1
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Caillier A, Oleksyn D, Fowell DJ, Miller J, Oakes PW. T cells use focal adhesions to pull themselves through confined environments. J Cell Biol 2024; 223:e202310067. [PMID: 38889096 PMCID: PMC11187980 DOI: 10.1083/jcb.202310067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 05/16/2024] [Accepted: 06/07/2024] [Indexed: 06/20/2024] Open
Abstract
Immune cells are highly dynamic and able to migrate through environments with diverse biochemical and mechanical compositions. Their migration has classically been defined as amoeboid under the assumption that it is integrin independent. Here, we show that activated primary Th1 T cells require both confinement and extracellular matrix proteins to migrate efficiently. This migration is mediated through small and dynamic focal adhesions that are composed of the same proteins associated with canonical mesenchymal cell focal adhesions, such as integrins, talin, and vinculin. These focal adhesions, furthermore, localize to sites of contractile traction stresses, enabling T cells to pull themselves through confined spaces. Finally, we show that Th1 T cells preferentially follow tracks of other T cells, suggesting that these adhesions modify the extracellular matrix to provide additional environmental guidance cues. These results demonstrate not only that the boundaries between amoeboid and mesenchymal migration modes are ambiguous, but that integrin-mediated focal adhesions play a key role in T cell motility.
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Affiliation(s)
- Alexia Caillier
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - David Oleksyn
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences, University of Rochester Medical Center, Rochester, NY, USA
| | - Deborah J. Fowell
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Jim Miller
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences, University of Rochester Medical Center, Rochester, NY, USA
| | - Patrick W. Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
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2
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Kunitomi A, Chiba S, Higashitani N, Higashitani A, Sato S, Mizuno K, Ohashi K. Solo regulates the localization and activity of PDZ-RhoGEF for actin cytoskeletal remodeling in response to substrate stiffness. Mol Biol Cell 2024; 35:ar87. [PMID: 38656797 PMCID: PMC11238083 DOI: 10.1091/mbc.e23-11-0421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 04/10/2024] [Accepted: 04/17/2024] [Indexed: 04/26/2024] Open
Abstract
Recent findings indicate that Solo, a RhoGEF, is involved in cellular mechanical stress responses. However, the mechanism of actin cytoskeletal remodeling via Solo remains unclear. Therefore, this study aimed to identify Solo-interacting proteins using the BioID, a proximal-dependent labeling method, and elucidate the molecular mechanisms of function of Solo. We identified PDZ-RhoGEF (PRG) as a Solo-interacting protein. PRG colocalized with Solo in the basal area of cells, depending on Solo localization, and enhanced actin polymerization at the Solo accumulation sites. Additionally, Solo and PRG interaction was necessary for actin cytoskeletal remodeling. Furthermore, the purified Solo itself had little or negligible GEF activity, even its GEF-inactive mutant directly activated the GEF activity of PRG through interaction. Moreover, overexpression of the Solo and PRG binding domains, respectively, had a dominant-negative effect on actin polymerization and actin stress fiber formation in response to substrate stiffness. Therefore, Solo restricts the localization of PRG and regulates actin cytoskeletal remodeling in synergy with PRG in response to the surrounding mechanical environment.
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Affiliation(s)
- Aoi Kunitomi
- Laboratory of Molecular and Cellular Biology, Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Shuhei Chiba
- Laboratory of Molecular and Cellular Biology, Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Nahoko Higashitani
- Laboratory of Molecular Genetics and Physiology, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Atsushi Higashitani
- Laboratory of Molecular Genetics and Physiology, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Shinichi Sato
- Laboratory of Bioactive Molecules, Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Kensaku Mizuno
- Laboratory of Molecular and Cellular Biology, Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Kazumasa Ohashi
- Laboratory of Molecular and Cellular Biology, Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
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3
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Sarkar M, Burkel BM, Ponik SM, Notbohm J. Unexpected softening of a fibrous matrix by contracting inclusions. Acta Biomater 2024; 177:253-264. [PMID: 38272198 PMCID: PMC10948310 DOI: 10.1016/j.actbio.2024.01.025] [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] [Received: 08/15/2023] [Revised: 01/16/2024] [Accepted: 01/18/2024] [Indexed: 01/27/2024]
Abstract
Cells respond to the stiffness of their surrounding environment, but quantifying the stiffness of a fibrous matrix at the scale of a cell is complicated, due to the effects of nonlinearity and complex force transmission pathways resulting from randomness in fiber density and connections. While it is known that forces produced by individual contractile cells can stiffen the matrix, it remains unclear how simultaneous contraction of multiple cells in a fibrous matrix alters the stiffness at the scale of a cell. Here, we used computational modeling and experiments to quantify the stiffness of a random fibrous matrix embedded with multiple contracting inclusions, which mimicked the contractile forces of a cell. The results showed that when the matrix was free to contract as a result of the forces produced by the inclusions, the matrix softened rather than stiffened, which was surprising given that the contracting inclusions applied tensile forces to the matrix. Using the computational model, we identified that the underlying cause of the softening was that the majority of the fibers were under a local state of axial compression, causing buckling. We verified that this buckling-induced matrix softening was sufficient for cells to sense and respond by altering their morphology and force generation. Our findings reveal that the localized forces induced by cells do not always stiffen the matrix; rather, softening can occur in instances wherein the matrix can contract in response to the cell-generated forces. This study opens up new possibilities to investigate whether cell-induced softening contributes to maintenance of homeostatic conditions or progression of disease. STATEMENT OF SIGNIFICANCE: Mechanical interactions between cells and the surrounding matrix strongly influence cellular functions. Cell-induced forces can alter matrix properties, and much prior literature in this area focused on the influence of individual contracting cells. Cells in tissues are rarely solitary; rather, they are interspersed with neighboring cells throughout the matrix. As a result, the mechanics are complicated, leaving it unclear how the multiple contracting cells affect matrix stiffness. Here, we show that multiple contracting inclusions within a fibrous matrix can cause softening that in turn affects cell sensing and response. Our findings provide new directions to determine impacts of cell-induced softening on maintenance of tissue or progression of disease.
