biosensors show notable spatial-polarized FRET emission ratio distribution, and the FRET ratio shows a recoverable tendency towards the initial state after withdrawing the electrical stimulation. The cell biofunctions and structures are not damaged during the experiment process, which indicates that CNC is a kind of non-invasive and bio-safe tip. The CNC tip is a powerful tool for exploring the mechanotransduction and electro-physiological characteristics of living cells.
Collapse
Affiliation(s)
- Peng Wang
- School of Physics, Dalian University of Technology, No. 2 Linggong Road, Ganjingzi District, Dalian, Liaoning 116024, P. R. China. and Physics Department, Xinzhou Teachers University, No. 10 Heping West Street, Xinzhou, Shanxi 034000, P. R. China
| | - Chunyang Geng
- School of Biomedical Engineering, Dalian University of Technology, Liaoning Key Lab of IC & BME System, No. 2 Linggong Road, Ganjingzi District, Dalian, Liaoning 116024, P. R. China.
| | - Lujun Pan
- School of Physics, Dalian University of Technology, No. 2 Linggong Road, Ganjingzi District, Dalian, Liaoning 116024, P. R. China.
| | - Bo Liu
- School of Biomedical Engineering, Dalian University of Technology, Liaoning Key Lab of IC & BME System, No. 2 Linggong Road, Ganjingzi District, Dalian, Liaoning 116024, P. R. China.
| |
Collapse
|
8
|
Indra I, Gasparski AN, Beningo KA. An in vitro correlation of metastatic capacity and dual mechanostimulation. PLoS One 2018; 13:e0207490. [PMID: 30427911 PMCID: PMC6241134 DOI: 10.1371/journal.pone.0207490] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 10/30/2018] [Indexed: 12/19/2022] Open
Abstract
Cells are under the influence of multiple forms of mechanical stimulation in vivo. For example, a cell is subjected to mechanical forces from tissue stiffness, shear and tensile stress and transient applied strain. Significant progress has been made in understanding the cellular mechanotransduction mechanisms in response to a single mechanical parameter. However, our knowledge of how a cell responds to multiple mechanical inputs is currently limited. In this study, we have tested the cellular response to the simultaneous application of two mechanical inputs: substrate compliance and transient tugging. Our results suggest that cells within a multicellular spheroid will restrict their response to a single mechanical input at a time and when provided with two mechanical inputs simultaneously, one will dominate. In normal and non-metastatic mammary epithelial cells, we found that they respond to applied stimulation and will override substrate compliance cues in favor of the applied mechanical stimulus. Surprisingly, however, metastatic mammary epithelial cells remain non-responsive to both mechanical cues. Our results suggest that, within our assay system, metastatic progression may involve the down-regulation of multiple mechanotransduction pathways.
Collapse
Affiliation(s)
- Indrajyoti Indra
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America
| | - Alexander N. Gasparski
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America
| | - Karen A. Beningo
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America
- * E-mail:
| |
Collapse
|
9
|
Sackmann E. Viscoelasticity of single cells-from subcellular to cellular level. Semin Cell Dev Biol 2018; 93:2-15. [PMID: 30267805 DOI: 10.1016/j.semcdb.2018.09.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 08/27/2018] [Accepted: 09/21/2018] [Indexed: 12/12/2022]
Abstract
This review deals with insights into complex cellular structures and processes obtained by measuring viscoelastic impedances of the cell envelope and the cytoplasm by colloidal bead microrheometry. I first introduce a mechanical cell model that allows us to understand their unique ability of mechanical self-stabilization by actin microtubule crosstalk. In the second part, I show how cell movements can be driven by pulsatile or propagating solitary actin gelatin waves (SAGW) that are generated on nascent adhesion domains by logistically controlled membrane recruitment of functional proteins by electrostatic-hydrophobic forces. The global polarization of cell migration is guided by actin-microtubule crosstalk that is mediated by the Ca++ and strain-sensitive supramolecular scaffolding protein IQGAP. In the third part, I introduce the traction force microscopy as a tool to measure the forces between somatic cells and the tissue ´Here I show, how absolute values of viscoelastic impedances of the composite cell envelope can be obtained by deformation field mapping techniques. In the fourth part, it is shown how the dynamic mechanical properties of the active viscoplastic cytoplasmic space can be evaluated using colloidal beads as phantom endosomes. Separate measurements of velocity distributions of directed and random motions of phantom endosomes, yield local values of transport forces, viscosities and life times of directed motion along microtubules. The last part deals with biomimetic experiments allowing us to quantitatively evaluate the mechanical properties of passive and active actin networks on the basis of the percolation theory of gelation.
Collapse
Affiliation(s)
- Erich Sackmann
- Physics Department E22, Technical University Munich, James Franck Str. 1, D85747, Garching, Germany.
| |
Collapse
|
10
|
Dabagh M, Jalali P, Butler PJ, Randles A, Tarbell JM. Mechanotransmission in endothelial cells subjected to oscillatory and multi-directional shear flow. J R Soc Interface 2018; 14:rsif.2017.0185. [PMID: 28515328 DOI: 10.1098/rsif.2017.0185] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 04/21/2017] [Indexed: 12/27/2022] Open
Abstract
Local haemodynamics are linked to the non-uniform distribution of atherosclerosic lesions in arteries. Low and oscillatory (reversing in the axial flow direction) wall shear stress (WSS) induce inflammatory responses in endothelial cells (ECs) mediating disease localization. The objective of this study is to investigate computationally how the flow direction (reflected in WSS variation on the EC surface over time) influences the forces experienced by structural components of ECs that are believed to play important roles in mechanotransduction. A three-dimensional, multi-scale, multi-component, viscoelastic model of focally adhered ECs is developed, in which oscillatory WSS (reversing or non-reversing) parallel to the principal flow direction, or multi-directional oscillatory WSS with reversing axial and transverse components are applied over the EC surface. The computational model includes the glycocalyx layer, actin cortical layer, nucleus, cytoskeleton, focal adhesions (FAs), stress fibres and adherens junctions (ADJs). We show the distinct effects of atherogenic flow profiles (reversing unidirectional flow and reversing multi-directional flow) on subcellular structures relative to non-atherogenic flow (non-reversing flow). Reversing flow lowers stresses and strains due to viscoelastic effects, and multi-directional flow alters stress on the ADJs perpendicular to the axial flow direction. The simulations predict forces on integrins, ADJ filaments and other substructures in the range that activate mechanotransduction.
Collapse
Affiliation(s)
- Mahsa Dabagh
- Department of Biomedical Engineering, Duke University, Durham, NC, USA .,School of Energy Systems, Lappeenranta University of Technology, Lappeenranta, Finland
| | - Payman Jalali
- School of Energy Systems, Lappeenranta University of Technology, Lappeenranta, Finland
| | - Peter J Butler
- Department of Biomedical Engineering, The Pennsylvania State University, Pennsylvania, PA, USA
| | - Amanda Randles
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - John M Tarbell
- Department of Biomedical Engineering, The City College of New York, New York, NY, USA
| |
Collapse
|
11
|
Zhu X, Liu L, Wang Z, Liu X. Axisymmetric Contact Problem for a Flattened Cell: Contributions of Substrate Effect and Cell Thickness to the Determination of Viscoelastic Properties by Using AFM Indentation. SCANNING 2017; 2017:8519539. [PMID: 29422981 PMCID: PMC5751394 DOI: 10.1155/2017/8519539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 10/22/2017] [Accepted: 11/01/2017] [Indexed: 06/08/2023]
Abstract
Nanoindentation technology has proven to be an effective method to investigate the viscoelastic properties of biological cells. The experimental data obtained by nanoindentation are frequently interpreted by Hertz contact model. However, in order to validate Hertz contact model, some studies assume that cells have infinite thickness which does not necessarily represent the real situation. In this study, a rigorous contact model based upon linear elasticity is developed for the interpretation of indentation tests of flattened cells. The cell, normally bonded to the Petri dish, is initially treated as an elastic layer of finite thickness perfectly fixed to a rigid substrate. The theory of linear elasticity is utilized to solve this contact issue and then the solutions are extended to viscoelastic situation which is regarded as a good indicator for mechanical properties of biological cells. To test the present model, AFM-based creep test has been conducted on living human hepatocellular carcinoma cell (SMMC-7721 cell) and its fullerenol-treated counterpart. The results indicate that the present model could not only describe very well the creep behavior of SMMC-7721 cells, but also curb overestimation of the mechanical properties due to substrate effect.
