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Benvenuti E, Reho GA, Palumbo S, Fraldi M. Pre-strains and buckling in mechanosensitivity of contractile cells and focal adhesions: A tensegrity model. J Mech Behav Biomed Mater 2022; 135:105413. [PMID: 36057207 DOI: 10.1016/j.jmbbm.2022.105413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/04/2022] [Accepted: 08/05/2022] [Indexed: 10/31/2022]
Abstract
We demonstrate that several key aspects of the contractile activity of a cell interacting with the substrate can be captured by means of a non linear elastic tensegrity mechanical system made of a tensile element in parallel with a buckling-prone component, and exchanging forces with the surroundings through an extracellular matrix-focal adhesion complex. Mechanosensitivity of the focal adhesion plaque is triggered by pre-strain-driven buckling of the system induced either by pre-contraction or pre-polymerization of the constituents. The impact of pre-polymerization on the mechanical force and the implications of using linear and nonlinear elasticity for the focal adhesion plaque are assessed.
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Affiliation(s)
- E Benvenuti
- Engineering Department, University of Ferrara, Italy.
| | - G A Reho
- Engineering Department, University of Ferrara, Italy
| | - S Palumbo
- Department of Structures for Engineering and Architecture, University of Napoli Federico II, Italy
| | - M Fraldi
- Department of Structures for Engineering and Architecture, University of Napoli Federico II, Italy.
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2
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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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3
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Agarwal T, Narayana GH, Banerjee I. Keratinocytes are mechanoresponsive to the microflow-induced shear stress. Cytoskeleton (Hoboken) 2019; 76:209-218. [PMID: 30969461 DOI: 10.1002/cm.21521] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Revised: 02/27/2019] [Accepted: 04/04/2019] [Indexed: 12/11/2022]
Abstract
Here, we have reported that keratinocytes respond to the microflow-induced shear stress both at the collective and individual cell level. Using a microfluidic setup, we categorically showed that low shear stress of magnitude 0.06 dyne/cm2 could induce morphological variation and cytoskeletal reorganization in keratinocyte, whereas higher shear stress (6 dyne/cm2 ) resulted in cellular disruption. Using a series of blocker molecules specific to different mechanotransducers, we demonstrated the pivotal role of actin network in keratinocyte mechanoresponsiveness in conjugation with myosin and lipid rafts. Flow-induced shear stress also induced significant elevation in E-cadherin and Zonula occludens-1 (ZO-1) expression levels. We further showed that under the influence of shear stress, the extent of colocalization of E-cadherin and ZO-1 was more at the cell-cell junction that indicates an improvement in the epithelial phenotype. An increase in the expression of nuclear lamin was also observed in the sheared cells that suggest the transmission of mechanical signals to the nucleus. It is envisioned that this study may find its application in basic and applied organogenesis of the epidermis.
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Affiliation(s)
- Tarun Agarwal
- Department of Biotechnology and Medical Engineering, National Institute of Technology Rourkela, India.,Department of Biotechnology, Indian Institute of Technology Kharagpur, India
| | - Gautham H Narayana
- Department of Biotechnology and Medical Engineering, National Institute of Technology Rourkela, India.,Jacques Monod Institute, Paris Diderot University & CNRS, Paris, France
| | - Indranil Banerjee
- Department of Biotechnology and Medical Engineering, National Institute of Technology Rourkela, India
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4
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Blumlein A, Williams N, McManus JJ. The mechanical properties of individual cell spheroids. Sci Rep 2017; 7:7346. [PMID: 28779182 PMCID: PMC5544704 DOI: 10.1038/s41598-017-07813-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 07/03/2017] [Indexed: 12/18/2022] Open
Abstract
The overall physical properties of tissues emerge in a complex manner from the properties of the component cells and other constituent materials from which the tissue is formed, across multiple length scales ranging from nanometres to millimetres. Recent studies have suggested that interfacial tension between cells contributes significantly to the mechanical properties of tissues and that the overall surface tension is determined by the ratio of adhesion tension to cortical tension. Using cavitation rheology (CR), we have measured the interfacial properties and the elastic modulus of spheroids formed from HEK cells. By comparing the work of bubble formation with deformation of the cell spheroid at different length scales, we have estimated the cortical tension for HEK cells. This innovative approach to understanding the fundamental physical properties associated with tissue mechanics may guide new approaches for the generation of materials to replace or regenerate damaged or diseased tissues.