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Affiliation(s)
- Mainak Sarkar
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Brian M Burkel
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI, USA; University of Wisconsin Carbone Cancer Center, Madison, WI, USA
| | - Suzanne M Ponik
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI, USA; University of Wisconsin Carbone Cancer Center, Madison, WI, USA
| | - Jacob Notbohm
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA; University of Wisconsin Carbone Cancer Center, Madison, WI, USA.
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4
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Schmitt MS, Colen J, Sala S, Devany J, Seetharaman S, Caillier A, Gardel ML, Oakes PW, Vitelli V. Machine learning interpretable models of cell mechanics from protein images. Cell 2024; 187:481-494.e24. [PMID: 38194965 PMCID: PMC11225795 DOI: 10.1016/j.cell.2023.11.041] [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] [Received: 03/21/2023] [Revised: 09/20/2023] [Accepted: 11/29/2023] [Indexed: 01/11/2024]
Abstract
Cellular form and function emerge from complex mechanochemical systems within the cytoplasm. Currently, no systematic strategy exists to infer large-scale physical properties of a cell from its molecular components. This is an obstacle to understanding processes such as cell adhesion and migration. Here, we develop a data-driven modeling pipeline to learn the mechanical behavior of adherent cells. We first train neural networks to predict cellular forces from images of cytoskeletal proteins. Strikingly, experimental images of a single focal adhesion (FA) protein, such as zyxin, are sufficient to predict forces and can generalize to unseen biological regimes. Using this observation, we develop two approaches-one constrained by physics and the other agnostic-to construct data-driven continuum models of cellular forces. Both reveal how cellular forces are encoded by two distinct length scales. Beyond adherent cell mechanics, our work serves as a case study for integrating neural networks into predictive models for cell biology.
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Affiliation(s)
- Matthew S Schmitt
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA; Department of Physics, University of Chicago, Chicago, IL 60637, USA; Kadanoff Center for Theoretical Physics, University of Chicago, Chicago, IL 60637, USA
| | - Jonathan Colen
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA; Department of Physics, University of Chicago, Chicago, IL 60637, USA; Kadanoff Center for Theoretical Physics, University of Chicago, Chicago, IL 60637, USA
| | - Stefano Sala
- Department of Cell & Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
| | - John Devany
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA; Department of Physics, University of Chicago, Chicago, IL 60637, USA
| | - Shailaja Seetharaman
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA; Department of Physics, University of Chicago, Chicago, IL 60637, USA
| | - Alexia Caillier
- Department of Cell & Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
| | - Margaret L Gardel
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA; Department of Physics, University of Chicago, Chicago, IL 60637, USA.
| | - Patrick W Oakes
- Department of Cell & Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA.
| | - Vincenzo Vitelli
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA; Department of Physics, University of Chicago, Chicago, IL 60637, USA; Kadanoff Center for Theoretical Physics, University of Chicago, Chicago, IL 60637, USA.
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5
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Caillier A, Oleksyn D, Fowell DJ, Miller J, Oakes PW. T cells Use Focal Adhesions to Pull Themselves Through Confined Environments. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.16.562587. [PMID: 37904911 PMCID: PMC10614902 DOI: 10.1101/2023.10.16.562587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2023]
Abstract
Immune cells are highly dynamic and able to migrate through environments with diverse biochemical and mechanical composition. Their migration has classically been defined as amoeboid under the assumption that it is integrin-independent. Here we show that activated primary Th1 T cells require both confinement and extracellular matrix protein to migrate efficiently. This migration is mediated through small and dynamic focal adhesions that are composed of the same proteins associated with canonical mesenchymal focal adhesions, such as integrins, talin, and vinculin. These focal adhesions, furthermore, localize to sites of contractile traction stresses, enabling T cells to pull themselves through confined spaces. Finally, we show that Th1 T cell preferentially follows tracks of other T cells, suggesting that these adhesions are modifying the extracellular matrix to provide additional environmental guidance cues. These results demonstrate not only that the boundaries between amoeboid and mesenchymal migration modes are ambiguous, but that integrin-mediated adhesions play a key role in T cell motility.