Collapse
Affiliation(s)
- Xinyao Zhu
- School of Engineering, University of Warwick, Coventry CV4 7AL, UK
| | - Lanjiao Liu
- International Research Centre for Nano Handling and Manufacturing of China, Changchun University of Science and Technology, Changchun 130022, China
| | - Zuobin Wang
- International Research Centre for Nano Handling and Manufacturing of China, Changchun University of Science and Technology, Changchun 130022, China
| | - X. Liu
- School of Engineering, University of Warwick, Coventry CV4 7AL, UK
| |
Collapse
|
12
|
Blumlein A, Williams N, McManus JJ. The mechanical properties of individual cell spheroids. Sci Rep 2017; 7:7346. [PMID: 28779182 PMCID: PMC5544704 DOI: 10.1038/s41598-017-07813-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 07/03/2017] [Indexed: 12/18/2022] Open
Abstract
The overall physical properties of tissues emerge in a complex manner from the properties of the component cells and other constituent materials from which the tissue is formed, across multiple length scales ranging from nanometres to millimetres. Recent studies have suggested that interfacial tension between cells contributes significantly to the mechanical properties of tissues and that the overall surface tension is determined by the ratio of adhesion tension to cortical tension. Using cavitation rheology (CR), we have measured the interfacial properties and the elastic modulus of spheroids formed from HEK cells. By comparing the work of bubble formation with deformation of the cell spheroid at different length scales, we have estimated the cortical tension for HEK cells. This innovative approach to understanding the fundamental physical properties associated with tissue mechanics may guide new approaches for the generation of materials to replace or regenerate damaged or diseased tissues.
Collapse
Affiliation(s)
- Alice Blumlein
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland
| | - Noel Williams
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland
| | - Jennifer J McManus
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland.
| |
Collapse
|
13
|
Schierbaum N, Rheinlaender J, Schäffer TE. Viscoelastic properties of normal and cancerous human breast cells are affected differently by contact to adjacent cells. Acta Biomater 2017; 55:239-248. [PMID: 28396292 DOI: 10.1016/j.actbio.2017.04.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 03/14/2017] [Accepted: 04/05/2017] [Indexed: 01/07/2023]
Abstract
Malignant transformation drastically alters the mechanical properties of the cell and its response to the surrounding cellular environment. We studied the influence of the physical contact between adjacent cells in an epithelial monolayer on the viscoelastic behavior of normal MCF10A, non-invasive cancerous MCF7, and invasive cancerous MDA-MB-231 human breast cells. Using an atomic force microscopy (AFM) imaging technique termed force clamp force mapping (FCFM) to record images of the viscoelastic material properties, we found that normal MCF10A cells are stiffer and have a lower fluidity at confluent than at sparse density. Contrarily, cancerous MCF7 and MDA-MB-231 cells do not stiffen and do not decrease their fluidity when progressing from sparse to confluent density. The behavior of normal MCF10A cells appears to be governed by the formation of stable cell-cell contacts, because their disruption with a calcium-chelator (EGTA) causes the stiffness and fluidity values to return to those at sparse density. In contrast, EGTA-treatment of MCF7 and MDA-MB-231 cells does not change their viscoelastic properties. Confocal fluorescence microscopy showed that the change of the viscoelastic behavior in MCF10A cells when going from sparse to confluent density is accompanied by a remodeling of the actin cytoskeleton into thick stress fiber bundles, while in MCF7 and MDA-MB-231 cells the actin cytoskeleton is only composed of thin and short fibers, regardless of cell density. While the observed behavior of normal MCF10A cells might be crucial for providing mechanical stability and thus in turn integrity of the epithelial monolayer, the dysregulation of this behavior in cancerous MCF7 and MDA-MB-231 cells is possibly a central aspect of cancer progression in the epithelium. STATEMENT OF SIGNIFICANCE We measured the viscoelastic properties of normal and cancerous human breast epithelial cells in different states of confluency using atomic force microscopy. We found that confluent normal cells are stiffer and have lower fluidity than sparse normal cells, which appears to be governed by the formation of cell-cell contacts. Contrarily, confluent cancer cells do not stiffen and not have a decreased fluidity compared to sparse cancer cells and their viscoelastic properties are independent of cell-cell contact formation. While the observed behavior of normal cells appears to be crucial for providing the mechanical stability and therefore the integrity of the epithelial monolayer, the dysregulation of this behavior in cancer cells might be a central aspect of early stage cancer progression and metastasis in the epithelium.
Collapse
Affiliation(s)
- Nicolas Schierbaum
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Johannes Rheinlaender
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Tilman E Schäffer
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
| |
Collapse
|
14
|
Pajic-Lijakovic I, Milivojevic M. Successive relaxation cycles during long-time cell aggregate rounding after uni-axial compression. J Biol Phys 2017; 43:197-209. [PMID: 28337554 PMCID: PMC5471168 DOI: 10.1007/s10867-017-9446-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 02/15/2017] [Indexed: 12/15/2022] Open
Abstract
The mean features of cell surface rearrangement during cell aggregate rounding after uni-axial compression between parallel plates are considered. This is based on long-time rheological modeling approaches in order to shed further light on collective cell migration. Many aspects of cell migration at the supra-cellular level, such as the coordination between surrounding migrating cell groups that leads to uncorrelated motility, have remained unclear. Aggregate shape changes during rounding are considered depending on the size and homogeneity of 2-D and 3-D cell aggregates. Cell aggregate shape changes that are taking place during successive relaxation cycles have various relaxation rates per cycle. Every relaxation rate is related to the corresponding cell migrating state. If most of the cells migrate per cycle, the relaxation rate is maximal. If most of the cells are in a resting state per cycle, the relaxation rate is nearing zero. If some cell groups migrate while the others, at the same time, stay in a resting state, the relaxation rate is lower than that obtained for the migrating cells. The relaxation rates per cycles are not random, but they have a tendency to gather around two or three values indicating an organized cell migrating pattern. Such behavior suggests that uncorrelated motility during collective cell migration in one cycle induces a decrease of the relaxation rate in the next cycle caused by an accumulation of cells in the resting state. However, cells have the ability to overcome these perturbations and re-establish an ordered migrating trend in the next cycle. These perturbations of the cell migrating state are more pronounced for: (1) more mobile cells, (2) a heterogeneous cell population, and (3) a larger cell population under the same experimental conditions.
Collapse
Affiliation(s)
| | - Milan Milivojevic
- Faculty of Technology and Metallurgy, University of Belgrade, Belgrade, Serbia
| |
Collapse
|
15
|
Suki B, Hu Y, Murata N, Imsirovic J, Mondoñedo JR, de Oliveira CLN, Schaible N, Allen PG, Krishnan R, Bartolák-Suki E. A microfluidic chamber-based approach to map the shear moduli of vascular cells and other soft materials. Sci Rep 2017; 7:2305. [PMID: 28536424 PMCID: PMC5442161 DOI: 10.1038/s41598-017-02659-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 04/18/2017] [Indexed: 11/09/2022] Open
Abstract
There is growing interest in quantifying vascular cell and tissue stiffness. Most measurement approaches, however, are incapable of assessing stiffness in the presence of physiological flows. We developed a microfluidic approach which allows measurement of shear modulus (G) during flow. The design included a chamber with glass windows allowing imaging with upright or inverted microscopes. Flow was controlled gravitationally to push culture media through the chamber. Fluorescent beads were conjugated to the sample surface and imaged before and during flow. Bead displacements were calculated from images and G was computed as the ratio of imposed shear stress to measured shear strain. Fluid-structure simulations showed that shear stress on the surface did not depend on sample stiffness. Our approach was verified by measuring the moduli of polyacrylamide gels of known stiffness. In human pulmonary microvascular endothelial cells, G was 20.4 ± 12 Pa and decreased by 20% and 22% with increasing shear stress and inhibition of non-muscle myosin II motors, respectively. The G showed a larger intra- than inter-cellular variability and it was mostly determined by the cytosol. Our shear modulus microscopy can thus map the spatial distribution of G of soft materials including gels, cells and tissues while allowing the visualization of microscopic structures such as the cytoskeleleton.
