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Vittum Z, Cocchiaro S, Mensah SA. Basal endothelial glycocalyx's response to shear stress: a review of structure, function, and clinical implications. Front Cell Dev Biol 2024; 12:1371769. [PMID: 38562144 PMCID: PMC10982814 DOI: 10.3389/fcell.2024.1371769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 03/04/2024] [Indexed: 04/04/2024] Open
Abstract
The endothelial glycocalyx encompasses the entire endothelial cell, transducing extracellular signals and regulating vascular permeability and barrier functions. The apical glycocalyx, which forms the lumen of the vessel, and the basal glycocalyx, at the smooth muscle cell interface, are often investigated separately as they are exposed to vastly different stimuli. The apical glycocalyx directly senses fluid shear forces transmitting them intracellularly through connection to the cytoskeleton of the endothelial cell. The basal glycocalyx has demonstrated sensitivity to shear due to blood flow transmitted through the cytoskeleton, promoting alternate signaling processes. In this review, we discuss current literature on the basal glycocalyx's response to shear stress in the context of mechanotransduction and remodeling. The possible implications of basal glycocalyx degradation in pathologies are also explored. Finally, this review seeks to highlight how addressing the gaps discussed would improve our wholistic understanding of the endothelial glycocalyx and its role in maintaining vascular homeostasis.
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Affiliation(s)
- Zoe Vittum
- Biomedical Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Samantha Cocchiaro
- Biomedical Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Solomon A. Mensah
- Biomedical Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
- Mechanical Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
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2
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Tamargo IA, Baek KI, Kim Y, Park C, Jo H. Flow-induced reprogramming of endothelial cells in atherosclerosis. Nat Rev Cardiol 2023; 20:738-753. [PMID: 37225873 PMCID: PMC10206587 DOI: 10.1038/s41569-023-00883-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/25/2023] [Indexed: 05/26/2023]
Abstract
Atherosclerotic diseases such as myocardial infarction, ischaemic stroke and peripheral artery disease continue to be leading causes of death worldwide despite the success of treatments with cholesterol-lowering drugs and drug-eluting stents, raising the need to identify additional therapeutic targets. Interestingly, atherosclerosis preferentially develops in curved and branching arterial regions, where endothelial cells are exposed to disturbed blood flow with characteristic low-magnitude oscillatory shear stress. By contrast, straight arterial regions exposed to stable flow, which is associated with high-magnitude, unidirectional shear stress, are relatively well protected from the disease through shear-dependent, atheroprotective endothelial cell responses. Flow potently regulates structural, functional, transcriptomic, epigenomic and metabolic changes in endothelial cells through mechanosensors and mechanosignal transduction pathways. A study using single-cell RNA sequencing and chromatin accessibility analysis in a mouse model of flow-induced atherosclerosis demonstrated that disturbed flow reprogrammes arterial endothelial cells in situ from healthy phenotypes to diseased ones characterized by endothelial inflammation, endothelial-to-mesenchymal transition, endothelial-to-immune cell-like transition and metabolic changes. In this Review, we discuss this emerging concept of disturbed-flow-induced reprogramming of endothelial cells (FIRE) as a potential pro-atherogenic mechanism. Defining the flow-induced mechanisms through which endothelial cells are reprogrammed to promote atherosclerosis is a crucial area of research that could lead to the identification of novel therapeutic targets to combat the high prevalence of atherosclerotic disease.
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Affiliation(s)
- Ian A Tamargo
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
- Molecular and Systems Pharmacology Program, Emory University, Atlanta, GA, USA
| | - Kyung In Baek
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
| | - Yerin Kim
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
| | - Christian Park
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
| | - Hanjoong Jo
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA.
- Molecular and Systems Pharmacology Program, Emory University, Atlanta, GA, USA.
- Department of Medicine, Emory University School, Atlanta, GA, USA.
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Rahaman SG, Mahanty M, Mukherjee P, Dutta B, Rahaman SO. Mechanosensing and Mechanosignal Transduction in Atherosclerosis. Curr Atheroscler Rep 2023; 25:711-721. [PMID: 37615786 DOI: 10.1007/s11883-023-01139-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/16/2023] [Indexed: 08/25/2023]
Abstract
PURPOSE OF REVIEW This review aims to summarize the latest findings on mechanosensing in atherosclerosis, elucidating the molecular mechanisms, cellular players, and potential therapeutic targets. RECENT FINDINGS Atherosclerosis, a chronic inflammatory disease characterized by the buildup of lipid-laden plaque within arterial walls, is a major contributor to cardiovascular disease-related mortality and morbidity. Interestingly, atherosclerosis predominantly occurs in arterial areas with curves and branches. In these regions, endothelial cells encounter irregular blood flow with distinctive low-intensity fluctuating shear stress. On the other hand, straight sections of arteries, subjected to a consistent flow and related high-intensity, one-way shear stress, are relatively safeguarded against atherosclerosis due to shear-dependent, disease-preventing endothelial cell reactions. In recent years, researchers have been investigating the role of mechanosensing in the development and progression of atherosclerosis. At the core of mechanosensing is the ability of various cells to sense and respond to biomechanical forces in their environment. In the context of atherosclerosis, endothelial cells, smooth muscle cells, and immune cells are subjected to various mechanical or physical stimuli, including shear stress, cyclic strain, and matrix stiffness. These mechanical cues play a crucial role in regulating cellular behavior and contribute to the pathophysiology of atherosclerosis. Accumulating evidence suggests that various mechanical or physical cues play a critical role in the development and promotion of atherosclerosis.
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Affiliation(s)
- Suneha G Rahaman
- University of Maryland, Department of Nutrition and Food Science, College Park, MD, 20742, USA
| | - Manisha Mahanty
- University of Maryland, Department of Nutrition and Food Science, College Park, MD, 20742, USA
| | - Pritha Mukherjee
- University of Maryland, Department of Nutrition and Food Science, College Park, MD, 20742, USA
| | - Bidisha Dutta
- University of Maryland, Department of Nutrition and Food Science, College Park, MD, 20742, USA
| | - Shaik O Rahaman
- University of Maryland, Department of Nutrition and Food Science, College Park, MD, 20742, USA.
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Aguilar VM, Paul A, Lazarko D, Levitan I. Paradigms of endothelial stiffening in cardiovascular disease and vascular aging. Front Physiol 2023; 13:1081119. [PMID: 36714307 PMCID: PMC9874005 DOI: 10.3389/fphys.2022.1081119] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 12/22/2022] [Indexed: 01/13/2023] Open
Abstract
Endothelial cells, the inner lining of the blood vessels, are well-known to play a critical role in vascular function, while endothelial dysfunction due to different cardiovascular risk factors or accumulation of disruptive mechanisms that arise with aging lead to cardiovascular disease. In this review, we focus on endothelial stiffness, a fundamental biomechanical property that reflects cell resistance to deformation. In the first part of the review, we describe the mechanisms that determine endothelial stiffness, including RhoA-dependent contractile response, actin architecture and crosslinking, as well as the contributions of the intermediate filaments, vimentin and lamin. Then, we review the factors that induce endothelial stiffening, with the emphasis on mechanical signals, such as fluid shear stress, stretch and stiffness of the extracellular matrix, which are well-known to control endothelial biomechanics. We also describe in detail the contribution of lipid factors, particularly oxidized lipids, that were also shown to be crucial in regulation of endothelial stiffness. Furthermore, we discuss the relative contributions of these two mechanisms of endothelial stiffening in vasculature in cardiovascular disease and aging. Finally, we present the current state of knowledge about the role of endothelial stiffening in the disruption of endothelial cell-cell junctions that are responsible for the maintenance of the endothelial barrier.