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Affiliation(s)
- Alexia Caillier
- Department of Cell & Molecular Physiology, Loyola University Chicago, Stritch School of Medicine, Maywood, IL 60153, USA
| | - David Oleksyn
- David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Deborah J Fowell
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Jim Miller
- David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Patrick W Oakes
- Department of Cell & Molecular Physiology, Loyola University Chicago, Stritch School of Medicine, Maywood, IL 60153, USA
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6
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Guo T, He C, Venado A, Zhou Y. Extracellular Matrix Stiffness in Lung Health and Disease. Compr Physiol 2022; 12:3523-3558. [PMID: 35766837 PMCID: PMC10088466 DOI: 10.1002/cphy.c210032] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The extracellular matrix (ECM) provides structural support and imparts a wide variety of environmental cues to cells. In the past decade, a growing body of work revealed that the mechanical properties of the ECM, commonly known as matrix stiffness, regulate the fundamental cellular processes of the lung. There is growing appreciation that mechanical interplays between cells and associated ECM are essential to maintain lung homeostasis. Dysregulation of ECM-derived mechanical signaling via altered mechanosensing and mechanotransduction pathways is associated with many common lung diseases. Matrix stiffening is a hallmark of lung fibrosis. The stiffened ECM is not merely a sequelae of lung fibrosis but can actively drive the progression of fibrotic lung disease. In this article, we provide a comprehensive view on the role of matrix stiffness in lung health and disease. We begin by summarizing the effects of matrix stiffness on the function and behavior of various lung cell types and on regulation of biomolecule activity and key physiological processes, including host immune response and cellular metabolism. We discuss the potential mechanisms by which cells probe matrix stiffness and convert mechanical signals to regulate gene expression. We highlight the factors that govern matrix stiffness and outline the role of matrix stiffness in lung development and the pathogenesis of pulmonary fibrosis, pulmonary hypertension, asthma, chronic obstructive pulmonary disease (COPD), and lung cancer. We envision targeting of deleterious matrix mechanical cues for treatment of fibrotic lung disease. Advances in technologies for matrix stiffness measurements and design of stiffness-tunable matrix substrates are also explored. © 2022 American Physiological Society. Compr Physiol 12:3523-3558, 2022.
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Affiliation(s)
- Ting Guo
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Alabama, USA.,Department of Respiratory Medicine, the Second Xiangya Hospital, Central-South University, Changsha, Hunan, China
| | - Chao He
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Alabama, USA
| | - Aida Venado
- Pulmonary, Critical Care, Allergy and Sleep Medicine, Department of Medicine, University of California San Francisco, San Francisco, California, USA
| | - Yong Zhou
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Alabama, USA
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7
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Ryu S, Zhang H, Emeigh C. The Dark Annulus of a Drop in a Hele-Shaw Cell Is Caused by the Refraction of Light through Its Meniscus. MICROMACHINES 2022; 13:mi13071021. [PMID: 35888838 PMCID: PMC9317764 DOI: 10.3390/mi13071021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/24/2022] [Accepted: 06/27/2022] [Indexed: 02/01/2023]
Abstract
Knowing the meniscus shape of confined drops is important for understanding how they make first contact and then coalesce. When imaged from the top view by brightfield microscopy, a liquid drop (e.g., corn syrup) confined in a Hele-Shaw cell, surrounded by immiscible liquid (e.g., mineral oil), had a dark annulus, and the width of the annulus decreased with increasing concentration of corn syrup. Since the difference in the annulus width was presumed to be related to the meniscus shape of the drops, three-dimensional images of the drops with different concentrations were obtained using confocal fluorescence microscopy, and their cross-sectional meniscus profile was determined by image processing. The meniscus of the drops remained circular despite varying concentration. Since the refractive index of corn syrup increased with concentration, while the surface tension coefficient between corn syrup and mineral oil remained unchanged, the observed change in the annulus width was then attributed to the refraction of light passing through the drop’s meniscus. As such, a ray optics model was developed, which predicted that the annulus width of the drop would decrease as the refractive index of the drop approached that of the surrounding liquid. Therefore, the dark annulus of the drops in the Hele-Shaw cell was caused by the refraction of light passing through the circular meniscus of the drop.
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Affiliation(s)
- Sangjin Ryu
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (H.Z.); (C.E.)
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
- Correspondence:
| | - Haipeng Zhang
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (H.Z.); (C.E.)
| | - Carson Emeigh
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (H.Z.); (C.E.)
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8
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Gao Y, Chai NKK, Garakani N, Datta SS, Cho HJ. Scaling laws to predict humidity-induced swelling and stiffness in hydrogels. SOFT MATTER 2021; 17:9893-9900. [PMID: 34605524 DOI: 10.1039/d1sm01186c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
From pasta to biological tissues to contact lenses, gel and gel-like materials inherently soften as they swell with water. In dry, low-relative-humidity environments, these materials stiffen as they de-swell with water. Here, we use semi-dilute polymer theory to develop a simple power-law relationship between hydrogel elastic modulus and swelling. From this relationship, we predict hydrogel stiffness or swelling at arbitrary relative humidities. Our close predictions of properties of hydrogels across three different polymer mesh families at varying crosslinking densities and relative humidities demonstrate the validity and generality of our understanding. This predictive capability enables more rapid material discovery and selection for hydrogel applications in varying humidity environments.
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Affiliation(s)
- Yiwei Gao
- Department of Mechanical Engineering, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA.
| | - Nicholas K K Chai
- Department of Mechanical Engineering, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA.
| | - Negin Garakani
- Department of Mechanical Engineering, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA.
| | - Sujit S Datta
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA.
| | - H Jeremy Cho
- Department of Mechanical Engineering, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA.