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Affiliation(s)
- Alice Blumlein
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland
| | - Noel Williams
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland
| | - Jennifer J McManus
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland.
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5
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Eldridge WJ, Steelman ZA, Loomis B, Wax A. Optical Phase Measurements of Disorder Strength Link Microstructure to Cell Stiffness. Biophys J 2017; 112:692-702. [PMID: 28256229 DOI: 10.1016/j.bpj.2016.12.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 11/13/2016] [Accepted: 12/09/2016] [Indexed: 01/01/2023] Open
Abstract
There have been sustained efforts on the part of cell biologists to understand the mechanisms by which cells respond to mechanical stimuli. To this end, many rheological tools have been developed to characterize cellular stiffness. However, measurement of cellular viscoelastic properties has been limited in scope by the nature of most microrheological methods, which require direct mechanical contact, applied at the single-cell level. In this article, we describe, to our knowledge, a new analysis approach for quantitative phase imaging that relates refractive index variance to disorder strength, a parameter that is linked to cell stiffness. Significantly, both disorder strength and cell stiffness are measured with the same phase imaging system, presenting a unique alternative for label-free, noncontact, single-shot imaging of cellular rheologic properties. To demonstrate the potential applicability of the technique, we measure phase disorder strength and shear stiffness across five cellular populations with varying mechanical properties and demonstrate an inverse relationship between these two parameters. The existence of this relationship suggests that predictions of cell mechanical properties can be obtained from examining the disorder strength of cell structure using this, to our knowledge, novel, noncontact technique.
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Affiliation(s)
- Will J Eldridge
- Duke University, Department of Biomedical Engineering, Durham, North Carolina
| | - Zachary A Steelman
- Duke University, Department of Biomedical Engineering, Durham, North Carolina
| | - Brianna Loomis
- Duke University, Department of Biomedical Engineering, Durham, North Carolina
| | - Adam Wax
- Duke University, Department of Biomedical Engineering, Durham, North Carolina.
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6
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Mennens SFB, van den Dries K, Cambi A. Role for Mechanotransduction in Macrophage and Dendritic Cell Immunobiology. Results Probl Cell Differ 2017; 62:209-242. [PMID: 28455711 DOI: 10.1007/978-3-319-54090-0_9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Tissue homeostasis is not only controlled by biochemical signals but also through mechanical forces that act on cells. Yet, while it has long been known that biochemical signals have profound effects on cell biology, the importance of mechanical forces has only been recognized much more recently. The types of mechanical stress that cells experience include stretch, compression, and shear stress, which are mainly induced by the extracellular matrix, cell-cell contacts, and fluid flow. Importantly, macroscale tissue deformation through stretch or compression also affects cellular function.Immune cells such as macrophages and dendritic cells are present in almost all peripheral tissues, and monocytes populate the vasculature throughout the body. These cells are unique in the sense that they are subject to a large variety of different mechanical environments, and it is therefore not surprising that key immune effector functions are altered by mechanical stimuli. In this chapter, we describe the different types of mechanical signals that cells encounter within the body and review the current knowledge on the role of mechanical signals in regulating macrophage, monocyte, and dendritic cell function.
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Affiliation(s)
- Svenja F B Mennens
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein Zuid 26-28, 6525 GA, Nijmegen, The Netherlands
| | - Koen van den Dries
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein Zuid 26-28, 6525 GA, Nijmegen, The Netherlands
| | - Alessandra Cambi
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein Zuid 26-28, 6525 GA, Nijmegen, The Netherlands.
