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Siddique A, Pause I, Narayan S, Kruse L, Stark RW. Endothelialization of PDMS-based microfluidic devices under high shear stress conditions. Colloids Surf B Biointerfaces 2020; 197:111394. [PMID: 33075662 DOI: 10.1016/j.colsurfb.2020.111394] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 09/02/2020] [Accepted: 09/28/2020] [Indexed: 10/23/2022]
Abstract
Microfluidic systems made out of polydimethylsiloxane (PDMS) offer a platform to mimic vascular flow conditions in model systems at well-defined shear stresses. However, extracellular matrix (ECM) proteins that are physisorbed on the PDMS are not reliably attached under high shear stress conditions, which makes long-term experiments difficult. To overcome this limitation, we functionalized PDMS surfaces with 3-aminopropyltriethoxysilane (APTES) by using different surface activation methods to develop a stable linkage between the PDMS surface and collagen, which served as a model ECM protein. The stability of the protein coating inside the microfluidic devices was evaluated in perfusion experiments with phosphate-buffered saline (PBS) at 10-40 dynes/cm2 wall shear stress. To assess the stability of cell adhesion, endothelial cells were grown in a multi-shear device over a shear stress range of 20-150 dynes/cm2. Cells on the APTES-mediated collagen coating were stable over the entire shear stress range in PBS (pH 9) for 48 h. The results suggest that at high pH values, the electrostatic interaction between APTES-coated surfaces and collagen molecules offer a very promising tool to modify PDMS-based microfluidic devices for long-term endothelialization under high shear stress conditions.
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Affiliation(s)
- Asma Siddique
- Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287, Darmstadt, Germany
| | - Isabelle Pause
- Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287, Darmstadt, Germany
| | - Suman Narayan
- Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287, Darmstadt, Germany
| | - Larissa Kruse
- Macromolecular Chemistry and Paper Chemistry, Department of Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Str. 4, 64287, Darmstadt, Germany
| | - Robert W Stark
- Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287, Darmstadt, Germany.
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Siddique A, Meckel T, Stark RW, Narayan S. Improved cell adhesion under shear stress in PDMS microfluidic devices. Colloids Surf B Biointerfaces 2017; 150:456-464. [DOI: 10.1016/j.colsurfb.2016.11.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2016] [Revised: 11/06/2016] [Accepted: 11/07/2016] [Indexed: 12/01/2022]
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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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Weyand B, Israelowitz M, Schroeder H, Vogt P. Fluid Dynamics in Bioreactor Design: Considerations for the Theoretical and Practical Approach. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2008. [DOI: 10.1007/10_2008_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Andrews KD, Feugier P, Black RA, Hunt JA. Vascular prostheses: performance related to cell-shear responses. J Surg Res 2007; 149:39-46. [PMID: 18395748 DOI: 10.1016/j.jss.2007.08.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Revised: 08/27/2007] [Accepted: 08/28/2007] [Indexed: 10/22/2022]
Abstract
BACKGROUND This work concerned the endothelialization of vascular prostheses and subsequent improvement of functionality with respect to tissue engineering. The aim of the study was to investigate the initial, pre-shear stress cellular behavior with respect to three vascular biomaterials to explain subsequent cellular responses to physiological shear stresses. MATERIALS AND METHODS Expanded polytetrafluoroethylene (ePTFE), polyethyleneterephthalate (polyester; Dacron; PET), and electrostatically spun polyurethane (PU) (all pre-impregnated with collagen I/III) were cell-seeded with L929 immortalized murine fibroblasts or human umbilical vein endothelial cells (HUVECs). Cytoskeletal involvement, cell height profiles, and immunohistochemistry were examined after 7 d static culture. RESULTS All three vascular biomaterials demonstrated different structures. Cell behavior varied both between the materials and the two cell types: cytoskeletal involvement was greater for the HUVECs and the more fibrous surfaces; height profiles were greater for the L929 and PET, and lowest on PU. Immunohistochemistry of HUVEC samples also showed differences: PU revealed the greatest expression of intercellular adhesion molecule-1 and E-selectin (PET and ePTFE the lowest, respectively); ePTFE produced the greatest for vascular cell adhesion molecule-1 (PET the lowest). CONCLUSIONS Material substrate influenced the cellular response. Cells demonstrating firm adhesion increased their cytoskeletal processes and expression of cell-substratum and inter-cellular adhesion markers, which may explain their ability to adapt more readily to shear stress. The fibrous PU structure appeared to be most suited to further shear stress exposure. This study demonstrated the potential of the underlying vascular material to affect the long-term cellular functionality of the prosthesis.
