The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform
Michael Cho - One of the best experts on this subject based on the ideXlab platform.
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Astrocyte Viability and Functionality in Spatially Confined Microcavitation Zone
2019Co-Authors: Bo Chen, Jessica Tjahja, Sameep Malla, Caleb Liebman, Michael ChoAbstract:Blast-induced traumatic brain injury (bTBI) can result in cell/tissue damage and lead to clinical and neuropsychiatric symptoms. Shock waves from a blast propagate through the brain and initiate cascades of mechanical and physiological events that can adversely affect the brain function. Although studies using animal models and brain slices have shown macroscale changes in the brain tissue in response to blast, systematic elucidation of coupling mechanisms is currently lacking. One mechanism that has been postulated and demonstrated repeatedly is the blast-induced generation and subsequent collapse of micron-size bubbles (i.e., microcavitation). Using a custom-designed exposure system, we have previously reported that upon collapsing of microbubbles, astrocytes exhibited changes in the cell viability, Cellular Biomechanics, production of reactive oxygen species, and activation of apoptotic signaling pathways. In this paper, we have applied microfabrication techniques and seeded astrocytes in a spatially controlled manner to determine the extent of cell damage from the site of the collapse of microbubbles. Such a novel experimental design is proven to facilitate our effort to examine the altered cell viability and functionality by monitoring the transient calcium spiking activity in real-time. We now report that the effect of microcavitation depends on the distance from which cells are seeded, and the cell functionality assessed by calcium dynamics is significantly diminished in the cells located within ∼800 μm of the collapsing microbubbles. Both calcium influx across the cell membrane via N-type calcium channels and intraCellular calcium store are altered in response to microcavitation. Finally, the FDA-approved poloxamer 188 (P188) was used to reconstitute the compromised cell membrane and restore the cell’s reparative capability. This finding may lead to a feasible treatment for partially mitigating the tissue damage associated with bTBI
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impact of oxidative stress on Cellular Biomechanics and rho signaling in c2c12 myoblasts
Journal of Biomechanics, 2014Co-Authors: Shan Sun, Sing Wan Wong, Arthur F T Mak, Michael ChoAbstract:Abstract Although cells often can tolerate oxidative environments, abnormal oxidative stress has been identified in inflammation, cardiovascular and neurodegenerative diseases, and aging. The impact of oxidative stress on the Cellular Biomechanics is poorly understood, however. In this study, we used C2C12 myoblasts to investigate the effect of oxidative stress, mimicked by hydrogen peroxide (H2O2), on the cell elasticity (i.e., Young׳s modulus), viability, and production of intraCellular reactive oxygen species (ROS). To better understand the mechanisms underlying the impact of H2O2, we examined various effectors of the Rho signaling pathway, which has been shown to play a key role in the control of cell mechanics. H2O2 decreased the cell stiffness in a dose-dependent manner, caused cell death, and reduced the RhoA expression that was accompanied by down-regulation of α-actin, cytoskeleton-membrane linker proteins (ezrin–radixin–moesion proteins), and focal adhesion. Modulating the Rho signaling by using a Rho activator partially restored the cell stiffness, enhanced the cell viability, and decreased the intraCellular ROS level, suggesting a potential intervention strategy to maintain the Cellular biomechanical homeostasis and rescue cell damage in the threat of oxidative stresses.
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altered osteogenic commitment of human mesenchymal stem cells by erm protein dependent modulation of Cellular Biomechanics
Journal of Biomechanics, 2011Co-Authors: Igor A. Titushkin, Michael ChoAbstract:Abstract Cellular mechanics is known to play an important role in many Cellular functions including adhesion, migration, proliferation, and differentiation. Human mesenchymal stem cells (hMSCs) demonstrate unique mechanical properties distinct from fully differentiated cells. This observation suggests that the stem cell mechanics may be modulated to regulate the hMSCs' lineage commitment. Specifically, ERM (ezrin, radixin, moesin) proteins are known to mediate the membrane–cytoskeleton adhesion, cell elasticity, actin cytoskeleton organization, and therefore could serve as potential targets for modulation of the Cellular mechanics. Combining silencing RNA, atomic force microscopy, and laser optical tweezers, the role of the ERM proteins involved in the regulation of stem cell Biomechanics and osteogenic differentiation was quantitatively determined. Transient ERM knockdown by RNAi causes disassembly of actin stress fibers and focal adhesions, a decrease in the cell stiffness, and membrane separation from the cytoskeleton. The silencing RNA treatment not only induced mechanical changes in stem cells but impaired biochemically-directed osteogenic differentiation. The intact actin cytoskeleton and focal adhesions of hMSCs appear critical for the osteogenic induction. Thus, ERM knockdown modulates the dynamics of cell mechanical changes during hMSC differentiation and regulates the expression of tissue specific molecular markers. These findings are of particular interest for modulation of the Cellular Biomechanics to control hMSCs' activities and fate in tissue engineering, regenerative medicine, and other stem cell-based therapeutic applications.