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Affiliation(s)
- Victor M. Aguilar
- Department of Medicine, Division of Pulmonary and Critical Care, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States,Richard and Loan Hill Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, United States
| | - Amit Paul
- Department of Medicine, Division of Pulmonary and Critical Care, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States
| | - Dana Lazarko
- Department of Medicine, Division of Pulmonary and Critical Care, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States
| | - Irena Levitan
- Department of Medicine, Division of Pulmonary and Critical Care, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States,Richard and Loan Hill Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, United States,*Correspondence: Irena Levitan,
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Miller B, Sewell-Loftin MK. Mechanoregulation of Vascular Endothelial Growth Factor Receptor 2 in Angiogenesis. Front Cardiovasc Med 2022; 8:804934. [PMID: 35087885 PMCID: PMC8787114 DOI: 10.3389/fcvm.2021.804934] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 12/10/2021] [Indexed: 12/17/2022] Open
Abstract
The endothelial cells that compose the vascular system in the body display a wide range of mechanotransductive behaviors and responses to biomechanical stimuli, which act in concert to control overall blood vessel structure and function. Such mechanosensitive activities allow blood vessels to constrict, dilate, grow, or remodel as needed during development as well as normal physiological functions, and the same processes can be dysregulated in various disease states. Mechanotransduction represents cellular responses to mechanical forces, translating such factors into chemical or electrical signals which alter the activation of various cell signaling pathways. Understanding how biomechanical forces drive vascular growth in healthy and diseased tissues could create new therapeutic strategies that would either enhance or halt these processes to assist with treatments of different diseases. In the cardiovascular system, new blood vessel formation from preexisting vasculature, in a process known as angiogenesis, is driven by vascular endothelial growth factor (VEGF) binding to VEGF receptor 2 (VEGFR-2) which promotes blood vessel development. However, physical forces such as shear stress, matrix stiffness, and interstitial flow are also major drivers and effectors of angiogenesis, and new research suggests that mechanical forces may regulate VEGFR-2 phosphorylation. In fact, VEGFR-2 activation has been linked to known mechanobiological agents including ERK/MAPK, c-Src, Rho/ROCK, and YAP/TAZ. In vascular disease states, endothelial cells can be subjected to altered mechanical stimuli which affect the pathways that control angiogenesis. Both normalizing and arresting angiogenesis associated with tumor growth have been strategies for anti-cancer treatments. In the field of regenerative medicine, harnessing biomechanical regulation of angiogenesis could enhance vascularization strategies for treating a variety of cardiovascular diseases, including ischemia or permit development of novel tissue engineering scaffolds. This review will focus on the impact of VEGFR-2 mechanosignaling in endothelial cells (ECs) and its interaction with other mechanotransductive pathways, as well as presenting a discussion on the relationship between VEGFR-2 activation and biomechanical forces in the extracellular matrix (ECM) that can help treat diseases with dysfunctional vascular growth.
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Affiliation(s)
- Bronte Miller
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Mary Kathryn Sewell-Loftin
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL, United States.,O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, United States
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Lucci G, Giverso C, Preziosi L. Cell orientation under stretch: Stability of a linear viscoelastic model. Math Biosci 2021; 337:108630. [PMID: 34015301 DOI: 10.1016/j.mbs.2021.108630] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 05/13/2021] [Accepted: 05/13/2021] [Indexed: 10/21/2022]
Abstract
The sensitivity of cells to alterations in the microenvironment and in particular to external mechanical stimuli is significant in many biological and physiological circumstances. In this regard, experimental assays demonstrated that, when a monolayer of cells cultured on an elastic substrate is subject to an external cyclic stretch with a sufficiently high frequency, a reorganization of actin stress fibres and focal adhesions happens in order to reach a stable equilibrium orientation, characterized by a precise angle between the cell major axis and the largest strain direction. To examine the frequency effect on the orientation dynamics, we propose a linear viscoelastic model that describes the coupled evolution of the cellular stress and the orientation angle. We find that cell orientation oscillates tending to an angle that is predicted by the minimization of a very general orthotropic elastic energy, as confirmed by a bifurcation analysis. Moreover, simulations show that the speed of convergence towards the predicted equilibrium orientation presents a changeover related to the viscous-elastic transition for viscoelastic materials. In particular, when the imposed oscillation period is lower than the characteristic turnover rate of the cytoskeleton and of adhesion molecules such as integrins, reorientation is significantly faster.
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Affiliation(s)
- Giulio Lucci
- Department of Mathematical Sciences "G.L. Lagrange" Dipartimento di Eccellenza 2018-2022, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy; Department of Mathematics "G. Peano", Università degli Studi di Torino, Via Carlo Alberto 10, 10123 Turin, Italy.
| | - Chiara Giverso
- Department of Mathematical Sciences "G.L. Lagrange" Dipartimento di Eccellenza 2018-2022, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy.
| | - Luigi Preziosi
- Department of Mathematical Sciences "G.L. Lagrange" Dipartimento di Eccellenza 2018-2022, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy.
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Mao T, He Y, Gu Y, Yang Y, Yu Y, Wang X, Ding J. Critical Frequency and Critical Stretching Rate for Reorientation of Cells on a Cyclically Stretched Polymer in a Microfluidic Chip. ACS APPLIED MATERIALS & INTERFACES 2021; 13:13934-13948. [PMID: 33739805 DOI: 10.1021/acsami.0c21186] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The ability of cells to sense and respond to mechanical signals from their surrounding microenvironments is one of the key issues in tissue engineering and regeneration, yet a fundamental study of cells with both cell observation and mechanical stimulus is challenging and should be based upon an appropriate microdevice. Herein we designed and fabricated a two-layer microfluidic chip to enable simultaneous observation of live cells and cyclic stretching of an elastic polymer, polydimethylsiloxane (PDMS), with a modified surface for enhanced cell adhesion. Human mesenchymal stem cells (hMSCs) were examined with a series of frequencies from 0.00003 to 2 Hz and varied amplitudes of 2%, 5%, or 10%. The cells with an initial random orientation were confirmed to be reoriented perpendicular to the stretching direction at frequencies greater than a threshold value, which we term critical frequency (fc); additionally, the critical frequency fc was amplitude-dependent. We further introduced the concept of critical stretching rate (Rc) and found that this quantity can unify both frequency and amplitude dependences. The reciprocal value of Rc in this study reads 8.3 min, which is consistent with the turnover time of actin filaments reported in the literature, suggesting that the supramolecular relaxation in the cytoskeleton within a cell might be responsible for the underlying cell mechanotransduction. The theoretical calculation of cell reorientation based on a two-dimensional tensegrity model under uniaxial cyclic stretching is well consistent with our experiments. The above findings provide new insight into the crucial role of critical frequency and critical stretching rate in regulating cells on biomaterials under biomechanical stimuli.
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Affiliation(s)
- Tianjiao Mao
- State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China
| | - Yingning He
- State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China
| | - Yexin Gu
- State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China
| | - Yuqian Yang
- State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China
| | - Yue Yu
- State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China
| | - Xinlei Wang
- State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China
| | - Jiandong Ding
- State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China
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Hetmanski JHR, Jones MC, Chunara F, Schwartz JM, Caswell PT. Combinatorial mathematical modelling approaches to interrogate rear retraction dynamics in 3D cell migration. PLoS Comput Biol 2021; 17:e1008213. [PMID: 33690598 PMCID: PMC7984637 DOI: 10.1371/journal.pcbi.1008213] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 03/22/2021] [Accepted: 02/05/2021] [Indexed: 12/17/2022] Open
Abstract
Cell migration in 3D microenvironments is a complex process which depends on the coordinated activity of leading edge protrusive force and rear retraction in a push-pull mechanism. While the potentiation of protrusions has been widely studied, the precise signalling and mechanical events that lead to retraction of the cell rear are much less well understood, particularly in physiological 3D extra-cellular matrix (ECM). We previously discovered that rear retraction in fast moving cells is a highly dynamic process involving the precise spatiotemporal interplay of mechanosensing by caveolae and signalling through RhoA. To further interrogate the dynamics of rear retraction, we have adopted three distinct mathematical modelling approaches here based on (i) Boolean logic, (ii) deterministic kinetic ordinary differential equations (ODEs) and (iii) stochastic simulations. The aims of this multi-faceted approach are twofold: firstly to derive new biological insight into cell rear dynamics via generation of testable hypotheses and predictions; and secondly to compare and contrast the distinct modelling approaches when used to describe the same, relatively under-studied system. Overall, our modelling approaches complement each other, suggesting that such a multi-faceted approach is more informative than methods based on a single modelling technique to interrogate biological systems. Whilst Boolean logic was not able to fully recapitulate the complexity of rear retraction signalling, an ODE model could make plausible population level predictions. Stochastic simulations added a further level of complexity by accurately mimicking previous experimental findings and acting as a single cell simulator. Our approach highlighted the unanticipated role for CDK1 in rear retraction, a prediction we confirmed experimentally. Moreover, our models led to a novel prediction regarding the potential existence of a 'set point' in local stiffness gradients that promotes polarisation and rapid rear retraction.