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A Chemomechanical Model of Matrix and Nuclear Rigidity Regulation of Focal Adhesion Size. Biophys J 2016; 109:1807-17. [PMID: 26536258 DOI: 10.1016/j.bpj.2015.08.048] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 08/22/2015] [Accepted: 08/31/2015] [Indexed: 10/24/2022] Open
Abstract
In this work, a chemomechanical model describing the growth dynamics of cell-matrix adhesion structures (i.e., focal adhesions (FAs)) is developed. We show that there are three regimes for FA evolution depending on their size. Specifically, nascent adhesions with initial lengths below a critical value that are yet to engage in actin fibers will dissolve, whereas bigger ones will grow into mature FAs with a steady state size. In adhesions where growth surpasses the steady state size, disassembly will occur until their sizes are reduced to the equilibrium state. This finding arises from the fact that polymerization of adhesion proteins is force-dependent. Under actomyosin contraction, individual integrin bonds within small FAs (i.e., nascent adhesions or focal complexes) must transmit higher loads while the phenomenon of stress concentration occurs at the edge of large adhesion patches. As such, an effective stiffness of the FA-extracellular matrix complex that is either too small or too large will be relatively low, resulting in a limited actomyosin pulling force developed at the edge that is insufficient to prevent disassembly. Furthermore, it is found that a stiffer extracellular matrix and/or nucleus, as well as a stronger chemomechanical feedback, will induce larger adhesions along with a higher level of contraction force. Interestingly, switching the extracellular side from an elastic half-space, corresponding to some widely used in vitro gel substrates, to a one-dimensional fiber (as in the case of cells anchoring to a fibrous scaffold in vivo) does not qualitative change these conclusions. Our model predictions are in good agreement with a variety of experimental observations obtained in this study as well as those reported in the literature. Furthermore, this new model, to our knowledge, provides a framework with which to understand how both intracellular and extracellular perturbations lead to changes in adhesion structure number and size.
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8
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Chen YQ, Su PT, Chen YH, Wei MT, Huang CH, Osterday K, del Álamo JC, Syu WJ, Chiou A. The effect of enterohemorrhagic E. coli infection on the cell mechanics of host cells. PLoS One 2014; 9:e112137. [PMID: 25369259 PMCID: PMC4219835 DOI: 10.1371/journal.pone.0112137] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 10/13/2014] [Indexed: 11/18/2022] Open
Abstract
Enterohaemorrhagic E. coli (EHEC) is a type of human pathogenic bacteria. The main virulence characteristics of EHEC include the formation of attaching and effacing lesions (A/E lesions) and the production of one or more Shiga-like toxins, which may induce human uremic complications. When EHEC infects host cells, it releases translocated intimin receptor (Tir) and effector proteins inside the host cells, inducing the rearrangement and accumulation of the F-actin cytoskeleton, a phenotype leading to the formation of pedestals in the apical cell surface, and the growth of stress fibers at the base of the cells. To examine the effect of EHEC infection on cell mechanics, we carried out a series of experiments to examine HeLa cells with and without EHEC infection to quantify the changes in (1) focal adhesion area, visualized by anti-vinculin staining; (2) the distribution and orientation of stress fibers; and (3) the intracellular viscoelasticity, via directional video particle tracking microrheology. Our results indicated that in EHEC-infected HeLa cells, the focal adhesion area increased and the actin stress fibers became thicker and more aligned. The cytoskeletal reorganization induced by EHEC infection mediated a dramatic increase in the cytoplasmic elastic shear modulus of the infected cells, and a transition in the viscoelastic behavior of the cells from viscous-like to elastic-like. These changes in mechanobiological characteristics might modulate the attachments between EHEC and the host cell to withstand exfoliation, and between the host cell and the extracellular matrix, and might also alter epithelial integrity.
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Affiliation(s)
- Yin-Quan Chen
- Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Pin-Tzu Su
- Institute of Microbiology & Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China
- Biophotonics & Molecular Imaging Research Center (BMIRC), National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Yu-Hsuan Chen
- Institute of Microbiology & Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Ming-Tzo Wei
- Bioengineering Program, Lehigh University, Bethlehem, PA, United States of America
| | - Chien-Hsiu Huang
- Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Kathryn Osterday
- Department of Mechanical and Aerospace Engineering, San Diego, California, United States of America
| | - Juan C. del Álamo
- Department of Mechanical and Aerospace Engineering, San Diego, California, United States of America
- Institute of Engineering in Medicine, University of California San Diego, San Diego, California, United States of America
- * E-mail: (JCA); (WJS); (AC)
| | - Wan-Jr Syu
- Institute of Microbiology & Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China
- Biophotonics & Molecular Imaging Research Center (BMIRC), National Yang-Ming University, Taipei, Taiwan, Republic of China
- * E-mail: (JCA); (WJS); (AC)
| | - Arthur Chiou
- Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan, Republic of China
- Biophotonics & Molecular Imaging Research Center (BMIRC), National Yang-Ming University, Taipei, Taiwan, Republic of China