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Affiliation(s)
- Kirstie D Andrews
- UKCTE, Division of Clinical Engineering, Duncan Building, University of Liverpool, Liverpool, United Kingdom.
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Ferko MC, Bhatnagar A, Garcia MB, Butler PJ. Finite-element stress analysis of a multicomponent model of sheared and focally-adhered endothelial cells. Ann Biomed Eng 2006; 35:208-23. [PMID: 17160699 PMCID: PMC3251212 DOI: 10.1007/s10439-006-9223-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Accepted: 10/23/2006] [Indexed: 11/25/2022]
Abstract
Hemodynamic forces applied at the apical surface of vascular endothelial cells may be redistributed to and amplified at remote intracellular organelles and protein complexes where they are transduced to biochemical signals. In this study we sought to quantify the effects of cellular material inhomogeneities and discrete attachment points on intracellular stresses resulting from physiological fluid flow. Steady-state shear- and magnetic bead-induced stress, strain, and displacement distributions were determined from finite-element stress analysis of a cell-specific, multicomponent elastic continuum model developed from multimodal fluorescence images of confluent endothelial cell (EC) monolayers and their nuclei. Focal adhesion locations and areas were determined from quantitative total internal reflection fluorescence microscopy and verified using green fluorescence protein-focal adhesion kinase (GFP-FAK). The model predicts that shear stress induces small heterogeneous deformations of the endothelial cell cytoplasm on the order of <100 nm. However, strain and stress were amplified 10-100-fold over apical values in and around the high-modulus nucleus and near focal adhesions (FAs) and stress distributions depended on flow direction. The presence of a 0.4 microm glycocalyx was predicted to increase intracellular stresses by approximately 2-fold. The model of magnetic bead twisting rheometry also predicted heterogeneous stress, strain, and displacement fields resulting from material heterogeneities and FAs. Thus, large differences in moduli between the nucleus and cytoplasm and the juxtaposition of constrained regions (e.g. FAs) and unattached regions provide two mechanisms of stress amplification in sheared endothelial cells. Such phenomena may play a role in subcellular localization of early mechanotransduction events.
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Affiliation(s)
- Michael C Ferko
- Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA
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Lu H, Koo LY, Wang WM, Lauffenburger DA, Griffith LG, Jensen KF. Microfluidic shear devices for quantitative analysis of cell adhesion. Anal Chem 2006; 76:5257-64. [PMID: 15362881 DOI: 10.1021/ac049837t] [Citation(s) in RCA: 249] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe the design, construction, and characterization of microfluidic devices for studying cell adhesion and cell mechanics. The method offers multiple advantages over previous approaches, including a wide range of distractive forces, high-throughput performance, simplicity in experimental setup and control, and potential for integration with other microanalytic modules. By manipulating the geometry and surface chemistry of the microdevices, we are able to vary the shear force and the biochemistry during an experiment. The dynamics of cell detachment under different conditions can be captured simultaneously using time-lapse videomicroscopy. We demonstrate assessment of cell adhesion to fibronectin-coated substrates as a function of the shear stress or fibronectin concentration in microchannels. Furthermore, a combined perfusion-shear device is designed to maintain cell viability for long-term culture as well as to introduce exogenous reagents for biochemical studies of cell adhesion regulation. In agreement with established literature, we show that fibroblasts cultured in the combined device reduced their adhesion strength to the substrate in response to epidermal growth factor stimulation.