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Affiliation(s)
- Joseph H. R. Hetmanski
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom
- * E-mail: (JHRH); (PTC)
| | - Matthew C. Jones
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom
| | - Fatima Chunara
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom
| | - Jean-Marc Schwartz
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom
| | - Patrick T. Caswell
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom
- * E-mail: (JHRH); (PTC)
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9
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Lucci G, Preziosi L. A nonlinear elastic description of cell preferential orientations over a stretched substrate. Biomech Model Mechanobiol 2021; 20:631-649. [PMID: 33449274 PMCID: PMC7979636 DOI: 10.1007/s10237-020-01406-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 11/24/2020] [Indexed: 11/27/2022]
Abstract
The active response of cells to mechanical cues due to their interaction with the environment has been of increasing interest, since it is involved in many physiological phenomena, pathologies, and in tissue engineering. In particular, several experiments have shown that, if a substrate with overlying cells is cyclically stretched, they will reorient to reach a well-defined angle between their major axis and the main stretching direction. Recent experimental findings, also supported by a linear elastic model, indicated that the minimization of an elastic energy might drive this reorientation process. Motivated by the fact that a similar behaviour is observed even for high strains, in this paper we address the problem in the framework of finite elasticity, in order to study the presence of nonlinear effects. We find that, for a very large class of constitutive orthotropic models and with very general assumptions, there is a single linear relationship between a parameter describing the biaxial deformation and \documentclass[12pt]{minimal}
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\begin{document}$$\cos ^2\theta _{\mathrm{eq}}$$\end{document}cos2θeq, where \documentclass[12pt]{minimal}
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\begin{document}$$\theta _{\mathrm{eq}}$$\end{document}θeq is the orientation angle of the cell, with the slope of the line depending on a specific combination of four parameters that characterize the nonlinear constitutive equation. We also study the effect of introducing a further dependence of the energy on the anisotropic invariants related to the square of the Cauchy–Green strain tensor. This leads to departures from the linear relationship mentioned above, that are again critically compared with experimental data.
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Affiliation(s)
- Giulio Lucci
- Department of Mathematical Sciences “G.L. Lagrange”, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy
- Department of Mathematics “G. Peano”, Università degli Studi di Torino, Via Carlo Alberto 10, 10123 Turin, Italy
| | - Luigi Preziosi
- Department of Mathematical Sciences “G.L. Lagrange” Dipartimento di Eccellenza 2018-2022, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy
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Rezk R, Jia BZ, Wendler A, Dimov I, Watts C, Markaki AE, Franze K, Kabla AJ. Spatial heterogeneity of cell-matrix adhesive forces predicts human glioblastoma migration. Neurooncol Adv 2020; 2:vdaa081. [PMID: 32793884 PMCID: PMC7415261 DOI: 10.1093/noajnl/vdaa081] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Background Glioblastoma (GBM) is a highly aggressive incurable brain tumor. The main cause of mortality in GBM patients is the invasive rim of cells migrating away from the main tumor mass and invading healthy parts of the brain. Although the motion is driven by forces, our current understanding of the physical factors involved in glioma infiltration remains limited. This study aims to investigate the adhesion properties within and between patients' tumors on a cellular level and test whether these properties correlate with cell migration. Methods Six tissue samples were taken from spatially separated sections during 5-aminolevulinic acid (5-ALA) fluorescence-guided surgery. Navigated biopsy samples were collected from strongly fluorescent tumor cores, a weak fluorescent tumor rim, and nonfluorescent tumor margins. A microfluidics device was built to induce controlled shear forces to detach cells from monolayer cultures. Cells were cultured on low modulus polydimethylsiloxane representative of the stiffness of brain tissue. Cell migration and morphology were then obtained using time-lapse microscopy. Results GBM cell populations from different tumor fractions of the same patient exhibited different migratory and adhesive behaviors. These differences were associated with sampling location and amount of 5-ALA fluorescence. Cells derived from weak- and nonfluorescent tumor tissue were smaller, adhered less well, and migrated quicker than cells derived from strongly fluorescent tumor mass. Conclusions GBM tumors are biomechanically heterogeneous. Selecting multiple populations and broad location sampling are therefore important to consider for drug testing.
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Affiliation(s)
- Rasha Rezk
- Department of Engineering, University of Cambridge, Cambridge, UK
| | - Bill Zong Jia
- Department of Engineering, University of Cambridge, Cambridge, UK
| | - Astrid Wendler
- Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
| | - Ivan Dimov
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Colin Watts
- Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
| | - Athina E Markaki
- Department of Engineering, University of Cambridge, Cambridge, UK
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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Kaunas R. Good advice for endothelial cells: Get in line, relax tension, and go with the flow. APL Bioeng 2020; 4:010905. [PMID: 32128470 PMCID: PMC7044000 DOI: 10.1063/1.5129812] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 01/19/2020] [Indexed: 11/26/2022] Open
Abstract
Endothelial cells (ECs) are continuously subjected to fluid wall shear stress (WSS) and cyclic strain caused by pulsatile blood flow and pressure. It is well established that these hemodynamic forces each play important roles in vascular disease, but their combined effects are not well understood. ECs remodel in response to both WSS and cyclic strain to align along the vessel axis, but in areas prone to atherogenesis, such an alignment is absent. In this perspective, experimental and clinical findings will be reviewed, which have revealed the characteristics of WSS and cyclic strain, which are associated with atherosclerosis, spanning studies on whole blood vessels to individual cells to mechanosensing molecules. Examples are described regarding the use of computational modeling to elucidate the mechanisms by which EC alignment contributes to mechanical homeostasis. Finally, the need to move toward an integrated understanding of how hemodynamic forces influence EC mechanotransduction is presented, which holds the potential to move our currently fragmented understanding to a true appreciation of the role of mechanical stimuli in atherosclerosis.
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Affiliation(s)
- Roland Kaunas
- Department of Biomedical Engineering and Department of Cellular and Molecular Medicine, Texas A&M University, College Station, Texas 77843-3120, USA
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12
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Santoro R, Perrucci GL, Gowran A, Pompilio G. Unchain My Heart: Integrins at the Basis of iPSC Cardiomyocyte Differentiation. Stem Cells Int 2019; 2019:8203950. [PMID: 30906328 PMCID: PMC6393933 DOI: 10.1155/2019/8203950] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 12/20/2018] [Accepted: 01/10/2019] [Indexed: 02/06/2023] Open
Abstract
The cellular response to the extracellular matrix (ECM) microenvironment mediated by integrin adhesion is of fundamental importance, in both developmental and pathological processes. In particular, mechanotransduction is of growing importance in groundbreaking cellular models such as induced pluripotent stem cells (iPSC), since this process may strongly influence cell fate and, thus, augment the precision of differentiation into specific cell types, e.g., cardiomyocytes. The decryption of the cellular machinery starting from ECM sensing to iPSC differentiation calls for new in vitro methods. Conveniently, engineered biomaterials activating controlled integrin-mediated responses through chemical, physical, and geometrical designs are key to resolving this issue and could foster clinical translation of optimized iPSC-based technology. This review introduces the main integrin-dependent mechanisms and signalling pathways involved in mechanotransduction. Special consideration is given to the integrin-iPSC linkage signalling chain in the cardiovascular field, focusing on biomaterial-based in vitro models to evaluate the relevance of this process in iPSC differentiation into cardiomyocytes.
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Affiliation(s)
- Rosaria Santoro
- Unità di Biologia Vascolare e Medicina Rigenerativa, Centro Cardiologico Monzino IRCCS, via Carlo Parea 4, Milan, Italy
| | - Gianluca Lorenzo Perrucci
- Unità di Biologia Vascolare e Medicina Rigenerativa, Centro Cardiologico Monzino IRCCS, via Carlo Parea 4, Milan, Italy
| | - Aoife Gowran
- Unità di Biologia Vascolare e Medicina Rigenerativa, Centro Cardiologico Monzino IRCCS, via Carlo Parea 4, Milan, Italy
| | - Giulio Pompilio
- Unità di Biologia Vascolare e Medicina Rigenerativa, Centro Cardiologico Monzino IRCCS, via Carlo Parea 4, Milan, Italy
- Dipartimento di Scienze Cliniche e di Comunità, Università degli Studi di Milano, via Festa del Perdono 7, Milan, Italy
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Xu GK, Feng XQ, Gao H. Orientations of Cells on Compliant Substrates under Biaxial Stretches: A Theoretical Study. Biophys J 2018; 114:701-710. [PMID: 29414715 PMCID: PMC5985023 DOI: 10.1016/j.bpj.2017.12.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/25/2017] [Accepted: 12/05/2017] [Indexed: 10/24/2022] Open
Abstract
Mechanical cues from the microenvironments play a regulating role in many physiological and pathological processes, such as stem cell differentiation and cancer cell metastasis. Experiments showed that cells adhered on a compliant substrate may change orientation with an externally applied strain in the substrate. By accounting for actin polymerization, actin retrograde flow, and integrin binding dynamics, here we develop a mechanism-based tensegrity model to study the orientations of polarized cells on a compliant substrate under biaxial stretches. We show that the cell can actively regulate its mechanical state by generating different traction force levels along its polarized direction. Under static or ultralow-frequency cyclic stretches, stretching a softer substrate leads to a higher increase in the traction force and induces a narrower distribution of cell alignment. Compared to static loadings, high-frequency cyclic loadings have a more significant influence on cell reorientation on a stiff substrate. In addition, the width of the cellular angular distribution scales inversely with the stretch amplitude under both static and cyclic stretches. Our results are in agreement with a wide range of experimental observations, and provide fundamental insights into the functioning of cellular mechanosensing systems.
