1
|
Atia L, Fredberg JJ. A life off the beaten track in biomechanics: Imperfect elasticity, cytoskeletal glassiness, and epithelial unjamming. BIOPHYSICS REVIEWS 2023; 4:041304. [PMID: 38156333 PMCID: PMC10751956 DOI: 10.1063/5.0179719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 11/17/2023] [Indexed: 12/30/2023]
Abstract
Textbook descriptions of elasticity, viscosity, and viscoelasticity fail to account for certain mechanical behaviors that typify soft living matter. Here, we consider three examples. First, strong empirical evidence suggests that within lung parenchymal tissues, the frictional stresses expressed at the microscale are fundamentally not of viscous origin. Second, the cytoskeleton (CSK) of the airway smooth muscle cell, as well as that of all eukaryotic cells, is more solid-like than fluid-like, yet its elastic modulus is softer than the softest of soft rubbers by a factor of 104-105. Moreover, the eukaryotic CSK expresses power law rheology, innate malleability, and fluidization when sheared. For these reasons, taken together, the CSK of the living eukaryotic cell is reminiscent of the class of materials called soft glasses, thus likening it to inert materials such as clays, pastes slurries, emulsions, and foams. Third, the cellular collective comprising a confluent epithelial layer can become solid-like and jammed, fluid-like and unjammed, or something in between. Esoteric though each may seem, these discoveries are consequential insofar as they impact our understanding of bronchospasm and wound healing as well as cancer cell invasion and embryonic development. Moreover, there are reasons to suspect that certain of these phenomena first arose in the early protist as a result of evolutionary pressures exerted by the primordial microenvironment. We have hypothesized, further, that each then became passed down virtually unchanged to the present day as a conserved core process. These topics are addressed here not only because they are interesting but also because they track the journey of one laboratory along a path less traveled by.
Collapse
Affiliation(s)
- Lior Atia
- Ben Gurion University of the Negev, Beer Sheva, Israel
| | | |
Collapse
|
2
|
Sun W, Gao X, Lei H, Wang W, Cao Y. Biophysical Approaches for Applying and Measuring Biological Forces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2105254. [PMID: 34923777 PMCID: PMC8844594 DOI: 10.1002/advs.202105254] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Indexed: 05/13/2023]
Abstract
Over the past decades, increasing evidence has indicated that mechanical loads can regulate the morphogenesis, proliferation, migration, and apoptosis of living cells. Investigations of how cells sense mechanical stimuli or the mechanotransduction mechanism is an active field of biomaterials and biophysics. Gaining a further understanding of mechanical regulation and depicting the mechanotransduction network inside cells require advanced experimental techniques and new theories. In this review, the fundamental principles of various experimental approaches that have been developed to characterize various types and magnitudes of forces experienced at the cellular and subcellular levels are summarized. The broad applications of these techniques are introduced with an emphasis on the difficulties in implementing these techniques in special biological systems. The advantages and disadvantages of each technique are discussed, which can guide readers to choose the most suitable technique for their questions. A perspective on future directions in this field is also provided. It is anticipated that technical advancement can be a driving force for the development of mechanobiology.
Collapse
Affiliation(s)
- Wenxu Sun
- School of SciencesNantong UniversityNantong226019P. R. China
| | - Xiang Gao
- Key Laboratory of Intelligent Optical Sensing and IntegrationNational Laboratory of Solid State Microstructureand Department of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing210023P. R. China
- Institute of Brain ScienceNanjing UniversityNanjing210023P. R. China
| | - Hai Lei
- Key Laboratory of Intelligent Optical Sensing and IntegrationNational Laboratory of Solid State Microstructureand Department of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing210023P. R. China
- Institute of Brain ScienceNanjing UniversityNanjing210023P. R. China
- Chemistry and Biomedicine Innovation CenterNanjing UniversityNanjing210023P. R. China
| | - Wei Wang
- Key Laboratory of Intelligent Optical Sensing and IntegrationNational Laboratory of Solid State Microstructureand Department of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing210023P. R. China
- Institute of Brain ScienceNanjing UniversityNanjing210023P. R. China
| | - Yi Cao
- Key Laboratory of Intelligent Optical Sensing and IntegrationNational Laboratory of Solid State Microstructureand Department of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing210023P. R. China
- Institute of Brain ScienceNanjing UniversityNanjing210023P. R. China
- MOE Key Laboratory of High Performance Polymer Materials and TechnologyDepartment of Polymer Science & EngineeringCollege of Chemistry & Chemical EngineeringNanjing UniversityNanjing210023P. R. China
- Chemistry and Biomedicine Innovation CenterNanjing UniversityNanjing210023P. R. China
