Continuous Visualization of Morphological Changes in Endothelial Cells in Response to Cyclic Stretch

Iwayoshi, Shunsuke; Furukawa, Katsuko; Ushida, Takashi

doi:10.1299/jsmec.49.545

Cited by 6 publications

(6 citation statements)

References 24 publications

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“…The endothelial cell response to cyclic stretch is as diverse and complex as that for fluid flow. The effects of cyclic stretch have been well-reviewed by several investigators and are summarized for the reader. ,,, Morphologically, endothelial cells elongate and align perpendicular to a uniaxial stretch direction, and the response is enhanced with greater applied strain and frequency, as shown for strains up to 10% and frequencies up to 1.5 Hz. ,− This has been visualized by actin stress fiber reorganization, which occurs to minimize tensile forces acting on the fibers . Conversely, no alignment is achieved for nonuniaxial stretch .…”

Section: Responding To the Mechanical Microenvironmentmentioning

confidence: 99%

Vascular Endothelial Cell Behavior in Complex Mechanical Microenvironments

James

Allen

2018

ACS Biomater. Sci. Eng.

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The vascular mechanical microenvironment consists of a mixture of spatially and temporally changing mechanical forces. This exposes vascular endothelial cells to both hemodynamic forces (fluid flow, cyclic stretching, lateral pressure) and vessel forces (basement membrane mechanical and topographical properties). The vascular mechanical microenvironment is "complex" because these forces are dynamic and interrelated. Endothelial cells sense these forces through mechanosensory structures and transduce them into functional responses via mechanotransduction pathways, culminating in behavior directly affecting vascular health. Recent in vitro studies have shown that endothelial cells respond in nuanced and unique ways to combinations of hemodynamic and vessel forces as compared to any single mechanical force. Understanding the interactive effects of the complex mechanical microenvironment on vascular endothelial behavior offers the opportunity to design future biomaterials and biomedical devices from the bottom-up by engineering for the cellular response. This review describes and defines (1) the blood vessel structure, (2) the complex mechanical microenvironment of the vascular endothelium, (3) the process in which vascular endothelial cells sense mechanical forces, and (4) the effect of mechanical forces on vascular endothelial cells with specific attention to recent works investigating the influence of combinations of mechanical forces. We conclude this review by providing our perspective on how the field can move forward to elucidate the effects of the complex mechanical microenvironment on vascular endothelial cell behavior.

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Section: Responding To the Mechanical Microenvironmentmentioning

confidence: 99%

Vascular Endothelial Cell Behavior in Complex Mechanical Microenvironments

James

Allen

2018

ACS Biomater. Sci. Eng.

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“…One major challenge is to account for stretch-induced horizontal movements in xy and focus changes in z which become more pronounced at higher magnifications and at higher stretch magnitudes. 15 Using our device, movements in xyz are relatively consistent between stretch cycles and are linear with respect to the stretch magnitude. This feature enabled easy compensation for these effects by moving the microscope stage relative to the objective lens.…”

Section: Discussionmentioning

confidence: 82%

“…Devices exist that allow continuous low-resolution visualization of cells during substrate stretch to determine cell shape, 15 to track exogenous markers on cell surfaces, 2 or to measure [Ca 2+ ] i at the length scale of individual cells. 7 However, high-resolution imaging of intracellular structural dynamics during stretch is not readily feasible.…”

Section: Discussionmentioning

confidence: 99%

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A Stretching Device for High-Resolution Live-Cell Imaging

