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Markova O, Clanet C, Husson J. Quantifying both viscoelasticity and surface tension: Why sharp tips overestimate cell stiffness. Biophys J 2024; 123:210-220. [PMID: 38087780 PMCID: PMC10808041 DOI: 10.1016/j.bpj.2023.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 09/10/2023] [Accepted: 12/07/2023] [Indexed: 12/23/2023] Open
Abstract
Quantifying the mechanical properties of cells is important to better understand how mechanics constrain cellular processes. Furthermore, because pathologies are usually paralleled by altered cell mechanical properties, mechanical parameters can be used as a novel way to characterize the pathological state of cells. Key features used in models are cell tension, cell viscoelasticity (representing the average of the cell bulk), or a combination of both. It is unclear which of these features is the most relevant or whether both should be included. To clarify this, we performed microindentation experiments on cells with microindenters of various tip radii, including micrometer-sized microneedles. We obtained different cell-indenter contact radii and measured the corresponding contact stiffness. We derived a model predicting that this contact stiffness should be an affine function of the contact radius and that, at vanishing contact radius, the cell stiffness should be equal to the cell tension multiplied by a constant. When microindenting leukocytes and both adherent and trypsinized adherent cells, the contact stiffness was indeed an affine function of the contact radius. For leukocytes, the deduced surface tension was consistent with that measured using micropipette aspiration. For detached endothelial cells, agreement between microindentation and micropipette aspiration was better when considering these as only viscoelastic when analyzing micropipette aspiration experiments. This work suggests that indenting cells with sharp tips but neglecting the presence of surface tension leads to an effective elastic modulus whose origin is in fact surface tension. Accordingly, using sharp tips when microindenting a cell is a good way to directly measure its surface tension without the need to let the viscoelastic modulus relax.
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Affiliation(s)
- Olga Markova
- Laboratoire d'Hydrodynamique (LadHyX), CNRS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
| | - Christophe Clanet
- Laboratoire d'Hydrodynamique (LadHyX), CNRS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
| | - Julien Husson
- Laboratoire d'Hydrodynamique (LadHyX), CNRS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau, France.
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2
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Arce FT, Younger S, Gaber AA, Mascarenhas JB, Rodriguez M, Dudek SM, Garcia JGN. Lamellipodia dynamics and microrheology in endothelial cell paracellular gap closure. Biophys J 2023; 122:4730-4747. [PMID: 37978804 PMCID: PMC10754712 DOI: 10.1016/j.bpj.2023.11.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 05/06/2023] [Accepted: 11/16/2023] [Indexed: 11/19/2023] Open
Abstract
Vascular endothelial cells (ECs) form a semipermeable barrier separating vascular contents from the interstitium, thereby regulating the movement of water and molecular solutes across small intercellular gaps, which are continuously forming and closing. Under inflammatory conditions, however, larger EC gaps form resulting in increased vascular leakiness to circulating fluid, proteins, and cells, which results in organ edema and dysfunction responsible for key pathophysiologic findings in numerous inflammatory disorders. In this study, we extend our earlier work examining the biophysical properties of EC gap formation and now address the role of lamellipodia, thin sheet-like membrane projections from the leading edge, in modulating EC spatial-specific contractile properties and gap closure. Micropillars, fabricated by soft lithography, were utilized to form reproducible paracellular gaps in human lung ECs. Using time-lapse imaging via optical microscopy, rates of EC gap closure and motility were measured with and without EC stimulation with the barrier-enhancing sphingolipid, sphingosine-1-phosphate. Peripheral ruffle formation was ubiquitous during gap closure. Kymographs were generated to quantitatively compare the lamellipodia dynamics of sphingosine-1-phosphate-stimulated and -unstimulated ECs. Utilizing atomic force microscopy, we characterized the viscoelastic behavior of EC lamellipodia. Our results indicate decreased stiffness and increased liquid-like behavior of expanding lamellipodia compared with regions away from the cellular edge (lamella and cell body) during EC gap closure, results in sync with the rapid kinetics of protrusion/retraction motion. We hypothesize this dissipative EC behavior during gap closure is linked to actomyosin cytoskeletal rearrangement and decreased cross-linking during lamellipodia expansion. In summary, these studies of the kinetic and mechanical properties of EC lamellipodia and ruffles at gap boundaries yield insights into the mechanisms of vascular barrier restoration and potentially a model system for examining the druggability of lamellipodial protein targets to enhance vascular barrier integrity.
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Affiliation(s)
- Fernando Teran Arce
- The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, Jupiter, Florida.
| | - Scott Younger
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona
| | - Amir A Gaber
- Department of Medicine, University of Arizona, Tucson, Arizona
| | | | - Marisela Rodriguez
- The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, Jupiter, Florida; Department of Medicine, University of Arizona, Tucson, Arizona
| | - Steven M Dudek
- Department of Medicine, The University of Illinois at Chicago, Chicago, Illinois
| | - Joe G N Garcia
- The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, Jupiter, Florida.
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3
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Hu S, Liu T, Xue C, Li Y, Yang Y, Xu X, Liu B, Chen X, Zhao Y, Qin K. A high-throughput microfluidic device inspired by the Wheatstone bridge principle for characterizing the mechanical properties of single cells. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2022; 14:4813-4821. [PMID: 36382629 DOI: 10.1039/d2ay01416e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The mechanical properties of single cells have been recognized as biomarkers for identifying individual cells and diagnosing human diseases. Microfluidic devices based on the flow cytometry principle, which are not limited by the vision field of a microscope and can achieve a very high throughput, have been extensively adopted to measure the mechanical properties of single cells. However, these kinds of microfluidic devices usually required pressure-driven pumps with a very low flow rate and high precision. In this study, we developed a high-throughput microfluidic device inspired by the Wheatstone bridge principle for characterizing the mechanical properties of single cells. The microfluidic analogue of the Wheatstone bridge not only took advantage of flow cytometry, but also allowed precise control of a very low flow rate through the constricted channel with a higher input flow rate generated by a commercially available pressure-driven pump. Under different input flow rates of the pump, the apparent elastic moduli and the fluidity of osteosarcoma (U-2OS) cells and cervical carcinoma (HeLa) cells were measured by monitoring their dynamic deformations passing through the bridge-channel with different sizes of rectangular constrictions. The results showed that the input flow rate had little effect on measuring the mechanical properties of the cells, while the ratio of cell radius to effective constriction radius was different, i.e., for U-2OS cells it was 1.20 and for HeLa cells it was 1.09. Under this condition compared with predecessors, our statistic results of cell mechanical properties exhibited minimal errors. Furthermore, the cell viability after measurements was kept above 90% that demonstrated the non-destructive property of our proposed method.
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Affiliation(s)
- Siyu Hu
- School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, Liaoning Province, China
| | - Tianmian Liu
- DUT-BSU Joint Institute, Dalian University of Technology, Dalian 116024, Liaoning Province, China
| | - Chundong Xue
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, Liaoning Province, China.
| | - Yongjiang Li
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, Liaoning Province, China.
| | - Yunong Yang
- School of Biomedical Engineering, Faculty of Medicine, Dalian University of Technology, Dalian 116024, Liaoning Province, China
| | - Xing Xu
- Department of Endoscopy, Liaoning Cancer Hospital and Institute, Shenyang, 110042, Liaoning Province, China
| | - Bo Liu
- School of Biomedical Engineering, Faculty of Medicine, Dalian University of Technology, Dalian 116024, Liaoning Province, China
| | - Xiaoming Chen
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, Liaoning Province, China.
| | - Yan Zhao
- School of Biomedical Engineering, Faculty of Medicine, Dalian University of Technology, Dalian 116024, Liaoning Province, China
- Department of Gastric Cancer, Liaoning Cancer Hospital and Institute, Cancer Hospital of Dalian University of Technology, Shenyang, 110042, Liaoning Province, China
| | - Kairong Qin
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, Liaoning Province, China.
- School of Biomedical Engineering, Faculty of Medicine, Dalian University of Technology, Dalian 116024, Liaoning Province, China
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4
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Shi Y, Sivarajan S, Crocker JC, Reich DH. Measuring Cytoskeletal Mechanical Fluctuations and Rheology with Active Micropost Arrays. Curr Protoc 2022; 2:e433. [PMID: 35612274 PMCID: PMC9321978 DOI: 10.1002/cpz1.433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The dynamics of the cellular actomyosin cytoskeleton are crucial to many aspects of cellular function. Here, we describe techniques that employ active micropost array detectors (AMPADs) to measure cytoskeletal rheology and mechanical force fluctuations. The AMPADS are arrays of flexible poly(dimethylsiloxane) (PDMS) microposts with magnetic nanowires embedded in a subset of microposts to enable actuation of those posts via an externally applied magnetic field. Techniques are described to track the magnetic microposts' motion with nanometer precision at up to 100 video frames per second to measure the local cellular rheology at well-defined positions. Application of these high-precision tracking techniques to the full array of microposts in contact with a cell also enables mapping of the cytoskeletal mechanical fluctuation dynamics with high spatial and temporal resolution. This article describes (1) the fabrication of magnetic micropost arrays, (2) measurement protocols for both local rheology and cytoskeletal force fluctuation mapping, and (3) special-purpose software routines to reduce and analyze these data. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Fabrication of magnetic micropost arrays Basic Protocol 2: Data acquisition for cellular force fluctuations on non-magnetic micropost arrays Basic Protocol 3: Data acquisition for local cellular rheology measurements with magnetic microposts Basic Protocol 4: Data reduction: determining microposts' motion Basic Protocol 5: Data analysis: determining local rheology from magnetic microposts Basic Protocol 6: Data analysis for force fluctuation measurements Support Protocol 1: Fabrication of magnetic Ni nanowires by electrodeposition Support Protocol 2: Configuring Streampix for magnetic rheology measurements.
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Affiliation(s)
- Yu Shi
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland.,Current address: Department of Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina
| | - Shankar Sivarajan
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland
| | - John C Crocker
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Daniel H Reich
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland
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5
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Hang JT, Xu GK, Gao H. Frequency-dependent transition in power-law rheological behavior of living cells. SCIENCE ADVANCES 2022; 8:eabn6093. [PMID: 35522746 PMCID: PMC9075802 DOI: 10.1126/sciadv.abn6093] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Living cells are active viscoelastic materials exhibiting diverse mechanical behaviors at different time scales. However, dynamical rheological characteristics of cells in frequency range spanning many orders of magnitude, especially in high frequencies, remain poorly understood. Here, we show that a self-similar hierarchical model can capture cell's power-law rheological characteristics in different frequency scales. In low-frequency scales, the storage and loss moduli exhibit a weak power-law dependence on frequency with same exponent. In high-frequency scales, the storage modulus becomes a constant, while the loss modulus shows a power-law dependence on frequency with an exponent of 1.0. The transition between low- and high-frequency scales is defined by a transition frequency based on cell's mechanical parameters. The cytoskeletal differences of different cell types or states can be characterized by changes in mechanical parameters in the model. This study provides valuable insights into potentially using mechanics-based markers for cell classification and cancer diagnosis.
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Affiliation(s)
- Jiu-Tao Hang
- Laboratory for Multiscale Mechanics and Medical Science, Department of Engineering Mechanics, SVL, School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an 710049, China
| | - Guang-Kui Xu
- Laboratory for Multiscale Mechanics and Medical Science, Department of Engineering Mechanics, SVL, School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an 710049, China
- Corresponding author. (G.-K.X.); (H.G.)
| | - Huajian Gao
- School of Mechanical and Aerospace Engineering, College of Engineering, Nanyang Technological University, Singapore 639798, Singapore
- Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore
- Corresponding author. (G.-K.X.); (H.G.)