| |
Collapse
|
3
|
Barravecchia I, De Cesari C, Forcato M, Scebba F, Pyankova OV, Bridger JM, Foster HA, Signore G, Borghini A, Andreassi M, Andreazzoli M, Bicciato S, Pè ME, Angeloni D. Microgravity and space radiation inhibit autophagy in human capillary endothelial cells, through either opposite or synergistic effects on specific molecular pathways. Cell Mol Life Sci 2021; 79:28. [PMID: 34936031 PMCID: PMC11072227 DOI: 10.1007/s00018-021-04025-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 10/12/2021] [Accepted: 11/05/2021] [Indexed: 12/13/2022]
Abstract
Microgravity and space radiation (SR) are two highly influential factors affecting humans in space flight (SF). Many health problems reported by astronauts derive from endothelial dysfunction and impaired homeostasis. Here, we describe the adaptive response of human, capillary endothelial cells to SF. Reference samples on the ground and at 1g onboard permitted discrimination between the contribution of microgravity and SR within the combined responses to SF. Cell softening and reduced motility occurred in SF cells, with a loss of actin stress fibers and a broader distribution of microtubules and intermediate filaments within the cytoplasm than in control cells. Furthermore, in space the number of primary cilia per cell increased and DNA repair mechanisms were found to be activated. Transcriptomics revealed the opposing effects of microgravity from SR for specific molecular pathways: SR, unlike microgravity, stimulated pathways for endothelial activation, such as hypoxia and inflammation, DNA repair and apoptosis, inhibiting autophagic flux and promoting an aged-like phenotype. Conversely, microgravity, unlike SR, activated pathways for metabolism and a pro-proliferative phenotype. Therefore, we suggest microgravity and SR should be considered separately to tailor effective countermeasures to protect astronauts' health.
Collapse
Affiliation(s)
- Ivana Barravecchia
- Institute of Life Sciences, Scuola Superiore Sant'Anna, Via G. Moruzzi, 1, 56124, Pisa, Italy
- Department of Pharmacy, University of Pisa, 56126, Pisa, Italy
| | - Chiara De Cesari
- Institute of Life Sciences, Scuola Superiore Sant'Anna, Via G. Moruzzi, 1, 56124, Pisa, Italy
- Department of Biology, University of Pisa, 56123, Pisa, Italy
| | - Mattia Forcato
- Center for Genome Research, Department of Life Science, University of Modena and Reggio Emilia, 41125, Modena, Italy
| | - Francesca Scebba
- Institute of Life Sciences, Scuola Superiore Sant'Anna, Via G. Moruzzi, 1, 56124, Pisa, Italy
| | - Olga V Pyankova
- Institute of Life Sciences, Scuola Superiore Sant'Anna, Via G. Moruzzi, 1, 56124, Pisa, Italy
| | - Joanna M Bridger
- Laboratory of Nuclear and Genomic Health, Centre of Genome Engineering and Maintenance, Division of Biosciences, Department of Life Sciences, College of Health and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Helen A Foster
- Department of Biological and Environmental Sciences, School of Life and Medical Sciences, University of Hertfordshire, Hatfield, UK
| | | | - Andrea Borghini
- Institute of Clinical Physiology, National Research Council, 56124, Pisa, Italy
| | | | | | - Silvio Bicciato
- Center for Genome Research, Department of Life Science, University of Modena and Reggio Emilia, 41125, Modena, Italy
| | - Mario Enrico Pè
- Institute of Life Sciences, Scuola Superiore Sant'Anna, Via G. Moruzzi, 1, 56124, Pisa, Italy
| | - Debora Angeloni
- Institute of Life Sciences, Scuola Superiore Sant'Anna, Via G. Moruzzi, 1, 56124, Pisa, Italy.
| |
Collapse
|
4
|
Janshoff A. Viscoelasticity of basal plasma membranes and cortices derived from MDCK II cells. BIOPHYSICAL REPORTS 2021; 1:100024. [PMID: 36425463 PMCID: PMC9680774 DOI: 10.1016/j.bpr.2021.100024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 09/08/2021] [Indexed: 06/16/2023]
Abstract
The mechanical properties of cells are largely determined by the architecture and dynamics of their viscoelastic cortex, which consists of a contractile, cross-linked actin mesh attached to the plasma membrane via linker proteins. Measuring the mechanical properties of adherent, polarized epithelial cells is usually limited to the upper, i.e., apical side, of the cells because of their accessibility on culture dishes. Therefore, less is known about the viscoelastic properties of basal membranes. Here, I investigate the viscoelastic properties of basolateral membranes derived from polarized MDCK II epithelia in response to external deformation and compare them to living cells probed at the apical side. MDCK II cells were grown on porous surfaces to confluence, and the upper cell body was removed via a squirting-lysis protocol. The free-standing, defoliated basal membranes were subject to force indentation and relaxation experiments permitting a precise assessment of cortical viscoelasticity. A new theoretical framework to describe the force cycles is developed and applied to obtain the time-dependent area compressibility modulus of cell cortices from adherent cells. Compared with the viscoelastic response of living cells, the basolateral membranes are substantially less fluid and stiffer but obey to the same universal scaling law if excess area is taken correctly into account.