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Affiliation(s)
- Guang-Kui Xu
- International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an, China.
| | - Xi-Qiao Feng
- Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing, China
| | - Huajian Gao
- School of Engineering, Brown University, Providence, Rhode Island
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14
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Cheng B, Lin M, Huang G, Li Y, Ji B, Genin GM, Deshpande VS, Lu TJ, Xu F. Cellular mechanosensing of the biophysical microenvironment: A review of mathematical models of biophysical regulation of cell responses. Phys Life Rev 2017; 22-23:88-119. [PMID: 28688729 PMCID: PMC5712490 DOI: 10.1016/j.plrev.2017.06.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 06/14/2017] [Indexed: 12/11/2022]
Abstract
Cells in vivo reside within complex microenvironments composed of both biochemical and biophysical cues. The dynamic feedback between cells and their microenvironments hinges upon biophysical cues that regulate critical cellular behaviors. Understanding this regulation from sensing to reaction to feedback is therefore critical, and a large effort is afoot to identify and mathematically model the fundamental mechanobiological mechanisms underlying this regulation. This review provides a critical perspective on recent progress in mathematical models for the responses of cells to the biophysical cues in their microenvironments, including dynamic strain, osmotic shock, fluid shear stress, mechanical force, matrix rigidity, porosity, and matrix shape. The review highlights key successes and failings of existing models, and discusses future opportunities and challenges in the field.
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Affiliation(s)
- Bo Cheng
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China
| | - Min Lin
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China
| | - Guoyou Huang
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China
| | - Yuhui Li
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China
| | - Baohua Ji
- Biomechanics and Biomaterials Laboratory, Department of Applied Mechanics, Beijing Institute of Technology, Beijing, China
| | - Guy M Genin
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China; Department of Mechanical Engineering & Materials Science, and NSF Science and Technology Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis 63130, MO, USA
| | - Vikram S Deshpande
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, United Kingdom
| | - Tian Jian Lu
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China
| | - Feng Xu
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
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15
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Xu GK, Li B, Feng XQ, Gao H. A Tensegrity Model of Cell Reorientation on Cyclically Stretched Substrates. Biophys J 2016; 111:1478-1486. [PMID: 27705770 PMCID: PMC5052513 DOI: 10.1016/j.bpj.2016.08.036] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 07/09/2016] [Accepted: 08/31/2016] [Indexed: 01/16/2023] Open
Abstract
Deciphering the mechanisms underlying the high sensitivity of cells to mechanical microenvironments is crucial for understanding many physiological and pathological processes, e.g., stem cell differentiation and cancer cell metastasis. Here, a cytoskeletal tensegrity model is proposed to study the reorientation of polarized cells on a substrate under biaxial cyclic deformation. The model consists of four bars, representing the longitudinal stress fibers and lateral actin network, and eight strings, denoting the microfilaments. It is found that the lateral bars in the tensegrity, which have been neglected in most of the existing models, can play a vital role in regulating the cellular orientation. The steady orientation of cells can be quantitatively determined by the geometric dimensions and elastic properties of the tensegrity elements, as well as the frequency and biaxial ratio of the cyclic stretches. It is shown that this tensegrity model can reproduce all available experimental observations. For example, the dynamics of cell reorientation is captured by an exponential scaling law with a characteristic time that is independent of the loading frequency at high frequencies and scales inversely with the square of the strain amplitude. This study suggests that tensegrity type models may be further developed to understand cellular responses to mechanical microenvironments and provide guidance for engineering delicate cellular mechanosensing systems.
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Affiliation(s)
- Guang-Kui Xu
- International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, China.
| | - Bo Li
- Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing, China
| | - Xi-Qiao Feng
- Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing, China.
| | - Huajian Gao
- School of Engineering, Brown University, Providence, Rhode Island
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16
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Hetmanski JHR, Schwartz JM, Caswell PT. Rationalizing Rac1 and RhoA GTPase signaling: A mathematical approach. Small GTPases 2016; 9:224-229. [PMID: 27572055 DOI: 10.1080/21541248.2016.1218406] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Precise spatiotemporal dynamics of Rho GTPases are essential for efficient cell migration. Manipulating Rac1 and RhoA signaling is thus a potential intervention strategy to abrogate harmful cell invasion and subsequent metastasis; however GTPase signaling can be extremely complicated due to crosstalk and the multitude of upstream regulators and downstream effectors. Studying Rho GTPase networks in a formal mathematical setting can therefore be of great use. We recently built a predictive model based on Boolean logic which identified a negative feedback loop critical for RhoA and Rac1 activity. Here, we discuss the value and potential pitfalls of different mathematical approaches which have been used to study Rho GTPase dynamics, and highlight the importance of choosing the correct approach given the data available and outputs desired. Overall, a mathematical approach, particularly when combined iteratively with in vitro experiments, can be of great use in deriving new biological insight to further harness the activity of Rho GTPases.
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Affiliation(s)
- Joseph H R Hetmanski
- a Wellcome Trust Center for Cell-Matrix Research, University of Manchester , Manchester , UK
| | - Jean-Marc Schwartz
- a Wellcome Trust Center for Cell-Matrix Research, University of Manchester , Manchester , UK
| | - Patrick T Caswell
- a Wellcome Trust Center for Cell-Matrix Research, University of Manchester , Manchester , UK
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17
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Koride S, He L, Xiong LP, Lan G, Montell DJ, Sun SX. Mechanochemical regulation of oscillatory follicle cell dynamics in the developing Drosophila egg chamber. Mol Biol Cell 2014; 25:3709-16. [PMID: 24943847 PMCID: PMC4230628 DOI: 10.1091/mbc.e14-04-0875] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In the epithelium of Drosophila during tissue elongation, contractile forces in follicle cells can oscillate. These oscillations correlate with increasing tension in the epithelium from egg chamber growth. A mathematical model is proposed to explain the observed oscillations, together with a mechanism of active regulation of cellular contractile forces. During tissue elongation from stage 9 to stage 10 in Drosophila oogenesis, the egg chamber increases in length by ∼1.7-fold while increasing in volume by eightfold. During these stages, spontaneous oscillations in the contraction of cell basal surfaces develop in a subset of follicle cells. This patterned activity is required for elongation of the egg chamber; however, the mechanisms generating the spatiotemporal pattern have been unclear. Here we use a combination of quantitative modeling and experimental perturbation to show that mechanochemical interactions are sufficient to generate oscillations of myosin contractile activity in the observed spatiotemporal pattern. We propose that follicle cells in the epithelial layer contract against pressure in the expanding egg chamber. As tension in the epithelial layer increases, Rho kinase signaling activates myosin assembly and contraction. The activation process is cooperative, leading to a limit cycle in the myosin dynamics. Our model produces asynchronous oscillations in follicle cell area and myosin content, consistent with experimental observations. In addition, we test the prediction that removal of the basal lamina will increase the average oscillation period. The model demonstrates that in principle, mechanochemical interactions are sufficient to drive patterning and morphogenesis, independent of patterned gene expression.
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Affiliation(s)
- Sarita Koride
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218
| | - Li He
- Howard Hughes Medical Institute, Department of Genetics, Harvard Medical School, Boston, MA 02115
| | - Li-Ping Xiong
- Department of Physics, George Washington University, Washington, DC 20052
| | - Ganhui Lan
- Department of Physics, George Washington University, Washington, DC 20052
| | - Denise J Montell
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Sean X Sun
- Johns Hopkins Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD 21218 Department of Mechanical Engineering, Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218
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18
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Abstract
Mechanical cues from the extracellular microenvironment play a central role in regulating the structure, function and fate of living cells. Nevertheless, the precise nature of the mechanisms and processes underlying this crucial cellular mechanosensitivity remains a fundamental open problem. Here we provide a novel framework for addressing cellular sensitivity and response to external forces by experimentally and theoretically studying one of its most striking manifestations – cell reorientation to a uniform angle in response to cyclic stretching of the underlying substrate. We first show that existing approaches are incompatible with our extensive measurements of cell reorientation. We then propose a fundamentally new theory that shows that dissipative relaxation of the cell’s passively-stored, two-dimensional, elastic energy to its minimum actively drives the reorientation process. Our theory is in excellent quantitative agreement with the complete temporal reorientation dynamics of individual cells, measured over a wide range of experimental conditions, thus elucidating a basic aspect of mechanosensitivity.
