A Computational Study of Stress Fiber-Focal Adhesion Dynamics Governing Cell Contractility

Maraldi, Mirko; Valero, Clara; Garikipati, Krishnakumar

doi:10.1016/j.bpj.2014.03.027

Cited by 9 publications

(15 citation statements)

References 41 publications

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“…3C). This observation suggests that FACs could be made to disassemble at 0° at long duration as a result of the persistent action of a gravity vector (28). Even in this case, the cell is mechanically stable as its anchorage strength is determined by total FAC area with similar values at 180 or 90° (Fig.…”

Section: Resultsmentioning

confidence: 99%

Mechanical remodeling of normally sized mammalian cells under a gravity vector

et al. 2016

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Translocation of the dense nucleus along a gravity vector initiates mechanical remodeling of a cell, but the underlying mechanisms of cytoskeletal network and focal adhesion complex (FAC) reorganization in a mammalian cell remain unclear. We quantified the remodeling of an MC3T3-E1 cell placed in upward-, downward-, or edgeon-orientated substrate. Nucleus longitudinal translocation presents a high value in downward orientation at 24 h or in edge-on orientation at 72 h, which is consistent with orientation-dependent distribution of perinuclear actin stress fibers and vimentin cords. Redistribution of total FAC area and fractionized super mature adhesion number coordinates this dependence at short duration. This orientation-dependent remodeling is associated with nucleus flattering and lamin A/C phosphorylation. Actin depolymerization or Rho-associated protein kinase signaling inhibition abolishes the orientation dependence of nucleus translocation, whereas tubulin polymerization inhibition or vimentin disruption reserves the dependence. A biomechanical model is therefore proposed for integrating the mechanosensing of nucleus translocation with cytoskeletal remodeling and FAC reorganization induced by a gravity vector.-Zhang, C., Zhou, L., Zhang, F., Lü, D., Li, N., Zheng, L., Xu, Y., Li, Z., Sun, S., Long, M. Mechanical remodeling of normally-sized mammalian cells under gravity vector. FASEB J. 31, 000-000 (2017). www.fasebj.org KEY WORDS: gravity-directed • mechanosensing • nucleus translocation • cytoskeletal remodeling • FAC reorganization Cells on Earth are subject to a variety of mechanical forces, including gravity. Statolith, or amyloplast, has long been assumed to be a gravity receptor for plant species to sense, transduce, and respond to altered gravity (1); however, little is known about mechanisms that underlie gravisensing and gravitransduction in mammalian cells, even though a body of evidence confirms the effect of gravity on their biological responses (2). Conceptual studies have indicated that the spreading and mitosis of normally sized (;10 1 mm) mammalian cells are sensitive to the change in gravity vector. For example, randomizing the direction of gravity has no effect on the division orientation of Chinese hamster ovary cells that are point-attached in a vertical plane (3). Inversion of culture substrate cannot alter the number and function of attached osteoblasts, even though an immediate response-diminished viable osteoblast number-is observed in sparse, early cultures (4). Cell area, nucleus translocation, cell cycle, and F-actin reorganization vary significantly in a duration-dependent manner when Ros 17/2.8 cells make up a monolayer and are spread on downward-or edge-on-orientated substrate compared with those on an upward orientation (5). More quantitative analysis is observed in large-sized Xenopus oocytes (;1 mm), where the nucleolus sedimentation is dominant compared with the thermal fluctuation at gravity potential . thermal energy scale (6), which implies that the sediment...

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Section: Resultsmentioning

confidence: 99%

Mechanical remodeling of normally sized mammalian cells under a gravity vector

et al. 2016

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“…The underlying functional principle is the interaction between cell-to-surface complexes, like focal adhesions and cell tension, generating cytoskeletal elements, like f-actin fibers. In their comprehensive theoretical approach, Maraldi and coworkers formulated optimal ratios between adhesion and contraction cell activity [ 50 ]. Based on this formulation, our periodic pattern serves as a surface that positions an individual cell to make a decision based on different ratios of surface adhesion protein complexes and cell tension-generating cytoskeleton elements.…”

Section: Discussionmentioning

confidence: 99%

Tissue-Mimicking Geometrical Constraints Stimulate Tissue-Like Constitution and Activity of Mouse Neonatal and Human-Induced Pluripotent Stem Cell-Derived Cardiac Myocytes