Collapse
Affiliation(s)
- Andreas Janshoff
- Department of Chemistry, Institute of Physical Chemistry, Göttingen
| |
Collapse
|
5
|
Fajrial AK, Liu K, Gao Y, Gu J, Lakerveld R, Ding X. Characterization of Single-Cell Osmotic Swelling Dynamics for New Physical Biomarkers. Anal Chem 2021; 93:1317-1325. [PMID: 33253534 DOI: 10.1021/acs.analchem.0c02289] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Characterization of cell physical biomarkers is vital to understand cell properties and applicable for disease diagnostics. Current methods used to analyze physical phenotypes involve external forces to deform the cells. Alternatively, internal tension forces via osmotic swelling can also deform the cells. However, an established assumption contends that the forces generated during hypotonic swelling concentrated on the plasma membrane are incapable of assessing the physical properties of nucleated cells. Here, we utilized an osmotic swelling approach to characterize different types of nucleated cells. Using a microfluidic device for cell trapping arrays with truncated hanging micropillars (CellHangars), we isolated single cells and evaluated the swelling dynamics during the hypotonic challenge at 1 s time resolution. We demonstrated that cells with different mechanical phenotypes showed unique swelling dynamics signature. Different types of cells can be classified with an accuracy of up to ∼99%. We also showed that swelling dynamics can detect cellular mechanical property changes due to cytoskeleton disruption. Considering its simplicity, swelling dynamics offers an invaluable label-free physical biomarker for cells with potential applications in both biological studies and clinical practice.
Collapse
Affiliation(s)
- Apresio K Fajrial
- Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Drive, UCB 427, Boulder, Colorado 80309, United States
| | - Kun Liu
- Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Drive, UCB 427, Boulder, Colorado 80309, United States
| | - Yu Gao
- Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Drive, UCB 427, Boulder, Colorado 80309, United States
| | - Junhao Gu
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Richard Lakerveld
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Xiaoyun Ding
- Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Drive, UCB 427, Boulder, Colorado 80309, United States.,Biomedical Engineering Program, University of Colorado Boulder, Boulder, Colorado 80309, United States
| |
Collapse
|
6
|
Hubrich H, Mey IP, Brückner BR, Mühlenbrock P, Nehls S, Grabenhorst L, Oswald T, Steinem C, Janshoff A. Viscoelasticity of Native and Artificial Actin Cortices Assessed by Nanoindentation Experiments. NANO LETTERS 2020; 20:6329-6335. [PMID: 32786944 DOI: 10.1021/acs.nanolett.0c01769] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Cell cortices are responsible for the resilience and morphological dynamics of cells. Measuring their mechanical properties is impeded by contributions from other filament types, organelles, and the crowded cytoplasm. We established a versatile concept for the precise assessment of cortical viscoelasticity based on force cycle experiments paired with continuum mechanics. Apical cell membranes of confluent MDCK II cells were deposited on porous substrates and locally deformed. Force cycles could be described with a time-dependent area compressibility modulus obeying the same power law as employed for whole cells. The reduced fluidity of apical cell membranes compared to living cells could partially be restored by reactivating myosin motors. A comparison with artificial minimal actin cortices (MACs) reveals lower stiffness and higher fluidity attributed to missing cross-links in MACs.
Collapse
Affiliation(s)
- Hanna Hubrich
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| | - Ingo P Mey
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Göttingen 37077, Germany
| | - Bastian R Brückner
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| | - Peter Mühlenbrock
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Göttingen 37077, Germany
| | - Stefan Nehls
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| | - Lennart Grabenhorst
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| | - Tabea Oswald
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Göttingen 37077, Germany
| | - Claudia Steinem
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Göttingen 37077, Germany
| | - Andreas Janshoff
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| |
Collapse
|
7
|
Deblais A, Woutersen S, Bonn D. Rheology of Entangled Active Polymer-Like T. Tubifex Worms. PHYSICAL REVIEW LETTERS 2020; 124:188002. [PMID: 32441969 DOI: 10.1103/physrevlett.124.188002] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 03/18/2020] [Accepted: 04/13/2020] [Indexed: 06/11/2023]
Abstract
We experimentally study the rheology of long, slender, and entangled living worms (Tubifex Tubifex). Their level of activity can be controlled by changing the temperature or by adding small amounts of alcohol to make the worms temporarily inactive. Performing classical rheology experiments on this entangled polymer-like system, we find that the rheology is qualitatively similar to that of usual polymers, but, quantitatively, (i) shear thinning is reduced by activity, (ii) the characteristic shear rate for the onset of shear-thinning is given by the time scale of the activity, and (iii) the low shear viscosity as a function of concentration shows a very different scaling from that of regular polymers. Our study paves the way towards a new experimental research field of active "polymer-like worms."