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adipogenic commitment of mesenchymal stem cells regulated by erm proteins mediated Cellular Biomechanics
Biophysical Journal, 2010Co-Authors: Igor A. Titushkin, Michael ChoAbstract:Cellular mechanics plays an important role in many cell activities including, to name just a few, morphogenesis, migration, proliferation, and differentiation. Adipogenic differentiation of human mesenchymal stem cells (hMSC) is found to cause a decrease both in the cytoskeleton elasticity and membrane-cytoskeleton association and is mediated by the ERM (ezrin, radixin, moesin) family of protein linkers. Transient knockdown of ERM proteins with RNAi technique results in membrane separation from the cytoskeleton in hMSC as determined using optically extracted membrane tethers. In addition, it leads to a substantial decrease in the cell elasticity measured using AFM microindentation. This cytoskeleton Biomechanics modulation is likely mediated by a partial disassembly of actin stress fibers and focal adhesions during ERM linkers knockdown. Although this kind of treatment induces changes in the stem cell mechanical properties similar to those of fully differentiated adipocytes, hMSC commitment by soluble adipogenic factors is impaired in the ERM-deficient cells. However, cell mechanics modulation by ERM knockdown following a 6-day adipogenic induction by soluble factors seems to facilitate adipogenesis. This observation is confirmed by up-regulation of lipid vacuoles formation and adipocyte-specific markers expression. Intact cytoskeleton and/or focal adhesion-mediated signaling appear to be the prerequisites for early adipogenic commitment of hMSC. However, following the initial biochemically-induced commitment, the Cellular mechanics plays an increasingly important role in enhancing the stem cell differentiation efficiency. Our findings have significant implications for tissue engineering, reconstructive and cosmetic surgery, and other stem cell-based therapeutic applications.
Igor A. Titushkin - One of the best experts on this subject based on the ideXlab platform.
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altered osteogenic commitment of human mesenchymal stem cells by erm protein dependent modulation of Cellular Biomechanics
Journal of Biomechanics, 2011Co-Authors: Igor A. Titushkin, Michael ChoAbstract:Abstract Cellular mechanics is known to play an important role in many Cellular functions including adhesion, migration, proliferation, and differentiation. Human mesenchymal stem cells (hMSCs) demonstrate unique mechanical properties distinct from fully differentiated cells. This observation suggests that the stem cell mechanics may be modulated to regulate the hMSCs' lineage commitment. Specifically, ERM (ezrin, radixin, moesin) proteins are known to mediate the membrane–cytoskeleton adhesion, cell elasticity, actin cytoskeleton organization, and therefore could serve as potential targets for modulation of the Cellular mechanics. Combining silencing RNA, atomic force microscopy, and laser optical tweezers, the role of the ERM proteins involved in the regulation of stem cell Biomechanics and osteogenic differentiation was quantitatively determined. Transient ERM knockdown by RNAi causes disassembly of actin stress fibers and focal adhesions, a decrease in the cell stiffness, and membrane separation from the cytoskeleton. The silencing RNA treatment not only induced mechanical changes in stem cells but impaired biochemically-directed osteogenic differentiation. The intact actin cytoskeleton and focal adhesions of hMSCs appear critical for the osteogenic induction. Thus, ERM knockdown modulates the dynamics of cell mechanical changes during hMSC differentiation and regulates the expression of tissue specific molecular markers. These findings are of particular interest for modulation of the Cellular Biomechanics to control hMSCs' activities and fate in tissue engineering, regenerative medicine, and other stem cell-based therapeutic applications.
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adipogenic commitment of mesenchymal stem cells regulated by erm proteins mediated Cellular Biomechanics
Biophysical Journal, 2010Co-Authors: Igor A. Titushkin, Michael ChoAbstract:Cellular mechanics plays an important role in many cell activities including, to name just a few, morphogenesis, migration, proliferation, and differentiation. Adipogenic differentiation of human mesenchymal stem cells (hMSC) is found to cause a decrease both in the cytoskeleton elasticity and membrane-cytoskeleton association and is mediated by the ERM (ezrin, radixin, moesin) family of protein linkers. Transient knockdown of ERM proteins with RNAi technique results in membrane separation from the cytoskeleton in hMSC as determined using optically extracted membrane tethers. In addition, it leads to a substantial decrease in the cell elasticity measured using AFM microindentation. This cytoskeleton Biomechanics modulation is likely mediated by a partial disassembly of actin stress fibers and focal adhesions during ERM linkers knockdown. Although this kind of treatment induces changes in the stem cell mechanical properties similar to those of fully differentiated adipocytes, hMSC commitment by soluble adipogenic factors is impaired in the ERM-deficient cells. However, cell mechanics modulation by ERM knockdown following a 6-day adipogenic induction by soluble factors seems to facilitate adipogenesis. This observation is confirmed by up-regulation of lipid vacuoles formation and adipocyte-specific markers expression. Intact cytoskeleton and/or focal adhesion-mediated signaling appear to be the prerequisites for early adipogenic commitment of hMSC. However, following the initial biochemically-induced commitment, the Cellular mechanics plays an increasingly important role in enhancing the stem cell differentiation efficiency. Our findings have significant implications for tissue engineering, reconstructive and cosmetic surgery, and other stem cell-based therapeutic applications.