Pilarczyk

Raulf

Gunkel³

et al. 2016

JFB

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The present work addresses the question of to what extent a geometrical support acts as a physiological determining template in the setup of artificial cardiac tissue. Surface patterns with alternating concave to convex transitions of cell size dimensions were used to organize and orientate human-induced pluripotent stem cell (hIPSC)-derived cardiac myocytes and mouse neonatal cardiac myocytes. The shape of the cells, as well as the organization of the contractile apparatus recapitulates the anisotropic line pattern geometry being derived from tissue geometry motives. The intracellular organization of the contractile apparatus and the cell coupling via gap junctions of cell assemblies growing in a random or organized pattern were examined. Cell spatial and temporal coordinated excitation and contraction has been compared on plain and patterned substrates. While the α-actinin cytoskeletal organization is comparable to terminally-developed native ventricular tissue, connexin-43 expression does not recapitulate gap junction distribution of heart muscle tissue. However, coordinated contractions could be observed. The results of tissue-like cell ensemble organization open new insights into geometry-dependent cell organization, the cultivation of artificial heart tissue from stem cells and the anisotropy-dependent activity of therapeutic compounds.

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“…The widths of the stress fibers are known to be strongly correlated with both cell contractility or activities of actin regulatory pathways [ 1 , 23 , 60 – 62 ], and thus can serve as a useful read-out of cell mechanical properties. Although this can be calculated interactively from line profile of stress fibers, due to the large numbers of stress fibers per cells, we sought to automate this process.…”

Section: Methodsmentioning

confidence: 99%

An integrated enhancement and reconstruction strategy for the quantitative extraction of actin stress fibers from fluorescence micrographs

Zhang¹,

Xia²,

Kanchanawong

2017

BMC Bioinformatics

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BackgroundThe stress fibers are prominent organization of actin filaments that perform important functions in cellular processes such as migration, polarization, and traction force generation, and whose collective organization reflects the physiological and mechanical activities of the cells. Easily visualized by fluorescence microscopy, the stress fibers are widely used as qualitative descriptors of cell phenotypes. However, due to the complexity of the stress fibers and the presence of other actin-containing cellular features, images of stress fibers are relatively challenging to quantitatively analyze using previously developed approaches, requiring significant user intervention. This poses a challenge for the automation of their detection, segmentation, and quantitative analysis.ResultHere we describe an open-source software package, SFEX (Stress Fiber Extractor), which is geared for efficient enhancement, segmentation, and analysis of actin stress fibers in adherent tissue culture cells. Our method made use of a carefully chosen image filtering technique to enhance filamentous structures, effectively facilitating the detection and segmentation of stress fibers by binary thresholding. We subdivided the skeletons of stress fiber traces into piecewise-linear fragments, and used a set of geometric criteria to reconstruct the stress fiber networks by pairing appropriate fiber fragments. Our strategy enables the trajectory of a majority of stress fibers within the cells to be comprehensively extracted. We also present a method for quantifying the dimensions of the stress fibers using an image gradient-based approach. We determine the optimal parameter space using sensitivity analysis, and demonstrate the utility of our approach by analyzing actin stress fibers in cells cultured on various micropattern substrates.ConclusionWe present an open-source graphically-interfaced computational tool for the extraction and quantification of stress fibers in adherent cells with minimal user input. This facilitates the automated extraction of actin stress fibers from fluorescence images. We highlight their potential uses by analyzing images of cells with shapes constrained by fibronectin micropatterns. The method we reported here could serve as the first step in the detection and characterization of the spatial properties of actin stress fibers to enable further detailed morphological analysis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12859-017-1684-y) contains supplementary material, which is available to authorized users.

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A Computational Study of Stress Fiber-Focal Adhesion Dynamics Governing Cell Contractility

Cited by 9 publications

References 41 publications

Mechanical remodeling of normally sized mammalian cells under a gravity vector

Mechanical remodeling of normally sized mammalian cells under a gravity vector

Tissue-Mimicking Geometrical Constraints Stimulate Tissue-Like Constitution and Activity of Mouse Neonatal and Human-Induced Pluripotent Stem Cell-Derived Cardiac Myocytes

An integrated enhancement and reconstruction strategy for the quantitative extraction of actin stress fibers from fluorescence micrographs

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