Collapse
Affiliation(s)
- A Deblais
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, 1098XH Amsterdam, The Netherlands
| | - S Woutersen
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
| | - D Bonn
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, 1098XH Amsterdam, The Netherlands
| |
Collapse
|
8
|
Gangotra A, Biviano M, Dagastine RR, Berry JD, Willmott GR. Use of microaspiration to study the mechanical properties of polymer gel microparticles. SOFT MATTER 2019; 15:7286-7294. [PMID: 31498362 DOI: 10.1039/c9sm00862d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The mechanical properties of polyacrylamide (PA) and polydimethylsiloxane (PDMS) microparticle populations have been measured using microaspiration, a recently developed experimental technique. Microaspiration is an augmented version of micropipette aspiration, in which optical microscopy data are obtained as individual soft particles pass through the tip of a micropipette. During microaspiration, the ion current passing through the pipette tip is also measured, and the synchronised optical and current data streams are used to study and quantify mechanical properties. Ion current signatures for the poroelastic PA particles were qualitatively different from those of the viscoelastic PDMS particles. For PA particles the current gradually reduced during each aspiration event, whereas for PDMS particles the current trace resembled a negative top hat function. For PA particles it was found that the maximum change in current during aspiration (ΔIh) increased with particle size. By considering the initial elastic response, a mean effective shear modulus (G') of 6.6 ± 0.2 kPa was found for aspiration of 115 PA particles of ∼10-20 μm diameter. Using a viscoelastic model to describe flow into the pipette, a mean initial effective elastic modulus (E0') of 3.5 ± 1.7 MPa was found for aspiration of 17 PDMS particles of ∼ 9-11 μm diameter. These moduli are consistent with previously reported literature values, providing initial validation of the microaspiration method.
Collapse
Affiliation(s)
- Ankita Gangotra
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand
| | | | | | | | | |
Collapse
|
9
|
Advances in Micropipette Aspiration: Applications in Cell Biomechanics, Models, and Extended Studies. Biophys J 2019; 116:587-594. [PMID: 30683304 DOI: 10.1016/j.bpj.2019.01.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 11/29/2018] [Accepted: 01/02/2019] [Indexed: 12/31/2022] Open
Abstract
With five decades of sustained application, micropipette aspiration has enabled a wide range of biomechanical studies in the field of cell mechanics. Here, we provide an update on the use of the technique, with a focus on recent developments in the analysis of the experiments, innovative microaspiration-based approaches, and applications in a broad variety of cell types. We first recapitulate experimental variations of the technique. We then discuss analysis models focusing on important limitations of widely used biomechanical models, which underpin the urge to adopt the appropriate ones to avoid misleading conclusions. The possibilities of performing different studies on the same cell are also considered.
Collapse
|
10
|
Nanoscale characterization of dynamic cellular viscoelasticity by atomic force microscopy with varying measurement parameters. J Mech Behav Biomed Mater 2018; 82:193-201. [DOI: 10.1016/j.jmbbm.2018.03.036] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 02/14/2018] [Accepted: 03/26/2018] [Indexed: 12/23/2022]
|
11
|
Dorta MP, de Brito IV, Pereira AC, Alencar AM. Quantification of alignment of vascular smooth muscle cells. Cytometry A 2018; 93:533-539. [DOI: 10.1002/cyto.a.23355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 02/05/2018] [Accepted: 02/13/2018] [Indexed: 12/18/2022]
Affiliation(s)
- Marcel P. Dorta
- Laboratory of Microrheology and Molecular Physiology, Department of General Physics, Physics InstituteUniversity of São PauloSão Paulo Brazil
| | - Isis V. de Brito
- Laboratory of Microrheology and Molecular Physiology, Department of General Physics, Physics InstituteUniversity of São PauloSão Paulo Brazil
| | - Alexandre C. Pereira
- Laboratory of Genetics and Molecular Cardiology, Department of Cardiology, Heart Institute, Medical SchoolUniversity of São PauloSão Paulo Brazil
| | - Adriano M. Alencar
- Laboratory of Microrheology and Molecular Physiology, Department of General Physics, Physics InstituteUniversity of São PauloSão Paulo Brazil
| |
Collapse
|
12
|
Li M, Liu L, Xi N, Wang Y. Atomic force microscopy studies on cellular elastic and viscoelastic properties. SCIENCE CHINA-LIFE SCIENCES 2017; 61:57-67. [DOI: 10.1007/s11427-016-9041-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Accepted: 04/07/2017] [Indexed: 01/03/2023]
|
13
|
Li M, Dang D, Liu L, Xi N, Wang Y. Atomic Force Microscopy in Characterizing Cell Mechanics for Biomedical Applications: A Review. IEEE Trans Nanobioscience 2017; 16:523-540. [PMID: 28613180 DOI: 10.1109/tnb.2017.2714462] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cell mechanics is a novel label-free biomarker for indicating cell states and pathological changes. The advent of atomic force microscopy (AFM) provides a powerful tool for quantifying the mechanical properties of single living cells in aqueous conditions. The wide use of AFM in characterizing cell mechanics in the past two decades has yielded remarkable novel insights in understanding the development and progression of certain diseases, such as cancer, showing the huge potential of cell mechanics for practical applications in the field of biomedicine. In this paper, we reviewed the utilization of AFM to characterize cell mechanics. First, the principle and method of AFM single-cell mechanical analysis was presented, along with the mechanical responses of cells to representative external stimuli measured by AFM. Next, the unique changes of cell mechanics in two types of physiological processes (stem cell differentiation, cancer metastasis) revealed by AFM were summarized. After that, the molecular mechanisms guiding cell mechanics were analyzed. Finally the challenges and future directions were discussed.