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9
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Physical and Mechanical Characterization of Fibrin-Based Bioprinted Constructs Containing Drug-Releasing Microspheres for Neural Tissue Engineering Applications. Processes (Basel) 2021. [DOI: 10.3390/pr9071205] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Three-dimensional bioprinting can fabricate precisely controlled 3D tissue constructs. This process uses bioinks—specially tailored materials that support the survival of incorporated cells—to produce tissue constructs. The properties of bioinks, such as stiffness and porosity, should mimic those found in desired tissues to support specialized cell types. Previous studies by our group validated soft substrates for neuronal cultures using neural cells derived from human-induced pluripotent stem cells (hiPSCs). It is important to confirm that these bioprinted tissues possess mechanical properties similar to native neural tissues. Here, we assessed the physical and mechanical properties of bioprinted constructs generated from our novel microsphere containing bioink. We measured the elastic moduli of bioprinted constructs with and without microspheres using a modified Hertz model. The storage and loss modulus, viscosity, and shear rates were also measured. Physical properties such as microstructure, porosity, swelling, and biodegradability were also analyzed. Our results showed that the elastic modulus of constructs with microspheres was 1032 ± 59.7 Pascal (Pa), and without microspheres was 728 ± 47.6 Pa. Mechanical strength and printability were significantly enhanced with the addition of microspheres. Thus, incorporating microspheres provides mechanical reinforcement, which indicates their suitability for future applications in neural tissue engineering.
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10
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Sennakesavan G, Mostakhdemin M, Dkhar L, Seyfoddin A, Fatihhi S. Acrylic acid/acrylamide based hydrogels and its properties - A review. Polym Degrad Stab 2020. [DOI: 10.1016/j.polymdegradstab.2020.109308] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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11
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Zareei A, Jiang H, Chittiboyina S, Zhou J, Marin BP, Lelièvre SA, Rahimi R. A lab-on-chip ultrasonic platform for real-time and nondestructive assessment of extracellular matrix stiffness. LAB ON A CHIP 2020; 20:778-788. [PMID: 31951245 DOI: 10.1039/c9lc00926d] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Extracellular matrix (ECM) mechanical stiffness and its dynamic change is one of the main cues that directly affects the differentiation and proliferation of normal cells as well as the progression of disease processes such as fibrosis and cancer. Recent advancements in biomaterials have enabled a wide range of polymer matrices that could mimic the ECM of different tissues for a wide range of in vitro basic research and drug discovery. However, most of the technologies utilized to quantify the stiffness of such ECM are either destructive or expensive, and therefore are unsuitable for the in situ, long-term monitoring of variations in ECM stiffness for on-chip cell culture applications. This work demonstrates a novel noninvasive on-chip platform for characterization of ECM stiffness in vitro, by monitoring ultrasonic wave attenuation through the targeted material. The device is composed of a pair of millimeter scale ultrasonic transmitter and receiver transducers with the test medium placed in between them. The transmitter generates an ultrasonic wave that propagates through the material, triggers the piezoelectric receiver and generates a corresponding electrical signal. The characterization reveals a linear (r2 = 0.86) decrease in the output voltage of the piezoelectric receiver with an average sensitivity of -15.86 μV kPa-1 by increasing the stiffnesses of hydrogels (from 4.3 kPa to 308 kPa made with various dry-weight concentrations of agarose and gelatin). The ultrasonic stiffness sensing is also demonstrated to successfully monitor dynamic changes in a simulated in vitro tissue by gradually changing the polymerization density of an agarose gel, as a proof-of-concept towards future use for 3D cell culture and drug screening. In situ long-term ultrasonic signal stability and thermal assessment of the device demonstrates its high robust performance even after two days of continuous operation, with negligible (<0.5 °C) heating of the hydrogel in contact with the piezoelectric transducers. In vitro biocompatibility assessment of the device with mammary fibroblasts further assures that the materials used in the platform did not produce a toxic response and cells remained viable under the applied ultrasound signals in the device.
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Affiliation(s)
- Amin Zareei
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA. and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
| | - Hongjie Jiang
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA and School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Shirisha Chittiboyina
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA and Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Jiawei Zhou
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA and School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Beatriz Plaza Marin
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA and Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Sophie A Lelièvre
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA and Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907, USA and Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
| | - Rahim Rahimi
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA. and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
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12
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Stratigaki M, Baumann C, van Breemen LCA, Heuts JPA, Sijbesma RP, Göstl R. Fractography of poly(N-isopropylacrylamide) hydrogel networks crosslinked with mechanofluorophores using confocal laser scanning microscopy. Polym Chem 2020. [DOI: 10.1039/c9py00819e] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Employing mechanofluorophores in polymer fractography to obtain new information on force-induced events when analyzed by confocal laser scanning microscopy.
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Affiliation(s)
- Maria Stratigaki
- DWI – Leibniz Institute for Interactive Materials
- 52056 Aachen
- Germany
| | - Christoph Baumann
- DWI – Leibniz Institute for Interactive Materials
- 52056 Aachen
- Germany
| | - Lambert C. A. van Breemen
- Department of Mechanical Engineering
- Polymer Technology
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
| | - Johan P. A. Heuts
- Laboratory of Supramolecular Polymer Chemistry
- Institute for Complex Molecular Systems
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
| | - Rint P. Sijbesma
- Laboratory of Supramolecular Polymer Chemistry
- Institute for Complex Molecular Systems
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
| | - Robert Göstl
- DWI – Leibniz Institute for Interactive Materials
- 52056 Aachen
- Germany
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13
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Lee D, Erickson A, Dudley AT, Ryu S. A Microfluidic Platform for Stimulating Chondrocytes with Dynamic Compression. J Vis Exp 2019. [PMID: 31566611 DOI: 10.3791/59676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Mechanical stimuli are known to modulate biological functions of cells and tissues. Recent studies have suggested that compressive stress alters growth plate cartilage architecture and results in growth modulation of long bones of children. To determine the role of compressive stress in bone growth, we created a microfluidic device actuated by pneumatic pressure, to dynamically (or statically) compress growth plate chondrocytes embedded in alginate hydrogel cylinders. In this article, we describe detailed methods for fabricating and characterizing this device. The advantages of our protocol are: 1) Five different magnitudes of compressive stress can be generated on five technical replicates in a single platform, 2) It is easy to visualize cell morphology via a conventional light microscope, 3) Cells can be rapidly isolated from the device after compression to facilitate downstream assays, and 4) The platform can be applied to study mechanobiology of any cell type that can grow in hydrogels.