2010

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Several custom-built and commercially available devices are available to investigate cellular responses to substrate strain. However, analysis of structural dynamics by microscopy in living cells during stretch is not readily feasible. We describe a novel stretch device optimized for high-resolution live-cell imaging. The unit assembles onto standard inverted microscopes and applies constant magnitude or cyclic stretch at physiological magnitudes to cultured cells on elastic membranes. Interchangeable modular indenters enable delivery of equibiaxial and uniaxial stretch profiles. Strain analysis performed by tracking fluorescent microspheres adhered onto the substrate demonstrated reproducible application of stretch profiles. In endothelial cells transiently expressing EGFP-vimentin and paxillin-DsRed2 and subjected to constant magnitude equibiaxial stretch, the 2-D strain tensor demonstrated efficient transmission through the extracellular matrix and focal adhesions. Decreased transmission to the intermediate filament network was measured, and a heterogeneous spatial distribution of maximum stretch magnitude revealed discrete sites of strain focusing. Spatial correlation of vimentin and paxillin displacement vectors provided an estimate of the extent of mechanical coupling between the structures. Interestingly, switching the spatial profile of substrate strain reveals that actin-mediated edge ruffling is not desensitized to repeated mechano-stimulation. These initial observations show that the stretch device is compatible with live-cell microscopy and is a novel tool for measuring dynamic structural remodeling under mechanical strain.

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“…The proposed method can easily be adapted to cell mechanics studies to replace the commonly employed measure of strain. Quantification of sample deformation in cell stretching experiments is mostly based on the crosshead displacement [35][36][37] or FEM analysis [38,39]. Using cross-head displacement, strain is calculated as the ratio of the total elongation to the original length of the sample.…”

Section: Introductionmentioning

confidence: 99%

High-resolution spatiotemporal strain mapping reveals non-uniform deformation in micropatterned elastomers

Aksoy¹,

Rehman²,

Bayraktar³

et al. 2017

J. Micromech. Microeng.

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Micropatterns are generated on a vast selection of polymeric substrates for various applications ranging from stretchable electronics to cellular mechanobiological systems. When these patterned substrates are exposed to external loading, strain field is primarily affected by the presence of microfabricated structures and similarly by fabrication-related defects. The capturing of such nonhomogeneous strain fields is of utmost importance in cases where study of the mechanical behavior with a high spatial resolution is necessary. Image-based non-contact strain measurement techniques are favorable and have recently been extended to scanning tunneling microscope and scanning electron microscope images for the characterization of mechanical properties of metallic materials, e.g. steel and aluminum, at the microscale. A similar real-time analysis of strain heterogeneity in elastomers is yet to be achieved during the entire loading sequence. The available measurement methods for polymeric materials mostly depend on cross-head displacement or precalibrated strain values. Thus, they suffer either from the lack of any real-time analysis, spatiotemporal distribution or high resolution in addition to a combination of these factors. In this work, these challenges are addressed by integrating a tensile stretcher with an inverted optical microscope and developing a subpixel particle tracking algorithm. As a proof of concept, the patterns with a critical dimension of 200 µm are generated on polydimethylsiloxane substrates and strain distribution in the vicinity of the patterns is captured with a high spatiotemporal resolution. In the field of strain measurement, there is always a tradeoff between minimum measurable strain value and spatial resolution. Current noncontact techniques on elastomers can deliver a strain resolution of 0.001% over a minimum length of 5 cm. More importantly, inhomogeneities within this quite large region cannot be captured. The proposed technique can overcome this challenge and provides a displacement measurement resolution of 116 nm and a strain resolution of 0.04% over a gage length of 300 µm. Similarly, the ability to capture inhomogeneities is demonstrated by mapping strain around a thru-hole. The robustness of the technique is also evaluated, where no appreciable change in strain measurement is observed despite the significant variations imposed on the measurement mesh. The proposed approach introduces critical improvements for the determination of displacement and strain gradients in elastomers regarding the real-time nature of strain mapping with a microscale spatial resolution.

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Continuous Visualization of Morphological Changes in Endothelial Cells in Response to Cyclic Stretch

Cited by 6 publications

References 24 publications

Vascular Endothelial Cell Behavior in Complex Mechanical Microenvironments

Vascular Endothelial Cell Behavior in Complex Mechanical Microenvironments

A Stretching Device for High-Resolution Live-Cell Imaging

High-resolution spatiotemporal strain mapping reveals non-uniform deformation in micropatterned elastomers

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