Collapse
|
14
|
Improved Measurement of Elastic Properties of Cells by Micropipette Aspiration and Its Application to Lymphocytes. Ann Biomed Eng 2017; 45:1375-1385. [DOI: 10.1007/s10439-017-1795-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 01/10/2017] [Indexed: 10/24/2022]
|
15
|
Park JA, Atia L, Mitchel JA, Fredberg JJ, Butler JP. Collective migration and cell jamming in asthma, cancer and development. J Cell Sci 2016; 129:3375-83. [PMID: 27550520 PMCID: PMC5047682 DOI: 10.1242/jcs.187922] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Collective cellular migration within the epithelial layer impacts upon development, wound healing and cancer invasion, but remains poorly understood. Prevailing conceptual frameworks tend to focus on the isolated role of each particular underlying factor - taken one at a time or at most a few at a time - and thus might not be tailored to describe a cellular collective that embodies a wide palette of physical and molecular interactions that are both strong and complex. To bridge this gap, we shift the spotlight to the emerging concept of cell jamming, which points to only a small set of parameters that govern when a cellular collective might jam and rigidify like a solid, or instead unjam and flow like a fluid. As gateways to cellular migration, the unjamming transition (UJT) and the epithelial-to-mesenchymal transition (EMT) share certain superficial similarities, but their congruence - or lack thereof - remains unclear. In this Commentary, we discuss aspects of cell jamming, its established role in human epithelial cell layers derived from the airways of non-asthmatic and asthmatic donors, and its speculative but emerging roles in development and cancer cell invasion.
Collapse
Affiliation(s)
- Jin-Ah Park
- Harvard T.H. Chan School of Public Health, Department of Environmental Health, Boston, MA 02115, USA
| | - Lior Atia
- Harvard T.H. Chan School of Public Health, Department of Environmental Health, Boston, MA 02115, USA
| | - Jennifer A Mitchel
- Harvard T.H. Chan School of Public Health, Department of Environmental Health, Boston, MA 02115, USA
| | - Jeffrey J Fredberg
- Harvard T.H. Chan School of Public Health, Department of Environmental Health, Boston, MA 02115, USA
| | - James P Butler
- Harvard T.H. Chan School of Public Health, Department of Environmental Health, Boston, MA 02115, USA Brigham and Women's Hospital, Harvard Medical School, Department of Medicine, Boston, MA 02115, USA
| |
Collapse
|
16
|
Roan E, Wilhelm KR, Waters CM. Kymographic Imaging of the Elastic Modulus of Epithelial Cells during the Onset of Migration. Biophys J 2016; 109:2051-7. [PMID: 26588564 DOI: 10.1016/j.bpj.2015.10.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 09/11/2015] [Accepted: 10/05/2015] [Indexed: 01/16/2023] Open
Abstract
Epithelial cell migration during wound repair involves a complex interplay of intracellular processes that enable motility while preserving contact among the cells. Recent evidence suggests that fluctuations of the intracellular biophysical state of cells generate traction forces at the basal side of the cells that are necessary for the cells to migrate. However, less is known about the biophysical and structural changes throughout the cells that accompany these fluctuations. Here, we utilized, to our knowledge, a novel kymographic nanoindentation method to obtain spatiotemporal measurements of the elastic moduli of living cells during migration after wounding. At the onset of migration, the elastic modulus increased near the migration front. In addition, the intensity of fluctuations in the elastic modulus changed at the migration front, and these changes were dependent upon f-actin, one of the major components of the cytoskeleton. These results demonstrate the unique biophysical changes that occur at the onset of migration as cells transition from a stationary to a migratory state.