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Controlling Cellular Biomechanics of human mesenchymal stem cells
2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009Co-Authors: Igor A. TitushkinAbstract:The therapeutic efficacy of human mesenchymal stem cells (hMSCs) depends on proper characterization and control of their unique biological, mechanical and physicochemical properties. For example, Cellular Biomechanics and environmental mechanical cues have been shown to critically influence cell commitment to a particular lineage. We characterized biomechanical properties of hMSCs including cytoskeleton elasticity and plasma membrane/cytoskeleton coupling. As expected, during osteogenic differentiation of hMSCs, the Cellular Biomechanics is remodeled, and such remodeling precedes up-regulation of the osteogenic markers. Further, application of an electrical stimulation modulates the Cellular Biomechanics and therefore may be used to facilitate stem cell differentiation for stem cell-based tissue engineering.
Massimo Vassalli - One of the best experts on this subject based on the ideXlab platform.
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Biophysical phenotyping of mesenchymal stem cells along the osteogenic differentiation pathway
Cell Biology and Toxicology, 2021Co-Authors: Paola Gavazzo, Federica Viti, Hannah Donnelly, Mariana Azevedo Gonzalez Oliva, Manuel Salmeron-sanchez, Matthew J. Dalby, Massimo VassalliAbstract:Mesenchymal stem cells represent an important resource, for bone regenerative medicine and therapeutic applications. This review focuses on new advancements and biophysical tools which exploit different physical and chemical markers of mesenchymal stem cell populations, to finely characterize phenotype changes along their osteogenic differentiation process. Special attention is paid to recently developed label-free methods, which allow monitoring cell populations with minimal invasiveness. Among them, quantitative phase imaging, suitable for single-cell morphometric analysis, and nanoindentation, functional to Cellular Biomechanics investigation. Moreover, the pool of ion channels expressed in cells during differentiation is discussed, with particular interest for calcium homoeostasis.Altogether, a biophysical perspective of osteogenesis is proposed, offering a valuable tool for the assessment of the cell stage, but also suggesting potential physiological links between apparently independent phenomena.
Irena Levitan - One of the best experts on this subject based on the ideXlab platform.
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hypotonic challenge of endothelial cells increases membrane stiffness with no effect on tether force
Biophysical Journal, 2018Co-Authors: Manuela A Ayee, Elizabeth Lemaster, Tao Teng, James C Lee, Irena LevitanAbstract:Abstract Regulation of cell volume is a fundamental property of all mammalian cells. Multiple signaling pathways are known to be activated by cell swelling and to contribute to cell volume homeostasis. Although cell mechanics and membrane tension have been proposed to couple cell swelling to signaling pathways, the impact of swelling on Cellular Biomechanics and membrane tension have yet to be fully elucidated. In this study, we use atomic force microscopy under isotonic and hypotonic conditions to measure mechanical properties of endothelial membranes including membrane stiffness, which reflects the stiffness of the submembrane cytoskeleton complex, and the force required for membrane tether formation, reflecting membrane tension and membrane-cytoskeleton attachment. We find that hypotonic swelling results in significant stiffening of the endothelial membrane without a change in membrane tension/membrane-cytoskeleton attachment. Furthermore, depolymerization of F-actin, which, as expected, results in a dramatic decrease in the Cellular elastic modulus of both the membrane and the deeper cytoskeleton, indicating a collapse of the cytoskeleton scaffold, does not abrogate swelling-induced stiffening of the membrane. Instead, this swelling-induced stiffening of the membrane is enhanced. We propose that the membrane stiffening should be attributed to an increase in hydrostatic pressure that results from an influx of solutes and water into the cells. Most importantly, our results suggest that increased hydrostatic pressure, rather than changes in membrane tension, could be responsible for activating volume-sensitive mechanisms in hypotonically swollen cells.