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19
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Vernerey FJ, Farsad M. A mathematical model of the coupled mechanisms of cell adhesion, contraction and spreading. J Math Biol 2014; 68:989-1022. [PMID: 23463540 PMCID: PMC3855150 DOI: 10.1007/s00285-013-0656-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 01/23/2013] [Indexed: 01/11/2023]
Abstract
Recent research has shown that cell spreading is highly dependent on the contractility of its cytoskeleton and the mechanical properties of the environment it is located in. The dynamics of such process is critical for the development of tissue engineering strategy but is also a key player in wound contraction, tissue maintenance and angiogenesis. To better understand the underlying physics of such phenomena, the paper describes a mathematical formulation of cell spreading and contraction that couples the processes of stress fiber formation, protrusion growth through actin polymerization at the cell edge and dynamics of cross-membrane protein (integrins) enabling cell-substrate attachment. The evolving cell's cytoskeleton is modeled as a mixture of fluid, proteins and filaments that can exchange mass and generate contraction. In particular, besides self-assembling into stress fibers, actin monomers able to polymerize into an actin meshwork at the cell's boundary in order to push the membrane forward and generate protrusion. These processes are possible via the development of cell-substrate attachment complexes that arise from the mechano-sensitive equilibrium of membrane proteins, known as integrins. After deriving the governing equation driving the dynamics of cell evolution and spreading, we introduce a numerical solution based on the extended finite element method, combined with a level set formulation. Numerical simulations show that the proposed model is able to capture the dependency of cell spreading and contraction on substrate stiffness and chemistry. The very good agreement between model predictions and experimental observations suggests that mechanics plays a strong role into the coupled mechanisms of contraction, adhesion and spreading of adherent cells.
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Affiliation(s)
- Franck J Vernerey
- Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, USA,
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20
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Abstract
Increased endothelial permeability and reduction of alveolar liquid clearance capacity are two leading pathogenic mechanisms of pulmonary edema, which is a major complication of acute lung injury, severe pneumonia, and acute respiratory distress syndrome, the pathologies characterized by unacceptably high rates of morbidity and mortality. Besides the success in protective ventilation strategies, no efficient pharmacological approaches exist to treat this devastating condition. Understanding of fundamental mechanisms involved in regulation of endothelial permeability is essential for development of barrier protective therapeutic strategies. Ongoing studies characterized specific barrier protective mechanisms and identified intracellular targets directly involved in regulation of endothelial permeability. Growing evidence suggests that, although each protective agonist triggers a unique pattern of signaling pathways, selected common mechanisms contributing to endothelial barrier protection may be shared by different barrier protective agents. Therefore, understanding of basic barrier protective mechanisms in pulmonary endothelium is essential for selection of optimal treatment of pulmonary edema of different etiology. This article focuses on mechanisms of lung vascular permeability, reviews major intracellular signaling cascades involved in endothelial monolayer barrier preservation and summarizes a current knowledge regarding recently identified compounds which either reduce pulmonary endothelial barrier disruption and hyperpermeability, or reverse preexisting lung vascular barrier compromise induced by pathologic insults.
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Affiliation(s)
- Konstantin G Birukov
- Lung Injury Center, Section of Pulmonary and Critical Care, Department of Medicine, University of Chicago, Chicago, Illinois, USA.
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21
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Hoffmann M, Schwarz US. A kinetic model for RNA-interference of focal adhesions. BMC SYSTEMS BIOLOGY 2013; 7:2. [PMID: 23311633 PMCID: PMC3616989 DOI: 10.1186/1752-0509-7-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Accepted: 12/21/2012] [Indexed: 01/09/2023]
Abstract
BACKGROUND Focal adhesions are integrin-based cell-matrix contacts that transduce and integrate mechanical and biochemical cues from the environment. They develop from smaller and more numerous focal complexes under the influence of mechanical force and are key elements for many physiological and disease-related processes, including wound healing and metastasis. More than 150 different proteins localize to focal adhesions and have been systematically classified in the adhesome project (http://www.adhesome.org). First RNAi-screens have been performed for focal adhesions and the effect of knockdown of many of these components on the number, size, shape and location of focal adhesions has been reported. RESULTS We have developed a kinetic model for RNA interference of focal adhesions which represents some of its main elements: a spatially layered structure, signaling through the small GTPases Rac and Rho, and maturation from focal complexes to focal adhesions under force. The response to force is described by two complementary scenarios corresponding to slip and catch bond behavior, respectively. Using estimated and literature values for the model parameters, three time scales of the dynamics of RNAi-influenced focal adhesions are identified: a sub-minute time scale for the assembly of focal complexes, a sub-hour time scale for the maturation to focal adhesions, and a time scale of days that controls the siRNA-mediated knockdown. Our model shows bistability between states dominated by focal complexes and focal adhesions, respectively. Catch bonding strongly extends the range of stability of the state dominated by focal adhesions. A sensitivity analysis predicts that knockdown of focal adhesion components is more efficient for focal adhesions with slip bonds or if the system is in a state dominated by focal complexes. Knockdown of Rho leads to an increase of focal complexes. CONCLUSIONS The suggested model provides a kinetic description of the effect of RNA-interference of focal adhesions. Its predictions are in good agreement with known experimental results and can now guide the design of RNAi-experiments. In the future, it can be extended to include more components of the adhesome. It also could be extended by spatial aspects, for example by the differential activation of the Rac- and Rho-pathways in different parts of the cell.
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Affiliation(s)
- Max Hoffmann
- BioQuant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany
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22
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Dado D, Sagi M, Levenberg S, Zemel A. Mechanical control of stem cell differentiation. Regen Med 2012; 7:101-16. [DOI: 10.2217/rme.11.99] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Numerous studies have focused on identifying the chemical and biological factors that govern the differentiation of stem cells; however, recent research has shown that mechanical cues may play an equally important role. Mechanical forces such as shear stresses and tensile loads, as well as the rigidity and topography of the extracellular matrix were shown to induce significant changes in the morphology and fate of stem cells. We survey experimental studies that focused on the response of stem cells to mechanical and geometrical properties of their environment and discuss the mechanical mechanisms that accompany their response including the remodeling of the cytoskeleton and determination of cell and nucleus size and shape.
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Affiliation(s)
- Dekel Dado
- Biomedical Engineering, Technion, Haifa, 32000, Israel
| | - Maayan Sagi
- Institute of Dental Sciences & the Fritz Haber Research Center, Hebrew-University, Hadassah Medical Center, Jerusalem, 91120, Israel
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23
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Deguchi S, Matsui TS, Iio K. The position and size of individual focal adhesions are determined by intracellular stress-dependent positive regulation. Cytoskeleton (Hoboken) 2011; 68:639-51. [DOI: 10.1002/cm.20541] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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24
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Kang J, Steward RL, Kim Y, Schwartz RS, LeDuc PR, Puskar KM. Response of an actin filament network model under cyclic stretching through a coarse grained Monte Carlo approach. J Theor Biol 2011; 274:109-19. [PMID: 21241710 PMCID: PMC3501734 DOI: 10.1016/j.jtbi.2011.01.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 01/07/2011] [Accepted: 01/10/2011] [Indexed: 02/03/2023]
Abstract
Cells are complex, dynamic systems that actively adapt to various stimuli including mechanical alterations. Central to understanding cellular response to mechanical stimulation is the organization of the cytoskeleton and its actin filament network. In this manuscript, we present a minimalistic network Monte Carlo based approach to model actin filament organization under cyclic stretching. Utilizing a coarse-grained model, a filament network is prescribed within a two-dimensional circular space through nodal connections. When cyclically stretched, the model demonstrates that a perpendicular alignment of the filaments to the direction of stretch emerges in response to nodal repositioning to minimize net nodal forces from filament stress states. In addition, the filaments in the network rearrange and redistribute themselves to reduce the overall stress by decreasing their individual stresses. In parallel, we cyclically stretch NIH 3T3 fibroblasts and find a similar cytoskeletal response. With this work, we test the hypothesis that a first-principles mechanical model of filament assembly in a confined space is by itself capable of yielding the remodeling behavior observed experimentally. Identifying minimal mechanisms sufficient to reproduce mechanical influences on cellular structure has important implications in a diversity of fields, including biology, physics, medicine, computer science, and engineering.