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6
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Vakhrusheva A, Murashko A, Trifonova E, Efremov Y, Timashev P, Sokolova O. Role of Actin-binding Proteins in the Regulation of Cellular Mechanics. Eur J Cell Biol 2022; 101:151241. [DOI: 10.1016/j.ejcb.2022.151241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 04/18/2022] [Accepted: 05/19/2022] [Indexed: 12/25/2022] Open
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7
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Taninaka A, Ugajin S, Kurokawa H, Nagoshi Y, Kamiyanagi M, Takeuchi O, Matsui H, Shigekawa H. Direct analysis of the actin-filament formation effect in photodynamic therapy. RSC Adv 2022; 12:5878-5889. [PMID: 35424553 PMCID: PMC8981521 DOI: 10.1039/d1ra09291j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 02/11/2022] [Indexed: 11/30/2022] Open
Abstract
Photodynamic therapy (PDT) is a method in which a photosensitizer is administered in vivo and irradiated with light to generate reactive oxygen species (ROS), thereby causing the selective death of cancer cells. Since PDT is a noninvasive cancer treatment method with few adverse effects, it has attracted considerable attention and is increasingly used. In PDT, there are two dominant processes based on the actin filament (A-filament) formation effect: the destruction of cells by necrosis and vascular shutdown. Despite the importance of its fine control, the mechanism of the reaction process from the generation of reactive oxygen by photoinduction inducing the formation of A-filament and its polymerization to form stress fibers (S-fibers) has not yet been clarified because, for example, it has been difficult to directly observe and quantify such processes in living cells by conventional methods. Here, we have combined atomic force microscopy (AFM) with other techniques to reveal the mechanism of the A-filament and S-fiber formation processes that underlie the cell death process due to PDT. First, it was confirmed that activation of the small G protein RhoA, which is a signal that induces an increase in A-filament production, begins immediately after PDT treatment. The production of A-filament did not increase with increasing light intensity when the amount of light was large. Namely, the activation of RhoA reached an equilibrium state in about 1 min: however, the production of A-filament and its polymerization continued. The observed process corresponds well with the change in the amount of phosphorylated myosin-light chains, which induce A-filament polymerization. The increase in the elastic modulus of cells following the formation of S-fiber was confirmed by AFM for the first time. The distribution of generated A-filament and S-fiber was consistent with the photosensitizer distribution. PDT increases A-filament production, and when the ROS concentration is high, blebbing occurs and cells die, but when it is low, cell death does not occur and S-fiber is formed. That is, it is expected that vascular shutdown can be controlled efficiently by adjusting the amount of photosensitizer and the light intensity. We have combined atomic force microscopy with other techniques to reveal the mechanism of the actin filament and stress fibers formation processes that underlies the cell death process due to photodynamic therapy.![]()
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Affiliation(s)
- Atsushi Taninaka
- Faculty of Pure and Applied Sciences, University of Tsukuba 305-8573 Ibaraki Japan .,TAKANO Co., LTD. Miyada-mura, Kamiina-gun Nagano 399-4301 Japan
| | - Shunta Ugajin
- Faculty of Pure and Applied Sciences, University of Tsukuba 305-8573 Ibaraki Japan
| | - Hiromi Kurokawa
- Faculty of Medicine, University of Tsukuba 305-8575 Ibaraki Japan
| | - Yu Nagoshi
- Faculty of Pure and Applied Sciences, University of Tsukuba 305-8573 Ibaraki Japan
| | - Mayuka Kamiyanagi
- Faculty of Pure and Applied Sciences, University of Tsukuba 305-8573 Ibaraki Japan
| | - Osamu Takeuchi
- Faculty of Pure and Applied Sciences, University of Tsukuba 305-8573 Ibaraki Japan
| | - Hirofumi Matsui
- Faculty of Medicine, University of Tsukuba 305-8575 Ibaraki Japan
| | - Hidemi Shigekawa
- Faculty of Pure and Applied Sciences, University of Tsukuba 305-8573 Ibaraki Japan
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8
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Jaslove JM, Goodwin K, Sundarakrishnan A, Spurlin JW, Mao S, Košmrlj A, Nelson CM. Transmural pressure signals through retinoic acid to regulate lung branching. Development 2022; 149:274047. [PMID: 35051272 PMCID: PMC8917413 DOI: 10.1242/dev.199726] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 12/10/2021] [Indexed: 01/22/2023]
Abstract
During development, the mammalian lung undergoes several rounds of branching, the rate of which is tuned by the relative pressure of the fluid within the lumen of the lung. We carried out bioinformatics analysis of RNA-sequencing of embryonic mouse lungs cultured under physiologic or sub-physiologic transmural pressure and identified transcription factor-binding motifs near genes whose expression changes in response to pressure. Surprisingly, we found retinoic acid (RA) receptor binding sites significantly overrepresented in the promoters and enhancers of pressure-responsive genes. Consistently, increasing transmural pressure activates RA signaling, and pharmacologically inhibiting RA signaling decreases airway epithelial branching and smooth muscle wrapping. We found that pressure activates RA signaling through the mechanosensor Yap. A computational model predicts that mechanical signaling through Yap and RA affects lung branching by altering the balance between epithelial proliferation and smooth muscle wrapping, which we test experimentally. Our results reveal that transmural pressure signals through RA to balance the relative rates of epithelial growth and smooth muscle differentiation in the developing mouse lung and identify RA as a previously unreported component in the mechanotransduction machinery of embryonic tissues.
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Affiliation(s)
- Jacob M. Jaslove
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA,Graduate School of Biomedical Sciences, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
| | - Katharine Goodwin
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Aswin Sundarakrishnan
- Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - James W. Spurlin
- Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA,Department of Biosciences, Rice University, Houston, TX 77005, USA
| | - Sheng Mao
- Department of Mechanics and Engineering Science, BIC-ESAT, College of Engineering, Peking University, Beijing 100871, People's Republic of China,Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Andrej Košmrlj
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA,Princeton Institute for the Science & Technology of Materials, Princeton, NJ 08544, USA
| | - Celeste M. Nelson
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA,Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA,Author for correspondence ()
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9
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Hang JT, Kang Y, Xu GK, Gao H. A hierarchical cellular structural model to unravel the universal power-law rheological behavior of living cells. Nat Commun 2021; 12:6067. [PMID: 34663821 PMCID: PMC8523554 DOI: 10.1038/s41467-021-26283-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 09/27/2021] [Indexed: 11/15/2022] Open
Abstract
Living cells are a complex soft material with fascinating mechanical properties. A striking feature is that, regardless of their types or states, cells exhibit a universal power-law rheological behavior which to this date still has not been captured by a single theoretical model. Here, we propose a cellular structural model that accounts for the essential mechanical responses of cell membrane, cytoplasm and cytoskeleton. We demonstrate that this model can naturally reproduce the universal power-law characteristics of cell rheology, as well as how its power-law exponent is related to cellular stiffness. More importantly, the power-law exponent can be quantitatively tuned in the range of 0.1 ~ 0.5, as found in most types of cells, by varying the stiffness or architecture of the cytoskeleton. Based on the structural characteristics, we further develop a self-similar hierarchical model that can spontaneously capture the power-law characteristics of creep compliance over time and complex modulus over frequency. The present model suggests that mechanical responses of cells may depend primarily on their generic architectural mechanism, rather than specific molecular properties. Different types of cells exhibit a universal power-law rheological behavior which to this date has not been captured by a single theoretical model. Here, the authors propose a self-similar hierarchical cellular model that can naturally reproduce the universal power-law characteristics of cell rheology.
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Affiliation(s)
- Jiu-Tao Hang
- Laboratory for Multiscale Mechanics and Medical Science, Department of Engineering Mechanics, SVL, School of Aerospace Engineering, Xi'an Jiaotong University, 710049, Xi'an, China
| | - Yu Kang
- College of Pharmaceutical Sciences, Zhejiang University, 310058, Hangzhou, China
| | - Guang-Kui Xu
- Laboratory for Multiscale Mechanics and Medical Science, Department of Engineering Mechanics, SVL, School of Aerospace Engineering, Xi'an Jiaotong University, 710049, Xi'an, China.
| | - Huajian Gao
- School of Mechanical and Aerospace Engineering, College of Engineering, Nanyang Technological University, 639798, Singapore, Singapore. .,Institute of High Performance Computing, A*STAR, 138632, Singapore, Singapore.
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10
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Jo MH, Kim BC, Sung K, Panettieri RA, An SS, Liu J, Ha T. Molecular Nanomechanical Mapping of Histamine-Induced Smooth Muscle Cell Contraction and Shortening. ACS NANO 2021; 15:11585-11596. [PMID: 34197709 PMCID: PMC10144385 DOI: 10.1021/acsnano.1c01782] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Mechanical response to external stimuli is a conserved feature of many cell types. For example, neurotransmitters (e.g., histamine) trigger calcium signals that induce actomyosin-regulated contraction of airway smooth muscle (ASM); the resulting cell shortening causes airway narrowing, the excess of which can cause asthma. Despite intensive studies, however, it remains unclear how physical forces are propagated through focal adhesion (FA)-the major force-transmission machinery of the cell-during ASM shortening. We provide a nanomechanical platform to directly image single molecule forces during ASM cell shortening by repurposing DNA tension sensors. Surprisingly, cell shortening and FA disassembly that immediately precedes it occurred long after histamine-evoked increases in intracellular calcium levels ([Ca2+]i). Our mathematical model that fully integrates cell edge protrusion and retraction with contractile forces acting on FA predicted that (1) stabilization of FA impedes cell shortening and (2) the disruption of FAs is preceded by their strengthening through actomyosin-activated molecular tension. We confirmed these predictions via real-time imaging and molecular force measurements. Together, our work highlights a key role of FA dynamics in regulating ASM contraction induced by an allergen with potential therapeutic implications.
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Affiliation(s)
- Myung Hyun Jo
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Byoung Choul Kim
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
- Division of Nano-Bioengineering, Incheon National University, Incheon 22012, South Korea
| | - Keewon Sung
- Department of Chemistry, Seoul National University, Seoul 08826, South Korea
| | - Reynold A. Panettieri
- Rutgers Institute for Translational Medicine and Science, The State University of New Jersey, New Brunswick, NJ 08901, USA
| | - Steven S. An
- Rutgers Institute for Translational Medicine and Science, The State University of New Jersey, New Brunswick, NJ 08901, USA
- Department of Pharmacology, Rutgers-Robert Wood Johnson Medical School, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Jian Liu
- Department of Cell Biology and Center for Cell Dynamics, Johns Hopkins School of Medicine, Baltimore, MD 20205, USA
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
- Howard Hughes Medical Institute, Baltimore, MD 21205, USA
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11
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Fläschner G, Roman CI, Strohmeyer N, Martinez-Martin D, Müller DJ. Rheology of rounded mammalian cells over continuous high-frequencies. Nat Commun 2021; 12:2922. [PMID: 34006873 PMCID: PMC8131594 DOI: 10.1038/s41467-021-23158-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 04/16/2021] [Indexed: 11/09/2022] Open
Abstract
Understanding the viscoelastic properties of living cells and their relation to cell state and morphology remains challenging. Low-frequency mechanical perturbations have contributed considerably to the understanding, yet higher frequencies promise to elucidate the link between cellular and molecular properties, such as polymer relaxation and monomer reaction kinetics. Here, we introduce an assay, that uses an actuated microcantilever to confine a single, rounded cell on a second microcantilever, which measures the cell mechanical response across a continuous frequency range ≈ 1-40 kHz. Cell mass measurements and optical microscopy are co-implemented. The fast, high-frequency measurements are applied to rheologically monitor cellular stiffening. We find that the rheology of rounded HeLa cells obeys a cytoskeleton-dependent power-law, similar to spread cells. Cell size and viscoelasticity are uncorrelated, which contrasts an assumption based on the Laplace law. Together with the presented theory of mechanical de-embedding, our assay is generally applicable to other rheological experiments.
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Affiliation(s)
- Gotthold Fläschner
- Eidgenössische Technische Hochschule (ETH) Zürich, Department of Biosystems Science and Engineering, Basel, Switzerland
| | - Cosmin I Roman
- Eidgenössische Technische Hochschule (ETH) Zürich, Department of Mechanical and Process Engineering, Zürich, Switzerland
| | - Nico Strohmeyer
- Eidgenössische Technische Hochschule (ETH) Zürich, Department of Biosystems Science and Engineering, Basel, Switzerland
| | - David Martinez-Martin
- Eidgenössische Technische Hochschule (ETH) Zürich, Department of Biosystems Science and Engineering, Basel, Switzerland.,The University of Sydney, School of Biomedical Engineering, NSW, Sydney, Australia
| | - Daniel J Müller
- Eidgenössische Technische Hochschule (ETH) Zürich, Department of Biosystems Science and Engineering, Basel, Switzerland.
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12
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Zak A, Merino-Cortés SV, Sadoun A, Mustapha F, Babataheri A, Dogniaux S, Dupré-Crochet S, Hudik E, He HT, Barakat AI, Carrasco YR, Hamon Y, Puech PH, Hivroz C, Nüsse O, Husson J. Rapid viscoelastic changes are a hallmark of early leukocyte activation. Biophys J 2021; 120:1692-1704. [PMID: 33730552 PMCID: PMC8204340 DOI: 10.1016/j.bpj.2021.02.042] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 11/23/2020] [Accepted: 02/23/2021] [Indexed: 11/27/2022] Open
Abstract
To accomplish their critical task of removing infected cells and fighting pathogens, leukocytes activate by forming specialized interfaces with other cells. The physics of this key immunological process are poorly understood, but it is important to understand them because leukocytes have been shown to react to their mechanical environment. Using an innovative micropipette rheometer, we show in three different types of leukocytes that, when stimulated by microbeads mimicking target cells, leukocytes become up to 10 times stiffer and more viscous. These mechanical changes start within seconds after contact and evolve rapidly over minutes. Remarkably, leukocyte elastic and viscous properties evolve in parallel, preserving a well-defined ratio that constitutes a mechanical signature specific to each cell type. Our results indicate that simultaneously tracking both elastic and viscous properties during an active cell process provides a new, to our knowledge, way to investigate cell mechanical processes. Our findings also suggest that dynamic immunomechanical measurements can help discriminate between leukocyte subtypes during activation.