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Affiliation(s)
- Hang Lu
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Feugier P, Black RA, Hunt JA, How TV. Attachment, morphology and adherence of human endothelial cells to vascular prosthesis materials under the action of shear stress. Biomaterials 2005; 26:1457-66. [PMID: 15522747 DOI: 10.1016/j.biomaterials.2004.04.050] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Accepted: 04/30/2004] [Indexed: 10/26/2022]
Abstract
In an effort to improve the long-term patency of vascular prostheses several groups now advocate seeding autologous endothelial cells (ECs) onto the lumen of the vessel prior to implantation, a procedure that involves pre-treating the prosthesis material with fibrin, collagen and/or other matrix molecules to promote cell attachment and retention. In this study, we examined the degree to which human umbilical venous endothelial cells (HUVECs) adhered to three materials commonly used polymeric vascular prosthesis that had been coated with the same commercial extra cellular matrix proteins, and after exposure to fluid shear stresses representative of femoro-distal bypass in a cone-and-plate shearing device. We quantified cell number, area of coverage and degree of cell spreading using image analysis techniques. The response of cells that adhered to the surface of each material, and following exposure to fluid shear stress, depended on surface treatment, topology and cell type. Whereas collagen coating improved primary cellular adhesion and coverage significantly, the degree of spreading depended on the underlying surface structure and on the application of the shear stress. In some cases, fewer than 30% of cells remained on the surface after only 1-h exposure to physiological levels of shear stress. The proportion of the surface that was covered by cells also decreased, despite an increase in the degree to which individual cells spread on exposure to shear stress. Moreover, the behaviour of HUVECs was distinct from that of fibroblasts, in that the human ECs were able to adapt to their environment by spreading to a much greater extent in response to shear. The quality of HUVEC attachment, as measured by extent of cell coverage and resistance to fluid shear stress, was greatest on expanded polytetrafluoroethylene samples that had been impregnated with Type I/III collagen.
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Affiliation(s)
- P Feugier
- Vascular Surgery Unit, Hôpital E. Herriot, Lyon, France
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Lavender MD, Pang Z, Wallace CS, Niklason LE, Truskey GA. A system for the direct co-culture of endothelium on smooth muscle cells. Biomaterials 2005; 26:4642-53. [PMID: 15722134 PMCID: PMC2929592 DOI: 10.1016/j.biomaterials.2004.11.045] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2004] [Accepted: 11/24/2004] [Indexed: 11/25/2022]
Abstract
The development of a functional, adherent endothelium is one of the major factors limiting the successful development of tissue engineered vascular grafts (TEVGs). The adhesion and function of endothelial cells (ECs) on smooth muscle cells (SMCs) are poorly understood. The goal of this research was to optimize conditions for the direct culture of endothelium on SMCs, and to develop an initial assessment of co-culture on EC function. The co-culture consisted of a culture substrate, a basal adhesion protein, a layer of porcine SMCs, a medial adhesion protein, and a layer of porcine ECs. Conditions that led to successful co-culture were: a polystyrene culture substrate, a quiescent state for SMCs, subconfluent density for SMC seeding and confluent density for EC seeding, and fibronectin (FN) for the basal adhesion protein. EC adhesion was not enhanced by addition of FN, collagen I, collagen IV or laminin (LN) to the medial layer. 3-D image reconstruction by confocal microscopy indicated that SMCs did not migrate over ECs and the cells were present in two distinct layers. Co-cultures could be consistently maintained for as long as 10 days. After exposure to 5 dyne/cm(2) for 7.5 h, ECs remained adherent to SMCs. PECAM staining indicated junction formation between ECs, but at a lower level than that observed with EC monocultures. Co-culturing ECs with SMCs did not change the growth rate of ECs, but EC DiI-Ac-LDL uptake was increased. Thus, a confluent and adherent layer of endothelium can be directly cultured on quiescent SMCs.