- * E-mail: (JCA); (WJS); (AC)
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9
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Vargas-Pinto R, Gong H, Vahabikashi A, Johnson M. The effect of the endothelial cell cortex on atomic force microscopy measurements. Biophys J 2014; 105:300-9. [PMID: 23870251 DOI: 10.1016/j.bpj.2013.05.034] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 04/24/2013] [Accepted: 05/13/2013] [Indexed: 10/26/2022] Open
Abstract
We examined whether the presence of the cell cortex might explain, in part, why previous studies using atomic force microscopy (AFM) to measure cell modulus (E) gave higher values with sharp tips than for larger spherical tips. We confirmed these AFM findings in human umbilical vein endothelial cells (HUVEC) and Schlemm's canal (SC) endothelial cells with AFM indentation ≤ 400 nm, two cell types with prominent cortices (312 ± 65 nm in HUVEC and 371 ± 91 nm in SC cells). With spherical tips, E (kPa) was 0.71 ± 0.16 in HUVEC and 0.94 ± 0.06 in SC cells. Much higher values of E were measured using sharp tips: 3.23 ± 0.54 in HUVEC and 6.67 ± 1.07 in SC cells. Previous explanations for this difference such as strain hardening or a substrate effect were shown to be inconsistent with our measurements. Finite element modeling studies showed that a stiff cell cortex could explain the results. In both cell types, Latrunculin-A greatly reduced E for sharp and rounded tips, and also reduced the ratio of the values measured with a sharp tip as compared to a rounded tip. Our results suggest that the cell cortex increases the apparent endothelial cell modulus considerably when measured using a sharp AFM tip.
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Affiliation(s)
- R Vargas-Pinto
- Biomedical Engineering Department, Northwestern University, Evanston, Illinois, USA
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Abstract
The nucleus is the distinguishing feature of eukaryotic cells. Until recently, it was often considered simply as a unique compartment containing the genetic information of the cell and associated machinery, without much attention to its structure and mechanical properties. This article provides compelling examples that illustrate how specific nuclear structures are associated with important cellular functions, and how defects in nuclear mechanics can cause a multitude of human diseases. During differentiation, embryonic stem cells modify their nuclear envelope composition and chromatin structure, resulting in stiffer nuclei that reflect decreased transcriptional plasticity. In contrast, neutrophils have evolved characteristic lobulated nuclei that increase their physical plasticity, enabling passage through narrow tissue spaces in their response to inflammation. Research on diverse cell types further demonstrates how induced nuclear deformations during cellular compression or stretch can modulate cellular function. Pathological examples of disturbed nuclear mechanics include the many diseases caused by mutations in the nuclear envelope proteins lamin A/C and associated proteins, as well as cancer cells that are often characterized by abnormal nuclear morphology. In this article, we will focus on determining the functional relationship between nuclear mechanics and cellular (dys-)function, describing the molecular changes associated with physiological and pathological examples, the resulting defects in nuclear mechanics, and the effects on cellular function. New insights into the close relationship between nuclear mechanics and cellular organization and function will yield a better understanding of normal biology and will offer new clues into therapeutic approaches to the various diseases associated with defective nuclear mechanics.
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Affiliation(s)
- Jan Lammerding
- Brigham and Women's Hospital/Harvard Medical School, Cambridge, Massachusetts, USA.
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Jiang J, Papoutsakis ET. Stem-cell niche based comparative analysis of chemical and nano-mechanical material properties impacting ex vivo expansion and differentiation of hematopoietic and mesenchymal stem cells. Adv Healthc Mater 2013. [PMID: 23184458 DOI: 10.1002/adhm.201200169] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The ability of stem cells to self-renew with minimal or no differentiation and, when appropriately cued, to give rise to many types of progenitor and mature cells, is the basis for applications in regenerative and transfusion medicine, but also in drug discovery and in vitro toxicology. Inspired by the complex interactions between stem cells and their microenvironment, the so-called stem-cell niche, the properties of supporting biomaterials, including surface biochemistry, topography (type, size, organization, and geometry of nanostructures), and mechanical properties, have been identified as important determinants of stem-cell fate in vitro. 3D culture environments that could recapitulate the complexity of the in vivo stem-cell microenvironment could further expand the complexity and repertoire of engineered environments with exciting translational applications. Herein, the material aspects that affect the expansion and differentiation fate of adult hematopoietic stem/progenitor cells (HSPCs) and mesenchymal stem cells (MSCs), two powerful cell types that co-reside in the bone-marrow niche, but with distinct, sometime complementary, differentiation fates, properties, and translational applications, are examined. Although MSCs are adherent cells and, in contrast, HSPCs are non- or weakly adherent cells, both can sense and respond to material properties, including surface (bio)chemistry, ECM composition, topography, and matrix elasticity, possibly through similar molecular mechanisms.