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Affiliation(s)
- John Kang
- Lane Center for Computational Biology, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
- Joint Carnegie Mellon University-University of Pittsburgh Ph.D. Program in Computational Biology, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
- Medical Scientist Training Program, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA 15261, USA
| | - Robert L. Steward
- Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - YongTae Kim
- Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Russell S. Schwartz
- Lane Center for Computational Biology, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
- Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Philip R. LeDuc
- Lane Center for Computational Biology, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
- Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
- Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, Pennsylvania 15213, USA
- Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Kathleen M. Puskar
- Department of Mechanical Engineering, California State Polytechnic University, Pomona, 3801 West Temple Avenue, Pomona, California 91768, USA
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25
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Allen RJ, Bogle IDL, Ridley AJ. A model of localised Rac1 activation in endothelial cells due to fluid flow. J Theor Biol 2011; 280:34-42. [PMID: 21439300 DOI: 10.1016/j.jtbi.2011.03.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 03/07/2011] [Accepted: 03/17/2011] [Indexed: 01/27/2023]
Abstract
Endothelial cells respond to fluid flow by elongating in the direction of flow. Cytoskeletal changes and activation of signalling molecules have been extensively studied in this response, including: activation of receptors by mechano-transduction, actin filament alignment in the direction of flow, changes to cell-substratum adhesions, actin-driven lamellipodium extension, and localised activation of Rho GTPases. To study this process we model the force over a single cell and couple this to a model of the Rho GTPases, Rac and Rho, via a Kelvin-body model of mechano-transduction. It is demonstrated that a mechano-transducer can respond to the normal component of the force is likely to be a necessary component of the signalling network in order to establish polarity. Furthermore, the rate-limiting step of Rac1 activation is predicted to be conversion of Rac-GDP to Rac-GTP, rather than activation of upstream components. Modelling illustrates that the aligned endothelial cell morphology could attenuate the signalling network.
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Affiliation(s)
- R J Allen
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, Gower Street, London WC1E 7JE, United Kingdom.
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26
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Haghighipour N, Tafazzoli-Shadpour M, Shokrgozar MA, Amini S. Effects of cyclic stretch waveform on endothelial cell morphology using fractal analysis. Artif Organs 2010; 34:481-90. [PMID: 20456326 DOI: 10.1111/j.1525-1594.2010.01003.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Endothelial cells are remodeled when subjected to cyclic loading. Previous in vitro studies have indicated that frequency, strain amplitude, and duration are determinants of endothelial cell morphology, when cells are subjected to cyclic strain. In addition to those parameters, the current study investigated the effects of strain waveform on morphology of cultured endothelial cells quantified by fractal and topological analyses. Cultured endothelial cells were subjected to cyclic stretch by a designed device, and cellular images before and after tests were obtained. Fractal and topological parameters were calculated by development of an image-processing code. Tests were performed for different load waveforms. Results indicated cellular alignment by application of cyclic stretch. By alteration of load waveform, statistically significant differences between cell morphology of test groups were observed. Such differences are more prominent when load cycles are elevated. The endothelial cell remodeling was optimized when the applied cyclic load waveform was similar to blood pressure waveform. Effects of load waveform on cell morphology are influenced by alterations in load amplitude and frequency. It is concluded that load waveform is a determinant of endothelial morphology in addition to amplitude and frequency, and such effect is elevated by increase of load cycles. Due to high correlation between fractal and topological analyses, it is recommended that fractal analysis can be used as a proper method for evaluation of alteration in cell morphology and tissue structure caused by application of external stimuli such as mechanical loading.
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Affiliation(s)
- Nooshin Haghighipour
- Cardiovascular Engineering Laboratory, Biomedical Engineering Department, Amirkabir University of Technology, Tehran, Iran
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27
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Abstract
Recent discoveries have established that mechanical properties of the cellular environment such as its rigidity, geometry, and external stresses play an important role in determining the cellular function and fate. Mechanical properties have been shown to influence cell shape and orientation, regulate cell proliferation and differentiation, and even govern the development and organization of tissues. In recent years, many theoretical and experimental investigations have been carried out to elucidate the mechanisms and consequences of the mechanosensitivity of cells. In this review, we discuss recent theoretical concepts and approaches that explain and predict cell mechanosensitivity. We focus on the interplay of active and passive processes that govern cell-cell and cell-matrix interactions and discuss the role of this interplay in the processes of cell adhesion, regulation of cytoskeleton mechanics and the response of cells to applied mechanical stresses.
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Affiliation(s)
- Rumi De
- Indian institute of Science Education and Research, Kolkata, Mohanpur 741252, Nadia, West Bengal, India
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28
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Silbert O, Wang Y, Maciejewski BS, Lee H, Shaw SK, Sanchez–Esteban J. ROLES OF RhoA AND Rac1 ON ACTIN REMODELING AND CELL ALIGNMENT AND DIFFERENTIATION IN FETAL TYPE II EPITHELIAL CELLS EXPOSED TO CYCLIC MECHANICAL STRETCH. Exp Lung Res 2009; 34:663-80. [DOI: 10.1080/01902140802339615] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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29
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Asparuhova MB, Gelman L, Chiquet M. Role of the actin cytoskeleton in tuning cellular responses to external mechanical stress. Scand J Med Sci Sports 2009; 19:490-9. [PMID: 19422655 DOI: 10.1111/j.1600-0838.2009.00928.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Mechanical forces are essential for tissue homeostasis. In adherent cells, cell-matrix adhesions connect the extracellular matrix (ECM) with the cytoskeleton and transmit forces in both directions. Integrin receptors and signaling molecules in cell-matrix adhesions transduce mechanical into chemical signals, thereby regulating many cellular processes. This review focuses on how cellular mechanotransduction is tuned by actin-generated cytoskeletal tension that balances external with internal mechanical forces. We point out that the cytoskeleton rapidly responds to external forces by RhoA-dependent actin assembly and contraction. This in turn induces remodeling of cell-matrix adhesions and changes in cell shape and orientation. As a consequence, a cell constantly modulates its response to new bouts of external mechanical stimulation. Changes in actin dynamics are monitored by MAL/MKL-1/MRTF-A, a co-activator of serum response factor. Recent evidence suggests that MAL is also involved in coupling mechanically induced changes in the actin cytoskeleton to gene expression. Compared with other, more rapid and transient signals evoked at the cell surface, this parallel mechanotransduction pathway is more sustained and provides spatial and temporal specificity to the response. We describe examples of genes that are regulated by mechanical stress in a manner depending on actin dynamics, among them the ECM protein, tenascin-C.
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Affiliation(s)
- M B Asparuhova
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
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Hsu HJ, Lee CF, Kaunas R. A dynamic stochastic model of frequency-dependent stress fiber alignment induced by cyclic stretch. PLoS One 2009; 4:e4853. [PMID: 19319193 PMCID: PMC2656616 DOI: 10.1371/journal.pone.0004853] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 02/16/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Actin stress fibers (SFs) are mechanosensitive structural elements that respond to forces to affect cell morphology, migration, signal transduction and cell function. Cells are internally stressed so that SFs are extended beyond their unloaded lengths, and SFs tend to self-adjust to an equilibrium level of extension. While there is much evidence that cells reorganize their SFs in response to matrix deformations, it is unclear how cells and their SFs determine their specific response to particular spatiotemporal changes in the matrix. METHODOLOGY/PRINCIPAL FINDINGS Bovine aortic endothelial cells were subjected to cyclic uniaxial stretch over a range of frequencies to quantify the rate and extent of stress fiber alignment. At a frequency of 1 Hz, SFs predominantly oriented perpendicular to stretch, while at 0.1 Hz the extent of SF alignment was markedly reduced and at 0.01 Hz there was no alignment at all. The results were interpreted using a simple kinematic model of SF networks in which the dynamic response depended on the rates of matrix stretching, SF turnover, and SF self-adjustment of extension. For these cells, the model predicted a threshold frequency of 0.01 Hz below which SFs no longer respond to matrix stretch, and a saturation frequency of 1 Hz above which no additional SF alignment would occur. The model also accurately described the dependence of SF alignment on matrix stretch magnitude. CONCLUSIONS The dynamic stochastic model was capable of describing SF reorganization in response to diverse temporal and spatial patterns of stretch. The model predicted that at high frequencies, SFs preferentially disassembled in the direction of stretch and achieved a new equilibrium by accumulating in the direction of lowest stretch. At low stretch frequencies, SFs self-adjusted to dissipate the effects of matrix stretch. Thus, SF turnover and self-adjustment are each important mechanisms that cells use to maintain mechanical homeostasis.
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Affiliation(s)
- Hui-Ju Hsu
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, United States of America
| | - Chin-Fu Lee
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, United States of America
| | - Roland Kaunas
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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31
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Mechanotransduction in vascular physiology and atherogenesis. Nat Rev Mol Cell Biol 2009; 10:53-62. [PMID: 19197332 DOI: 10.1038/nrm2596] [Citation(s) in RCA: 805] [Impact Index Per Article: 53.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Forces that are associated with blood flow are major determinants of vascular morphogenesis and physiology. Blood flow is crucial for blood vessel development during embryogenesis and for regulation of vessel diameter in adult life. It is also a key factor in atherosclerosis, which, despite the systemic nature of major risk factors, occurs mainly in regions of arteries that experience disturbances in fluid flow. Recent data have highlighted the potential endothelial mechanotransducers that might mediate responses to blood flow, the effects of atheroprotective rather than atherogenic flow, the mechanisms that contribute to the progression of the disease and how systemic factors interact with flow patterns to cause atherosclerosis.