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Affiliation(s)
- Alexandra Zak
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Palaiseau, France; Institut de Chimie Physique, CNRS UMR8000, Université Paris-Saclay, Orsay, France
| | | | - Anaïs Sadoun
- Aix-Marseille University, LAI UM 61, Marseille, France; Inserm, UMR_S 1067, Marseille, France; CNRS, UMR 7333, Marseille, France
| | - Farah Mustapha
- Aix-Marseille University, LAI UM 61, Marseille, France; Inserm, UMR_S 1067, Marseille, France; CNRS, UMR 7333, Marseille, France; Centre Interdisciplinaire de Nanoscience de Marseille, CNRS, Aix-Marseille University, Marseille, France
| | - Avin Babataheri
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Palaiseau, France
| | - Stéphanie Dogniaux
- Integrative analysis of T cell activation team, Institut Curie-PSL Research University, INSERM U932, Paris, France
| | - Sophie Dupré-Crochet
- Institut de Chimie Physique, CNRS UMR8000, Université Paris-Saclay, Orsay, France
| | - Elodie Hudik
- Institut de Chimie Physique, CNRS UMR8000, Université Paris-Saclay, Orsay, France
| | - Hai-Tao He
- Aix-Marseille University, CNRS, INSERM, CIML, Marseille, France
| | - Abdul I Barakat
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Palaiseau, France
| | - Yolanda R Carrasco
- B Lymphocyte Dynamics Laboratory, Centro Nacional de Biotecnología (CNB)-CSIC, Madrid, Spain
| | - Yannick Hamon
- Aix-Marseille University, CNRS, INSERM, CIML, Marseille, France
| | - Pierre-Henri Puech
- Aix-Marseille University, LAI UM 61, Marseille, France; Inserm, UMR_S 1067, Marseille, France; CNRS, UMR 7333, Marseille, France
| | - Claire Hivroz
- Integrative analysis of T cell activation team, Institut Curie-PSL Research University, INSERM U932, Paris, France
| | - Oliver Nüsse
- Institut de Chimie Physique, CNRS UMR8000, Université Paris-Saclay, Orsay, France
| | - Julien Husson
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Palaiseau, France.
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13
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Abstract
Epithelial cells possess the ability to change their shape in response to mechanical stress by remodelling their junctions and their cytoskeleton. This property lies at the heart of tissue morphogenesis in embryos. A key feature of embryonic cell shape changes is that they result from repeated mechanical inputs that make them partially irreversible at each step. Past work on cell rheology has rarely addressed how changes can become irreversible in a complex tissue. Here, we review new and exciting findings dissecting some of the physical principles and molecular mechanisms accounting for irreversible cell shape changes. We discuss concepts of mechanical ratchets and tension thresholds required to induce permanent cell deformations akin to mechanical plasticity. Work in different systems has highlighted the importance of actin remodelling and of E-cadherin endocytosis. We also list some novel experimental approaches to fine-tune mechanical tension, using optogenetics, magnetic beads or stretching of suspended epithelial tissues. Finally, we discuss some mathematical models that have been used to describe the quantitative aspects of accounting for mechanical cell plasticity and offer perspectives on this rapidly evolving field.
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Affiliation(s)
- Kelly Molnar
- Sorbonne Université, Institut de Biologie Paris-Seine (IBPS), CNRS UMR7622, 9 Quai St-Bernard, 75005 Paris, France
| | - Michel Labouesse
- Sorbonne Université, Institut de Biologie Paris-Seine (IBPS), CNRS UMR7622, 9 Quai St-Bernard, 75005 Paris, France
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14
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Liang X, Liu S, Wang X, Xia D, Li Q. Alteration of nanomechanical properties of pancreatic cancer cells through anticancer drug treatment revealed by atomic force microscopy. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2021; 12:1372-1379. [PMID: 34987950 PMCID: PMC8685561 DOI: 10.3762/bjnano.12.101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 11/26/2021] [Indexed: 05/09/2023]
Abstract
The mechanical properties of cells are key to the regulation of cell activity, and hence to the health level of organisms. Here, the morphology and mechanical properties of normal pancreatic cells (HDPE6-C7) and pancreatic cancer cells (AsPC-1, MIA PaCa-2, BxPC-3) were studied by atomic force microscopy. In addition, the mechanical properties of MIA PaCa-2 after treatment with different concentrations of doxorubicin hydrochloride (DOX) were also investigated. The results show the Young's modulus of normal cells is greater than that of three kinds of cancer cells. The Young's modulus of more aggressive cancer cell AsPC-1 is smaller than that of less aggressive cancer cell BxPC-3. In addition, the Young's modulus of MIA PaCa-2 rises with the increasing of DOX concentration. This study may provide a new strategy of detecting cancer, and evaluate the possible interaction of drugs on cells.
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Affiliation(s)
- Xiaoteng Liang
- School of Materials Science and Engineering, Hebei University of Technology and Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology, Tianjin, 300130, China
- Key Laboratory of Colloid and Interface Chemistry of Ministry of Education, And School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, Shandong, China
| | - Shuai Liu
- School of Materials Science and Engineering, Hebei University of Technology and Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology, Tianjin, 300130, China
- Key Laboratory of Colloid and Interface Chemistry of Ministry of Education, And School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, Shandong, China
| | - Xiuchao Wang
- Tianjin Medical University Cancer Institute & Hospital, Tianjin, 300060, China
| | - Dan Xia
- School of Materials Science and Engineering, Hebei University of Technology and Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology, Tianjin, 300130, China
| | - Qiang Li
- Key Laboratory of Colloid and Interface Chemistry of Ministry of Education, And School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, Shandong, China
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15
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Romanov V, Silvani G, Zhu H, Cox CD, Martinac B. An Acoustic Platform for Single-Cell, High-Throughput Measurements of the Viscoelastic Properties of Cells. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2005759. [PMID: 33326190 DOI: 10.1002/smll.202005759] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/01/2020] [Indexed: 06/12/2023]
Abstract
Cellular processes including adhesion, migration, and differentiation are governed by the distinct mechanical properties of each cell. Importantly, the mechanical properties of individual cells can vary depending on local physical and biochemical cues in a time-dependent manner resulting in significant inter-cell heterogeneity. While several different methods have been developed to interrogate the mechanical properties of single cells, throughput to capture this heterogeneity remains an issue. Here, single-cell, high-throughput characterization of adherent cells is demonstrated using acoustic force spectroscopy (AFS). AFS works by simultaneously, acoustically driving tens to hundreds of silica beads attached to cells away from the cell surface, allowing the user to measure the stiffness of adherent cells under multiple experimental conditions. It is shown that cells undergo marked changes in viscoelasticity as a function of temperature, by altering the temperature within the AFS microfluidic circuit between 21 and 37 °C. In addition, quantitative differences in cells exposed to different pharmacological treatments specifically targeting the membrane-cytoskeleton interface are shown. Further, the high-throughput format of the AFS is utilized to rapidly probe, in excess of 1000 cells, three different cell lines expressing different levels of a mechanosensitive protein, Piezo1, demonstrating the ability to differentiate between cells based on protein expression levels.
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Affiliation(s)
- Valentin Romanov
- Department of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, Darlinghurst, Sydney, NSW, 2010, Australia
| | - Giulia Silvani
- Department of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, Darlinghurst, Sydney, NSW, 2010, Australia
| | - Huiyu Zhu
- Faculty of Science, University of Technology Sydney, Ultimo, Sydney, NSW, 2007, Australia
| | - Charles D Cox
- Department of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, Darlinghurst, Sydney, NSW, 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney, NSW, 2010, Australia
| | - Boris Martinac
- Department of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, Darlinghurst, Sydney, NSW, 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney, NSW, 2010, Australia
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16
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Ouyang M, Qian Z, Bu B, Jin Y, Wang J, Zhu Y, Liu L, Pan Y, Deng L. Sensing Traction Force on the Matrix Induces Cell-Cell Distant Mechanical Communications for Self-Assembly. ACS Biomater Sci Eng 2020; 6:5833-5848. [PMID: 33320570 DOI: 10.1021/acsbiomaterials.0c01035] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The long-range biomechanical force propagating across a large scale may reserve the capability to trigger coordinative responses within cell population such as during angiogenesis, epithelial tubulogenesis, and cancer metastasis. How cells communicate in a distant manner within the group for self-assembly remains largely unknown. Here, we found that airway smooth muscle cells (ASMCs) rapidly self-assembled into a well-constructed network on 3D Matrigel containing type I collagen (COL), which relied on long-range biomechanical force across the matrix to direct cell-cell distant interactions. Similar results happened by HUVEC cells to mimic angiogenesis. Interestingly, single ASMCs initiated multiple extended protrusions precisely pointing to neighboring cells in distance (100-300 μm away or 5-10 folds of the diameter of a round single cell), depending on traction force sensing. Individual ASMCs mechanosensed each other to move directionally on both nonfibrous Matrigel only and Matrigel containing fibrous COL but lost mutual sensing on the cross-linked gel or coated glass due to no long-range force transmission. The bead tracking assay demonstrated distant transmission of traction force (up to 400 μm) during the matrix deformation, and finite element method modeling confirmed the consistency between maximum strain distribution on the matrix and cell directional movements in experiments. Furthermore, ASMCs recruited COL from the hydrogel to build a fibrous network to mechanically stabilize the cell network. Our results revealed principally that cells can sense traction force transmitted through the matrix to initiate cell-cell distant mechanical communications, resulting in cell directional migration and coordinated cell and COL self-assembly with active matrix remodeling. As an interesting phenomenon, cells seem to be able to "make a phone call" via long-range biomechanics, which implicates physiological importance such as for tissue pattern formation.
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Affiliation(s)
- Mingxing Ouyang
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
| | - Zhili Qian
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
| | - Bing Bu
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
| | - Yang Jin
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
| | - Jiajia Wang
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
| | - Yiming Zhu
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
| | - Lei Liu
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
| | - Yan Pan
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
| | - Linhong Deng
- Institute of Biomedical Engineering and Health Sciences, School of Medicine, Changzhou University, 1 Gehu Road, Wujin District, Changzhou City, Jiangsu Province 213164, China
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17
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Durand-Smet P, Spelman TA, Meyerowitz EM, Jönsson H. Cytoskeletal organization in isolated plant cells under geometry control. Proc Natl Acad Sci U S A 2020; 117:17399-17408. [PMID: 32641513 PMCID: PMC7382239 DOI: 10.1073/pnas.2003184117] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The cytoskeleton plays a key role in establishing robust cell shape. In animals, it is well established that cell shape can also influence cytoskeletal organization. Cytoskeletal proteins are well conserved between animal and plant kingdoms; nevertheless, because plant cells exhibit major structural differences to animal cells, the question arises whether the plant cytoskeleton also responds to geometrical cues. Recent numerical simulations predicted that a geometry-based rule is sufficient to explain the microtubule (MT) organization observed in cells. Due to their high flexural rigidity and persistence length of the order of a few millimeters, MTs are rigid over cellular dimensions and are thus expected to align along their long axis if constrained in specific geometries. This hypothesis remains to be tested in cellulo Here, we explore the relative contribution of geometry to the final organization of actin and MT cytoskeletons in single plant cells of Arabidopsis thaliana We show that the cytoskeleton aligns with the long axis of the cells. We find that actin organization relies on MTs but not the opposite. We develop a model of self-organizing MTs in three dimensions, which predicts the importance of MT severing, which we confirm experimentally. This work is a first step toward assessing quantitatively how cellular geometry contributes to the control of cytoskeletal organization in living plant cells.
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Affiliation(s)
- Pauline Durand-Smet
- The Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom
| | - Tamsin A Spelman
- The Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom
| | - Elliot M Meyerowitz
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125;
- Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125
| | - Henrik Jönsson
- The Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom;
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, United Kingdom
- Department of Astronomy and Theoretical Physics, Computational Biology and Biological Physics, Lund University, 221 00 Lund, Sweden
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18
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Bonfanti A, Kaplan JL, Charras G, Kabla A. Fractional viscoelastic models for power-law materials. SOFT MATTER 2020; 16:6002-6020. [PMID: 32638812 DOI: 10.1039/d0sm00354a] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Soft materials often exhibit a distinctive power-law viscoelastic response arising from broad distribution of time-scales present in their complex internal structure. A promising tool to accurately describe the rheological behaviour of soft materials is fractional calculus. However, its use in the scientific community remains limited due to the unusual notation and non-trivial properties of fractional operators. This review aims to provide a clear and accessible description of fractional viscoelastic models for a broad audience and to demonstrate the ability of these models to deliver a unified approach for the characterisation of power-law materials. The use of a consistent framework for the analysis of rheological data would help classify the empirical behaviours of soft and biological materials, and better understand their response.