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Affiliation(s)
- Mark D. Lavender
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Campus Box 90281, Durham, NC 27708-0281, USA
| | - Zhengyu Pang
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Campus Box 90281, Durham, NC 27708-0281, USA
| | - Charles S. Wallace
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Campus Box 90281, Durham, NC 27708-0281, USA
| | - Laura E. Niklason
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Campus Box 90281, Durham, NC 27708-0281, USA
- Department of Anesthesiology, Duke University, Medical Center, Durham, NC 27710, USA
| | - George A. Truskey
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Campus Box 90281, Durham, NC 27708-0281, USA
- Corresponding author. Tel.: +1 919 660 5147; fax: +1 919 684 4488. (G.A. Truskey)
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Chafik D, Bear D, Bui P, Patel A, Jones NF, Kim BT, Hung CT, Gupta R. Optimization of Schwann cell adhesion in response to shear stress in an in vitro model for peripheral nerve tissue engineering. TISSUE ENGINEERING 2003; 9:233-41. [PMID: 12740086 DOI: 10.1089/107632703764664701] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The design of nerve guidance channels (NGCs) is evolving to produce a favorable environment for neural regeneration. We created an in vitro model to evaluate the interactions between three centrally important components of this altered host environment: (1). Schwann cells, (2). substrate, and (3). sustained mechanical stimulus in the form of shear stress with laminar fluid flow. Preconfluent Schwann cells were plated on slides coated either with laminin, poly-D-lysine, type IV collagen, or fibronectin. These slides were placed into custom-designed, parallel-plate, flow chambers and were administered laminar fluid flow at a rate of 15 mL/min for 2 h. Schwann cell adhesion assays demonstrated that laminin (mean, 86.1%; SEM, 4.47%) and fibronectin (mean, 81.7%; SEM, 3.24%) were statistically superior to collagen type IV (mean, 57.7%; SEM, 3.96%) and poly-D-lysine (mean, 58.0%; SEM, 4.97%) (p < 0.001). Fibronectin (mean, 12.20%; SEM, 0.374%) induced statistically greater Schwann cell proliferation than did laminin (mean, 8.14%; SEM, 0.682%) (p < 0.001). Therefore, we recommend that fibronectin should be used as an important component of NGCs with further in vivo studies. As mechanical stress is an integral part of the host environment, our study is the first to incorporate this factor into an in vitro model for peripheral nerve tissue engineering.
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Affiliation(s)
- Dara Chafik
- Department of Orthopedic Surgery, University of California, Irvine, Irvine, California 92657, USA
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Albuquerque ML, Flozak AS. Patterns of living beta-actin movement in wounded human coronary artery endothelial cells exposed to shear stress. Exp Cell Res 2001; 270:223-34. [PMID: 11640886 DOI: 10.1006/excr.2001.5351] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We previously demonstrated that physiologic levels of shear stress enhance endothelial repair. Cell spreading and migration, but not proliferation, were the major mechanisms accounting for the increases in wound closure rate (Albuquerque et al., 2000, Am. J. Physiol. Heart Circ. Physiol. 279, H293-H302). However, the patterns and movements of beta-actin filaments responsible for cell motility and translocation in human coronary artery endothelial cells (HCAECs) have not been previously investigated under physiologic flow. HCAECs transfected with beta-actin-GFP were cultured on type I collagen-coated coverslips. Confluent cell monolayers were subjected to laminar shear stress of 12 dynes/cm(2) for 18 h in a parallel-plate flow chamber to attain cellular alignment and then wounded by scraping with a metal spatula and subsequently exposed to a laminar shear stress of 20 dynes/cm(2) (S-W-sH) or static (S-W-sT) conditions. Time-lapse imaging and deconvolution microscopy was performed during the first 3 h after imposition of S-W-sH or S-W-sT conditions. The spatial and temporal dynamics of beta-actin-GFP motility and translocation during wound closure in HCAEC monolayers were analyzed under both conditions. Compared with HCAEC under S-W-sT conditions, our data show that HCAEC under S-W-sH conditions demonstrated greater beta-actin-GFP motility, filament and clumping patterns, and filament arcs used during cellular attachment and detachment. These findings demonstrate intriguing patterns of beta-actin organization and movement during wound closure in HCAEC exposed to physiological flow.
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Affiliation(s)
- M L Albuquerque
- Critical Care and Pulmonary Laboratory of Vascular Research, (Children's Memorial Hospital), Chicago, Illinois 60611, USA.