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32
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Cell fate regulation by coupling mechanical cycles to biochemical signaling pathways. Curr Opin Cell Biol 2009; 21:38-46. [PMID: 19217273 DOI: 10.1016/j.ceb.2009.01.002] [Citation(s) in RCA: 222] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 12/22/2008] [Accepted: 01/05/2009] [Indexed: 01/23/2023]
Abstract
Many aspects of cellular motility and mechanics are cyclic in nature such as the extension and retraction of lamellipodia or filopodia. Inherent to the cycles of extension and retraction that test the environment is the production of mechano-chemical signals that can alter long-term cell behavior, transcription patterns, and cell fate. We are just starting to define such cycles in several aspects of cell motility, including periodic contractions, integrin cycles of binding and release as well as the normal oscillations in motile activity. Cycles of local cell contraction and release are directly coupled to cycles of stressing and releasing extracellular contacts (matrix or cells) as well as cytoplasmic mechanotransducers. Stretching can alter external physical properties or sites exposed by matrix molecules as well as internal networks; thus, cell contractions can cause a secondary wave of mechano-regulated outside-in and internal cell signal changes. In some cases, the integration of both external and internal signals in space and time can stimulate a change in cell state from quiescence to growth or differentiation. In this review we will develop the basic concept of the mechano-chemical cycles and the ways in which they can be described and understood.
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Chandran PL, Wolf CB, Mofrad MRK. Band-like Stress Fiber Propagation in a Continuum and Implications for Myosin Contractile Stresses. Cell Mol Bioeng 2009. [DOI: 10.1007/s12195-009-0044-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Shifrin Y, Arora PD, Ohta Y, Calderwood DA, McCulloch CA. The role of FilGAP-filamin A interactions in mechanoprotection. Mol Biol Cell 2009; 20:1269-79. [PMID: 19144823 DOI: 10.1091/mbc.e08-08-0872] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Cells in mechanically active environments are subjected to high-amplitude exogenous forces that can lead to cell death. Filamin A (FLNa) may protect cells from mechanically induced death by mechanisms that are not yet defined. We found that mechanical forces applied through integrins enhanced Rac-mediated lamellae formation in FLNa-null but not FLNa-expressing cells. Suppression of force-induced lamella formation was mediated by repeat 23 of FLNa, which also binds FilGAP, a recently discovered Rac GTPase-activating protein (GAP). We found that FilGAP is targeted to sites of force transfer by FLNa. This force-induced redistribution of FilGAP was essential for the suppression of Rac activity and lamellae formation in cells treated with tensile forces. Depletion of FilGAP by small interfering RNA, inhibition of FilGAP activity by dominant-negative mutation or deletion of its FLNa-binding domain, all resulted in a dramatic force-induced increase of the percentage of annexin-V-positive cells. FilGAP therefore plays a role in protecting cells against force-induced apoptosis, and this function is mediated by FLNa.
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Affiliation(s)
- Yulia Shifrin
- CIHR Group in Matrix Dynamics, University of Toronto, Toronto, Ontario, Canada.
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Fraser SA, Ting YH, Mallon KS, Wendt AE, Murphy CJ, Nealey PF. Sub-micron and nanoscale feature depth modulates alignment of stromal fibroblasts and corneal epithelial cells in serum-rich and serum-free media. J Biomed Mater Res A 2008; 86:725-35. [PMID: 18041718 DOI: 10.1002/jbm.a.31519] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Topographic features are generally accepted as being capable of modulating cell alignment. Of particular interest is the potential that topographic feature geometry induces cell alignment indirectly through impacting adsorbed proteins from the cell culture medium on the surface of the substrate. However, it has also been reported that micron-scale feature depth significantly impacts the level of alignment of cellular populations on topography, despite being orders of magnitude larger than the average adsorbed protein layer (nm). In order to better determine the impact of biomimetic length scale topography and adsorbed protein interaction on cellular morphology we have systematically investigated the effect of combinations of sub-micron to nanoscale feature depth and lateral pitch on corneal epithelial cell alignment. In addition we have used the unique properties of a serum-free media alternative in direct comparison to serum-rich medium to investigate the role of culture medium protein composition on cellular alignment to topographically patterned surfaces. Our observation that increasing groove depth elicited larger populations of corneal epithelial cells to align regardless of culture medium composition and of cell orientation with respect to the topography, suggests that these cells can sense changes in topographic feature depths independent of adsorbed proteins localized along ridge edges and tops. However, our data also suggests a strong combinatory effect of topography with culture medium composition, and also a cell type dependency in determining the level of cell elongation and alignment to nanoscale topographic features.
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Affiliation(s)
- Sarah A Fraser
- Department of Chemical Engineering, School of Engineering, University of Wisconsin, Madison, Madison, Wisconsin 53706, USA
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36
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Birukov KG. Small GTPases in mechanosensitive regulation of endothelial barrier. Microvasc Res 2008; 77:46-52. [PMID: 18938185 DOI: 10.1016/j.mvr.2008.09.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 09/08/2008] [Indexed: 12/31/2022]
Abstract
Alterations in vascular permeability are defining feature of diverse processes including atherosclerosis, inflammation, ischemia/reperfusion injury, and ventilator-induced lung injury. Clinical observations and experimental studies support an essential role of mechanical forces in pathophysiologic regulation of lung barrier. Accumulating data demonstrate that decreased levels of blood flow and increased cyclic stretch of lung tissues associated with lung mechanical ventilation at high tidal volumes increase vascular permeability, activate inflammatory cytokine production, alveolar flooding, leukocyte infiltration, and hypoxemia, and increase morbidity and mortality. Potential synergism between pathologic mechanical stimulation and inflammatory molecules resulting in vascular leak and lung injury becomes increasingly recognized. This review will discuss a role of Rho family of small GTPases in the mechanochemical regulation of pulmonary endothelial permeability associated with ventilator induced lung injury.
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Affiliation(s)
- Konstantin G Birukov
- Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA.
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37
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Abstract
This work is motivated by experimental observations that cells on stretched substrate exhibit different responses to static and dynamic loads. A model of focal adhesion that can consider the mechanics of stress fiber, adhesion bonds, and substrate was developed at the molecular level by treating the focal adhesion as an adhesion cluster. The stability of the cluster under dynamic load was studied by applying cyclic external strain on the substrate. We show that a threshold value of external strain amplitude exists beyond which the adhesion cluster disrupts quickly. In addition, our results show that the adhesion cluster is prone to losing stability under high-frequency loading, because the receptors and ligands cannot get enough contact time to form bonds due to the high-speed deformation of the substrate. At the same time, the viscoelastic stress fiber becomes rigid at high frequency, which leads to significant deformation of the bonds. Furthermore, we find that the stiffness and relaxation time of stress fibers play important roles in the stability of the adhesion cluster. The essence of this work is to connect the dynamics of the adhesion bonds (molecular level) with the cell's behavior during reorientation (cell level) through the mechanics of stress fiber. The predictions of the cluster model are consistent with experimental observations.
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Hirata H, Tatsumi H, Sokabe M. Dynamics of actin filaments during tension-dependent formation of actin bundles. Biochim Biophys Acta Gen Subj 2007; 1770:1115-27. [PMID: 17498881 DOI: 10.1016/j.bbagen.2007.03.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Revised: 03/07/2007] [Accepted: 03/22/2007] [Indexed: 01/09/2023]
Abstract
The actin cytoskeleton stress fiber is an actomyosin-based contractile structure seen as a bundle of actin filaments. Although tension development in a cell is believed to regulate stress fiber formation, little is known for the underlying biophysical mechanisms. To address this question, we examined the effects of tension on the behaviors of individual actin filaments during stress fiber (actin bundle) formation using cytosol-free semi-intact fibroblast cells that were pre-treated with the Rho kinase inhibitor Y-27632 to disassemble stress fibers into a meshwork of actin filaments. These filaments were sparsely labeled with quantum dots for live tracking of their motions. When ATP and Ca(2+) were applied to the semi-intact cells to generate actomyosin-based forces, actin meshwork in the protruded lamellae was dragged toward the cell body, while the periphery of the meshwork remained in the original region, indicating that centripetally directed tension developed in the meshwork. Then the individual actin filaments in the meshwork moved towards the cell body accompanied with sudden changes in the direction of their movements, finally forming actin bundles along the direction of tension. Dragging the meshwork by externally applied mechanical forces also exerted essentially the same effects. These results suggest the existence of tension-dependent remodeling of cross-links within the meshwork during the rearrangement of actin filaments, thus demonstrating that tension is a key player to regulate the dynamics of individual actin filaments that leads to actin bundle formation.