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Affiliation(s)
- Jinlin Jiang
- Dept. of Chemical & Biomolecular Engineering, University of Delaware, Newark, DE 19711, USA
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12
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Tsai M, Kita A, Leach J, Rounsevell R, Huang JN, Moake J, Ware RE, Fletcher DA, Lam WA. In vitro modeling of the microvascular occlusion and thrombosis that occur in hematologic diseases using microfluidic technology. J Clin Invest 2011; 122:408-18. [PMID: 22156199 DOI: 10.1172/jci58753] [Citation(s) in RCA: 207] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 11/02/2011] [Indexed: 12/11/2022] Open
Abstract
In hematologic diseases, such as sickle cell disease (SCD) and hemolytic uremic syndrome (HUS), pathological biophysical interactions among blood cells, endothelial cells, and soluble factors lead to microvascular occlusion and thrombosis. Here, we report an in vitro "endothelialized" microfluidic microvasculature model that recapitulates and integrates this ensemble of pathophysiological processes. Under controlled flow conditions, the model enabled quantitative investigation of how biophysical alterations in hematologic disease collectively lead to microvascular occlusion and thrombosis. Using blood samples from patients with SCD, we investigated how the drug hydroxyurea quantitatively affects microvascular obstruction in SCD, an unresolved issue pivotal to understanding its clinical efficacy in such patients. In addition, we demonstrated that our microsystem can function as an in vitro model of HUS and showed that shear stress influences microvascular thrombosis/obstruction and the efficacy of the drug eptifibatide, which decreases platelet aggregation, in the context of HUS. These experiments establish the versatility and clinical relevance of our microvasculature-on-a-chip model as a biophysical assay of hematologic pathophysiology as well as a drug discovery platform.
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Affiliation(s)
- Michelle Tsai
- Department of Bioengineering, University of California, Berkeley, California, USA
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13
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Cao L, Wu A, Truskey GA. Biomechanical effects of flow and coculture on human aortic and cord blood-derived endothelial cells. J Biomech 2011; 44:2150-7. [PMID: 21683362 DOI: 10.1016/j.jbiomech.2011.05.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 04/12/2011] [Accepted: 05/23/2011] [Indexed: 02/05/2023]
Abstract
Human endothelial cells derived from umbilical cord blood (hCB-ECs) represent a promising cell source for endothelialization of tissue engineered blood vessels. hCB-ECs cultured directly above human aortic smooth muscle cells (SMCs), which model native and tissue engineered blood vessels, produce a confluent endothelium that responds to flow like normal human aortic endothelial cells (HAECs). The objective of this study was to quantify the elastic modulus of hCB-ECs cocultured with SMCs under static and flow conditions using atomic force microscopy (AFM). Cytoskeleton structures were assessed by AFM cell surface imaging and immunofluorescence of F-actin. The elastic moduli of hCB-ECs and HAECs were similar and significantly smaller than the value for SMCs in monoculture under static conditions (p<0.05). In coculture, hCB-ECs and HAECs became significantly stiffer with moduli 160-180% larger than their corresponding values in monoculture. While the moduli of hCB-ECs and HAECs almost doubled in monoculture and flow condition, their corresponding values in coculture declined after exposure to flow. Both the number and diameter of cortical stress fiber per cell width increased in coculture and/or flow conditions, whereas the subcortical stress fiber density throughout the cell interior increased by a smaller amount. These findings indicate that changes to biomechanical properties in coculture and/or exposure to flow are correlated with changes in the cortical stress fiber density. For ECs, fluid shear stress appeared to have greater effect on the elastic modulus than the presence of SMCs and changes to the elastic modulus in coculture may be due to EC-SMC communication.