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Affiliation(s)
- Donghee Lee
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center
| | - Alek Erickson
- Department of Physiology and Pharmacology, Karolinska Institutet
| | - Andrew T Dudley
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center;
| | - Sangjin Ryu
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln; Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln;
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14
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Johannes KG, Calahan KN, Qi Y, Long R, Rentschler ME. Three-Dimensional Microscale Imaging and Measurement of Soft Material Contact Interfaces under Quasi-Static Normal Indentation and Shear. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:10725-10733. [PMID: 31291542 DOI: 10.1021/acs.langmuir.9b00830] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Understanding the contact and friction between soft materials is vital to a wide variety of engineering applications including soft sealants and medical devices such as catheters and stents. Although the mechanisms of friction between stiff materials have been extensively studied, the mechanisms of friction between soft materials are much less understood. Time-dependent material responses, large deformations, and fluid layers at the contact interface, common in soft materials, pose new challenges toward understanding the friction between soft materials. This article aims to characterize the three-dimensional (3D) contact interfaces in soft materials under large deformations and complex contact conditions. Specifically, we introduce a microindentation and visualization (MIV) system capable of investigating soft material contact interfaces with combined normal and shear loading. When combined with a laser scanning confocal microscope, the MIV system enables the acquisition of 3D image stacks of the deformed substrate and the indenter under fixed normal and shear displacements. The 3D imaging data allows us to quantify the 3D contact profiles and correlate them with the applied normal and shear displacements. Using a spherical indenter and a hydrogel substrate as a model system, we demonstrate that the MIV system and the associated analysis techniques accurately measure the contact area under combined normal and shear loading. Although the limited speed of confocal scanning implies that this method is most suitable for quasi-static loading conditions, potential methods to increase the imaging speed and the corresponding trade-off in image resolution are discussed. The method presented here will be useful for the future investigation of soft material contact and friction involving complex surface geometries.
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Affiliation(s)
- Karl G Johannes
- Department of Mechanical Engineering , University of Colorado , Boulder , Colorado 80309 , United States
| | - Kristin N Calahan
- Department of Mechanical Engineering , University of Colorado , Boulder , Colorado 80309 , United States
| | - Yuan Qi
- Department of Mechanical Engineering , University of Colorado , Boulder , Colorado 80309 , United States
| | - Rong Long
- Department of Mechanical Engineering , University of Colorado , Boulder , Colorado 80309 , United States
| | - Mark E Rentschler
- Department of Mechanical Engineering , University of Colorado , Boulder , Colorado 80309 , United States
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15
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Valente KP, Thind SS, Akbari M, Suleman A, Brolo AG. Collagen Type I-Gelatin Methacryloyl Composites: Mimicking the Tumor Microenvironment. ACS Biomater Sci Eng 2019; 5:2887-2898. [PMID: 33405592 DOI: 10.1021/acsbiomaterials.9b00264] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Therapeutic drugs can penetrate tissues by diffusion and advection. In a healthy tissue, the interstitial fluid is composed of an influx of nutrients and oxygen from blood vessels. In the case of cancerous tissue, the interstitial fluid is poorly drained because of the lack of lymphatic vasculature, resulting in an increase in interstitial pressure. Furthermore, cancer cells invade healthy tissue by pressing and pushing the surrounding environment, creating an increase in pressure inside the tumor area. This results in a large differential pressure between the tumor and the healthy tissue, leading to an increase in extracellular matrix (ECM) stiffness. Because of high interstitial pressure in addition to matrix stiffening, penetration and distribution of systemic therapies are limited to diffusion, decreasing the efficacy of cancer treatment. This work reports on the development of a microfluidic system that mimics in vitro healthy and cancerous microenvironments using collagen I and gelatin methacryloyl (GelMA) composite hydrogels. The microfluidic device developed here contains a simplistic design with a central chamber and two lateral channels. In the central chamber, hydrogel composites were used to mimic the ECM, whereas lateral channels simulated capillary vessels. The transport of fluorescein sodium salt and fluorescently labeled gold nanoparticles from capillary-mimicking channels through the ECM-mimicking hydrogel was explored by tracking fluorescence. By tuning the hydrogel composition and concentration, the impact of the tumor microenvironment properties on the transport of those species was evaluated. In addition, breast cancer MCF-7 cells were embedded in the hydrogel composites, displaying the formation of 3D clusters with high viability and, consequently, the development of an in vitro tumor model.