Collapse
Affiliation(s)
- Esra Roan
- Biomedical Engineering Department, University of Memphis, Memphis, Tennessee.
| | - Kristina R Wilhelm
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Christopher M Waters
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee; Department of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee
| |
Collapse
|
17
|
Katta S, Krieg M, Goodman MB. Feeling force: physical and physiological principles enabling sensory mechanotransduction. Annu Rev Cell Dev Biol 2016; 31:347-71. [PMID: 26566115 DOI: 10.1146/annurev-cellbio-100913-013426] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Organisms as diverse as microbes, roundworms, insects, and mammals detect and respond to applied force. In animals, this ability depends on ionotropic force receptors, known as mechanoelectrical transduction (MeT) channels, that are expressed by specialized mechanoreceptor cells embedded in diverse tissues and distributed throughout the body. These cells mediate hearing, touch, and proprioception and play a crucial role in regulating organ function. Here, we attempt to integrate knowledge about the architecture of mechanoreceptor cells and their sensory organs with principles of cell mechanics, and we consider how engulfing tissues contribute to mechanical filtering. We address progress in the quest to identify the proteins that form MeT channels and to understand how these channels are gated. For clarity and convenience, we focus on sensory mechanobiology in nematodes, fruit flies, and mice. These themes are emphasized: asymmetric responses to applied forces, which may reflect anisotropy of the structure and mechanics of sensory mechanoreceptor cells, and proteins that function as MeT channels, which appear to have emerged many times through evolution.
Collapse
Affiliation(s)
- Samata Katta
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305;
| | - Michael Krieg
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305;
| | - Miriam B Goodman
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305;
| |
Collapse
|
18
|
Effects of methotrexate on the viscoelastic properties of single cells probed by atomic force microscopy. J Biol Phys 2016; 42:551-569. [PMID: 27438703 DOI: 10.1007/s10867-016-9423-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Accepted: 06/20/2016] [Indexed: 12/20/2022] Open
Abstract
Methotrexate is a commonly used anti-cancer chemotherapy drug. Cellular mechanical properties are fundamental parameters that reflect the physiological state of a cell. However, so far the role of cellular mechanical properties in the actions of methotrexate is still unclear. In recent years, probing the behaviors of single cells with the use of atomic force microscopy (AFM) has contributed much to the field of cell biomechanics. In this work, with the use of AFM, the effects of methotrexate on the viscoelastic properties of four types of cells were quantitatively investigated. The inhibitory and cytotoxic effects of methotrexate on the proliferation of cells were observed by optical and fluorescence microscopy. AFM indenting was used to measure the changes of cellular viscoelastic properties (Young's modulus and relaxation time) by using both conical tip and spherical tip, quantitatively showing that the stimulation of methotrexate resulted in a significant decrease of both cellular Young's modulus and relaxation times. The morphological changes of cells induced by methotrexate were visualized by AFM imaging. The study improves our understanding of methotrexate action and offers a novel way to quantify drug actions at the single-cell level by measuring cellular viscoelastic properties, which may have potential impacts on developing label-free methods for drug evaluation.
Collapse
|
19
|
Metzler R, Jeon JH, Cherstvy AG. Non-Brownian diffusion in lipid membranes: Experiments and simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2451-2467. [PMID: 26826272 DOI: 10.1016/j.bbamem.2016.01.022] [Citation(s) in RCA: 126] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 01/21/2016] [Accepted: 01/23/2016] [Indexed: 12/14/2022]
Abstract
The dynamics of constituents and the surface response of cellular membranes-also in connection to the binding of various particles and macromolecules to the membrane-are still a matter of controversy in the membrane biophysics community, particularly with respect to crowded membranes of living biological cells. We here put into perspective recent single particle tracking experiments in the plasma membranes of living cells and supercomputing studies of lipid bilayer model membranes with and without protein crowding. Special emphasis is put on the observation of anomalous, non-Brownian diffusion of both lipid molecules and proteins embedded in the lipid bilayer. While single component, pure lipid bilayers in simulations exhibit only transient anomalous diffusion of lipid molecules on nanosecond time scales, the persistence of anomalous diffusion becomes significantly longer ranged on the addition of disorder-through the addition of cholesterol or proteins-and on passing of the membrane lipids to the gel phase. Concurrently, experiments demonstrate the anomalous diffusion of membrane embedded proteins up to macroscopic time scales in the minute time range. Particular emphasis will be put on the physical character of the anomalous diffusion, in particular, the occurrence of ageing observed in the experiments-the effective diffusivity of the measured particles is a decreasing function of time. Moreover, we present results for the time dependent local scaling exponent of the mean squared displacement of the monitored particles. Recent results finding deviations from the commonly assumed Gaussian diffusion patterns in protein crowded membranes are reported. The properties of the displacement autocorrelation function of the lipid molecules are discussed in the light of their appropriate physical anomalous diffusion models, both for non-crowded and crowded membranes. In the last part of this review we address the upcoming field of membrane distortion by elongated membrane-binding particles. We discuss how membrane compartmentalisation and the particle-membrane binding energy may impact the dynamics and response of lipid membranes. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
Collapse
Affiliation(s)
- R Metzler
- Institute for Physics & Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany; Department of Physics, Tampere University of Technology, 33101 Tampere, Finland.