Collapse
Affiliation(s)
- Béla Suki
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA.
| | - Yingying Hu
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | - Naohiko Murata
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | - Jasmin Imsirovic
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | - Jarred R Mondoñedo
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | | | - Niccole Schaible
- Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Philip G Allen
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | - Ramaswamy Krishnan
- Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | | |
Collapse
|
16
|
Rapid and Localized Mechanical Stimulation and Adhesion Assay: TRPM7 Involvement in Calcium Signaling and Cell Adhesion. PLoS One 2015; 10:e0126440. [PMID: 25946314 PMCID: PMC4422584 DOI: 10.1371/journal.pone.0126440] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 04/01/2015] [Indexed: 01/16/2023] Open
Abstract
A cell mechanical stimulation equipment, based on cell substrate deformation, and a more sensitive method for measuring adhesion of cells were developed. A probe, precisely positioned close to the cell, was capable of a vertical localized mechanical stimulation with a temporal frequency of 207 Hz, and strain magnitude of 50%. This setup was characterized and used to probe the response of Human Umbilical Endothelial Vein Cells (HUVECs) in terms of calcium signaling. The intracellular calcium ion concentration was measured by the genetically encoded Cameleon biosensor, with the Transient Receptor Potential cation channel, subfamily M, member 7 (TRPM7) expression inhibited. As TRPM7 expression also regulates adhesion, a relatively simple method for measuring adhesion of cells was also developed, tested and used to study the effect of adhesion alone. Three adhesion conditions of HUVECs on polyacrylamide gel dishes were compared. In the first condition, the substrate is fully treated with Sulfo-SANPAH crosslinking and fibronectin. The other two conditions had increasingly reduced adhesion: partially treated (only coated with fibronectin, with no use of Sulfo-SANPAH, at 5% of the normal amount) and non-treated polyacrylamide gels. The cells showed adhesion and calcium response to the mechanical stimulation correlated to the degree of gel treatment: highest for fully treated gels and lowest for non-treated ones. TRPM7 inhibition by siRNA on HUVECs caused an increase in adhesion relative to control (no siRNA treatment) and non-targeting siRNA, but a decrease to 80% of calcium response relative to non-targeting siRNA which confirms the important role of TRPM7 in mechanotransduction despite the increase in adhesion.
Collapse
|
17
|
Pajic-Lijakovic I, Milivojevic M. Actin Cortex Rearrangement Caused by Coupling with the Lipid Bilayer-Modeling Considerations. J Membr Biol 2015; 248:337-47. [DOI: 10.1007/s00232-015-9775-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 01/23/2015] [Indexed: 10/24/2022]
|
18
|
Hwang JY, Lim HG, Yoon CW, Lam KH, Yoon S, Lee C, Chiu CT, Kang BJ, Kim HH, Shung KK. Non-contact high-frequency ultrasound microbeam stimulation for studying mechanotransduction in human umbilical vein endothelial cells. ULTRASOUND IN MEDICINE & BIOLOGY 2014; 40:2172-82. [PMID: 25023109 PMCID: PMC4130794 DOI: 10.1016/j.ultrasmedbio.2014.03.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 03/09/2014] [Accepted: 03/12/2014] [Indexed: 05/03/2023]
Abstract
We describe how contactless high-frequency ultrasound microbeam stimulation (HFUMS) is capable of eliciting cytoplasmic calcium (Ca(2+)) elevation in human umbilical vein endothelial cells. The cellular mechanotransduction process, which includes cell sensing and adaptation to the mechanical micro-environment, has been studied extensively in recent years. A variety of tools for mechanical stimulation have been developed to produce cellular responses. We developed a novel tool, a highly focused ultrasound microbeam, for non-contact cell stimulation at a microscale. This tool, at 200 MHz, was applied to human umbilical vein endothelial cells to investigate its potential to elicit an elevation in cytoplasmic Ca(2+) levels. It was found that the response was dose dependent, and moreover, extracellular Ca(2+) and cytoplasmic Ca(2+) stores were involved in the Ca(2+) elevation. These results suggest that high-frequency ultrasound microbeam stimulation is potentially a novel non-contact tool for studying cellular mechanotransduction if the acoustic pressures at such high frequencies can be quantified.
Collapse
Affiliation(s)
- Jae Youn Hwang
- Department of Information and Communication Engineering, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea.
| | - Hae Gyun Lim
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Chi Woo Yoon
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Kwok Ho Lam
- Department of Electrical Engineering, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong
| | - Sangpil Yoon
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Changyang Lee
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Chi Tat Chiu
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Bong Jin Kang
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Hyung Ham Kim
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - K Kirk Shung
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| |
Collapse
|
19
|
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.
Collapse
Affiliation(s)
- John M Maloney
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | | | | | | |
Collapse
|
20
|
Sackmann E, Smith AS. Physics of cell adhesion: some lessons from cell-mimetic systems. SOFT MATTER 2014; 10:1644-59. [PMID: 24651316 PMCID: PMC4028615 DOI: 10.1039/c3sm51910d] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cell adhesion is a paradigm of the ubiquitous interplay of cell signalling, modulation of material properties and biological functions of cells. It is controlled by competition of short range attractive forces, medium range repellant forces and the elastic stresses associated with local and global deformation of the composite cell envelopes. We review the basic physical rules governing the physics of cell adhesion learned by studying cell-mimetic systems and demonstrate the importance of these rules in the context of cellular systems. We review how adhesion induced micro-domains couple to the intracellular actin and microtubule networks allowing cells to generate strong forces with a minimum of attractive cell adhesion molecules (CAMs) and to manipulate other cells through filopodia over micrometer distances. The adhesion strength can be adapted to external force fluctuations within seconds by varying the density of attractive and repellant CAMs through exocytosis and endocytosis or protease-mediated dismantling of the CAM-cytoskeleton link. Adhesion domains form local end global biochemical reaction centres enabling the control of enzymes. Actin-microtubule crosstalk at adhesion foci facilitates the mechanical stabilization of polarized cell shapes. Axon growth in tissue is guided by attractive and repulsive clues controlled by antagonistic signalling pathways.
Collapse
Affiliation(s)
- Erich Sackmann
- Physics Department Technical University Munich, Germany
- Department of Physics, Ludwig-Maximillian University, Munich, Germany
| | - Ana-Sunčana Smith
- Institute for Theoretical Physics, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
- Institute Rud̷er Bošković, Zagreb, Croatia.
| |
Collapse
|
21
|
Sokolov I, Dokukin ME, Guz NV. Method for quantitative measurements of the elastic modulus of biological cells in AFM indentation experiments. Methods 2013; 60:202-13. [PMID: 23639869 DOI: 10.1016/j.ymeth.2013.03.037] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Revised: 02/25/2013] [Accepted: 03/01/2013] [Indexed: 02/09/2023] Open
Abstract
Here we overview and further develop a quantitative method to measure mechanics of biological cells in indentation experiments, which is based on the use of atomic force microscopy (AFM). We demonstrate how the elastic modulus of the cell body should be measured when the cellular brush is taken into account. The brush is an essential inelastic part of the cell, which surrounds all eukaryotic (the brush is mostly microvilli and glycocalyx) and gram-negative prokaryotic cells (the brush is polysaccharides). The other main feature of the described method is the use of a relatively dull AFM probe to stay in the linear stress-strain regime. In particular, we show that the elastic modulus (aka the Young's modulus) of cells is independent of the indentation depth up to 10-20% deformation for the eukaryotic cells studied here. Besides the elastic modulus, the method presented allows obtaining the parameters of cellular brush, such as the effective length and grafting density of the brush. Although the method is demonstrated on eukaryotic cells, it is directly applicable for all types of cells, and even non-biological soft materials surrounded by either a brush or any field of long-range forces.
