Cellular mechanoadaptation to substrate mechanical properties: contributions of substrate stiffness and thickness to cell stiffness measurements using AFM

Ezrin, a member of the ERM (ezrin/radixin/moesin) family of proteins, serves as a crosslinker between the plasma membrane and the actin cytoskeleton. By doing so, it provides structural links to strengthen the connection between the cell cortex and the plasma membrane, acting also as a signal transducer in multiple pathways during migration, proliferation, and endocytosis. In this study, we investigated the role of ezrin phosphorylation and its intracellular localization on cell motility, cytoskeleton organization, and cell stiffness, using fluorescence live-cell imaging, image quantification, and atomic force microscopy (AFM). Our results show that cells expressing constitutively active ezrin T567D (phosphomimetic) migrate faster and in a more directional manner, especially when ezrin accumulates at the cell rear. Similarly, image quantification results reveal that transfection with ezrin T567D alters the cell’s gross morphology and decreases cortical stiffness. In contrast, constitutively inactive ezrin T567A accumulates around the nucleus, and although it does not impair cell migration, it leads to a significant buildup of actin fibers, a decrease in nuclear volume, and an increase in cytoskeletal stiffness. Finally, cell transfection with the dominant negative ezrin FERM domain induces significant morphological and nuclear changes and affects actin, microtubules, and the intermediate filament vimentin, resulting in cytoskeletal fibers that are longer, thicker, and more aligned. Collectively, our results suggest that ezrin’s phosphorylation state and its intracellular localization plays a pivotal role in cell migration, modulating also biophysical properties, such as membrane–cortex linkage, cytoskeletal and nuclear organization, and the mechanical properties of cells.

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Substrate Stiffness Affects Laminin-332 Matrix Deposition in Cultured Keretinocytes

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176292 ◽

2007 ◽

Author(s):

Abel L. Thangawng ◽

Rodney S. Ruoff ◽

Jonathan C. Jones ◽

Matthew R. Glucksberg

Keyword(s):

Mechanical Properties ◽

Extracellular Matrix ◽

Cell Motility ◽

Substrate Stiffness ◽

Mechanical Environment ◽

Matrix Deposition ◽

Laminin 332 ◽

Substrate Influence

It has been reported that the mechanical properties of a substrate influence cell motility, morphology, and adhesion [1–3]. This work is an attempt to move a step further beyond cells’ sensing the mechanical properties of their environment, by determining whether the secretion and assembly of laminin extracellular matrix is regulated by the mechanical environment in which the cell is placed. We hypothesize that this matrix then influences the behavior of the cell, particularly with regard to its motility.

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Contribution of intermediate filaments to cell stiffness, stiffening, and growth

AJP Cell Physiology ◽

10.1152/ajpcell.2000.279.1.c188 ◽

2000 ◽

Vol 279 (1) ◽

pp. C188-C194 ◽

Cited By ~ 195

Author(s):

Ning Wang ◽

Dimitrije Stamenović

Keyword(s):

Mechanical Properties ◽

Applied Stress ◽

Extended Period ◽

Direct Consequence ◽

Cell Stiffness ◽

Cell Integrity ◽

Wild Type ◽

The Difference ◽

High Degree

It has been shown previously that intermediate filament (IF) gels in vitro exhibit stiffening at high-applied stress, and it was suggested that this stiffening property of IFs might be important for maintaining cell integrity at large deformations (Janmey PA, Evtenever V, Traub P, and Schliwa M, J Cell Biol 113: 155–160, 1991). In this study, the contribution of IFs to cell mechanical behavior was investigated by measuring cell stiffness in response to applied stress in adherent wild-type and vimentin-deficient fibroblasts using magnetic twisting cytometry. It was found that vimentin-deficient cells were less stiff and exhibited less stiffening than wild-type cells, except at the lowest applied stress (10 dyn/cm2) where the difference in the stiffness was not significant. Similar results were obtained from measurements on wild-type fibroblasts and endothelial cells after vimentin IFs were disrupted by acrylamide. If, however, cells were plated over an extended period of time (16 h), they exhibited a significantly greater stiffness before than after acrylamide, even at the lowest applied stress. A possible reason could be that the initially slack IFs became fully extended due to a high degree of cell spreading and thus contributed to the transmission of mechanical stress across the cell. Taken together, these findings were consistent with the notion that IFs play important roles in the mechanical properties of the cell during large deformation. The experimental data also showed that depleting or disrupting IFs reduced, but did not entirely abolish, cell stiffening. This residual stiffening might be attributed to the effect of geometrical realignment of cytoskeletal filaments in the direction of applied load. It was also found that vimentin-deficient cells exhibited a slower rate of proliferation and DNA synthesis than wild-type cells. This could be a direct consequence of the absence of the intracellular IFs that may be necessary for efficient mediation of mechanical signals within the cell. Taken together, results of this study suggest that IFs play important roles in the mechanical properties of cells and in cell growth.