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Affiliation(s)
- A Bonfanti
- Department of Engineering, University of Cambridge, UK.
| | - J L Kaplan
- Department of Engineering, University of Cambridge, UK.
| | - G Charras
- London Centre for Nanotechnology, University College London, UK and Department of Cell and Developmental Biology, University College London, UK
| | - A Kabla
- Department of Engineering, University of Cambridge, UK.
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19
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Ferreira JPS, Kuang M, Parente MPL, Natal Jorge RM, Wang R, Eppell SJ, Damaser M. Altered mechanics of vaginal smooth muscle cells due to the lysyl oxidase-like1 knockout. Acta Biomater 2020; 110:175-187. [PMID: 32335309 DOI: 10.1016/j.actbio.2020.03.046] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 03/26/2020] [Accepted: 03/31/2020] [Indexed: 01/04/2023]
Abstract
The remodeling mechanisms that cause connective tissue of the vaginal wall, consisting mostly of smooth muscle, to weaken after vaginal delivery are not fully understood. Abnormal remodeling after delivery can contribute to development of pelvic organ prolapse and other pelvic floor disorders. The present study used vaginal smooth muscle cells (vSMCs) isolated from knockout mice lacking the expression of the lysyl oxidase-like1 (LOXL1) enzyme, a well-characterized animal model for pelvic organ prolapse. We tested if vaginal smooth muscle cells from LOXL1 knockout mice have altered mechanics including stiffness and surface adhesion. Using atomic force microscopy, we performed nanoindentations on both isolated and confluent cells to evaluate the effect of LOXL1 knockout on in vitro cultures of vSMCs cells from nulliparous mice. The results show that LOXL1 knockout vSMCs have increased stiffness in pre-confluent but decreased stiffness in confluent cultures (p* < 0.05) and significant decreased surface adhesion in pre-confluent cultures (p* < 0.05). This study provides evidence that the weakening of vaginal connective tissue in the absense of LOXL1 changes the mechanical properties of the vSMCs. STATEMENT OF SIGNIFICANCE: Pelvic organ prolapse is a common condition affecting millions of women worldwide, which significantly impacts their quality of life. Alterations in vaginal and pelvic floor mechanical properties can change their ability to support the pelvic organs. This study provides evidence of altered stiffness of vaginal smooth muscle cells from mice resembling pelvic organ prolapse. The results from this study set a foundation to develop pathophysiology-driven therapies focused on the interplay between smooth muscle mechanics and extracellular matrix remodeling.
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Affiliation(s)
- J P S Ferreira
- Department of Mechanical Engineering, Faculty of Engineering, University of Porto, Porto, Portugal; Institute of Science and Innovation in Mechanical and Industrial Engineering, Porto, Portugal; Department of Biomedical Engineering, Lerner Research Institute and Glickman Urological Institute, Cleveland Clinic Foundation, OH, USA.
| | - M Kuang
- Department of Biomedical Engineering, Lerner Research Institute and Glickman Urological Institute, Cleveland Clinic Foundation, OH, USA
| | - M P L Parente
- Department of Mechanical Engineering, Faculty of Engineering, University of Porto, Porto, Portugal; Institute of Science and Innovation in Mechanical and Industrial Engineering, Porto, Portugal
| | - R M Natal Jorge
- Department of Mechanical Engineering, Faculty of Engineering, University of Porto, Porto, Portugal; Institute of Science and Innovation in Mechanical and Industrial Engineering, Porto, Portugal
| | - R Wang
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL, USA
| | - S J Eppell
- Department of Biomedical Engineering, Case Western Reserve, Cleveland, OH, USA
| | - M Damaser
- Department of Biomedical Engineering, Lerner Research Institute and Glickman Urological Institute, Cleveland Clinic Foundation, OH, USA; Department of Biomedical Engineering, Case Western Reserve, Cleveland, OH, USA; Advanced Platform Technology Center, Louis Stokes Cleveland Veteran's Administration Medical Center, Cleveland, OH, USA.
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20
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de Sousa JS, Freire RS, Sousa FD, Radmacher M, Silva AFB, Ramos MV, Monteiro-Moreira ACO, Mesquita FP, Moraes MEA, Montenegro RC, Oliveira CLN. Double power-law viscoelastic relaxation of living cells encodes motility trends. Sci Rep 2020; 10:4749. [PMID: 32179816 PMCID: PMC7075927 DOI: 10.1038/s41598-020-61631-w] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 02/26/2020] [Indexed: 02/08/2023] Open
Abstract
Living cells are constantly exchanging momentum with their surroundings. So far, there is no consensus regarding how cells respond to such external stimuli, although it reveals much about their internal structures, motility as well as the emergence of disorders. Here, we report that twelve cell lines, ranging from healthy fibroblasts to cancer cells, hold a ubiquitous double power-law viscoelastic relaxation compatible with the fractional Kelvin-Voigt viscoelastic model. Atomic Force Microscopy measurements in time domain were employed to determine the mechanical parameters, namely, the fast and slow relaxation exponents, the crossover timescale between power law regimes, and the cell stiffness. These cell-dependent quantities show strong correlation with their collective migration and invasiveness properties. Beyond that, the crossover timescale sets the fastest timescale for cells to perform their biological functions.
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Affiliation(s)
- J S de Sousa
- Departamento de Física, Universidade Federal do Ceará, 60455-970, Fortaleza, Ceará, Brazil.
| | - R S Freire
- Central Analítica, Universidade Federal do Ceará, 60455-970, Fortaleza, Ceará, Brazil
| | - F D Sousa
- Departamento de Física, Universidade Federal do Ceará, 60455-970, Fortaleza, Ceará, Brazil
| | - M Radmacher
- Institute of Biophysics, University of Bremen, Otto-Hahn Allee 1, 28359, Bremen, Germany
| | - A F B Silva
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, 60440-554, Fortaleza, Ceará, Brazil
| | - M V Ramos
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, 60440-554, Fortaleza, Ceará, Brazil
| | - A C O Monteiro-Moreira
- Centro de Biologia Experimental, Universidade de Fortaleza, 60811-905, Fortaleza, Ceará, Brazil
| | - F P Mesquita
- Núcleo de Pesquisa e Desenvolvimento de Medicamentos, Universidade Federal do Ceará, 60430-275, Fortaleza, Ceará, Brazil
| | - M E A Moraes
- Núcleo de Pesquisa e Desenvolvimento de Medicamentos, Universidade Federal do Ceará, 60430-275, Fortaleza, Ceará, Brazil
| | - R C Montenegro
- Núcleo de Pesquisa e Desenvolvimento de Medicamentos, Universidade Federal do Ceará, 60430-275, Fortaleza, Ceará, Brazil
| | - C L N Oliveira
- Departamento de Física, Universidade Federal do Ceará, 60455-970, Fortaleza, Ceará, Brazil
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21
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Nguyen AV, Trompetto B, Tan XHM, Scott MB, Hu KHH, Deeds E, Butte MJ, Chiou PY, Rowat AC. Differential Contributions of Actin and Myosin to the Physical Phenotypes and Invasion of Pancreatic Cancer Cells. Cell Mol Bioeng 2020; 13:27-44. [PMID: 32030106 PMCID: PMC6981337 DOI: 10.1007/s12195-019-00603-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 10/04/2019] [Indexed: 02/07/2023] Open
Abstract
INTRODUCTION Metastasis is a fundamentally physical process in which cells deform through narrow gaps and generate forces to invade surrounding tissues. While it is commonly thought that increased cell deformability is an advantage for invading cells, we previously found that more invasive pancreatic ductal adenocarcinoma (PDAC) cells are stiffer than less invasive PDAC cells. Here we investigate potential mechanisms of the simultaneous increase in PDAC cell stiffness and invasion, focusing on the contributions of myosin II, Arp2/3, and formins. METHOD We measure cell invasion using a 3D scratch wound invasion assay and cell stiffness using atomic force microscopy (AFM). To determine the effects of actin- and myosin-mediated force generation on cell stiffness and invasion, we treat cells with pharmacologic inhibitors of myosin II (blebbistatin), Arp2/3 (CK-666), and formins (SMIFH2). RESULTS We find that the activity of myosin II, Arp2/3, and formins all contribute to the stiffness of PDAC cells. Interestingly, we find that the invasion of PDAC cell lines is differentially affected when the activity of myosin II, Arp2/3, or formins is inhibited, suggesting that despite having similar tissue origins, different PDAC cell lines may rely on different mechanisms for invasion. CONCLUSIONS These findings deepen our knowledge of the factors that regulate cancer cell mechanotype and invasion, and incite further studies to develop therapeutics that target multiple mechanisms of invasion for improved clinical benefit.
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Affiliation(s)
- Angelyn V. Nguyen
- Department of Integrative Biology and Physiology, University of California, 610 Charles E Young Dr. East, Los Angeles, CA 90095 USA
| | - Brittany Trompetto
- Department of Integrative Biology and Physiology, University of California, 610 Charles E Young Dr. East, Los Angeles, CA 90095 USA
| | | | - Michael B. Scott
- Department of Integrative Biology and Physiology, University of California, 610 Charles E Young Dr. East, Los Angeles, CA 90095 USA
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, USA
- Present Address: Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, USA
- Department of Biomedical Engineering, Northwestern McCormick School of Engineering, Evanston, USA
| | | | - Eric Deeds
- Department of Integrative Biology and Physiology, University of California, 610 Charles E Young Dr. East, Los Angeles, CA 90095 USA
- Institute for Quantitative and Computational Biology, University of California, Los Angeles, USA
| | - Manish J. Butte
- Department of Pediatrics, University of California, Los Angeles, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, USA
| | - Pei Yu Chiou
- Department of Bioengineering, University of California, Los Angeles, USA
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, USA
| | - Amy C. Rowat
- Department of Integrative Biology and Physiology, University of California, 610 Charles E Young Dr. East, Los Angeles, CA 90095 USA
- Department of Bioengineering, University of California, Los Angeles, USA
- Jonsson Comprehensive Cancer Center, University of California, Los Angeles, USA
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22
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Efremov YM, Okajima T, Raman A. Measuring viscoelasticity of soft biological samples using atomic force microscopy. SOFT MATTER 2020; 16:64-81. [PMID: 31720656 DOI: 10.1039/c9sm01020c] [Citation(s) in RCA: 103] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Mechanical properties play important roles at different scales in biology. At the level of a single cell, the mechanical properties mediate mechanosensing and mechanotransduction, while at the tissue and organ levels, changes in mechanical properties are closely connected to disease and physiological processes. Over the past three decades, atomic force microscopy (AFM) has become one of the most widely used tools in the mechanical characterization of soft samples, ranging from molecules, cell organoids and cells to whole tissue. AFM methods can be used to quantify both elastic and viscoelastic properties, and significant recent developments in the latter have been enabled by the introduction of new techniques and models for data analysis. Here, we review AFM techniques developed in recent years for examining the viscoelastic properties of cells and soft gels, describe the main steps in typical data acquisition and analysis protocols, and discuss relevant viscoelastic models and how these have been used to characterize the specific features of cellular and other biological samples. We also discuss recent trends and potential directions for this field.
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Affiliation(s)
- Yuri M Efremov
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA. and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, USA and Institute for Regenerative Medicine, Sechenov University, Moscow, Russia
| | - Takaharu Okajima
- Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Japan
| | - Arvind Raman
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA. and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, USA
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23
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Panzetta V, Fusco S, Netti PA. Cell mechanosensing is regulated by substrate strain energy rather than stiffness. Proc Natl Acad Sci U S A 2019; 116:22004-22013. [PMID: 31570575 PMCID: PMC6825315 DOI: 10.1073/pnas.1904660116] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ability of cells to perceive the mechanical identity of extracellular matrix, generally known as mechanosensing, is generally depicted as a consequence of an intricate balance between pulling forces actuated by the actin fibers on the adhesion plaques and the mechanical reaction of the supporting material. However, whether the cell is sensitive to the stiffness or to the energy required to deform the material remains unclear. To address this important issue, here the cytoskeleton mechanics of BALB/3T3 and MC3T3 cells seeded on linearly elastic substrates under different levels of deformation were studied. In particular, the effect of prestrain on cell mechanics was evaluated by seeding cells both on substrates with no prestrain and on substrates with different levels of prestrain. Results indicated that cells recognize the existence of prestrain, exhibiting a stiffer cytoskeleton on stretched material compared to cells seeded on unstretched substrate. Cytoskeleton mechanics of cells seeded on stretched material were, in addition, comparable to those measured after the stretching of the substrate and cells together to the same level of deformation. This observation clearly suggests that cell mechanosensing is not mediated only by the stiffness of the substrate, as widely assumed in the literature, but also by the deformation energy associated with the substrate. Indeed, the clutch model, based on the exclusive dependence of cell mechanics upon substrate stiffness, fails to describe our experimental results. By modifying the clutch model equations to incorporate the dependence on the strain energy, we were able to correctly interpret the experimental evidence.