Collapse
Affiliation(s)
- Igor Sokolov
- Department of Mechanical Engineering, Department of Biomedical Engineering, Tufts University, Medford, MA 02155, USA.
| | | | | |
Collapse
|
22
|
Irmscher M, de Jong AM, Kress H, Prins MWJ. A method for time-resolved measurements of the mechanics of phagocytic cups. J R Soc Interface 2013; 10:20121048. [PMID: 23466558 DOI: 10.1098/rsif.2012.1048] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The internalization of matter by phagocytosis is of key importance in the defence against bacterial pathogens and in the control of cancerous tumour growth. Despite the fact that phagocytosis is an inherently mechanical process, little is known about the forces and energies that a cell requires for internalization. Here, we use functionalized magnetic particles as phagocytic targets and track their motion while actuating them in an oscillating magnetic field, in order to measure the translational and rotational stiffnesses of the phagocytic cup as a function of time. The measured evolution of stiffness reveals a characteristic pattern with a pronounced peak preceding the finalization of uptake. The measured stiffness values and their time dependence can be interpreted with a model that describes the phagocytic cup as a prestressed membrane connected to an elastically deformable actin cortex. In the context of this model, the stiffness peak is a direct manifestation of a previously described mechanical bottleneck, and a comparison of model and data suggests that the membrane advances around the particle at a speed of about 20 nm s(-1). This approach is a novel way of measuring the progression of emerging phagocytic cups and their mechanical properties in situ and in real time.
Collapse
Affiliation(s)
- Matthias Irmscher
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands
| | | | | | | |
Collapse
|
23
|
Gan RZ, Nakmali D, Zhang X. Dynamic properties of round window membrane in guinea pig otitis media model measured with electromagnetic stimulation. Hear Res 2013; 301:125-36. [PMID: 23333258 DOI: 10.1016/j.heares.2013.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 12/05/2012] [Accepted: 01/07/2013] [Indexed: 11/29/2022]
Abstract
The round window, one of two openings into the cochlea from the middle ear, plays an important role in hearing and is known to be structurally altered during otitis media. However, there have been no published studies systematically describing the changes in biomechanical properties of the round window membrane (RWM) that accompany bacterial otitis media. Here we describe the occurrence of significant changes in the dynamic properties of the RWM between normal guinea pigs and those with acute otitis media (AOM) that are detectable by electromagnetic force stimulation and laser Doppler vibrometry (LDV) measurements. AOM was induced by transbullar injection of streptococcus pneumoniae into the middle ear, and RWM specimens were prepared three days after challenge. Vibration of the RWM induced by coil-magnet coupling was measured by LDV over frequencies of 0.2-40 kHz. The experiment was then simulated in a finite element model, and the inverse-problem solving method was used to determine the complex modulus in the frequency domain and the relaxation modulus in the time domain. Results from 18 ears (9 control ears and 9 AOM ears) established that both the storage modulus and loss modulus of the RWM from ears with AOM were significantly lower than those of RWM from uninfected ears. The average decrease of the storage modulus in AOM ears ranged from 1.5 to 2.2 MPa and the average decrease of the loss modulus was 0.025-0.48 MPa. Our findings suggest that middle ear infection primarily affects the stiffness of the RWM due to the morphological changes that occur in AOM ears. We also conclude that the coil-magnet coupling method for assessment of RWM function may provide a valuable new approach to characterizing the mechanical response of the RWM when reverse driving is selected for middle ear implantable devices. This article is part of a special issue entitled "MEMRO 2012".
Collapse
Affiliation(s)
- Rong Z Gan
- School of Aerospace and Mechanical Engineering and Bioengineering Center, University of Oklahoma, Norman, OK 73019, USA.
| | | | | |
Collapse
|
24
|
Abstract
Cross-linked actomyosin bundles retract when severed in vivo by laser ablation, or when isolated from the cell and micromanipulated in vitro in the presence of ATP. We identify the timescale for contraction as a viscoelastic time τ, where the viscosity is due to (internal) protein friction. We obtain an estimate of the order of magnitude of the contraction time τ ≈ 10-100 s, consistent with available experimental data for circumferential microfilament bundles and stress fibers. Our results are supported by an exactly solvable, hydrodynamic model of a retracting bundle as a cylinder of isotropic, active matter, from which the order of magnitude of the active stress is estimated.
Collapse
Affiliation(s)
- Natsuhiko Yoshinaga
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
| | | |
Collapse
|
25
|
Reichenberg Y, Lanir Y. Duration of microbead seeding on endothelial cells significantly affects their response to magnetic excitation. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:041915. [PMID: 22680506 DOI: 10.1103/physreve.85.041915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 03/10/2012] [Indexed: 06/01/2023]
Abstract
Our investigation of endothelial cell rheology using optical magnetic twisting cytometry revealed that with time following incubation of ferromagnetic beads on the cells, beads were sinking into the cells and an increasing number of beads demonstrated apparent absurd negative rheological properties. In parallel, the beads' average rheological response changed considerably over time, both in magnitude and in distribution. It was hypothesized that the apparent negative rheological response was related to the above sinking process of seeded beads into the cells, resulting in an elevation of the beads' rotation axis, thus causing a reversal of the beads' lateral movement direction in response to twisting external magnetic excitation. The results suggest that microbead-based rheological characterization of cells should be interpreted with caution, while considering the time of data acquisition.
Collapse
Affiliation(s)
- Yaniv Reichenberg
- Faculty of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel.
| | | |
Collapse
|
26
|
Potter CMF, Schobesberger S, Lundberg MH, Weinberg PD, Mitchell JA, Gorelik J. Shape and compliance of endothelial cells after shear stress in vitro or from different aortic regions: scanning ion conductance microscopy study. PLoS One 2012; 7:e31228. [PMID: 22359578 PMCID: PMC3281062 DOI: 10.1371/journal.pone.0031228] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Accepted: 01/04/2012] [Indexed: 12/03/2022] Open
Abstract
OBJECTIVE To measure the elongation and compliance of endothelial cells subjected to different patterns of shear stress in vitro, and to compare these parameters with the elongation and compliance of endothelial cells from different regions of the intact aorta. MATERIALS AND METHODS Porcine aortic endothelial cells were cultured for 6 days under static conditions or on an orbital shaker. The shaker generated a wave of medium, inducing pulsatile shear stress with a preferred orientation at the edge of the well or steadier shear stress with changing orientation at its centre. The topography and compliance of these cells and cells from the inner and outer curvature of ex vivo porcine aortic arches were measured by scanning ion conductance microscopy (SICM). RESULTS Cells cultured under oriented shear stress were more elongated and less compliant than cells grown under static conditions or under shear stress with no preferred orientation. Cells from the outer curvature of the aorta were more elongated and less compliant than cells from the inner curvature. CONCLUSION The elongation and compliance of cultured endothelial cells vary according to the pattern of applied shear stress, and are inversely correlated. A similar inverse correlation occurs in the aortic arch, with variation between regions thought to experience different haemodynamic stresses.
Collapse
Affiliation(s)
- Claire M. F. Potter
- Cardiothoracic Pharmacology, Pharmacology and Toxicology and Functional Microscopy, Cardiovascular Sciences, National Heart and Lung Institute, London, United Kingdom
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Sophie Schobesberger
- Cardiothoracic Pharmacology, Pharmacology and Toxicology and Functional Microscopy, Cardiovascular Sciences, National Heart and Lung Institute, London, United Kingdom
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Martina H. Lundberg
- Cardiothoracic Pharmacology, Pharmacology and Toxicology and Functional Microscopy, Cardiovascular Sciences, National Heart and Lung Institute, London, United Kingdom
| | - Peter D. Weinberg
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Jane A. Mitchell
- Cardiothoracic Pharmacology, Pharmacology and Toxicology and Functional Microscopy, Cardiovascular Sciences, National Heart and Lung Institute, London, United Kingdom
| | - Julia Gorelik
- Cardiothoracic Pharmacology, Pharmacology and Toxicology and Functional Microscopy, Cardiovascular Sciences, National Heart and Lung Institute, London, United Kingdom
| |
Collapse
|
27
|
Nishitani WS, Saif TA, Wang Y. Calcium signaling in live cells on elastic gels under mechanical vibration at subcellular levels. PLoS One 2011; 6:e26181. [PMID: 22053183 PMCID: PMC3203865 DOI: 10.1371/journal.pone.0026181] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2011] [Accepted: 09/21/2011] [Indexed: 12/22/2022] Open
Abstract
A new device was designed to generate a localized mechanical vibration of flexible gels where human umbilical vein endothelial cells (HUVECs) were cultured to mechanically stimulate these cells at subcellular locations. A Fluorescence Resonance Energy Transfer (FRET)-based calcium biosensor (an improved Cameleon) was used to monitor the spatiotemporal distribution of intracellular calcium concentrations in the cells upon this mechanical stimulation. A clear increase in intracellular calcium concentrations over the whole cell body (global) can be observed in the majority of cells under mechanical stimulation. The chelation of extracellular calcium with EGTA or the blockage of stretch-activated calcium channels on the plasma membrane with streptomycin or gadolinium chloride significantly inhibited the calcium responses upon mechanical stimulation. Thapsigargin, an endoplasmic reticulum (ER) calcium pump inhibitor, or U73122, a phospholipase C (PLC) inhibitor, resulted in mainly local calcium responses occurring at regions close to the stimulation site. The disruption of actin filaments with cytochalasin D or inhibition of actomyosin contractility with ML-7 also inhibited the global calcium responses. Therefore, the global calcium response in HUVEC depends on the influx of calcium through membrane stretch-activated channels, followed by the release of inositol trisphosphate (IP3) via PLC activation to trigger the ER calcium release. Our newly developed mechanical stimulation device can also provide a powerful tool for the study of molecular mechanism by which cells perceive the mechanical cues at subcellular levels.