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micropipette aspiration of substrate attached cells to estimate cell stiffness
Journal of Visualized Experiments, 2012Co-Authors: Frank Kuhr, Fitzroy J Byfield, Irena LevitanAbstract:Growing number of studies show that biomechanical properties of individual cells play major roles in multiple Cellular functions, including cell proliferation, differentiation, migration and cell-cell interactions. The two key parameters of Cellular Biomechanics are Cellular deformability or stiffness and the ability of the cells to contract and generate force. Here we describe a quick and simple method to estimate cell stiffness by measuring the degree of membrane deformation in response to negative pressure applied by a glass micropipette to the cell surface, a technique that is called Micropipette Aspiration or Microaspiration. Microaspiration is performed by pulling a glass capillary to create a micropipette with a very small tip (2-50 μm diameter depending on the size of a cell or a tissue sample), which is then connected to a pneumatic pressure transducer and brought to a close vicinity of a cell under a microscope. When the tip of the pipette touches a cell, a step of negative pressure is applied to the pipette by the pneumatic pressure transducer generating well-defined pressure on the cell membrane. In response to pressure, the membrane is aspirated into the pipette and progressive membrane deformation or "membrane projection" into the pipette is measured as a function of time. The basic principle of this experimental approach is that the degree of membrane deformation in response to a defined mechanical force is a function of membrane stiffness. The stiffer the membrane is, the slower the rate of membrane deformation and the shorter the steady-state aspiration length.The technique can be performed on isolated cells, both in suspension and substrate-attached, large organelles, and liposomes. Analysis is performed by comparing maximal membrane deformations achieved under a given pressure for different cell populations or experimental conditions. A "stiffness coefficient" is estimated by plotting the aspirated length of membrane deformation as a function of the applied pressure. Furthermore, the data can be further analyzed to estimate the Young's modulus of the cells (E), the most common parameter to characterize stiffness of materials. It is important to note that plasma membranes of eukaryotic cells can be viewed as a bi-component system where membrane lipid bilayer is underlied by the sub-membrane cytoskeleton and that it is the cytoskeleton that constitutes the mechanical scaffold of the membrane and dominates the deformability of the Cellular envelope. This approach, therefore, allows probing the biomechanical properties of the sub-membrane cytoskeleton.
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lipid rafts in membrane cytoskeleton interactions and control of Cellular Biomechanics actions of oxldl
Antioxidants & Redox Signaling, 2007Co-Authors: Irena Levitan, Keith J GoochAbstract:Membrane-cytoskeleton coupling is known to play major roles in a plethora of Cellular responses, such as cell growth, differentiation, polarization, motility, and others. In this review, the authors discuss the growing amount of evidence indicating that membrane-cytoskeleton interactions are regulated by the lipid composition of the plasma membrane, suggesting that cholesterol-rich membrane domains (lipid rafts), including caveolae, are essential for membrane-cytoskeleton coupling. Several models for raft-cytoskeleton interactions are discussed. Also described is the evidence suggesting that raft-cytoskeleton interactions play key roles in several cytoskeleton-dependent processes, particularly in the regulation of Cellular biomechanical properties. To address further the physiological significance of raft-cytoskeleton coupling, the authors focus on the impact of oxidized low density lipoproteins, one of the major cholesterol carriers and proatherogenic factors, on the integrity of lipid rafts/caveolae, and on the organization of the cytoskeleton. Finally, the authors review the recent studies showing that oxLDL and cholesterol depletion have similar impacts on the biomechanical properties of vascular endothelial cells, which in turn affect endothelial angiogenic potential.
Kazuaki Nagayama - One of the best experts on this subject based on the ideXlab platform.
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tensile properties of vascular smooth muscle cells bridging vascular and Cellular Biomechanics
Journal of Biomechanics, 2012Co-Authors: Takeo Matsumoto, Kazuaki NagayamaAbstract:Vascular walls change their dimensions and mechanical properties adaptively in response to blood pressure. Because these responses are driven by the smooth muscle cells (SMCs) in the media, a detailed understanding of the mechanical environment of the SMCs should reveal the mechanism of the adaptation. As the mechanical properties of the media are highly heterogeneous at the microscopic level, the mechanical properties of the cells should be measured directly. The tensile properties of SMCs are, thus, important to reveal the microscopic mechanical environment in vascular tissues; their tensile properties have a close correlation with the distribution and arrangement of elements of the cytoskeletal networks, such as stress fibers and microtubules. In this review, we first introduce the experimental techniques used for tensile testing and discuss the various factors affecting the tensile properties of vascular SMCs. Cytoskeletal networks are particularly important for the mechanical properties of a cell and its mechanism of mechanotransduction; thus, the mechanical properties of cytoskeletal filaments and their effects on whole-cell mechanical properties are discussed with special attention to the balance of intraCellular forces among the intraCellular components that determines the force applied to each element of the cytoskeletal filaments, which is the key to revealing the mechanotransduction events regulating mechanical adaptation. Lastly, we suggest future directions to connect tissue and cell mechanics and to elucidate the mechanism of mechanical adaptation, one of the key issues of cardiovascular solid Biomechanics.