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16
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Robinson M, Valente KP, Willerth SM. A Novel Toolkit for Characterizing the Mechanical and Electrical Properties of Engineered Neural Tissues. BIOSENSORS 2019; 9:E51. [PMID: 30939804 PMCID: PMC6627085 DOI: 10.3390/bios9020051] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/24/2019] [Accepted: 03/27/2019] [Indexed: 12/30/2022]
Abstract
We have designed and validated a set of robust and non-toxic protocols for directly evaluating the properties of engineered neural tissue. These protocols characterize the mechanical properties of engineered neural tissues and measure their electrophysical activity. The protocols obtain elastic moduli of very soft fibrin hydrogel scaffolds and voltage readings from motor neuron cultures. Neurons require soft substrates to differentiate and mature, however measuring the elastic moduli of soft substrates remains difficult to accurately measure using standard protocols such as atomic force microscopy or shear rheology. Here we validate a direct method for acquiring elastic modulus of fibrin using a modified Hertz model for thin films. In this method, spherical indenters are positioned on top of the fibrin samples, generating an indentation depth that is then correlated with elastic modulus. Neurons function by transmitting electrical signals to one another and being able to assess the development of electrical signaling serves is an important verification step when engineering neural tissues. We then validated a protocol wherein the electrical activity of motor neural cultures is measured directly by a voltage sensitive dye and a microplate reader without causing damage to the cells. These protocols provide a non-destructive method for characterizing the mechanical and electrical properties of living spinal cord tissues using novel biosensing methods.
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Affiliation(s)
- Meghan Robinson
- Biomedical Engineering Program, University of Victoria, Victoria, B.C. V8W 2Y2, Canada.
| | - Karolina Papera Valente
- Department of Mechanical Engineering, University of Victoria, Victoria, B.C. V8W 2Y2, Canada.
| | - Stephanie M Willerth
- Department of Mechanical Engineering, University of Victoria, Victoria, B.C. V8W 2Y2, Canada.
- Division of Medical Sciences, University of Victoria, Victoria, B.C. V8W 2Y2, Canada.
- Centre for Biomedical Research, University of Victoria, Victoria, B.C. V8W 2Y2, Canada.
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17
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Garreta E, Prado P, Tarantino C, Oria R, Fanlo L, Martí E, Zalvidea D, Trepat X, Roca-Cusachs P, Gavaldà-Navarro A, Cozzuto L, Campistol JM, Izpisúa Belmonte JC, Hurtado Del Pozo C, Montserrat N. Fine tuning the extracellular environment accelerates the derivation of kidney organoids from human pluripotent stem cells. NATURE MATERIALS 2019; 18:397-405. [PMID: 30778227 PMCID: PMC9845070 DOI: 10.1038/s41563-019-0287-6] [Citation(s) in RCA: 164] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 01/08/2019] [Indexed: 05/19/2023]
Abstract
The generation of organoids is one of the biggest scientific advances in regenerative medicine. Here, by lengthening the time that human pluripotent stem cells (hPSCs) were exposed to a three-dimensional microenvironment, and by applying defined renal inductive signals, we generated kidney organoids that transcriptomically matched second-trimester human fetal kidneys. We validated these results using ex vivo and in vitro assays that model renal development. Furthermore, we developed a transplantation method that utilizes the chick chorioallantoic membrane. This approach created a soft in vivo microenvironment that promoted the growth and differentiation of implanted kidney organoids, as well as providing a vascular component. The stiffness of the in ovo chorioallantoic membrane microenvironment was recapitulated in vitro by fabricating compliant hydrogels. These biomaterials promoted the efficient generation of renal vesicles and nephron structures, demonstrating that a soft environment accelerates the differentiation of hPSC-derived kidney organoids.
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Affiliation(s)
- Elena Garreta
- Pluripotency for Organ Regeneration, Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain
| | - Patricia Prado
- Pluripotency for Organ Regeneration, Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain
| | - Carolina Tarantino
- Pluripotency for Organ Regeneration, Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain
| | - Roger Oria
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain
- University of Barcelona, Barcelona, Spain
| | - Lucia Fanlo
- Instituto de Biología Molecular de Barcelona (IBMB-CSIC), Parc Científic de Barcelona, Barcelona, Spain
| | - Elisa Martí
- Instituto de Biología Molecular de Barcelona (IBMB-CSIC), Parc Científic de Barcelona, Barcelona, Spain
| | - Dobryna Zalvidea
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain
| | - Xavier Trepat
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain
- University of Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Madrid, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
| | - Pere Roca-Cusachs
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain
- University of Barcelona, Barcelona, Spain
| | - Aleix Gavaldà-Navarro
- Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona and CIBER Fisiopatología de la Obesidad y Nutrición, Barcelona, Spain
| | - Luca Cozzuto
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | | | | | - Carmen Hurtado Del Pozo
- Pluripotency for Organ Regeneration, Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain
| | - Nuria Montserrat
- Pluripotency for Organ Regeneration, Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Technology (BIST), Barcelona, Spain.
- Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Madrid, Spain.
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain.
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18
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Obst F, Simon D, Mehner PJ, Neubauer JW, Beck A, Stroyuk O, Richter A, Voit B, Appelhans D. One-step photostructuring of multiple hydrogel arrays for compartmentalized enzyme reactions in microfluidic devices. REACT CHEM ENG 2019. [DOI: 10.1039/c9re00349e] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A moulding technique is presented for the simultaneous photostructuring on the μm scale of hydrogels with nanomaterials on one substrate, usable for the fabrication of microfluidic double-chamber reactors.