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Astrogliosis in a dish: substrate stiffness induces astrogliosis in primary rat astrocytes

RSC Advances ◽

10.1039/c5ra25916a ◽

2016 ◽

Vol 6 (41) ◽

pp. 34447-34457 ◽

Cited By ~ 11

Author(s):

Christina L. Wilson ◽

Stephen L. Hayward ◽

Srivatsan Kidambi

Keyword(s):

Mechanical Properties ◽

Substrate Stiffness ◽

Cellular Microenvironment ◽

Rat Astrocytes

Mechanical properties of the cellular microenvironment induces astrogliosisin vitroin primary rat astrocytes.

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Cell stiffness and receptors: evidence for cytoskeletal subnetworks

AJP Cell Physiology ◽

10.1152/ajpcell.00056.2004 ◽

2005 ◽

Vol 288 (1) ◽

pp. C72-C80 ◽

Cited By ~ 33

Author(s):

Hayden Huang ◽

Jeremy Sylvan ◽

Maxine Jonas ◽

Rita Barresi ◽

Peter T. C. So ◽

...

Keyword(s):

Mechanical Properties ◽

Magnetic Beads ◽

Membrane Receptors ◽

Cell Stiffness ◽

Cell Type ◽

Specific Receptor ◽

Mechanical Stiffness ◽

Intracellular Space ◽

Physical Response ◽

Cytoskeletal Networks

Viscoelastic models of cells often treat cells as homogeneous objects. However, studies have demonstrated that cellular properties are local and can change dramatically on the basis of the location probed. Because membrane receptors are linked in various ways to the intracellular space, with some receptors linking to the cytoskeleton and others diffusing freely without apparent linkages, the cellular physical response to mechanical stresses is expected to depend on the receptor engaged. In this study, we tested the hypothesis that cellular mechanical stiffness as measured via cytoskeletally linked receptors is greater than stiffness measured via receptors that are not cytoskeletally linked. We used a magnetic micromanipulator to apply linear stresses to magnetic beads attached to living cells via selected receptors. One of the receptor classes probed, the dystroglycan receptors, is linked to the cytoskeleton, while the other, the transferrin receptors, is not. Fibronectin-coated beads were used to test cellular mechanical properties of the cytoskeleton without membrane dependence by allowing the beads to endocytose. For epithelial cells, transferrin-dependent stiffness and endocytosed bead-dependent stiffness were similar, while dystroglycan-dependent stiffness was significantly lower. For smooth muscle cells, dystroglycan-dependent stiffness was similar to the endocytosed bead-dependent stiffness, while the transferrin-dependent stiffness was lower. The conclusion of this study is that the measured cellular stiffness is critically influenced by specific receptor linkage and by cell type and raises the intriguing possibility of the existence of separate cytoskeletal networks with distinct mechanical properties that link different classes of receptors.

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Development of an in-process micro tensile tester and its application for measurement of the mechanical properties and adhesion forces of cells (Quantitative analysis of a cancer cell stiffness and adhesion forces)

Transactions of the JSME (in Japanese) ◽

10.1299/transjsme.20-00311 ◽

2020 ◽

Vol 86 (892) ◽

pp. 20-00311-20-00311

Author(s):

Shota OBATA ◽

Kazuaki NAGAYAMA

Keyword(s):

Mechanical Properties ◽

Quantitative Analysis ◽

Cancer Cell ◽

Cell Stiffness ◽

Adhesion Forces ◽

Tensile Tester

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Effect of Substrate Stiffness on Physicochemical Properties of Normal and Fibrotic Lung Fibroblasts

Materials ◽

10.3390/ma13204495 ◽

2020 ◽

Vol 13 (20) ◽

pp. 4495

Author(s):

Joanna Raczkowska ◽

Barbara Orzechowska ◽

Sabina Patryas ◽

Kamil Awsiuk ◽

Andrzej Kubiak ◽

...