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Affiliation(s)
- Valeria Panzetta
- Centro di Ricerca Interdipartimentale sui Biomateriali, Università degli Studi di Napoli Federico II, 80125 Napoli, Italy
| | - Sabato Fusco
- Centro di Ricerca Interdipartimentale sui Biomateriali, Università degli Studi di Napoli Federico II, 80125 Napoli, Italy;
| | - Paolo A Netti
- Centro di Ricerca Interdipartimentale sui Biomateriali, Università degli Studi di Napoli Federico II, 80125 Napoli, Italy
- Centre for Advanced Biomaterial for Health Care, Istituto Italiano di Tecnologia, 80125 Napoli, Italy
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24
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Shi Y, Porter CL, Crocker JC, Reich DH. Dissecting fat-tailed fluctuations in the cytoskeleton with active micropost arrays. Proc Natl Acad Sci U S A 2019; 116:13839-13846. [PMID: 31239336 PMCID: PMC6628664 DOI: 10.1073/pnas.1900963116] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ability of animal cells to crawl, change their shape, and respond to applied force is due to their cytoskeleton: A dynamic, cross-linked network of actin protein filaments and myosin motors. How these building blocks assemble to give rise to cells' mechanics and behavior remains poorly understood. Using active micropost array detectors containing magnetic actuators, we have characterized the mechanics and fluctuations of cells' actomyosin cortex and stress fiber network in detail. Here, we find that both structures display remarkably consistent power law viscoelastic behavior along with highly intermittent fluctuations with fat-tailed distributions of amplitudes. Notably, this motion in the cortex is dominated by occasional large, step-like displacement events, with a spatial extent of several micrometers. Overall, our findings for the cortex appear contrary to the predictions of a recent active gel model, while suggesting that different actomyosin contractile units act in a highly collective and cooperative manner. We hypothesize that cells' actomyosin components robustly self-organize into marginally stable, plastic networks that give cells' their unique biomechanical properties.
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Affiliation(s)
- Yu Shi
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218
| | - Christopher L Porter
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104
| | - John C Crocker
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104
| | - Daniel H Reich
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218;
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25
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Rheinlaender J, Schäffer TE. Mapping the creep compliance of living cells with scanning ion conductance microscopy reveals a subcellular correlation between stiffness and fluidity. NANOSCALE 2019; 11:6982-6989. [PMID: 30916074 DOI: 10.1039/c8nr09428d] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Living cells exhibit complex material properties, which play a crucial role in many aspects of cell function in health and disease, including migration, proliferation, differentiation, and apoptosis. Various techniques exist to probe the viscoelastic material properties of living cells and a frequent observation is a cell-to-cell correlation between average stiffness and fluidity in populations of cells. However, the origin of this correlation is still under discussion. Here, we introduce an imaging technique based on the scanning ion conductance microscope (SICM) to measure the creep compliance of soft samples, which allowed us to generate images of viscoelastic material properties of living cells with high spatial and temporal resolution. We observe a strong subcellular correlation between the local stiffness and fluidity across the individual living cell: stiff regions exhibit lower fluidity while soft regions exhibit higher fluidity. We find that this subcellular correlation is identical to the previously observed cell-to-cell correlation. The subcellular correlation reversibly vanishes after drug-induced disruption of the cytoskeleton, indicating that the subcellular correlation is a property of the intact cytoskeleton of the living cell.
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Affiliation(s)
- Johannes Rheinlaender
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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26
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Power Dissipation in the Cochlea Can Enhance Frequency Selectivity. Biophys J 2019; 116:1362-1375. [PMID: 30878199 PMCID: PMC6451036 DOI: 10.1016/j.bpj.2019.02.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 01/15/2019] [Accepted: 02/22/2019] [Indexed: 12/22/2022] Open
Abstract
The cochlear cavity is filled with viscous fluids, and it is partitioned by a viscoelastic structure called the organ of Corti complex. Acoustic energy propagates toward the apex of the cochlea through vibrations of the organ of Corti complex. The dimensions of the vibrating structures range from a few hundred (e.g., the basilar membrane) to a few micrometers (e.g., the stereocilia bundle). Vibrations of microstructures in viscous fluid are subjected to energy dissipation. Because the viscous dissipation is considered to be detrimental to the function of hearing-sound amplification and frequency tuning-the cochlea uses cellular actuators to overcome the dissipation. Compared to extensive investigations on the cellular actuators, the dissipating mechanisms have not been given appropriate attention, and there is little consensus on damping models. For example, many theoretical studies use an inviscid fluid approximation and lump the viscous effect to viscous damping components. Others neglect viscous dissipation in the organ of Corti but consider fluid viscosity. We have developed a computational model of the cochlea that incorporates viscous fluid dynamics, organ of Corti microstructural mechanics, and electrophysiology of the outer hair cells. The model is validated by comparing with existing measurements, such as the viscoelastic response of the tectorial membrane, and the cochlear input impedance. Using the model, we investigated how dissipation components in the cochlea affect its function. We found that the majority of acoustic energy dissipation of the cochlea occurs within the organ of Corti complex, not in the scalar fluids. Our model suggests that an appropriate dissipation can enhance the tuning quality by reducing the spread of energy provided by the outer hair cells' somatic motility.
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27
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A study of Love wave acoustic biosensors monitoring the adhesion process of tendon stem cells (TSCs). EUROPEAN BIOPHYSICS JOURNAL: EBJ 2019; 48:249-260. [PMID: 30783690 DOI: 10.1007/s00249-019-01349-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 12/06/2018] [Accepted: 02/06/2019] [Indexed: 10/27/2022]
Abstract
The Love wave biosensor is considered to be one of the most promising probing methods in biomedical research and diagnosis, and has been applied to detect the mechano-biological behaviour of cells attached to the surface of the device. More efforts should be devoted to basic theoretical research and relevant device performance analysis that may contribute to the further developments of Love wave sensors. In this study, a 36º YX-LiTaO3-based Love wave sensor with a parylene-C wave guiding layer was adopted as a cell-based biosensor to monitor the adhesion process of tendon stem/progenitor cells (TSCs), a newly discovered cell type in tendons. A theoretical model is proposed to describe the Love wave propagation, in which the adherent cells are considered as a uniform viscoelastic layer. The effects of viscoelastic cell layer and wave guiding layer on the propagation velocity υ and propagation loss (PL) are investigated. The numerical results indicate that adherent cell layers of different storage or loss shear modulus in certain ranges can induce pronounced and characteristic variations in υ and PL, revealing the potential of Love wave sensors to provide useful quantitative measures on cellular mechanical properties. The sensor response to the adhesion of TSCs exhibits high consistency with experimental observations, which demonstrates the Love wave biosensor as a very promising sensor platform for investigating cellular activities under multiple physiological conditions.
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28
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Abstract
Cancer cells are usually found to be softer than normal cells, but their stiffness changes when they are in contact with different environments because of mechanosensitivity. For example, they adhere to a given substrate by tuning their cytoskeleton, thus affecting their rheological properties. This mechanism could become efficient when cancer cells invade the surrounding tissues, and they have to remodel their cytoskeleton in order to achieve particular deformations. Here we use an atomic force microscope in force modulation mode to study how local rheological properties of cancer cells are affected by a change of the environment. Cancer cells were plated on functionalized polyacrylamide substrates of different stiffnesses as well as on an endothelium substrate. A new correction of the Hertz model was developed because measurements require one to account for the precise properties of the thin, layered viscoelastic substrates. The main results show the influence of local cell rheology (the nucleus, perinuclear region, and edge locations) and the role of invasiveness. A general mechanosensitive trend is found by which the cell elastic modulus and transition frequency increase with substrate elasticity, but this tendency breaks down with a real endothelium substrate. These effects are investigated further during cell transmigration, when the actin cytoskeleton undergoes a rapid reorganization process necessary to push through the endothelial gap, in agreement with the local viscoelastic changes measured by atomic force microscopy. Taken together, these results introduce a paradigm for a new-to our knowledge-possible extravasation mechanism.
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29
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Huang H, Sun Z, Hill MA, Meininger GA. A Calcium Mediated Mechanism Coordinating Vascular Smooth Muscle Cell Adhesion During KCl Activation. Front Physiol 2018; 9:1810. [PMID: 30618822 PMCID: PMC6305448 DOI: 10.3389/fphys.2018.01810] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 12/04/2018] [Indexed: 12/21/2022] Open
Abstract
Efficient mechanotransduction in vascular smooth muscle cells (VSMCs) is intimately coupled to physical coupling of the cell to extracellular matrix proteins (ECM) by integrins. Integrin adhesion receptors are essential for normal vascular function and defective integrin signaling is associated with cardiovascular disease. However, less is known about the mechanism of integrin activation in VSMCs in relation to vasoregulation. Our laboratory previously demonstrated that the vasoconstrictor Angiotensin II increases VSMC stiffness in concert with enhanced adhesion to fibronectin (FN), indicating an important role for adhesion in contraction. However, the mechanism of this coordination remains to be clarified. In this study, intracellular Ca2+ ([Ca2+]i) was hypothesized to link integrin activation through inside-out signaling pathways leading to enhanced adhesion in response to AII. By using atomic force microscopy (AFM) with an anti-α5 antibody coated AFM probe, we confirmed that cell stiffness was increased by AII, while we observed no change in adhesion to an α5 integrin antibody. This indicated that increases in cell adhesion to FN induced by AII were occurring through an integrin activation process, as increased membrane integrin expression/receptor density would have been accompanied by increased adhesion to the anti-α5 antibody. Further studies were performed using either KCl or BAPTA-AM to modulate the level of [Ca2+]i. After KCl, VSMCs showed a rapid transient increase in cell stiffness as well as cell adhesion to FN, and these two events were synchronized with superimposed transient increases in the level of [Ca2+]i, which was measured using the Ca2+ indicator, fluo-4. These relationships were unaffected in VSMCs pretreated with the myosin light chain kinase inhibitor, ML-7. In contrast, unstimulated VSMCs incubated with an intracellular calcium chelator, BAPTA-AM, showed reduced cell adhesion to FN as well the expected decrease in [Ca2+]i. These data suggest that in VSMCs, integrin activation is linked to signaling events tied to levels of [Ca2+]i while being less dependent on events at the level of contractile protein activation. These findings provide additional evidence to support a role for adhesion in VSMC contraction and suggest that following cell contractile activation, that adhesion may be regulated in tandem with the contractile event.
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Affiliation(s)
- Huang Huang
- Dalton Cardiovascular Research Center, Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
| | - Zhe Sun
- Dalton Cardiovascular Research Center, Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
| | - Michael A Hill
- Dalton Cardiovascular Research Center, Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
| | - Gerald A Meininger
- Dalton Cardiovascular Research Center, Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
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30
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Jaslove JM, Nelson CM. Smooth muscle: a stiff sculptor of epithelial shapes. Philos Trans R Soc Lond B Biol Sci 2018; 373:20170318. [PMID: 30249770 PMCID: PMC6158200 DOI: 10.1098/rstb.2017.0318] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2018] [Indexed: 12/11/2022] Open
Abstract
Smooth muscle is increasingly recognized as a key mechanical sculptor of epithelia during embryonic development. Smooth muscle is a mesenchymal tissue that surrounds the epithelia of organs including the gut, blood vessels, lungs, bladder, ureter, uterus, oviduct and epididymis. Smooth muscle is stiffer than its adjacent epithelium and often serves its morphogenetic function by physically constraining the growth of a proliferating epithelial layer. This constraint leads to mechanical instabilities and epithelial morphogenesis through buckling. Smooth muscle stiffness alone, without smooth muscle cell shortening, seems to be sufficient to drive epithelial morphogenesis. Fully understanding the development of organs that use smooth muscle stiffness as a driver of morphogenesis requires investigating how smooth muscle develops, a key aspect of which is distinguishing smooth muscle-like tissues from one another in vivo and in culture. This necessitates a comprehensive appreciation of the genetic, anatomical and functional markers that are used to distinguish the different subtypes of smooth muscle (for example, vascular versus visceral) from similar cell types (including myofibroblasts and myoepithelial cells). Here, we review how smooth muscle acts as a mechanical driver of morphogenesis and discuss ways of identifying smooth muscle, which is critical for understanding these morphogenetic events.This article is part of the Theo Murphy meeting issue 'Mechanics of Development'.