Collapse
Affiliation(s)
- Wagner Shin Nishitani
- Department of Bioengineering and Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States of America
- The Capes Foundation, Ministry of Education of Brazil, Brasília, Distrito Federal, Brazil
| | - Taher A. Saif
- Department of Mechanical Science and Engineering, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail: (YW); (TAS)
| | - Yingxiao Wang
- Department of Bioengineering and Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States of America
- Integrative and Molecular Physiology, Center for Biophysics and Computational Biology, Institute for Genomic Biology, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail: (YW); (TAS)
| |
Collapse
|
28
|
Zidovska A, Sackmann E. On the mechanical stabilization of filopodia. Biophys J 2011; 100:1428-37. [PMID: 21402024 DOI: 10.1016/j.bpj.2011.01.069] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 01/12/2011] [Accepted: 01/27/2011] [Indexed: 01/13/2023] Open
Abstract
We studied force-induced elongation of filopodia by coupling magnetic tweezers to the tip through the bacterial coat protein invasin, which couples the force generator to the actin bundles (through myosin X), thus impeding the growth of the actin plus end. Single force pulses (15-30 s) with amplitudes between 20 and 600 pN and staircase-like force scenarios (amplitudes, ∼50 pN; step widths, 30 s) were applied. In both cases, the responses consist of a fast viscoelastic deflection followed by a linear flow regime. The deflections are reversible after switching off the forces, suggesting a mechanical memory. The elongation velocity exhibits an exponential distribution (half-width <v(1/2)>, ∼0.02 μm s(-1)) and did not increase systematically with the force amplitudes. We estimate the bending modulus (0.4 × 10(-23) J m) and the number of actin filaments (∼10) by analyzing filopodium bending fluctuations. Sequestering of intracellular Ca(2+) by BAPTA caused a strong reduction in the amplitude of elongation, whereas latrunculin A resulted in loss of the elastic response. We attribute the force-independent velocity to the elongation of actin bundles enabled by the force-induced actin membrane uncoupling and the reversibility by the treadmilling mechanism and an elastic response.
Collapse
|
29
|
Wilson LG, Poon WCK. Small-world rheology: an introduction to probe-based active microrheology. Phys Chem Chem Phys 2011; 13:10617-30. [PMID: 21556428 DOI: 10.1039/c0cp01564d] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We introduce active, probe-based microrheological techniques for measuring the flow and deformation of complex fluids. These techniques are ideal for mechanical characterization either when little sample is available, or when samples show significant spatial heterogeneity. We review recent results, paying particular attention to comparing and contrasting rheological parameters obtained from micro- and macro-rheological techniques.
Collapse
Affiliation(s)
- Laurence G Wilson
- SUPA and School of Physics and Astronomy, The University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ, UK
| | | |
Collapse
|
30
|
Schillers H, Wälte M, Urbanova K, Oberleithner H. Real-time monitoring of cell elasticity reveals oscillating myosin activity. Biophys J 2011; 99:3639-46. [PMID: 21112288 DOI: 10.1016/j.bpj.2010.09.048] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 08/30/2010] [Accepted: 09/22/2010] [Indexed: 10/18/2022] Open
Abstract
The cytoskeleton is the physical and biochemical interface for a large variety of cellular processes. Its complex regulation machinery is involved upstream and downstream in various signaling pathways. The cytoskeleton determines the mechanical properties of a cell. Thus, cell elasticity could serve as a parameter reflecting the behavior of the system rather than reflecting the specific properties of isolated components. In this study, we used atomic force microscopy to perform real-time monitoring of cell elasticity unveiling cytoskeletal dynamics of living bronchial epithelial cells. In resting cells, we found a periodic activity of the cytoskeleton. Amplitude and frequency of this spontaneous oscillation were strongly affected by intracellular calcium. Experiments reveal that basal cell elasticity and superimposed elasticity oscillations are caused by the collective action of myosin motor proteins. We characterized the cell as a mechanically multilayered structure, and followed cytoskeletal dynamics in the different layers with high time resolution. In conclusion, the collective activities of the myosin motor proteins define overall mechanical cell dynamics, reflecting specific changes of the chemical and mechanical environment.
Collapse
Affiliation(s)
- Hermann Schillers
- Institute of Physiology II, University of Münster, Münster, Germany.
| | | | | | | |
Collapse
|
31
|
Colbert MJ, Brochard-Wyart F, Fradin C, Dalnoki-Veress K. Squeezing and detachment of living cells. Biophys J 2011; 99:3555-62. [PMID: 21112279 DOI: 10.1016/j.bpj.2010.10.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Revised: 10/03/2010] [Accepted: 10/06/2010] [Indexed: 01/16/2023] Open
Abstract
The interaction of living cells with their environment is linked to their adhesive and elastic properties. Even if the mechanics of simple lipid membranes is fairly well understood, the analysis of single cell experiments remains challenging in part because of the mechanosensory response of cells to their environment. To study the mechanical properties of living cells we have developed a tool that borrows from micropipette aspiration techniques, atomic force microscopy, and the classical Johnson-Kendall-Roberts test. We show results from a study of the adhesion properties of living cells, as well as the elastic response and relaxation. We present models that are applied throughout the different stages of an experiment, which indicate that the contribution of the different components of the cell are active at various stages of compression, retraction, and detachment. Finally, we present a model that attempts to elucidate the surprising logarithmic relaxation observed when the cell is subjected to a given deformation.
Collapse
Affiliation(s)
- Marie-Josée Colbert
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada
| | | | | | | |
Collapse
|
32
|
Dubiel EA, Martin Y, Vermette P. Bridging the Gap Between Physicochemistry and Interpretation Prevalent in Cell−Surface Interactions. Chem Rev 2011; 111:2900-36. [DOI: 10.1021/cr9002598] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Evan A. Dubiel
- Laboratoire de bio-ingénierie et de biophysique de l’Université de Sherbrooke, Department of Chemical and Biotechnological Engineering, Université de Sherbrooke, 2500 Boulevard de l’Université, Sherbrooke, Québec, Canada J1K 2R1
- Research Centre on Aging, Institut universitaire de gériatrie de Sherbrooke, 1036 rue Belvédère Sud, Sherbrooke, Québec, Canada J1H 4C4
| | - Yves Martin
- Laboratoire de bio-ingénierie et de biophysique de l’Université de Sherbrooke, Department of Chemical and Biotechnological Engineering, Université de Sherbrooke, 2500 Boulevard de l’Université, Sherbrooke, Québec, Canada J1K 2R1
- Research Centre on Aging, Institut universitaire de gériatrie de Sherbrooke, 1036 rue Belvédère Sud, Sherbrooke, Québec, Canada J1H 4C4
| | - Patrick Vermette
- Laboratoire de bio-ingénierie et de biophysique de l’Université de Sherbrooke, Department of Chemical and Biotechnological Engineering, Université de Sherbrooke, 2500 Boulevard de l’Université, Sherbrooke, Québec, Canada J1K 2R1
- Research Centre on Aging, Institut universitaire de gériatrie de Sherbrooke, 1036 rue Belvédère Sud, Sherbrooke, Québec, Canada J1H 4C4
| |
Collapse
|
33
|
Abstract
An outstanding problem in cell biology is how cells sense mechanical forces and how those forces affect cellular functions. During past decades, it has become evident that the deformable cytoskeleton (CSK), an intracellular network of various filamentous biopolymers, provides a physical basis for transducing mechanical signals into biochemical responses. To understand how mechanical forces regulate cellular functions, it is necessary to first understand how the CSK develops mechanical stresses in response to applied forces, and how those stresses are propagated through the CSK where various signaling molecules are immobilized. New experimental techniques have been developed to quantify cytoskeletal mechanics, which together with new computational approaches have given rise to new theories and models for describing mechanics of living cells. In this article, we discuss current understanding of cell biomechanics by focusing on the biophysical mechanisms that are responsible for the development and transmission of mechanical stresses in the cell and their effect on cellular functions. We compare and contrast various theories and models of cytoskeletal mechanics, emphasizing common mechanisms that those theories are built upon, while not ignoring irreconcilable differences. We highlight most recent advances in the understanding of mechanotransduction in the cytoplasm of living cells and the central role of the cytoskeletal prestress in propagating mechanical forces along the cytoskeletal filaments to activate cytoplasmic enzymes. It is anticipated that advances in cell mechanics will help developing novel therapeutics to treat pulmonary diseases like asthma, pulmonary fibrosis, and chronic obstructive pulmonary disease.