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Affiliation(s)
- Franziska Obst
- Leibniz-Institut für Polymerforschung Dresden e.V
- 01069 Dresden
- Germany
- Technische Universität Dresden
- Organische Chemie der Polymere
| | - David Simon
- Leibniz-Institut für Polymerforschung Dresden e.V
- 01069 Dresden
- Germany
- Technische Universität Dresden
- Organische Chemie der Polymere
| | - Philipp J. Mehner
- Technische Universität Dresden
- Institut für Halbleiter- und Mikrosystemtechnik
- 01187 Dresden
- Germany
| | - Jens W. Neubauer
- Leibniz-Institut für Polymerforschung Dresden e.V
- 01069 Dresden
- Germany
| | - Anthony Beck
- Technische Universität Dresden
- Institut für Halbleiter- und Mikrosystemtechnik
- 01187 Dresden
- Germany
| | - Oleksandr Stroyuk
- Technische Universität Dresden
- Physikalische Chemie
- 01069 Dresden
- Germany
| | - Andreas Richter
- Technische Universität Dresden
- Institut für Halbleiter- und Mikrosystemtechnik
- 01187 Dresden
- Germany
| | - Brigitte Voit
- Leibniz-Institut für Polymerforschung Dresden e.V
- 01069 Dresden
- Germany
- Technische Universität Dresden
- Organische Chemie der Polymere
| | - Dietmar Appelhans
- Leibniz-Institut für Polymerforschung Dresden e.V
- 01069 Dresden
- Germany
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19
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Lee D, Erickson A, You T, Dudley AT, Ryu S. Pneumatic microfluidic cell compression device for high-throughput study of chondrocyte mechanobiology. LAB ON A CHIP 2018; 18:2077-2086. [PMID: 29897088 PMCID: PMC6467204 DOI: 10.1039/c8lc00320c] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Hyaline cartilage is a specialized type of connective tissue that lines many moveable joints (articular cartilage) and contributes to bone growth (growth plate cartilage). Hyaline cartilage is composed of a single cell type, the chondrocyte, which produces a unique hydrated matrix to resist compressive stress. Although compressive stress has profound effects on transcriptional networks and matrix biosynthesis in chondrocytes, mechanistic relationships between strain, signal transduction, cell metabolism, and matrix production remain superficial. Here, we describe development and validation of a polydimethylsiloxane (PDMS)-based pneumatic microfluidic cell compression device which generates multiple compression conditions in a single platform. The device contained an array of PDMS balloons of different sizes which were actuated by pressurized air, and the balloons compressed chondrocytes cells in alginate hydrogel constructs. Our characterization and testing of the device showed that the developed platform could compress chondrocytes with various magnitudes simultaneously with negligible effect on cell viability. Also, the device is compatible with live cell imaging to probe early effects of compressive stress, and it can be rapidly dismantled to facilitate molecular studies of compressive stress on transcriptional networks. Therefore, the proposed device will enhance the productivity of chondrocyte mechanobiology studies, and it can be applied to study mechanobiology of other cell types.
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Affiliation(s)
- Donghee Lee
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
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20
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Bashirzadeh Y, Chatterji S, Palmer D, Dumbali S, Qian S, Maruthamuthu V. Stiffness Measurement of Soft Silicone Substrates for Mechanobiology Studies Using a Widefield Fluorescence Microscope. J Vis Exp 2018. [PMID: 30035766 DOI: 10.3791/57797] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Soft tissues in the human body typically have stiffness in the kilopascal (kPa) range. Accordingly, silicone and hydrogel flexible substrates have been proven to be useful substrates for culturing cells in a physical microenvironment that partially mimics in vivo conditions. Here, we present a simple protocol for characterizing the Young's moduli of isotropic linear elastic substrates typically used for mechanobiology studies. The protocol consists of preparing a soft silicone substrate on a Petri dish or stiff silicone, coating the top surface of the silicone substrate with fluorescent beads, using a millimeter-scale sphere to indent the top surface (by gravity), imaging the fluorescent beads on the indented silicone surface using a fluorescence microscope, and analyzing the resultant images to calculate the Young's modulus of the silicone substrate. Coupling the substrate's top surface with a moduli extracellular matrix protein (in addition to the fluorescent beads) allows the silicone substrate to be readily used for cell plating and subsequent studies using traction force microscopy experiments. The use of stiff silicone, instead of a Petri dish, as the base of the soft silicone, enables the use of mechanobiology studies involving external stretch. A specific advantage of this protocol is that a widefield fluorescence microscope, which is commonly available in many labs, is the major equipment necessary for this procedure. We demonstrate this protocol by measuring the Young's modulus of soft silicone substrates of different elastic moduli.
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Affiliation(s)
- Yashar Bashirzadeh
- Department of Mechanical & Aerospace Engineering, Old Dominion University
| | | | - Dakota Palmer
- Department of Biological Sciences, Old Dominion University
| | - Sandeep Dumbali
- Department of Mechanical & Aerospace Engineering, Old Dominion University
| | - Shizhi Qian
- Department of Mechanical & Aerospace Engineering, Old Dominion University
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21
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22
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Kim CL, Kim DE. Durability and Self-healing Effects of Hydrogel Coatings with respect to Contact Condition. Sci Rep 2017; 7:6896. [PMID: 28761116 PMCID: PMC5537306 DOI: 10.1038/s41598-017-07106-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 06/22/2017] [Indexed: 11/17/2022] Open
Abstract
The self-healing property of a hydrogel applied to a glass substrate as a thin polymer coating was assessed. The motivation was to develop a durable hydrogel coating that may be used to protect the surface of precision components from surface damage and scratches. The intrinsic swelling behavior of hydrogel fibers when they are exposed to moisture was exploited to attain the self-healing effect. The mechanical and self-healing properties of the dehydrated hydrogel coating by the freeze-drying process and the hydrated hydrogel coating that was reconstituted by the addition of water were analyzed. After conducting sliding tests with different loads and sliding distances, the wear area was hydrated with water to successfully induce self-healing of the hydrogel coating. It was also found that both the dehydrated hydrogel coating and the hydrated hydrogel coating had improved friction characteristics. In particular, the hydrated hydrogel coating had a much higher durability than the dehydrated coating.