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Affiliation(s)
- Li Cao
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Durham, NC 27708, USA
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14
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Lee SY, Zaske AM, Novellino T, Danila D, Ferrari M, Conyers J, Decuzzi P. Probing the mechanical properties of TNF-α stimulated endothelial cell with atomic force microscopy. Int J Nanomedicine 2011; 6:179-95. [PMID: 21499414 PMCID: PMC3075881 DOI: 10.2147/ijn.s12760] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
TNF-α (tumor necrosis factor-α) is a potent pro-inflammatory cytokine that regulates the permeability of blood and lymphatic vessels. The plasma concentration of TNF-α is elevated (> 1 pg/mL) in several pathologies, including rheumatoid arthritis, atherosclerosis, cancer, pre-eclampsia; in obese individuals; and in trauma patients. To test whether circulating TNF-α could induce similar alterations in different districts along the vascular system, three endothelial cell lines, namely HUVEC, HPMEC, and HCAEC, were characterized in terms of 1) mechanical properties, employing atomic force microscopy; 2) cytoskeletal organization, through fluorescence microscopy; and 3) membrane overexpression of adhesion molecules, employing ELISA and immunostaining. Upon stimulation with TNF-α (10 ng/mL for 20 h), for all three endothelial cells, the mechanical stiffness increased by about 50% with a mean apparent elastic modulus of E ~5 ± 0.5 kPa (~3.3 ± 0.35 kPa for the control cells); the density of F-actin filaments increased in the apical and median planes; and the ICAM-1 receptors were overexpressed compared with controls. Collectively, these results demonstrate that sufficiently high levels of circulating TNF-α have similar effects on different endothelial districts, and provide additional information for unraveling the possible correlations between circulating pro-inflammatory cytokines and systemic vascular dysfunction.
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Affiliation(s)
- Sei-Young Lee
- Department of Nanomedicine and Biomedical Engineering, The University of Texas Medical School at Houston, Houston, TX, USA
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15
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Hsiao SW, Thien DVH, Ho MH, Hsieh HJ, Li CH, Hung CH, Li HH. Interactions between chitosan and cells measured by AFM. Biomed Mater 2010; 5:054117. [DOI: 10.1088/1748-6041/5/5/054117] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Zeng D, Juzkiw T, Read AT, Chan DWH, Glucksberg MR, Ethier CR, Johnson M. Young's modulus of elasticity of Schlemm's canal endothelial cells. Biomech Model Mechanobiol 2010; 9:19-33. [PMID: 19387710 PMCID: PMC4319365 DOI: 10.1007/s10237-009-0156-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Accepted: 04/02/2009] [Indexed: 01/29/2023]
Abstract
Schlemm's canal (SC) endothelial cells are likely important in the physiology and pathophysiology of the aqueous drainage system of the eye, particularly in glaucoma. The mechanical stiffness of these cells determines, in part, the extent to which they can support a pressure gradient and thus can be used to place limits on the flow resistance that this layer can generate in the eye. However, little is known about the biomechanical properties of SC endothelial cells. Our goal in this study was to estimate the effective Young's modulus of elasticity of normal SC cells. To do so, we combined magnetic pulling cytometry of isolated cultured human SC cells with finite element modeling of the mechanical response of the cell to traction forces applied by adherent beads. Preliminary work showed that the immersion angles of beads attached to the SC cells had a major influence on bead response; therefore, we also measured bead immersion angle by confocal microscopy, using an empirical technique to correct for axial distortion of the confocal images. Our results showed that the upper bound for the effective Young's modulus of elasticity of the cultured SC cells examined in this study, in central, non-nuclear regions, ranged between 1,007 and 3,053 Pa, which is similar to, although somewhat larger than values that have been measured for other endothelial cell types. We compared these values to estimates of the modulus of primate SC cells in vivo, based on images of these cells under pressure loading, and found good agreement at low intraocular pressure (8-15 mm Hg). However, increasing intraocular pressure (22-30 mm Hg) appeared to cause a significant increase in the modulus of these cells. These moduli can be used to estimate the extent to which SC cells deform in response to the pressure drop across the inner wall endothelium and thereby estimate the extent to which they can generate outflow resistance.