Collapse
|
34
|
Zeng D, Juzkiw T, Read AT, Chan DWH, Glucksberg MR, Ethier CR, Johnson M. Young's modulus of elasticity of Schlemm's canal endothelial cells. Biomech Model Mechanobiol 2010; 9:19-33. [PMID: 19387710 PMCID: PMC4319365 DOI: 10.1007/s10237-009-0156-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Accepted: 04/02/2009] [Indexed: 01/29/2023]
Abstract
Schlemm's canal (SC) endothelial cells are likely important in the physiology and pathophysiology of the aqueous drainage system of the eye, particularly in glaucoma. The mechanical stiffness of these cells determines, in part, the extent to which they can support a pressure gradient and thus can be used to place limits on the flow resistance that this layer can generate in the eye. However, little is known about the biomechanical properties of SC endothelial cells. Our goal in this study was to estimate the effective Young's modulus of elasticity of normal SC cells. To do so, we combined magnetic pulling cytometry of isolated cultured human SC cells with finite element modeling of the mechanical response of the cell to traction forces applied by adherent beads. Preliminary work showed that the immersion angles of beads attached to the SC cells had a major influence on bead response; therefore, we also measured bead immersion angle by confocal microscopy, using an empirical technique to correct for axial distortion of the confocal images. Our results showed that the upper bound for the effective Young's modulus of elasticity of the cultured SC cells examined in this study, in central, non-nuclear regions, ranged between 1,007 and 3,053 Pa, which is similar to, although somewhat larger than values that have been measured for other endothelial cell types. We compared these values to estimates of the modulus of primate SC cells in vivo, based on images of these cells under pressure loading, and found good agreement at low intraocular pressure (8-15 mm Hg). However, increasing intraocular pressure (22-30 mm Hg) appeared to cause a significant increase in the modulus of these cells. These moduli can be used to estimate the extent to which SC cells deform in response to the pressure drop across the inner wall endothelium and thereby estimate the extent to which they can generate outflow resistance.
Collapse
Affiliation(s)
- Dehong Zeng
- Department of Biomedical Engineering, Northwestern University, Evanston, USA
| | - Taras Juzkiw
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | - A. Thomas Read
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | - Darren W.-H. Chan
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | | | - C. Ross Ethier
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada. Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada. Department of Bioengineering, Imperial College London, London, UK
| | - Mark Johnson
- Department of Biomedical Engineering, Northwestern University, Evanston, USA
| |
Collapse
|
35
|
Proposed Spring Network Cell Model Based on a Minimum Energy Concept. Ann Biomed Eng 2010; 38:1530-8. [DOI: 10.1007/s10439-010-9930-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Accepted: 01/13/2010] [Indexed: 11/29/2022]
|
36
|
Lee SK, Kim Y, Kim SS, Lee JH, Cho K, Lee SS, Lee ZW, Kwon KH, Kim YH, Suh-Kim H, Yoo JS, Park YM. Differential expression of cell surface proteins in human bone marrow mesenchymal stem cells cultured with or without basic fibroblast growth factor containing medium. Proteomics 2009; 9:4389-405. [PMID: 19655310 DOI: 10.1002/pmic.200900165] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Mesenchymal stem cells (MSCs) are multipotent cells, which have the capability to differentiate into various mesenchymal tissues such as bone, cartilage, fat, tendon, muscle, and marrow stroma. However, they lose the capability of multi-lineage differentiation after several passages. It is known that basic fibroblast growth factor (bFGF) increases growth rate, differentiation potential, and morphological changes of MSCs in vitro. In this report, we have used 2-DE coupled to MS to identify differentially expressed proteins at the cell membrane level in MSCs growing in bFGF containing medium. The cell surface proteins isolated by the biotin-avidin affinity column were separated by 2-DE in triplicate experiments. A total of 15 differentially expressed proteins were identified by quadrupole-time of flight tandem MS. Nine of the proteins were upregulated and six proteins were downregulated in the MSCs cultured with bFGF containing medium. The expression level of three actin-related proteins, F-actin-capping protein subunit alpha-1, actin-related protein 2/3 complex subunit 2, and myosin regulatory light chain 2, was confirmed by Western blot analysis. The results indicate that the expression levels of F-actin-capping protein subunit alpha-1, actin-related protein 2/3 complex subunit 2, and myosin regulatory light chain 2 are important in bFGF-induced morphological change of MSCs.
Collapse
Affiliation(s)
- Sang Kwang Lee
- Mass Spectrometry Research Center, Korea Basic Science Institute, Daejeon, Republic of Korea
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Paszek MJ, Boettiger D, Weaver VM, Hammer DA. Integrin clustering is driven by mechanical resistance from the glycocalyx and the substrate. PLoS Comput Biol 2009; 5:e1000604. [PMID: 20011123 PMCID: PMC2782178 DOI: 10.1371/journal.pcbi.1000604] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Accepted: 11/09/2009] [Indexed: 01/16/2023] Open
Abstract
Integrins have emerged as key sensory molecules that translate chemical and physical cues from the extracellular matrix (ECM) into biochemical signals that regulate cell behavior. Integrins function by clustering into adhesion plaques, but the molecular mechanisms that drive integrin clustering in response to interaction with the ECM remain unclear. To explore how deformations in the cell-ECM interface influence integrin clustering, we developed a spatial-temporal simulation that integrates the micro-mechanics of the cell, glycocalyx, and ECM with a simple chemical model of integrin activation and ligand interaction. Due to mechanical coupling, we find that integrin-ligand interactions are highly cooperative, and this cooperativity is sufficient to drive integrin clustering even in the absence of cytoskeletal crosslinking or homotypic integrin-integrin interactions. The glycocalyx largely mediates this cooperativity and hence may be a key regulator of integrin function. Remarkably, integrin clustering in the model is naturally responsive to the chemical and physical properties of the ECM, including ligand density, matrix rigidity, and the chemical affinity of ligand for receptor. Consistent with experimental observations, we find that integrin clustering is robust on rigid substrates with high ligand density, but is impaired on substrates that are highly compliant or have low ligand density. We thus demonstrate how integrins themselves could function as sensory molecules that begin sensing matrix properties even before large multi-molecular adhesion complexes are assembled. Critical cell decisions, including whether to live, proliferate, or assemble into tissue structures, are directed by cues from the extracellular matrix, the external protein scaffold that surrounds cells. Integrin receptors on the cell surface bind to the extracellular matrix and cluster into complexes that translate matrix cues into the set of instructions a cell follows. Using a newly developed model of the cell-matrix interface, in this work we detail a simple yet efficient mechanism by which integrins could “sense” important matrix properties, including chemical composition and mechanical stiffness, and cluster appropriately. This mechanism relies on mechanical resistance to integrin-matrix interaction provided by the glycocalyx, the slimy sugar and protein coating on the cell, as well as the stiffness of the matrix and the cell itself. In general, the resistance alters integrin-ligand reaction rates, such that integrin clustering is favored for many physiologically relevant conditions. Interestingly, the mechanical properties of the cell and ECM are altered in many prevalent diseases, such as cancer, and our work suggests how these mechanical perturbations might adversely influence integrin function.