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Affiliation(s)
- Jacob M Jaslove
- Department of Molecular Biology, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544, USA
- Graduate School of Biomedical Sciences, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
| | - Celeste M Nelson
- Department of Molecular Biology, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544, USA
- Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544, USA
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31
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Galior K, Ma VPY, Liu Y, Su H, Baker N, Panettieri RA, Wongtrakool C, Salaita K. Molecular Tension Probes to Investigate the Mechanopharmacology of Single Cells: A Step toward Personalized Mechanomedicine. Adv Healthc Mater 2018; 7:e1800069. [PMID: 29785773 PMCID: PMC6105437 DOI: 10.1002/adhm.201800069] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 03/15/2018] [Indexed: 01/03/2023]
Abstract
Given that dysregulation of mechanics contributes to diseases ranging from cancer metastasis to lung disease, it is important to develop methods for screening the efficacy of drugs that target cellular forces. Here, nanoparticle-based tension sensors are used to quantify the mechanical response of individual cells upon drug treatment. As a proof-of-concept, the activity of bronchodilators is tested on human airway smooth muscle cells derived from seven donors, four of which are asthmatic. It is revealed that airway smooth muscle cells isolated from asthmatic donors exhibit greater traction forces compared to the control donors. Additionally, the mechanical signal is abolished using myosin inhibitors or further enhanced in the presence of inflammatory inducers, such as nicotine. Using the signal generated by the probes, single-cell dose-response measurements are performed to determine the "mechano" effective concentration (mechano-EC50 ) of albuterol, a bronchodilator, which reduces integrin forces by 50%. Mechano-EC50 values for each donor present discrete readings that are differentially enhanced as a function of nicotine treatment. Importantly, donor mechano-EC50 values varied by orders of magnitude, suggesting significant variability in their sensitivity to nicotine and albuterol treatment. To the best of the authors' knowledge, this is the first study harnessing a piconewton tension sensor platform for mechanopharmacology.
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Affiliation(s)
- Kornelia Galior
- Department of Chemistry, Emory University, Atlanta, GA, 30322, USA
| | | | - Yang Liu
- Department of Chemistry, Emory University, Atlanta, GA, 30322, USA
| | - Hanquan Su
- Department of Chemistry, Emory University, Atlanta, GA, 30322, USA
| | - Nusaiba Baker
- Emory University School of Medicine, Emory University, Atlanta, GA, 30307, USA
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, 30332, USA
| | - Reynold A Panettieri
- Rutgers Institute for Translational Medicine and Science, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08901, USA
| | - Cherry Wongtrakool
- Emory University School of Medicine, Emory University, Atlanta, GA, 30307, USA
- Atlanta Veterans Affairs Medical Center, Decatur, GA, 30033, USA
| | - Khalid Salaita
- Department of Chemistry, Emory University, Atlanta, GA, 30322, USA
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, 30332, USA
- Winship Cancer Institute, Emory University, Atlanta, GA, 30322, USA
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32
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Kain L, Andriotis OG, Gruber P, Frank M, Markovic M, Grech D, Nedelkovski V, Stolz M, Ovsianikov A, Thurner PJ. Calibration of colloidal probes with atomic force microscopy for micromechanical assessment. J Mech Behav Biomed Mater 2018; 85:225-236. [PMID: 29933150 DOI: 10.1016/j.jmbbm.2018.05.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 05/08/2018] [Accepted: 05/16/2018] [Indexed: 10/24/2022]
Abstract
Mechanical assessment of biological materials and tissue-engineered scaffolds is increasingly focusing at lower length scale levels. Amongst other techniques, atomic force microscopy (AFM) has gained popularity as an instrument to interrogate material properties, such as the indentation modulus, at the microscale via cantilever-based indentation tests equipped with colloidal probes. Current analysis approaches of the indentation modulus from such tests require the size and shape of the colloidal probe as well as the spring constant of the cantilever. To make this technique reproducible, there still exist the challenge of proper calibration and validation of such mechanical assessment. Here, we present a method to (a) fabricate and characterize cantilevers with colloidal probes and (b) provide a guide for estimating the spring constant and the sphere diameter that should be used for a given sample to achieve the highest possible measurement sensitivity. We validated our method by testing agarose samples with indentation moduli ranging over three orders of magnitude via AFM and compared these results with bulk compression tests. Our results show that quantitative measurements of indentation modulus is achieved over three orders of magnitude ranging from 1 kPa to 1000 kPa via AFM cantilever-based microindentation experiments. Therefore, our approach could be used for quantitative micromechanical measurements without the need to perform further validation via bulk compression experiments.
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Affiliation(s)
- Lukas Kain
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria.
| | - Peter Gruber
- Institute of Materials Science and Technology, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - Martin Frank
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - Marica Markovic
- Institute of Materials Science and Technology, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - David Grech
- Nano Research Group, Department of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK
| | - Vedran Nedelkovski
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - Martin Stolz
- National Centre for Advanced Tribology at Southampton, Faculty of Engineering and the Environment, University of Southampton, UK
| | - Aleksandr Ovsianikov
- Institute of Materials Science and Technology, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
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33
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Yan B, Ren J, Liu Y, Huang H, Zheng X, Zou Q. Study of Cholesterol Repletion Effect on Nanomechanical Properties of Human Umbilical Vein Endothelial Cell Via Rapid Broadband Atomic Force Microscopy. J Biomech Eng 2017; 139:2588202. [PMID: 27893051 DOI: 10.1115/1.4035260] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Indexed: 02/04/2023]
Abstract
Abnormalities of blood cholesterol concentration are associated with increased risks for vascular disease, especially heart attacks and strokes. As one of the main lipid components of plasma membrane in all mammalian cells, cholesterol has a major impact on the mechanical properties of the membrane of endothelial cells. Although the effect of cholesterol depletion on cell mechanical properties has been studied, no results yet have been reported on quantitative investigation of cholesterol repletion effect. In this study, the cholesterol repletion effect on the nanomechanical properties of human umbilical vein endothelial cell (EA.hy926) was studied using a control-based atomic force microscope (AFM) nanomechanical measurement protocol. The viscoelasticity of EA.hy926 cells were measured over a large frequency range (0.1-100 Hz) using both constant-rate excitation force with different loading rates and a broadband excitation force. The viscoelasticity oscillation of the cell membranes under the cholesterol effect was also monitored in real-time. The experiment results showed that under the effect of cholesterol repletion, both the Young's modulus and the complex modulus of EA.hy926 cell were increased over 30%, respectively, and moreover, the amplitudes of both the elasticity oscillation and the viscosity oscillation at a period of around 200 s were increased over 70%, respectively. Therefore, this work is among the first to investigate the mechanical properties, particularly, the broadband viscoelasticity variations of EA.hy926 cells under cholesterol repletion treatment. The results revealed that cholesterol repletion may reinforce the coupling of F-actin to plasma membrane by increasing actin stability, and the cholesterol might have modified the submembrane cytoskeletal organization of EA.hy926 cell by causing the involvement of the motor protein nonmuscle myosin II.
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Affiliation(s)
- Bo Yan
- School of Electrical Engineering, University of Electrical Science and Engineering, Chengdu 60054, China
| | - Juan Ren
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011
| | - Yue Liu
- Department of Chemical Biology, Rutgers University, Piscataway, NJ 08854
| | - Huarong Huang
- Allan H. Conney Laboratory, Guangdong University of Technology, Guangzhou 510006, China
| | - Xi Zheng
- Department of Chemical Biology, Rutgers University, Piscataway, NJ 08854
| | - Qingze Zou
- Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, NJ 08854 e-mail:
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34
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Pajic-Lijakovic I, Milivojevic M. Viscoelasticity of multicellular surfaces. J Biomech 2017; 60:1-8. [PMID: 28712545 DOI: 10.1016/j.jbiomech.2017.06.035] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 05/25/2017] [Accepted: 06/20/2017] [Indexed: 11/18/2022]
Abstract
Various modeling approaches have been applied to describe viscoelasticity of multicellular surfaces. The viscoelasticity is considered within three time regimes: (1) short time regime for milliseconds to seconds time scale which corresponds to sub-cellular level; (2) middle time regime for several tens of seconds to several minutes time scale which corresponds to cellular level; and (3) long time regime for several tens of minutes to several hours time scale which corresponds to supra-cellular level. Short and middle time regimes have been successfully elaborated in the literature, whereas long time viscoelasticity remains unclear. Long time regime accounts for collective cell migration. Collective cell migration could induce uncorrelated motility which has an impact to energy storage and dissipation during cell surface rearrangement. Uncorrelated motility influences: (1) volume fraction of migrating cells, (2) distribution of migrating cells, (3) shapes of migrating cell groups. These parameters influence mechanical coupling between migrating and resting subpopulations and consequently the constitutive model for long time regime. This modeling consideration indicates that additional experimental work is needed to confirm the feasibility of constitutive models which have been applied in literature for long time regime as: (1) relaxation of stress and strain, (2) storage and loss moduli as the function of time, (3) distribution of migrating cells.
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Affiliation(s)
- Ivana Pajic-Lijakovic
- Faculty of Technology and Metallurgy, Belgrade University, Karnegijeva 4, Belgrade, Serbia.
| | - Milan Milivojevic
- Faculty of Technology and Metallurgy, Belgrade University, Karnegijeva 4, Belgrade, Serbia
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35
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Novel insights into cardiomyocytes provided by atomic force microscopy. Semin Cell Dev Biol 2017; 73:4-12. [PMID: 28687239 DOI: 10.1016/j.semcdb.2017.07.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 06/29/2017] [Accepted: 07/03/2017] [Indexed: 01/04/2023]
Abstract
Cardiovascular diseases (CVDs) are the number one cause of death globally, therefore interest in studying aetiology, hallmarks, progress and therapies for these disorders is constantly growing. Over the last decades, the introduction and development of atomic force microscopy (AFM) technique allowed the study of biological samples at the micro- and nanoscopic level, hence revealing noteworthy details and paving the way for investigations on physiological and pathological conditions at cellular scale. The present work is aimed to collect and review the literature on cardiomyocytes (CMs) studied by AFM, in order to emphasise the numerous potentialities of this approach and provide a platform for researchers in the field of cardiovascular diseases. Original data are also presented to highlight the application of AFM to characterise the viscoelastic properties of CMs.
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36
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Wu H, Zhao G, Zu H, Wang JHC, Wang QM. Real-Time Monitoring of Platelet Activation Using Quartz Thickness-Shear Mode Resonator Sensors. Biophys J 2017; 110:669-679. [PMID: 26840731 DOI: 10.1016/j.bpj.2015.11.3511] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 11/11/2015] [Accepted: 11/19/2015] [Indexed: 12/16/2022] Open
Abstract
In this study, quartz thickness-shear mode (TSM) resonator sensors were adopted to monitor the process of platelet activation. Resting platelets adhering to fibrinogen-coated electrodes were activated by different concentrations of thrombin (1, 10, and 100 U/mL), and the corresponding electrical admittance spectra of TSM resonators during this process were recorded. Based on a bilayer-loading transmission line model of TSM resonators, the complex shear modulus (G' + jG″) and the average thickness (hPL) of the platelet monolayer at a series of time points were obtained. Decrease in thrombin concentration from 100 to 1 U/mL shifted all peaks and plateaus in G', G″, and hPL to higher time points, which could be attributed to the partial activation of platelets by low concentrations of thrombin. The peak value of hPL was acquired when platelets presented their typical spherical shape as the first transformation in activation process. The G' peak appeared 10 ∼ 20 min after hPL peak, when some filopods were observed along the periphery of platelets but without obvious cell spreading. As platelet spreading began and continued, G', G″, and hPL decreased, leading to a steady rise of resonance frequency shift of TSM resonator sensors. The results show high reliability and stability of TSM resonator sensors in monitoring the process of platelet activation, revealing an effective method to measure platelet activities in real-time under multiple experimental conditions. The G', G″, and hPL values could provide useful quantitative measures on platelet structure variations in activation process, indicating potential of TSM resonators in characterization of cells during their transformation.
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Affiliation(s)
- Huiyan Wu
- Department of Mechanical Engineering & Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Guangyi Zhao
- MechanoBiology Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Hongfei Zu
- Department of Mechanical Engineering & Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - James H-C Wang
- MechanoBiology Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania.
| | - Qing-Ming Wang
- Department of Mechanical Engineering & Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania.
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Barlow BM, Bertrand M, Joós B. Relaxation of a simulated lipid bilayer vesicle compressed by an atomic force microscope. Phys Rev E 2016; 94:052408. [PMID: 27967024 DOI: 10.1103/physreve.94.052408] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Indexed: 06/06/2023]
Abstract
Using coarse-grained molecular dynamics simulations, we study the relaxation of bilayer vesicles, uniaxially compressed by an atomic force microscope cantilever. The relaxation time exhibits a strong force dependence. Force-compression curves are very similar to recent experiments wherein giant unilamellar vesicles were compressed in a nearly identical manner.