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Haier J, Nicolson GL. Role of the cytoskeleton in adhesion stabilization of human colorectal carcinoma cells to extracellular matrix components under dynamic conditions of laminar flow. Clin Exp Metastasis 2000; 17:713-21. [PMID: 10919716 DOI: 10.1023/a:1006754829564] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Adhesion stabilization of malignant cells in the microcirculation is necessary for successful metastasis formation. The adhesion of colon carcinoma cells to microcirculation extracellular matrix (ECM) components is mediated, in part, by integrins that can be intracellularly linked to cytoskeletal proteins. Thus the functional status of at least certain integrins can be regulated by complex interactions with cytosolic, cytoskeletal and membrane-bound proteins. Wall shear stress caused by fluid flow also influences cellular functions, such as cell morphology, cytoskeletal arrangements and cell signaling. Using a parallel plate laminar flow chamber dynamic adhesion of human HT-29 colon carcinoma cells to collagen was investigated and compared with cell adhesion under static conditions. Cells were pretreated with cytochalasin D, nocodazole, colchicine or acrylamide to disrupt actin filaments, microtubules or intermediate filaments. Disruption of actin filaments completely inhibited all types of adhesive interactions. In contrast, impairment of tubulin polymerization or disruption of intermediate filaments resulted in different effects on static and dynamic adhesion. Treatment with acrylamide did not interfere with dynamic cell adhesion, whereas under static conditions it partially reduced adhesion rates. Under dynamic conditions increased initial adhesive interactions between HT-29 cells and collagen were found after disruption of microtubules, and the adherent cells demonstrated extensive crawling on collagen surfaces. In contrast, under static adhesion disrupting microtubules did not affect cell adhesion rates. Cytochalasin D and acrylamide were found to inhibit Tyr-phosphorylation of FAK and paxillin, whereas microtubule disrupting agents at low but not high concentrations increased phosphorylation of these focal adhesion proteins. Our results revealed that cytoskeletal components appear to be involved in adhesion stabilization of HT-29 cells to ECM components, and hydrodynamic shear forces modulate this involvement. Tyr-phosphorylation of focal adhesion proteins, such as paxillin and FAK, appears to be a part of this cytoskeleton-mediated process.
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Affiliation(s)
- J Haier
- The Institute for Molecular Medicine, Huntington Beach, California, USA.
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Mathur AB, Truskey GA, Reichert WM. Atomic force and total internal reflection fluorescence microscopy for the study of force transmission in endothelial cells. Biophys J 2000; 78:1725-35. [PMID: 10733955 PMCID: PMC1300769 DOI: 10.1016/s0006-3495(00)76724-5] [Citation(s) in RCA: 232] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
This paper describes the combined use of atomic force microscopy (AFM) and total internal reflection fluorescence microscopy (TIRFM) to examine the transmission of force from the apical cell membrane to the basal cell membrane. A Bioscope AFM was mounted on an inverted microscope, the stage of which was configured for TIRFM imaging of fluorescently labeled human umbilical vein endothelial cells (HUVECs). Variable-angle TIRFM experiments were conducted to calibrate the coupling angle with the depth of penetration of the evanescent wave. A measure of cellular mechanical properties was obtained by collecting a set of force curves over the entire apical cell surface. A linear regression fit of the force-indentation curves to an elastic model yields an elastic modulus of 7.22 +/- 0. 46 kPa over the nucleus, 2.97 +/- 0.79 kPa over the cell body in proximity to the nucleus, and 1.27 +/- 0.36 kPa on the cell body near the edge. Stress transmission was investigated by imaging the response of the basal surface to localized force application over the apical surface. The focal contacts changed in position and contact area when forces of 0.3-0.5 nN were applied. There was a significant increase in focal contact area when the force was removed (p < 0.01) from the nucleus as compared to the contact area before force application. There was no significant change in focal contact coverage area before and after force application over the edge. The results suggest that cells transfer localized stress from the apical to the basal surface globally, resulting in rearrangement of contacts on the basal surface.
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Affiliation(s)
- A B Mathur
- Center for Cellular and Biosurface Engineering, and Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708-0281, USA
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