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Affiliation(s)
- Dehong Zeng
- Department of Biomedical Engineering, Northwestern University, Evanston, USA
| | - Taras Juzkiw
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | - A. Thomas Read
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | - Darren W.-H. Chan
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | | | - C. Ross Ethier
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada. Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada. Department of Bioengineering, Imperial College London, London, UK
| | - Mark Johnson
- Department of Biomedical Engineering, Northwestern University, Evanston, USA
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17
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Philip JT, Dahl KN. Nuclear mechanotransduction: response of the lamina to extracellular stress with implications in aging. J Biomech 2008; 41:3164-70. [PMID: 18945430 DOI: 10.1016/j.jbiomech.2008.08.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 08/26/2008] [Accepted: 08/27/2008] [Indexed: 11/18/2022]
Abstract
Mechnotransduction, the phenomenon by which cells respond to applied force, is necessary for normal cell processes and is implicated in the pathology of several diseases including atherosclerosis. The exact mechanisms which govern how forces can affect gene expression have not been determined, but putative direct force effects on the genome would require transduction through the nuclear lamina. In this study we show that nuclei in cells exposed to shear stress significantly change shape, upregulate nuclear lamins and move lamins from the nuclear interior to the nuclear periphery. We hypothesize that the augmentation of the nuclear lamina at the nuclear periphery protects the nuclear interior from the force and allows a nuclear adaptation to shear stress. We also investigate the shear stress response of nuclei in cells that have been transfected with lamin A Delta50, which significantly stiffens nuclei. Lamin A Delta50 causes the premature aging syndrome Hutchinson-Gilford progeria syndrome (HGPS) and models many aspects of normal aging. We find that the presence of lamin A Delta50 in only 30% of cells greatly reduces the response of the nuclear lamina in all cells in the flow field. We suggest that cells expressing lamin A Delta50 lack the ability to adapt to flow and may prevent neighboring cells from adapting as well. These results provide insight into the development of cardiovascular disease both in patients with HGPS and in normal aging.
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Affiliation(s)
- Julia T Philip
- Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
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18
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Abstract
In eukaryotic cells, the nucleus contains the genome and is the site of transcriptional regulation. The nucleus is the largest and stiffest organelle and is exposed to mechanical forces transmitted through the cytoskeleton from outside the cell and from force generation within the cell. Here, we discuss the effect of intra- and extracellular forces on nuclear shape and structure and how these force-induced changes could be implicated in nuclear mechanotransduction, ie, force-induced changes in cell signaling and gene transcription. We review mechanical studies of the nucleus and nuclear structural proteins, such as lamins. Dramatic changes in nuclear shape, organization, and stiffness are seen in cells where lamin proteins are mutated or absent, as in genetically engineered mice, RNA interference studies, or human disease. We examine the different mechanical pathways from the force-responsive cytoskeleton to the nucleus. We also highlight studies that link changes in nuclear shape with cell function during developmental, physiological, and pathological modifications. Together, these studies suggest that the nucleus itself may play an important role in the response of the cell to force.
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Affiliation(s)
- Kris Noel Dahl
- Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA.
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19
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Dyachenko V, Christ A, Gubanov R, Isenberg G. Bending of z-lines by mechanical stimuli: an input signal for integrin dependent modulation of ion channels? PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:196-216. [PMID: 18367237 DOI: 10.1016/j.pbiomolbio.2008.02.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
We studied which components of mechanical cell deformation are involved in "stretch modulated ion currents" (SMIC). Murine ventricular myocytes were attached to glass coverslips and deformed in x, y and z with a 16 microm thin glass stylus (S) of calibrated stiffness. Three-dimensional confocal microscopy characterized cell deformation (T-tubular membranes, mitochondria) and bending of S (indicative of the applied force). Axial (x-) displacement of S sheared the upper cell part versus the attached bottom, close to S, it changed sarcomere length and bent z-lines ("z-line displacement"). Vertical (z-press) or transversal (y-shear) displacement of S bulged cytoplasm and mitochondria transversally without detectable z-line displacement. Axial stiffness increased with the extent of stress ("stress stiffening"). Depolymerization of F-actin or block of integrin receptors reduced stiffness. SMIC served as a proxy readout of deformation-induced signaling. Axial deformation activated a non-selective cation conductance (Gns) and deactivated an inwardly rectifying K+ conductance (GK1), z-press or y-shear did not induce SMIC. Depolymerization of F-actin or block of integrin receptors reduced SMIC. SMIC did not depend on changes in sarcomere length but correlated with the extent of z-line bending. We discuss that both shear stress at the attached cell bottom and z-line bending could activate mechanosensors. Since SMIC was absent during deformations without z-line bending we postulate that z-line bending is a necessary component for SMIC signaling.
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Affiliation(s)
- V Dyachenko
- Department of Physiology, Martin-Luther-University Halle, Halle, Germany
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