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Affiliation(s)
- Ben M Barlow
- Ottawa-Carleton Institute for Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 6N5
| | - Martine Bertrand
- Ottawa-Carleton Institute for Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 6N5
| | - Béla Joós
- Ottawa-Carleton Institute for Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 6N5
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38
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Rothdiener M, Hegemann M, Uynuk-Ool T, Walters B, Papugy P, Nguyen P, Claus V, Seeger T, Stoeckle U, Boehme KA, Aicher WK, Stegemann JP, Hart ML, Kurz B, Klein G, Rolauffs B. Stretching human mesenchymal stromal cells on stiffness-customized collagen type I generates a smooth muscle marker profile without growth factor addition. Sci Rep 2016; 6:35840. [PMID: 27775041 PMCID: PMC5075785 DOI: 10.1038/srep35840] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 10/05/2016] [Indexed: 12/18/2022] Open
Abstract
Using matrix elasticity and cyclic stretch have been investigated for inducing mesenchymal stromal cell (MSC) differentiation towards the smooth muscle cell (SMC) lineage but not in combination. We hypothesized that combining lineage-specific stiffness with cyclic stretch would result in a significantly increased expression of SMC markers, compared to non-stretched controls. First, we generated dense collagen type I sheets by mechanically compressing collagen hydrogels. Atomic force microscopy revealed a nanoscale stiffness range known to support myogenic differentiation. Further characterization revealed viscoelasticity and stable biomechanical properties under cyclic stretch with >99% viable adherent human MSC. MSCs on collagen sheets demonstrated a significantly increased mRNA but not protein expression of SMC markers, compared to on culture flasks. However, cyclic stretch of MSCs on collagen sheets significantly increased both mRNA and protein expression of α-smooth muscle actin, transgelin, and calponin versus plastic and non-stretched sheets. Thus, lineage-specific stiffness and cyclic stretch can be applied together for inducing MSC differentiation towards SMCs without the addition of recombinant growth factors or other soluble factors. This represents a novel stimulation method for modulating the phenotype of MSCs towards SMCs that could easily be incorporated into currently available methodologies to obtain a more targeted control of MSC phenotype.
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Affiliation(s)
- Miriam Rothdiener
- Siegfried Weller Institute for Trauma Research, BG Trauma Clinic Tuebingen, University of Tuebingen, Germany
| | | | - Tatiana Uynuk-Ool
- Siegfried Weller Institute for Trauma Research, BG Trauma Clinic Tuebingen, University of Tuebingen, Germany
| | - Brandan Walters
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Piruntha Papugy
- Siegfried Weller Institute for Trauma Research, BG Trauma Clinic Tuebingen, University of Tuebingen, Germany
| | - Phong Nguyen
- Siegfried Weller Institute for Trauma Research, BG Trauma Clinic Tuebingen, University of Tuebingen, Germany
| | - Valentin Claus
- Siegfried Weller Institute for Trauma Research, BG Trauma Clinic Tuebingen, University of Tuebingen, Germany
| | - Tanja Seeger
- Center for Medical Research, Medical University Clinic II, University of Tuebingen, Germany
| | - Ulrich Stoeckle
- Clinic for Trauma and Restorative Surgery, BG Trauma Clinic Tuebingen, University of Tuebingen, Germany
| | - Karen A. Boehme
- Department of Orthopaedic Surgery, University of Tuebingen, Germany
| | | | - Jan P. Stegemann
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Melanie L. Hart
- Department of Orthopedics and Trauma Surgery, Albert-Ludwigs-University, Freiburg, Germany
| | - Bodo Kurz
- Department of Anatomy, Christian-Albrechts-University, Kiel, Germany
| | - Gerd Klein
- Center for Medical Research, Medical University Clinic II, University of Tuebingen, Germany
| | - Bernd Rolauffs
- Department of Orthopedics and Trauma Surgery, Albert-Ludwigs-University, Freiburg, Germany
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Hellwig J, Micciulla S, Strebe J, von Klitzing R. Separation of Storage and Loss Modulus of Polyelectrolyte Multilayers on a Nanoscale: A Dynamic AFM Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:10505-10512. [PMID: 27610635 DOI: 10.1021/acs.langmuir.6b02764] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Atomic force microscopy (AFM) is used to carry out rheology measurements on the nanoscale and to determine the mechanical properties of poly(l-lysine) (PLL)/hyaluronic acid (HA) multilayer films. Storage (G') and loss modulus (G″) of the films are calculated and compared with the values obtained from quartz crystal microbalance with dissipation monitoring measurements (QCM-D). A predominant elastic behavior independently of the applied frequencies (5-100 Hz) is observed for native HA/PLL films consisting of 36 double layer. If the layers are cross-linked, the value of G' increases by 2 orders of magnitude, while the loss modulus becomes negligible, making these films a purely elastic chemical gel. The values of G' and G'' extracted from QCM-D measurements on native films are much higher, due to the different frequency regime of the applied shear stress. However, the viscoelastic ratio from the two methods is the same and proves the elastic dominated response of the multilayer in both frequency regimes.
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Affiliation(s)
- Johannes Hellwig
- Stranski-Laboratorium, Department of Chemistry, TU Berlin , Strasse des 17. Juni 124, D-10623 Berlin, Germany
| | - Samantha Micciulla
- Stranski-Laboratorium, Department of Chemistry, TU Berlin , Strasse des 17. Juni 124, D-10623 Berlin, Germany
| | - Julia Strebe
- Stranski-Laboratorium, Department of Chemistry, TU Berlin , Strasse des 17. Juni 124, D-10623 Berlin, Germany
| | - Regine von Klitzing
- Stranski-Laboratorium, Department of Chemistry, TU Berlin , Strasse des 17. Juni 124, D-10623 Berlin, Germany
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40
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Bonakdar N, Gerum R, Kuhn M, Spörrer M, Lippert A, Schneider W, Aifantis KE, Fabry B. Mechanical plasticity of cells. NATURE MATERIALS 2016; 15:1090-4. [PMID: 27376682 DOI: 10.1038/nmat4689] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 06/01/2016] [Indexed: 05/06/2023]
Abstract
Under mechanical loading, most living cells show a viscoelastic deformation that follows a power law in time. After removal of the mechanical load, the cell shape recovers only incompletely to its original undeformed configuration. Here, we show that incomplete shape recovery is due to an additive plastic deformation that displays the same power-law dynamics as the fully reversible viscoelastic deformation response. Moreover, the plastic deformation is a constant fraction of the total cell deformation and originates from bond ruptures within the cytoskeleton. A simple extension of the prevailing viscoelastic power-law response theory with a plastic element correctly predicts the cell behaviour under cyclic loading. Our findings show that plastic energy dissipation during cell deformation is tightly linked to elastic cytoskeletal stresses, which suggests the existence of an adaptive mechanism that protects the cell against mechanical damage.
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Affiliation(s)
- Navid Bonakdar
- Department of Physics, University of Erlangen-Nuremberg, 91054 Erlangen, Germany
- Max-Planck Institute for the Science of Light, 91058 Erlangen, Germany
| | - Richard Gerum
- Department of Physics, University of Erlangen-Nuremberg, 91054 Erlangen, Germany
| | - Michael Kuhn
- Department of Physics, University of Erlangen-Nuremberg, 91054 Erlangen, Germany
| | - Marina Spörrer
- Department of Physics, University of Erlangen-Nuremberg, 91054 Erlangen, Germany
| | - Anna Lippert
- Department of Physics, University of Erlangen-Nuremberg, 91054 Erlangen, Germany
| | - Werner Schneider
- Department of Physics, University of Erlangen-Nuremberg, 91054 Erlangen, Germany
| | - Katerina E Aifantis
- Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, Arizona 85721, USA
| | - Ben Fabry
- Department of Physics, University of Erlangen-Nuremberg, 91054 Erlangen, Germany
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41
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Shaker DS, Shaker MA, Klingner A, Hanafy MS. In situ thermosensitive Tamoxifen citrate loaded hydrogels: An effective tool in breast cancer loco-regional therapy. J Drug Deliv Sci Technol 2016. [DOI: 10.1016/j.jddst.2016.05.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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42
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Hiorns JE, Jensen OE, Brook BS. Nonlinear compliance modulates dynamic bronchoconstriction in a multiscale airway model. Biophys J 2016; 107:3030-3042. [PMID: 25517167 PMCID: PMC4269780 DOI: 10.1016/j.bpj.2014.10.067] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 10/28/2014] [Accepted: 10/29/2014] [Indexed: 02/02/2023] Open
Abstract
The role of breathing and deep inspirations (DI) in modulating airway hyperresponsiveness remains poorly understood. In particular, DIs are potent bronchodilators of constricted airways in nonasthmatic subjects but not in asthmatic subjects. Additionally, length fluctuations (mimicking DIs) have been shown to reduce mean contractile force when applied to airway smooth muscle (ASM) cells and tissue strips. However, these observations are not recapitulated on application of transmural pressure (PTM) oscillations (that mimic tidal breathing and DIs) in isolated intact airways. To shed light on this paradox, we have developed a biomechanical model of the intact airway, accounting for strain-stiffening due to collagen recruitment (a large component of the extracellular matrix (ECM)), and dynamic actomyosin-driven force generation by ASM cells. In agreement with intact airway studies, our model shows that PTM fluctuations at particular mean transmural pressures can lead to only limited bronchodilation. However, our model predicts that moving the airway to a more compliant point on the static pressure-radius relationship (which may involve reducing mean PTM), before applying pressure fluctuations, can generate greater bronchodilation. This difference arises from competition between passive strain-stiffening of ECM and force generation by ASM yielding a highly nonlinear relationship between effective airway stiffness and PTM, which is modified by the presence of contractile agonist. Effectively, the airway at its most compliant may allow for greater strain to be transmitted to subcellular contractile machinery. The model predictions lead us to hypothesize that the maximum possible bronchodilation of an airway depends on its static compliance at the PTM about which the fluctuations are applied. We suggest the design of additional experimental protocols to test this hypothesis.
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Affiliation(s)
- Jonathan E Hiorns
- School of Mathematical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Oliver E Jensen
- School of Mathematics, University of Manchester, Manchester, United Kingdom
| | - Bindi S Brook
- School of Mathematical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom.
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43
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Lange JR, Steinwachs J, Kolb T, Lautscham LA, Harder I, Whyte G, Fabry B. Microconstriction arrays for high-throughput quantitative measurements of cell mechanical properties. Biophys J 2016; 109:26-34. [PMID: 26153699 DOI: 10.1016/j.bpj.2015.05.029] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 05/22/2015] [Accepted: 05/26/2015] [Indexed: 12/15/2022] Open
Abstract
We describe a method for quantifying the mechanical properties of cells in suspension with a microfluidic device consisting of a parallel array of micron-sized constrictions. Using a high-speed charge-coupled device camera, we measure the flow speed, cell deformation, and entry time into the constrictions of several hundred cells per minute during their passage through the device. From the flow speed and the occupation state of the microconstriction array with cells, the driving pressure across each constriction is continuously computed. Cell entry times into microconstrictions decrease with increased driving pressure and decreased cell size according to a power law. From this power-law relationship, the cell elasticity and fluidity can be estimated. When cells are treated with drugs that depolymerize or stabilize the cytoskeleton or the nucleus, elasticity and fluidity data from all treatments collapse onto a master curve. Power-law rheology and collapse onto a master curve are predicted by the theory of soft glassy materials and have been previously shown to describe the mechanical behavior of cells adhering to a substrate. Our finding that this theory also applies to cells in suspension provides the foundation for a quantitative high-throughput measurement of cell mechanical properties with microfluidic devices.
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Affiliation(s)
- Janina R Lange
- Biophysics Group, Department of Physics, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Julian Steinwachs
- Biophysics Group, Department of Physics, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Thorsten Kolb
- Biophysics Group, Department of Physics, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany; Division of Molecular Genetics, German Cancer Research Center, Heidelberg, Germany
| | - Lena A Lautscham
- Biophysics Group, Department of Physics, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Irina Harder
- Max Planck Institute for the Science of Light, Erlangen, Germany
| | - Graeme Whyte
- Institute of Biological Chemistry, Biophysics and Bioengineering, Department of Physics, Heriot-Watt University, Edinburgh, UK
| | - Ben Fabry
- Biophysics Group, Department of Physics, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany.
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Abstract
Vascular smooth muscle (VSM; see Table 1 for a list of abbreviations) is a heterogeneous biomaterial comprised of cells and extracellular matrix. By surrounding tubes of endothelial cells, VSM forms a regulated network, the vasculature, through which oxygenated blood supplies specialized organs, permitting the development of large multicellular organisms. VSM cells, the engine of the vasculature, house a set of regulated nanomotors that permit rapid stress-development, sustained stress-maintenance and vessel constriction. Viscoelastic materials within, surrounding and attached to VSM cells, comprised largely of polymeric proteins with complex mechanical characteristics, assist the engine with countering loads imposed by the heart pump, and with control of relengthening after constriction. The complexity of this smart material can be reduced by classical mechanical studies combined with circuit modeling using spring and dashpot elements. Evaluation of the mechanical characteristics of VSM requires a more complete understanding of the mechanics and regulation of its biochemical parts, and ultimately, an understanding of how these parts work together to form the machinery of the vascular tree. Current molecular studies provide detailed mechanical data about single polymeric molecules, revealing viscoelasticity and plasticity at the protein domain level, the unique biological slip-catch bond, and a regulated two-step actomyosin power stroke. At the tissue level, new insight into acutely dynamic stress-strain behavior reveals smooth muscle to exhibit adaptive plasticity. At its core, physiology aims to describe the complex interactions of molecular systems, clarifying structure-function relationships and regulation of biological machines. The intent of this review is to provide a comprehensive presentation of one biomachine, VSM.