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Affiliation(s)
- Chang-Lae Kim
- Center for Nano-Wear, School of Mechanical Engineering, Yonsei University, Seoul, 03722, Republic of Korea
| | - Dae-Eun Kim
- Center for Nano-Wear, School of Mechanical Engineering, Yonsei University, Seoul, 03722, Republic of Korea.
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23
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Lv H, Wang H, Zhang Z, Yang W, Liu W, Li Y, Li L. Biomaterial stiffness determines stem cell fate. Life Sci 2017; 178:42-48. [PMID: 28433510 DOI: 10.1016/j.lfs.2017.04.014] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 04/11/2017] [Accepted: 04/18/2017] [Indexed: 01/01/2023]
Abstract
Stem cells have potential to develop into numerous cell types, thus they are good cell source for tissue engineering. As an external physical signal, material stiffness is capable of regulating stem cell fate. Biomaterial stiffness is an important parameter in tissue engineering. We summarize main measurements of material stiffness under different condition, then list and compare three main methods of controlling stiffness (material amount, crosslinking density and photopolymeriztion time) which interplay with one another and correlate with stiffness positively, and current advances in effects of biomaterial stiffness on stem cell fate. We discuss the unsolved problems and future directions of biomaterial stiffness in tissue engineering.
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Affiliation(s)
- Hongwei Lv
- The Key Laboratory of Pathobiology, Ministry of Education, Norman Bethune Medical College, Jilin University, Changchun 130021, China
| | - Heping Wang
- Department of Neurosurgery, Tongji Hospital, Tongji Medical School, Huazhong University of Science and Technology, Wuhan, China
| | - Zhijun Zhang
- College of Clinical Medicine, Jilin University, Changchun, China
| | - Wang Yang
- College of Clinical Medicine, Jilin University, Changchun, China
| | - Wenbin Liu
- College of Clinical Medicine, Jilin University, Changchun, China
| | - Yulin Li
- The Key Laboratory of Pathobiology, Ministry of Education, Norman Bethune Medical College, Jilin University, Changchun 130021, China.
| | - Lisha Li
- The Key Laboratory of Pathobiology, Ministry of Education, Norman Bethune Medical College, Jilin University, Changchun 130021, China.
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24
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Lee D, Ryu S. A Validation Study of the Repeatability and Accuracy of Atomic Force Microscopy Indentation Using Polyacrylamide Gels and Colloidal Probes. J Biomech Eng 2017; 139:2595195. [DOI: 10.1115/1.4035536] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Indexed: 01/06/2023]
Abstract
The elasticity of soft biological materials is a critical property to understand their biomechanical behaviors. Atomic force microscopy (AFM) indentation method has been widely employed to measure the Young's modulus (E) of such materials. Although the accuracy of the method has been recently evaluated based on comparisons with macroscale E measurements, the repeatability of the method has yet to be validated for rigorous biomechanical studies of soft elastic materials. We tested the AFM indentation method using colloidal probes and polyacrylamide (PAAM) gels of E < 20 kPa as a model soft elastic material after having identified optimal trigger force and probe speed. AFM indentations repeated with time intervals show that the method is well repeatable when performed carefully. Compared with the rheometric method and the confocal microscopy indentation method, the AFM indentation method is evaluated to have comparable accuracy and better precision, although these elasticity measurements appear to rely on the compositions of PAAM gels and the length scale of measurement. Therefore, we have confirmed that the AFM indentation method can reliably measure the elasticity of soft elastic materials.
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Affiliation(s)
- Donghee Lee
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 e-mail:
| | - Sangjin Ryu
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 e-mail:
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25
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Gross W, Kress H. Simultaneous measurement of the Young's modulus and the Poisson ratio of thin elastic layers. SOFT MATTER 2017; 13:1048-1055. [PMID: 28094390 DOI: 10.1039/c6sm02470j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The behavior of cells and tissue is greatly influenced by the mechanical properties of their environment. For studies on the interactions between cells and soft matrices, especially those applying traction force microscopy the characterization of the mechanical properties of thin substrate layers is essential. Various techniques to measure the elastic modulus are available. Methods to accurately measure the Poisson ratio of such substrates are rare and often imply either a combination of multiple techniques or additional equipment which is not needed for the actual biological studies. Here we describe a novel technique to measure both parameters, the Youngs's modulus and the Poisson ratio in a single experiment. The technique requires only a standard inverted epifluorescence microscope. As a model system, we chose cross-linked polyacrylamide and poly-N-isopropylacrylamide hydrogels which are known to obey Hooke's law. We place millimeter-sized steel spheres on the substrates which indent the surface. The data are evaluated using a previously published model which takes finite thickness effects of the substrate layer into account. We demonstrate experimentally for the first time that the application of the model allows the simultaneous determination of both the Young's modulus and the Poisson ratio. Since the method is easy to adapt and comes without the need of special equipment, we envision the technique to become a standard tool for the characterization of substrates for a wide range of investigations of cell and tissue behavior in various mechanical environments as well as other samples, including biological materials.
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Affiliation(s)
- Wolfgang Gross
- Department of Physics, University of Bayreuth, Bayreuth, Germany.
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