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Affiliation(s)
- Hiroaki Hirata
- ICORP/SORST, Cell Mechanosensing Project, Japan Science and Technology Agency, 65 Tsurumai, Showa-ku, Nagoya, Aichi 466-8550, Japan
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39
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Cao Y, Bly R, Moore W, Gao Z, Cuitino AM, Soboyejo W. On the measurement of human osteosarcoma cell elastic modulus using shear assay experiments. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2007; 18:103-9. [PMID: 17200819 DOI: 10.1007/s10856-006-0667-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Accepted: 02/28/2006] [Indexed: 05/13/2023]
Abstract
This paper presents a method for determining the elastic modulus of human osteosarcoma (HOS) cells. The method involves a combination of shear assay experiments and finite element analysis. Following in-situ observations of cell deformation during shear assay experiments, a digital image correlation (DIC) technique was used to determine the local displacement and strain fields. Finite element analysis was then used to determine the Young's moduli of HOS cells. This involved a match of the maximum shear stresses estimated from the experimental shear assay measurements and those calculated from finite element simulations.
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Affiliation(s)
- Yifang Cao
- Princeton Institute for Science and Technology of Materials (PRISM) and Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
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40
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Dawes AT, Edelstein-Keshet L. Phosphoinositides and Rho proteins spatially regulate actin polymerization to initiate and maintain directed movement in a one-dimensional model of a motile cell. Biophys J 2006; 92:744-68. [PMID: 17098793 PMCID: PMC1779977 DOI: 10.1529/biophysj.106.090514] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Gradient sensing, polarization, and chemotaxis of motile cells involve the actin cytoskeleton, and regulatory modules, including the phosphoinositides (PIs), their kinases/phosphatases, and small GTPases (Rho proteins). Here we model their individual components (PIP1, PIP2, PIP3; PTEN, PI3K, PI5K; Cdc42, Rac, Rho; Arp2/3, and actin), their interconversions, interactions, and modular functions in the context of a one-dimensional dynamic model for protrusive cell motility, with parameter values derived from in vitro and in vivo studies. In response to a spatially graded stimulus, the model produces stable amplified internal profiles of regulatory components, and initiates persistent motility (consistent with experimental observations). By connecting the modules, we find that Rho GTPases work as a spatial switch, and that the PIs filter noise, and define the front versus back. Relatively fast PI diffusion also leads to selection of a unique pattern of Rho distribution from a collection of possible patterns. We use the model to explore the importance of specific hypothesized interactions, to explore mutant phenotypes, and to study the role of actin polymerization in the maintenance of the PI asymmetry. We also suggest a mechanism to explain the spatial exclusion of Cdc42 and PTEN and the inability of cells lacking active Cdc42 to properly detect chemoattractant gradients.
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Affiliation(s)
- Adriana T Dawes
- Institute of Applied Mathematics and Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada.
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41
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Bershadsky A, Kozlov M, Geiger B. Adhesion-mediated mechanosensitivity: a time to experiment, and a time to theorize. Curr Opin Cell Biol 2006; 18:472-81. [PMID: 16930976 DOI: 10.1016/j.ceb.2006.08.012] [Citation(s) in RCA: 310] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Accepted: 08/07/2006] [Indexed: 01/27/2023]
Abstract
Adhesion-mediated signaling provides cells with information about multiple parameters of their microenvironment, including mechanical characteristics. Often, such signaling is based on a unique feature of adhesion structures: their ability to grow and strengthen when force is applied to them, either from within the cell or from the outside. Such adhesion reinforcement is characteristic of integrin-mediated cell-matrix adhesions, but may also operate in other types of adhesion structures. Though the amount of knowledge about adhesion-mediated signaling is growing rapidly, the mechanisms underlying force-dependent regulation of junction assembly are largely unknown. Experiments have been carried out that have started to uncover the major signaling pathways involved in the response of adhesion sites to force. Theoretical models have also been used to address the physical mechanisms underlying adhesion-mediated mechanosensing.
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Affiliation(s)
- Alexander Bershadsky
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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42
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Vogel V, Sheetz M. Local force and geometry sensing regulate cell functions. Nat Rev Mol Cell Biol 2006; 7:265-75. [PMID: 16607289 DOI: 10.1038/nrm1890] [Citation(s) in RCA: 1576] [Impact Index Per Article: 87.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The shapes of eukaryotic cells and ultimately the organisms that they form are defined by cycles of mechanosensing, mechanotransduction and mechanoresponse. Local sensing of force or geometry is transduced into biochemical signals that result in cell responses even for complex mechanical parameters such as substrate rigidity and cell-level form. These responses regulate cell growth, differentiation, shape changes and cell death. Recent tissue scaffolds that have been engineered at the micro- and nanoscale level now enable better dissection of the mechanosensing, transduction and response mechanisms.
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Affiliation(s)
- Viola Vogel
- Laboratory for Biologically Oriented Materials, Department of Materials, Swiss Federal Institute of Technology (ETH), Zurich, Wolfgang-Pauli-Strasse 10, ETH Hönggerberg, HCI F443, CH-8093 Zürich, Switzerland.
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Abstract
Cell/matrix adhesions are modulated by cytoskeletal or external stresses and adapt to the mechanical properties of the extracellular matrix. We propose that this mechanosensitivity arises from the activation of a mechanosensor located within the adhesion itself. We show that this mechanism accounts for the observed directional growth of focal adhesions and the reduction or even cessation of their growth when cells adhere to a soft extracellular matrix. We predict quantitatively that both the elasticity and the thickness of the matrix play a key role in the dynamics of focal adhesions. Two different types of dynamics are expected depending on whether the thickness of the matrix is of order of or much larger than the adhesion size. In the latter situation, we predict that the adhesion region reaches a saturation size that can be tuned by the mechanical properties of the matrix.
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Affiliation(s)
- Alice Nicolas
- Laboratoire de Physique de la Matière Condensée, Centre National de la Recherche Scientifique, Nice, France.
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Abstract
Fluid shear stress caused by blood flow is a major determinant of vascular remodeling and arterial tone and can lead to development of atherosclerosis. The endothelial monolayer in vivo acts as a signal transduction interface for hemodynamic forces; these forces determine the shape, cytoskeletal organization, and function of endothelial cells, allowing the vessels to cope with physiological or pathological conditions. The Ras superfamily of GTPases have been revealed to be master regulators of many cellular activities. In particular, the GTPases RhoA, Rac1, and Cdc42 are known to regulate cell shape changes through effects on the cytoskeleton, but their ability to influence polarity, microtubule dynamics, and transcription factor activity is just as significant. Shear stress modulates the activity of small GTPases, which are critical for both cytoskeletal reorganization and changes in gene expression in response to shear stress. The goal of this article is to review what is known about Ras and more so about Rho GTPases in mechanotransduction and the responses of cells to fluid flow. Several distinct signaling pathways can be coordinately activated by flow, and small GTPases are strongly implicated in some of them; thus possible connections will be explored and a unifying hypothesis offered.
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Affiliation(s)
- Eleni Tzima
- Department of Cell and Molecular Physiology, Carolina Cardiovascular Biology Center, University of North Carolina, Chapel Hill, NC 27599, USA.
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Zaidel-Bar R, Kam Z, Geiger B. Polarized downregulation of the paxillin-p130CAS-Rac1 pathway induced by shear flow. J Cell Sci 2005; 118:3997-4007. [PMID: 16129884 DOI: 10.1242/jcs.02523] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Exposure of sparsely plated endothelial cells or a wounded monolayer to shear flow induces an instantaneous inhibition of 'upstream' lamellipodial protrusion and suppresses cell migration against the flow. This phenomenon is caused by the inhibition of Rac1 activity in the upstream lamellae, as demonstrated by fluorescence resonance energy transfer experiments, and by the capacity of constitutively active Rac1 to abolish flow-induced cell polarization. The local inactivation of Rac1 coincides with rapid dephosphorylation of paxillin and the adapter protein p130CAS, which, in their phosphorylated state, participate in the activation of the Rac1 exchange factor complex DOCK180/ELMO. Indeed, overexpression of DOCK180 and ELMO rescue upstream protrusion in cells exposed to flow. Searching for the mechanosensors responsible for the polarized p130CAS dephosphorylation, we discovered that shear stress stimulates the turnover and overall growth of upstream focal adhesions, whereas downstream adhesions tend to shrink. We propose that polarized, shear stress-induced signaling from focal adhesions at the upstream lamellae, leads to the local inactivation of Rac1 by inhibiting paxillin and p130CAS phosphorylation, and consequently blocking the DOCK180/ELMO pathway.
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Affiliation(s)
- Ronen Zaidel-Bar
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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