Collapse
Affiliation(s)
- Matthew J. Paszek
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, California, United States of America
| | - David Boettiger
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Valerie M. Weaver
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, California, United States of America
- Department of Anatomy, University of California, San Francisco, San Francisco, California, United States of America
- Department of Bioengineering and Therapeutic Sciences, Institute for Regenerative Medicine and UCSF Comprehensive Cancer Center, University of California, San Francisco, San Francisco, California, United States of America
| | - Daniel A. Hammer
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
| |
Collapse
|
38
|
Hoffman BD, Crocker JC. Cell mechanics: dissecting the physical responses of cells to force. Annu Rev Biomed Eng 2009; 11:259-88. [PMID: 19400709 DOI: 10.1146/annurev.bioeng.10.061807.160511] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
It is now widely appreciated that normal tissue morphology and function rely upon cells' ability to sense and generate forces appropriate to their correct tissue context. Although the effects of forces on cells have been studied for decades, our understanding of how those forces propagate through and act on different cell substructures remains at an early stage. The past decade has seen a resurgence of interest, with a variety of different micromechanical methods in current use that probe cells' dynamic deformation in response to a time-varying force. The ability of researchers to carefully measure the mechanical properties of cells subjected to a variety of pharmacological and genetic interventions, however, currently outstrips our ability to quantitatively interpret the data in many cases. Despite these challenges, the stage is now set for the development of detailed models for cell deformability, motility, and mechanosensing that are rooted at the molecular level.
Collapse
Affiliation(s)
- Brenton D Hoffman
- Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia 22901, USA.
| | | |
Collapse
|
39
|
Cuerrier CM, Gagner A, Lebel R, Gobeil F, Grandbois M. Effect of thrombin and bradykinin on endothelial cell mechanical properties monitored through membrane deformation. J Mol Recognit 2009; 22:389-96. [DOI: 10.1002/jmr.953] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
|
40
|
Abstract
Life is a mechanical process. Cells, tissues, and bodies must act within their environments to grow, divide, move, communicate, and defend themselves. The stiffness and viscosity of cells and biologic materials will vary depending upon a wide variety of variables including for example environmental conditions, activation of signaling pathways, stage of development, gene expression. By pushing and pulling cells or materials such as mucus or extracellular matrix, one can learn about their mechanical properties. By varying the conditions, signaling pathways or genetic background, one can also assess how the response of the cell or material is modulated by that pathway. Magnetic particles are available commercially in many useful sizes, magnetic contents, and surface chemistries. The variety of surface chemistries allow forces to be applied to a specimen through specific linkages such as receptors or particular proteins, allowing the biologist to ask fundamental questions about the role of those linkages in the transduction of force or motion. In this chapter, we discuss the use of a magnetic system designed to apply a wide range of forces and force patterns fully integrated into a high numerical aperture inverted fluorescence microscope. Fine, thin and flat magnetic poles allow the use of high magnification microscope objectives, and flexible software to control the direction and pattern of applied forces supports a variety of experimental situations. The system can be coupled with simple video acquisition for medium-bandwidth, two-dimensional particle tracking. Alternatively, the system can be coupled with a laser tracking and position feedback system for higher resolution, high bandwidth, three-dimensional tracking.
Collapse
|
41
|
Elasticity measurement of living cells with an atomic force microscope: data acquisition and processing. Pflugers Arch 2008; 457:551-9. [DOI: 10.1007/s00424-008-0524-3] [Citation(s) in RCA: 172] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Accepted: 04/22/2008] [Indexed: 01/19/2023]
|
42
|
Brevier J, Montero D, Svitkina T, Riveline D. The asymmetric self-assembly mechanism of adherens junctions: a cellular push-pull unit. Phys Biol 2008; 5:016005. [PMID: 18379019 DOI: 10.1088/1478-3975/5/1/016005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
To form adherens junctions (AJ), cells first establish contact by sending out lamellipodia onto neighboring cells. We investigated the role of contacting cells in AJ assembly by studying an asymmetric AJ motif: finger-like AJ extending across the cell-cell interface. Using a cytoskeleton replica and immunofluorescence, we observed that actin bundles embedded in the lamellipodia are co-localized with stress fibers in the neighboring cell at the AJ. This suggests that donor lamellipodia present actin fingers, which are stabilized by acceptor lamellae via acto-myosin contractility. Indeed, we show that changes in actin network geometry promoted by Rac overexpression lead to corresponding changes in AJ morphology. Moreover, contractility inhibition and enhancement (via drugs or local traction) lead respectively to the disappearance and further growth of AJ fingers. Thus, we propose that receiving lamellae exert a local pull on AJ, promoting further polymerization of the donor actin bundles. In spite of different compositions, AJ and focal contacts both act as cellular mechanosensors.
Collapse
Affiliation(s)
- Julien Brevier
- Laboratoire de Spectrométrie Physique, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5588, Université Joseph Fourier, 38402 Saint-Martin d'Hères, France
| | | | | | | |
Collapse
|
43
|
Hoffman BD, Massiera G, Crocker JC. Fragility and mechanosensing in a thermalized cytoskeleton model with forced protein unfolding. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:051906. [PMID: 18233686 DOI: 10.1103/physreve.76.051906] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Indexed: 05/25/2023]
Abstract
We describe a model of cytoskeletal mechanics based on the force-induced conformational change of protein cross-links in a stressed polymer network. Slow deformation of simulated networks containing cross-links that undergo repeated, serial domain unfolding leads to an unusual state-with many cross-links accumulating near the critical force for further unfolding. This state is robust to thermalization and does not occur in similar protein unbinding based simulations. Moreover, we note that the unusual configuration of near-critical protein cross-links in the fragile state provides a physical mechanism for the chemical transduction of cell-level mechanical strain and extra-cellular matrix stiffness.
Collapse
Affiliation(s)
- Brenton D Hoffman
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | | | | |
Collapse
|
44
|
Kamgoué A, Ohayon J, Tracqui P. Estimation of cell Young's modulus of adherent cells probed by optical and magnetic tweezers: influence of cell thickness and bead immersion. J Biomech Eng 2007; 129:523-30. [PMID: 17655473 DOI: 10.1115/1.2746374] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
A precise characterization of cell elastic properties is crucial for understanding the mechanisms by which cells sense mechanical stimuli and how these factors alter cellular functions. Optical and magnetic tweezers are micromanipulation techniques which are widely used for quantifying the stiffness of adherent cells from their response to an external force applied on a bead partially embedded within the cell cortex. However, the relationships between imposed external force and resulting bead translation or rotation obtained from these experimental techniques only characterize the apparent cell stiffness. Indeed, the value of the estimated apparent cell stiffness integrates the effect of different geometrical parameters, the most important being the bead embedding angle 2gamma, bead radius R, and cell height h. In this paper, a three-dimensional finite element analysis was used to compute the cell mechanical response to applied force in tweezer experiments and to explicit the correcting functions which have to be used in order to infer the intrinsic cell Young's modulus from the apparent elasticity modulus. Our analysis, performed for an extensive set of values of gamma, h, and R, shows that the most relevant parameters for computing the correcting functions are the embedding half angle gamma and the ratio h(u)/2R, where h(u) is the under bead cell thickness. This paper provides original analytical expressions of these correcting functions as well as the critical values of the cell thickness below which corrections of the apparent modulus are necessary to get an accurate value of cell Young's modulus. Moreover, considering these results and taking benefit of previous results obtained on the estimation of cell Young's modulus of adherent cells probed by magnetic twisting cytometry (MTC) (Ohayon, J., and Tracqui, P., 2005, Ann. Biomed. Eng., 33, pp. 131-141), we were able to clarify and to solve the still unexplained discrepancies reported between estimations of elasticity modulus performed on the same cell type and probed with MTC and optical tweezers (OT). More generally, this study may strengthen the applicability of optical and magnetic tweezers techniques by insuring a more precise estimation of the intrinsic cell Young's modulus (CYM).