| | - J-H Jeon
- Korea Institute for Advanced Study (KIAS), Seoul, Republic of Korea
| | - A G Cherstvy
- Institute for Physics & Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany
| |
Collapse
|
20
|
Plaza GR, Uyeda TQP, Mirzaei Z, Simmons CA. Study of the influence of actin-binding proteins using linear analyses of cell deformability. SOFT MATTER 2015; 11:5435-5446. [PMID: 26059185 DOI: 10.1039/c5sm00125k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The actin cytoskeleton plays a key role in the deformability of the cell and in mechanosensing. Here we analyze the contributions of three major actin cross-linking proteins, myosin II, α-actinin and filamin, to cell deformability, by using micropipette aspiration of Dictyostelium cells. We examine the applicability of three simple mechanical models: for small deformation, linear viscoelasticity and drop of liquid with a tense cortex; and for large deformation, a Newtonian viscous fluid. For these models, we have derived linearized equations and we provide a novel, straightforward methodology to analyze the experiments. This methodology allowed us to differentiate the effects of the cross-linking proteins in the different regimes of deformation. Our results confirm some previous observations and suggest important relations between the molecular characteristics of the actin-binding proteins and the cell behavior: the effect of myosin is explained in terms of the relation between the lifetime of the bond to actin and the resistive force; the presence of α-actinin obstructs the deformation of the cytoskeleton, presumably mainly due to the higher molecular stiffness and to the lower dissociation rate constants; and filamin contributes critically to the global connectivity of the network, possibly by rapidly turning over cross-links during the remodeling of the cytoskeletal network, thanks to the higher rate constants, flexibility and larger size. The results suggest a sophisticated relationship between the expression levels of actin-binding proteins, deformability and mechanosensing.
Collapse
Affiliation(s)
- Gustavo R Plaza
- Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain.
| | | | | | | |
Collapse
|
21
|
Nguyen TD, Oloyede A, Singh S, Gu Y. Microscale consolidation analysis of relaxation behavior of single living chondrocytes subjected to varying strain-rates. J Mech Behav Biomed Mater 2015; 49:343-54. [PMID: 26093345 DOI: 10.1016/j.jmbbm.2015.05.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 05/01/2015] [Accepted: 05/06/2015] [Indexed: 11/19/2022]
Abstract
Besides the elastic stiffness, the relaxation behavior of single living cells is also of interest of various researchers when studying cell mechanics. It is hypothesized that the relaxation response of the cells is governed by both intrinsic viscoelasticity of the solid phase and fluid-solid interactions mechanisms. There are a number of mechanical models have been developed to investigate the relaxation behavior of single cells. However, there is lack of model enable to accurately capture both of the mechanisms. Therefore, in this study, the porohyperelastic (PHE) model, which is an extension of the consolidation theory, combined with inverse Finite Element Analysis (FEA) technique was used at the first time to investigate the relaxation response of living chondrocytes. This model was also utilized to study the dependence of relaxation behavior of the cells on strain-rates. The stress-relaxation experiments under the various strain-rates were conducted with the Atomic Force Microscopy (AFM). The results have demonstrated that the PHE model could effectively capture the stress-relaxation behavior of the living chondrocytes, especially at intermediate to high strain-rates. Although this model gave some errors at lower strain-rates, its performance was acceptable. Therefore, the PHE model is properly a promising model for single cell mechanics studies. Moreover, it has been found that the hydraulic permeability of living chondrocytes reduced with decreasing of strain-rates. It might be due to the intracellular fluid volume fraction and the fluid pore pressure gradients of chondrocytes were higher when higher strain-rates applied.
Collapse
Affiliation(s)
- Trung Dung Nguyen
- School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Adekunle Oloyede
- School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Sanjleena Singh
- School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia
| | - YuanTong Gu
- School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia.
| |
Collapse
|
22
|
Fredberg JJ. Power steering, power brakes, and jamming: evolution of collective cell-cell interactions. Physiology (Bethesda) 2015; 29:218-9. [PMID: 24985324 DOI: 10.1152/physiol.00026.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
23
|
Plaza GR, Marí N, Gálvez BG, Bernal A, Guinea GV, Daza R, Pérez-Rigueiro J, Solanas C, Elices M. Simple measurement of the apparent viscosity of a cell from only one picture: Application to cardiac stem cells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:052715. [PMID: 25493824 DOI: 10.1103/physreve.90.052715] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Indexed: 06/04/2023]
Abstract
Mechanical deformability of cells is a key property that influences their ability to migrate and their contribution to tissue development and regeneration. We analyze here the possibility of characterizing the overall deformability of cells by their apparent viscosity, using a simplified method to estimate that parameter. The proposed method simplifies the quantitative analysis of micropipette-aspiration experiments. We have studied by this procedure the overall apparent viscosity of cardiac stem cells, which are considered a promising tool to regenerate damaged cardiac tissue. Comparison with the apparent viscosity of low-viscosity cells such as immune-system cells suggests that treatments to reduce the viscosity of these cells could enhance their ability to repair damaged cardiac tissue.