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Affiliation(s)
- Paul H Ratz
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA
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45
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Kilpatrick JI, Revenko I, Rodriguez BJ. Nanomechanics of Cells and Biomaterials Studied by Atomic Force Microscopy. Adv Healthc Mater 2015. [PMID: 26200464 DOI: 10.1002/adhm.201500229] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The behavior and mechanical properties of cells are strongly dependent on the biochemical and biomechanical properties of their microenvironment. Thus, understanding the mechanical properties of cells, extracellular matrices, and biomaterials is key to understanding cell function and to develop new materials with tailored mechanical properties for tissue engineering and regenerative medicine applications. Atomic force microscopy (AFM) has emerged as an indispensable technique for measuring the mechanical properties of biomaterials and cells with high spatial resolution and force sensitivity within physiologically relevant environments and timescales in the kPa to GPa elastic modulus range. The growing interest in this field of bionanomechanics has been accompanied by an expanding array of models to describe the complexity of indentation of hierarchical biological samples. Furthermore, the integration of AFM with optical microscopy techniques has further opened the door to a wide range of mechanotransduction studies. In recent years, new multidimensional and multiharmonic AFM approaches for mapping mechanical properties have been developed, which allow the rapid determination of, for example, cell elasticity. This Progress Report provides an introduction and practical guide to making AFM-based nanomechanical measurements of cells and surfaces for tissue engineering applications.
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Affiliation(s)
- Jason I. Kilpatrick
- Conway Institute of Biomolecular and Biomedical Research; University College Dublin; Belfield Dublin 4 Ireland
| | - Irène Revenko
- Asylum Research an Oxford Instruments Company; 6310 Hollister Avenue Santa Barbara CA 93117 USA
| | - Brian J. Rodriguez
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin; Belfield, Dublin 4, Ireland; School of Physics; University College Dublin; Belfield Dublin 4 Ireland
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46
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Nalam PC, Gosvami NN, Caporizzo MA, Composto RJ, Carpick RW. Nano-rheology of hydrogels using direct drive force modulation atomic force microscopy. SOFT MATTER 2015; 11:8165-78. [PMID: 26337502 PMCID: PMC4839974 DOI: 10.1039/c5sm01143d] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We present a magnetic force-based direct drive modulation method to measure local nano-rheological properties of soft materials across a broad frequency range (10 Hz to 2 kHz) using colloid-attached atomic force microscope (AFM) probes in liquid. The direct drive method enables artefact-free measurements over several decades of excitation frequency, and avoids the need to evaluate medium-induced hydrodynamic drag effects. The method was applied to measure the local mechanical properties of polyacrylamide hydrogels. The frequency-dependent storage stiffness, loss stiffness, and loss tangent (tan δ) were quantified for hydrogels having high and low crosslinking densities by measuring the amplitude and the phase response of the cantilever while the colloid was in contact with the hydrogel. The frequency bandwidth was further expanded to lower effective frequencies (0.1 Hz to 10 Hz) by obtaining force-displacement (FD) curves. Slow FD measurements showed a recoverable but highly hysteretic response, with the contact mechanical behaviour dependent on the loading direction: approach curves showed Hertzian behaviour while retraction curves fit the JKR contact mechanics model well into the adhesive regime, after which multiple detachment instabilities occurred. Using small amplitude dynamic modulation to explore faster rates, the load dependence of the storage stiffness transitioned from Hertzian to a dynamic punch-type (constant contact area) model, indicating significant influence of material dissipation coupled with adhesion. Using the appropriate contact model across the full frequency range measured, the storage moduli were found to remain nearly constant until an increase began near ∼100 Hz. The softer gels' storage modulus increased from 7.9 ± 0.4 to 14.5 ± 2.1 kPa (∼85%), and the stiffer gels' storage modulus increased from 16.3 ± 1.1 to 31.7 ± 5.0 kPa (∼95%). This increase at high frequencies may be attributed to a contribution from solvent confinement in the hydrogel (poroelasticity). The storage moduli measured by both macro-rheometry and AFM FD curves were comparable to those measured using the modulation method at their overlapping frequencies (10-25 Hz). In all cases, care was taken to ensure the contact mechanics models were applied within the important limit of small relative deformations. This study thus highlights possible transitions in the probe-material contact mechanical behaviour for soft matter, especially when the applied strain rates and the material relaxation rates become comparable. In particular, at low frequencies, the modulus follows Hertzian contact mechanics, while at high frequencies adhesive contact is well represented by punch-like behaviour. More generally, use of the Hertz model on hydrogels at high loading rates, at high strains, or during the retraction portion of FD curves, leads to significant errors in the calculated moduli.
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Affiliation(s)
- Prathima C Nalam
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, USA.
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47
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ZHAO SHIJIA, STAMM ALEX, LEE JEONGSOON, GRUVERMAN ALEXEI, LIM JUNGYUL, GU LINXIA. ELASTICITY OF DIFFERENTIATED AND UNDIFFERENTIATED HUMAN NEUROBLASTOMA CELLS CHARACTERIZED BY ATOMIC FORCE MICROSCOPY. J MECH MED BIOL 2015. [DOI: 10.1142/s0219519415500694] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Human neuroblastoma (SH-SY5Y) cells, with its ability to differentiate into neurons, have been widely used as the in vitro cell culture model for neuroscience research, especially in studying the pathogenesis of Parkinson's disease (PD) and developing therapeutic strategies. Cellular elasticity could potentially serve as a biomarker to quantitatively distinguish undifferentiated and differentiated SH-SY5Y cells. The goal of this work is to characterize the retinoic acid (RA) induced alternations of elastic properties of SH-SY5Y cells using atomic force microscopy (AFM). The elasticity was measured at multiple points of a single cell. Results have shown that the differentiation of SH-SY5Y cell led to a larger elastic modulus, which is three times more than that of undifferentiated cells. A higher indentation rate applied during AFM measurements led to a larger elastic modulus of the cell. This work provides new insights into the differentiation process identified by the elasticity marker, which could be extended to investigate the function, health and ageing of cells.
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Affiliation(s)
- SHIJIA ZHAO
- Department of Mechanical & Materials Engineering, University of Nebraska, Lincoln, NE 68588, USA
| | - ALEX STAMM
- Department of Physics & Astronomy, University of Nebraska, Lincoln, NE 68588, USA
| | - JEONG SOON LEE
- Department of Mechanical & Materials Engineering, University of Nebraska, Lincoln, NE 68588, USA
| | - ALEXEI GRUVERMAN
- Department of Physics & Astronomy, University of Nebraska, Lincoln, NE 68588, USA
| | - JUNG YUL LIM
- Department of Mechanical & Materials Engineering, University of Nebraska, Lincoln, NE 68588, USA
- The Graduate School of Dentistry, Kyung Hee University, Seoul 130–701, South Korea
| | - LINXIA GU
- Department of Mechanical & Materials Engineering, University of Nebraska, Lincoln, NE 68588, USA
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48
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A comparative mechanical analysis of plant and animal cells reveals convergence across kingdoms. Biophys J 2015; 107:2237-44. [PMID: 25418292 DOI: 10.1016/j.bpj.2014.10.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 09/29/2014] [Accepted: 10/03/2014] [Indexed: 12/12/2022] Open
Abstract
Plant and animals have evolved different strategies for their development. Whether this is linked to major differences in their cell mechanics remains unclear, mainly because measurements on plant and animal cells relied on independent experiments and setups, thus hindering any direct comparison. In this study we used the same micro-rheometer to compare animal and plant single cell rheology. We found that wall-less plant cells exhibit the same weak power law rheology as animal cells, with comparable values of elastic and loss moduli. Remarkably, microtubules primarily contributed to the rheological behavior of wall-less plant cells whereas rheology of animal cells was mainly dependent on the actin network. Thus, plant and animal cells evolved different molecular strategies to reach a comparable cytoplasmic mechanical core, suggesting that evolutionary convergence could include the internal biophysical properties of cells.
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49
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Tian J, Tu C, Liang Y, Zhou J, Ye X. Study of laser uncaging induced morphological alteration of rat cortical neurites using atomic force microscopy. J Neurosci Methods 2015; 253:151-60. [PMID: 26149288 DOI: 10.1016/j.jneumeth.2015.06.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 06/18/2015] [Accepted: 06/26/2015] [Indexed: 11/28/2022]
Abstract
Activity-dependent structural remodeling is an important aspect of neuronal plasticity. In the previous researches, neuronal structure variations resulting from external interventions were detected by the imaging instruments such as the fluorescence microscopy, the scanning/transmission electron microscopy (SEM/TEM) and the laser confocal microscopy. In this article, a new platform which combined the photochemical stimulation with atomic force microscopy (AFM) was set up to detect the activity-dependent structural remodeling. In the experiments, the cortical neurites on the glass coverslips were stimulated by locally uncaged glutamate under the ultraviolet (UV) laser pulses, and a calcium-related structural collapse of neurites (about 250 nm height decrease) was observed by an AFM. This was the first attempt to combine the laser uncaging with AFM in living cell researches. With the advantages of highly localized stimulation (<5 μm), super resolution imaging (<3.8 nm), and convenient platform building, this system was suitable for the quantitative observation of the neuron mechanical property variations and morphological alterations modified by neural activities under different photochemical stimulations, which would be helpful for studying physiological and pathological mechanisms of structural and functional changes induced by the biomolecule acting.
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Affiliation(s)
- Jian Tian
- Biosensor National Special Laboratory, Key Laboratory of BME of the Ministry of Education, Zhejiang University, Hangzhou 310027, PR China; Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, PR China.
| | - Chunlong Tu
- Biosensor National Special Laboratory, Key Laboratory of BME of the Ministry of Education, Zhejiang University, Hangzhou 310027, PR China; Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, PR China.
| | - Yitao Liang
- Biosensor National Special Laboratory, Key Laboratory of BME of the Ministry of Education, Zhejiang University, Hangzhou 310027, PR China; Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, PR China.
| | - Jian Zhou
- Biosensor National Special Laboratory, Key Laboratory of BME of the Ministry of Education, Zhejiang University, Hangzhou 310027, PR China; Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, PR China.
| | - Xuesong Ye
- Biosensor National Special Laboratory, Key Laboratory of BME of the Ministry of Education, Zhejiang University, Hangzhou 310027, PR China; Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, PR China.
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Hecht FM, Rheinlaender J, Schierbaum N, Goldmann WH, Fabry B, Schäffer TE. Imaging viscoelastic properties of live cells by AFM: power-law rheology on the nanoscale. SOFT MATTER 2015; 11:4584-4591. [PMID: 25891371 DOI: 10.1039/c4sm02718c] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We developed force clamp force mapping (FCFM), an atomic force microscopy (AFM) technique for measuring the viscoelastic creep behavior of live cells with sub-micrometer spatial resolution. FCFM combines force-distance curves with an added force clamp phase during tip-sample contact. From the creep behavior measured during the force clamp phase, quantitative viscoelastic sample properties are extracted. We validate FCFM on soft polyacrylamide gels. We find that the creep behavior of living cells conforms to a power-law material model. By recording short (50-60 ms) force clamp measurements in rapid succession, we generate, for the first time, two-dimensional maps of power-law exponent and modulus scaling parameter. Although these maps reveal large spatial variations of both parameters across the cell surface, we obtain robust mean values from the several hundreds of measurements performed on each cell. Measurements on mouse embryonic fibroblasts show that the mean power-law exponents and the mean modulus scaling parameters differ greatly among individual cells, but both parameters are highly correlated: stiffer cells consistently show a smaller power-law exponent. This correlation allows us to distinguish between wild-type cells and cells that lack vinculin, a dominant protein of the focal adhesion complex, even though the mean values of viscoelastic properties between wildtype and knockout cells did not differ significantly. Therefore, FCFM spatially resolves viscoelastic sample properties and can uncover subtle mechanical signatures of proteins in living cells.
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Affiliation(s)
- Fabian M Hecht
- 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.
| | - Nicolas Schierbaum
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
| | - Wolfgang H Goldmann
- Department of Physics, University of Erlangen-Nuremberg, Henkestraße 91, 91052 Erlangen, Germany
| | - Ben Fabry
- Department of Physics, University of Erlangen-Nuremberg, Henkestraße 91, 91052 Erlangen, Germany
| | - Tilman E Schäffer
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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