Keyword(s):

Mechanical Properties ◽

Idiopathic Pulmonary Fibrosis ◽

Pulmonary Fibrosis ◽

Physicochemical Properties ◽

Chemical Properties ◽

Principal Component ◽

Lung Fibroblasts ◽

Substrate Stiffness ◽

Significant Difference ◽

The Impact

The presented research aims to verify whether physicochemical properties of lung fibroblasts, modified by substrate stiffness, can be used to discriminate between normal and fibrotic cells from idiopathic pulmonary fibrosis (IPF). The impact of polydimethylsiloxane (PDMS) substrate stiffness on the physicochemical properties of normal (LL24) and IPF-derived lung fibroblasts (LL97A) was examined in detail. The growth and elasticity of cells were assessed using fluorescence microscopy and atomic force microscopy working in force spectroscopy mode, respectively. The number of fibroblasts, as well as their shape and the arrangement, strongly depends on the mechanical properties of the substrate. Moreover, normal fibroblasts remain more rigid as compared to their fibrotic counterparts, which may indicate the impairments of IPF-derived fibroblasts induced by the fibrosis process. The chemical properties of normal and IPF-derived lung fibroblasts inspected using time-of-flight secondary ion mass spectrometry, and analyzed complexly with principal component analysis (PCA), show a significant difference in the distribution of cholesterol and phospholipids. Based on the observed distinctions between healthy and fibrotic cells, the mechanical properties of cells may serve as prospective diagnostic biomarkers enabling fast and reliable identification of idiopathic pulmonary fibrosis (IPF).

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The Effect of Substrate Stiffness on Endothelial Cell Stiffness and Monolayer Permeability in Response to Inflammation

10.17918/etd-6674 ◽

2021 ◽

Author(s):

Rebecca Lownes Urbano

Keyword(s):

Endothelial Cell ◽

Substrate Stiffness ◽

Cell Stiffness ◽

Monolayer Permeability

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Abstract 13664: Membrane Stiffness as a Function of Plakophilin-2 Expression: Implications to Arrhythmogenic Right Ventricular Cardiomyopathy

Circulation ◽

10.1161/circ.142.suppl_3.13664 ◽

2020 ◽

Vol 142 (Suppl_3) ◽

Author(s):

Pamela Swiatlowska ◽

Mario Delmar

Keyword(s):

Mechanical Properties ◽

Right Ventricular ◽

Arrhythmogenic Right Ventricular Cardiomyopathy ◽

Inverse Correlation ◽

Substrate Stiffness ◽

Disease Stage ◽

Membrane Mechanics ◽

Time Points ◽

Plakophilin 2 ◽

Membrane Stiffness

Mutations in PKP2 , the gene coding for the desmosomal protein Plakophilin-2 (PKP2), can lead to an inheritable cardiac disease called Arrhythmogenic Right Ventricle Cardiomyopathy (ARVC). Various studies investigated the molecular and electrical properties of cardiomyocytes (CMs) with PKP2 deficiency. However, systematic studies on the mechanical properties of PKP2-deficient CMs, and their relation to the cardiomyopathic phenotype, are lacking. We studied the relation between PKP2 expression, membrane transverse Young’s modulus (tYM; a surrogate measure of membrane stiffness), and their correlation with tubulin expression and with substrate stiffness. Left and right ventricular (LV, RV) CMs were isolated from murine hearts control (ctrl), or with a cardiomyocyte-specific, tamoxifen-activated knockout of PKP2 (PKP2cKO). Three time points were studied: 14, 15 and 21 days post-tamoxifen injection (dpi). The phenotypes at these time points correspond to three disease stages: concealed, arrhythmogenic and cardiomyopathy of RV predominance, respectively. tYM was evaluated by mechanoSICM. Tubulin was visualized by confocal microscopy. tYM in LV myocytes from control hearts showed a tendency toward higher values when compared to RV myocytes (LV 2.9±0.2 kPa vs RV 2.6±0.2 kPa, n=53-59). At 14 dpi, LV and RV PKP2cKO CMs were softer than ctrl (LV 2.1±0.1 kPa, RV 2.1±0.1 kPa vs ctrl, n=30-59). The trend reversed a day later and by 21 dpi there was a clear increase in tYM, particularly in PKP2cKO RV myocytes (LV 4.5±0.3 kPa, RV 4.8±0.6 kPa vs ctrl, n=44-59). Z-groove index, a parameter of membrane organization, decreased in PKP2cKO CMs. Increased tYM at 21 dpi corresponded to upregulation of α-tubulin and particularly, acetylated tubulin, which was reduced at 14dpi but went up in 21dpi. We also observed an inverse correlation between membrane tYM, and substrate stiffness. We conclude that loss of PKP2 expression affects, in a disease stage-specific manner, CM mechanical properties and the MT network organization. Whether these effects are correlative or one is consequence of the other, remains to be determined. We speculate that changes in membrane mechanics at the single cell level are a component of mechanical dysfunction in hearts affected with ARVC.

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