Collapse
Affiliation(s)
- Alain Kamgoué
- Laboratoire TIMC-IMAG, Equipe DynaCell, CNRS UMR 5525, Institut de l'Ingénierie de l'Information de Santé, Faculté de Médecine, 38706 La Tronche Cedex, France.
| | | | | |
Collapse
|
45
|
Lenormand G, Bursac P, Butler JP, Fredberg JJ. Out-of-equilibrium dynamics in the cytoskeleton of the living cell. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:041901. [PMID: 17995020 DOI: 10.1103/physreve.76.041901] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Revised: 07/09/2007] [Indexed: 05/05/2023]
Abstract
We report here measurements of rheological properties of the human airway smooth muscle cell using forced nanoscale motions of Arg-Gly-Asp RGD-coated microbeads tightly bound to the cytoskeleton. With changes of forcing amplitude, the storage modulus showed small but systematic nonlinearities, especially after treatment with a contractile agonist. In a dose-dependent manner, a large oscillatory shear applied from a few seconds up to 400 s caused the cytoskeleton matrix to soften, a behavior comparable to physical rejuvenation observed in certain inert soft materials; the stiffness remained constant for as long as the large oscillatory shear was maintained, but suddenly fell with shear cessation. Stiffness then followed a slow scale-free recovery, a phenomenon comparable to physical aging. However, acetylated low-density lipoprotein acLDL-coated microbeads, which connect mainly to scavenger receptors, did not show similar out-of-equilibrium behaviors. Taken together, these data demonstrate in the cytoskeleton of the living cell behaviors with all the same signatures as that of soft inert condensed systems. This unexpected intersection of condensed matter physics and cytoskeletal biology suggests that trapping, intermittency, and approach to kinetic arrest represent central mesoscale features linking underlying molecular events to integrative cellular functions.
Collapse
Affiliation(s)
- Guillaume Lenormand
- Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, Massachusetts 02115, USA
| | | | | | | |
Collapse
|
46
|
Hirata H, Tatsumi H, Sokabe M. Dynamics of actin filaments during tension-dependent formation of actin bundles. Biochim Biophys Acta Gen Subj 2007; 1770:1115-27. [PMID: 17498881 DOI: 10.1016/j.bbagen.2007.03.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Revised: 03/07/2007] [Accepted: 03/22/2007] [Indexed: 01/09/2023]
Abstract
The actin cytoskeleton stress fiber is an actomyosin-based contractile structure seen as a bundle of actin filaments. Although tension development in a cell is believed to regulate stress fiber formation, little is known for the underlying biophysical mechanisms. To address this question, we examined the effects of tension on the behaviors of individual actin filaments during stress fiber (actin bundle) formation using cytosol-free semi-intact fibroblast cells that were pre-treated with the Rho kinase inhibitor Y-27632 to disassemble stress fibers into a meshwork of actin filaments. These filaments were sparsely labeled with quantum dots for live tracking of their motions. When ATP and Ca(2+) were applied to the semi-intact cells to generate actomyosin-based forces, actin meshwork in the protruded lamellae was dragged toward the cell body, while the periphery of the meshwork remained in the original region, indicating that centripetally directed tension developed in the meshwork. Then the individual actin filaments in the meshwork moved towards the cell body accompanied with sudden changes in the direction of their movements, finally forming actin bundles along the direction of tension. Dragging the meshwork by externally applied mechanical forces also exerted essentially the same effects. These results suggest the existence of tension-dependent remodeling of cross-links within the meshwork during the rearrangement of actin filaments, thus demonstrating that tension is a key player to regulate the dynamics of individual actin filaments that leads to actin bundle formation.
Collapse
Affiliation(s)
- Hiroaki Hirata
- ICORP/SORST, Cell Mechanosensing Project, Japan Science and Technology Agency, 65 Tsurumai, Showa-ku, Nagoya, Aichi 466-8550, Japan
| | | | | |
Collapse
|
47
|
Tada S, Dong C, Tarbell JM. Effect of the stress phase angle on the strain energy density of the endothelial plasma membrane. Biophys J 2007; 93:3026-33. [PMID: 17660317 PMCID: PMC2025663 DOI: 10.1529/biophysj.106.100685] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Endothelial cells are simultaneously exposed to the mechanical forces of fluid wall shear stress (WSS) imposed by blood flow and solid circumferential stress (CS) induced by the blood vessel's elastic response to the pressure pulse. Experiments have demonstrated that these combined forces induce unique endothelial biomolecular responses that are not characteristic of either driving force alone and that the temporal phase angle between WSS and CS, referred to as the stress phase angle, modulates endothelial responses. In this article, we provide the first theoretical model to examine the combined forces of WSS and CS on a model of the endothelial cell plasma membrane. We focus on the strain energy density of the membrane that modulates the opening of ion channels that can mediate signal transduction. The model shows a significant influence of the stress phase angle on the strain energy density at the upstream and downstream ends of the cell where mechanotransduction is most likely to occur.
Collapse
Affiliation(s)
- Shigeru Tada
- Department of Applied Physics, National Defense Academy, Yokosuka City, Japan
| | | | | |
Collapse
|
48
|
Unnikrishnan GU, Unnikrishnan VU, Reddy JN. Constitutive material modeling of cell: a micromechanics approach. J Biomech Eng 2007; 129:315-23. [PMID: 17536898 DOI: 10.1115/1.2720908] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The variations in mechanical properties of cells obtained from experimental and theoretical studies can be overcome only through the development of a sound mathematical framework correlating the derived mechanical property with the cellular structure. Such a formulation accounting for the inhomogeneity of the cytoplasm due to stress fibers and actin cortex is developed in this work. The proposed model is developed using the Mori-Tanaka method of homogenization by treating the cell as a fiber-reinforced composite medium satisfying the continuum hypothesis. The validation of the constitutive model using finite element analysis on atomic force microscopy (AFM) and magnetic twisting cytometry (MTC) has been carried out and is found to yield good correlation with reported experimental results. It is observed from the study that as the volume fraction of the stress fiber increases, the stiffness of the cell increases and it alters the force displacement behavior for the AFM and MTC experiments. Through this model, we have also been able to find the stress fiber as a likely cause of the differences in the derived mechanical property from the AFM and MTC experiments. The correlation of the mechanical behavior of the cell with the cell composition, as obtained through this study, is an important observation in cell mechanics.
Collapse
Affiliation(s)
- G U Unnikrishnan
- Advanced Computational Mechanics Laboratory, Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123, USA
| | | | | |
Collapse
|
49
|
McDowell EJ, Ellerbee AK, Choma MA, Applegate BE, Izatt JA. Spectral domain phase microscopy for local measurements of cytoskeletal rheology in single cells. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:044008. [PMID: 17867812 DOI: 10.1117/1.2753755] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We present spectral domain phase microscopy (SDPM) as a new tool for measurements at the cellular scale. SDPM is a functional extension of spectral domain optical coherence tomography that allows for the detection of cellular motions and dynamics with nanometer-scale sensitivity in real time. Our goal was to use SDPM to investigate the mechanical properties of the cytoskeleton of MCF-7 cells. Magnetic tweezers were designed to apply a vertical force to ligand-coated magnetic beads attached to integrin receptors on the cell surfaces. SDPM was used to resolve cell surface motions induced by the applied stresses. The cytoskeletal response to an applied force is shown for both normal cells and those with compromised actin networks due to treatment with Cytochalasin D. The cell response data were fit to several models for cytoskeletal rheology, including one- and two-exponential mechanical models, as well as a power law. Finally, we correlated displacement measurements to physical characteristics of individual cells to better compare properties across many cells, reducing the coefficient of variation of extracted model parameters by up to 50%.
Collapse
Affiliation(s)
- Emily J McDowell
- Duke University, Department of Biomedical Engineering, Durham, North Carolina 27708, USA.
| | | | | | | | | |
Collapse
|
50
|
Brevier J, Vallade M, Riveline D. Force-extension relationship of cell-cell contacts. PHYSICAL REVIEW LETTERS 2007; 98:268101. [PMID: 17678130 DOI: 10.1103/physrevlett.98.268101] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Indexed: 05/16/2023]
Abstract
Adherens junctions (AJ) are adhesive motifs joining neighboring cells. The physical contacts are fingerlike structures which grow perpendicular to the cell-cell interface. While their length may vary with the applied force, their density is independent of length. Here we measure AJ contact lengths while varying the mean contractile force of the cell using nocodazole. Using this assay and a simple mechanical model, we measure an effective spring constant of about 30 pN/microm per finger. This measurement may enable the estimation of cell monolayer force distributions from a simple AJ image.
Collapse
Affiliation(s)
- Julien Brevier
- Laboratoire de Spectrométrie Physique (CNRS), UMR 5588, Université Joseph Fourier, Saint-Martin d'Hères, France
| | | | | |
Collapse
|