Collapse
Affiliation(s)
- G R Plaza
- Center for Biomedical Technology, Universidad Politécnica de Madrid, 28223 Pozuelo de Alarcón, Spain and Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| | - N Marí
- Center for Biomedical Technology, Universidad Politécnica de Madrid, 28223 Pozuelo de Alarcón, Spain and Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| | - B G Gálvez
- Department of Regenerative Cardiology, Centro Nacional de Investigaciones Cardiovasculares, 28029 Madrid, Spain
| | - A Bernal
- Department of Regenerative Cardiology, Centro Nacional de Investigaciones Cardiovasculares, 28029 Madrid, Spain
| | - G V Guinea
- Center for Biomedical Technology, Universidad Politécnica de Madrid, 28223 Pozuelo de Alarcón, Spain and Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| | - R Daza
- Center for Biomedical Technology, Universidad Politécnica de Madrid, 28223 Pozuelo de Alarcón, Spain and Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| | - J Pérez-Rigueiro
- Center for Biomedical Technology, Universidad Politécnica de Madrid, 28223 Pozuelo de Alarcón, Spain and Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| | - C Solanas
- Center for Biomedical Technology, Universidad Politécnica de Madrid, 28223 Pozuelo de Alarcón, Spain and Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| | - M Elices
- Center for Biomedical Technology, Universidad Politécnica de Madrid, 28223 Pozuelo de Alarcón, Spain and Departamento de Ciencia de Materiales, ETSI de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| |
Collapse
|
24
|
Patrício P, Almeida PL, Portela R, Sobral RG, Grilo IR, Cidade T, Leal CR. Living bacteria rheology: population growth, aggregation patterns, and collective behavior under different shear flows. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:022720. [PMID: 25215771 DOI: 10.1103/physreve.90.022720] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Indexed: 06/03/2023]
Abstract
The activity of growing living bacteria was investigated using real-time and in situ rheology-in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus-strain COL and its isogenic cell wall autolysis mutant, RUSAL9-were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage.
Collapse
Affiliation(s)
- P Patrício
- ISEL, Rua Conselheiro Emídio Navarro 1, P-1959-007 Lisboa, Portugal and CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal
| | - P L Almeida
- ISEL, Rua Conselheiro Emídio Navarro 1, P-1959-007 Lisboa, Portugal and CENIMAT/I3N, Faculdade Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - R Portela
- Centro de Recursos Microbiológicos, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - R G Sobral
- Centro de Recursos Microbiológicos, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - I R Grilo
- Laboratório de Genética Molecular, ITQB, Universidade Nova de Lisboa, 2780 Oeiras, Portugal
| | - T Cidade
- CENIMAT/I3N, Faculdade Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal and Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - C R Leal
- ISEL, Rua Conselheiro Emídio Navarro 1, P-1959-007 Lisboa, Portugal and CENIMAT/I3N, Faculdade Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| |
Collapse
|
25
|
Lan B, Wang L, Zhang J, Pascoe CD, Norris BA, Liu JCY, Solomon D, Paré PD, Deng L, Seow CY. Rho-kinase mediated cytoskeletal stiffness in skinned smooth muscle. J Appl Physiol (1985) 2013; 115:1540-52. [PMID: 24072407 DOI: 10.1152/japplphysiol.00654.2013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The structurally dynamic cytoskeleton is important in many cell functions. Large gaps still exist in our knowledge regarding what regulates cytoskeletal dynamics and what underlies the structural plasticity. Because Rho-kinase is an upstream regulator of signaling events leading to phosphorylation of many cytoskeletal proteins in many cell types, we have chosen this kinase as the focus of the present study. In detergent skinned tracheal smooth muscle preparations, we quantified the proteins eluted from the muscle cells over time and monitored the muscle's ability to respond to acetylcholine (ACh) stimulation to produce force and stiffness. In a partially skinned preparation not able to generate active force but could still stiffen upon ACh stimulation, we found that the ACh-induced stiffness was independent of calcium and myosin light chain phosphorylation. This indicates that the myosin light chain-dependent actively cycling crossbridges are not likely the source of the stiffness. The results also indicate that Rho-kinase is central to the ACh-induced stiffness, because inhibition of the kinase by H1152 (1 μM) abolished the stiffening. Furthermore, the rate of relaxation of calcium-induced stiffness in the skinned preparation was faster than that of ACh-induced stiffness, with or without calcium, suggesting that different signaling pathways lead to different means of maintenance of stiffness in the skinned preparation.
Collapse
Affiliation(s)
- Bo Lan
- Bioengineering College, Chongqing University, Chongqing, China
| | | | | | | | | | | | | | | | | | | |
Collapse
|