Cells exploit a phase transition to mechanically remodel the fibrous extracellular matrix

Grekas, Georgios; Proestaki, Maria; Rosakis, Phoebus; Notbohm, Jacob; Makridakis, Charalambos; Ravichandran, G.

doi:10.1098/rsif.2020.0823

Cited by 26 publications

(19 citation statements)

References 70 publications

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“…Continuum methods can approach these problems by describing a disordered matrix as a continuous function that varies in space and time. For example, Grekas and colleagues [139] used a continuum approach to demonstrate that the strongly nonlinear relation between stress and strain for individual fibrils translates at the network level to a mechanical phase transition, with tension applied by cells forming bundles of laterally compressed fibres within the matrix. A network of fibrils can thereby reorganise into “tethers” that radiate out from a contracting cell, allowing the cell to remodel its environment.…”

Section: Collagen Assembly In Vivomentioning

confidence: 99%

Collagen fibril assembly: New approaches to unanswered questions

Revell

Jensen

Shearer

et al. 2021

Matrix Biology Plus

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Collagen fibrils are essential for metazoan life. They are the largest, most abundant, and most versatile protein polymers in animals, where they occur in the extracellular matrix to form the structural basis of tissues and organs. Collagen fibrils were first observed at the turn of the 20th century. During the last 40 years, the genes that encode the family of collagens have been identified, the structure of the collagen triple helix has been solved, the many enzymes involved in the post-translational modifications of collagens have been identified, mutations in the genes encoding collagen and collagen-associated proteins have been linked to heritable disorders, and changes in collagen levels have been associated with a wide range of diseases, including cancer. Yet despite extensive research, a full understanding of how cells assemble collagen fibrils remains elusive. Here, we review current models of collagen fibril self-assembly, and how cells might exert control over the self-assembly process to define the number, length and organisation of fibrils in tissues.

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Section: Collagen Assembly In Vivomentioning

confidence: 99%

Collagen fibril assembly: New approaches to unanswered questions

Revell

Jensen

Shearer

et al. 2021

Matrix Biology Plus

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“…The necking in of the network is reminiscent of cellular induced compression of the extracellular matrix which may have implications for mechanosensing 26 . Elastin fibers began elongating immediately upon tissue stretch because they start at their resting lengths so the only mechanical percolation phenomenon in our model involves collagen recruitment.…”

Section: Discussionmentioning

confidence: 99%

Percolation of collagen stress in a random network model of the alveolar wall

Casey

Jawde

Herrmann

et al. 2021

Sci Rep

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Fibrotic diseases are characterized by progressive and often irreversible scarring of connective tissue in various organs, leading to substantial changes in tissue mechanics largely as a result of alterations in collagen structure. This is particularly important in the lung because its bulk modulus is so critical to the volume changes that take place during breathing. Nevertheless, it remains unclear how fibrotic abnormalities in the mechanical properties of pulmonary connective tissue can be linked to the stiffening of its individual collagen fibers. To address this question, we developed a network model of randomly oriented collagen and elastin fibers to represent pulmonary alveolar wall tissue. We show that the stress–strain behavior of this model arises via the interactions of collagen and elastin fiber networks and is critically dependent on the relative fiber stiffnesses of the individual collagen and elastin fibers themselves. We also show that the progression from linear to nonlinear stress–strain behavior of the model is associated with the percolation of stress across the collagen fiber network, but that the location of the percolation threshold is influenced by the waviness of collagen fibers.

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“…"frozen in" dipoles) have an electrically-induced compressive stiffness [52]. These cases could give rise to interesting behavior such as microbuckling [53], bistability, and phase transitions when loaded in compression [54,55]. While not relevant to the current study, the implications of these effects on electroactive polymer networks and electromechanical actuation present an interesting opportunity for future research.…”

Section: Statistical Mechanics Of a Dielectric Elastomer Chainmentioning

confidence: 94%

Nonlinear Statistical Mechanics Drives Intrinsic Electrostriction and Volumetric Torque in Polymer Networks

Grasinger,

Majidi,

Dayal

2021

Preprint

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Statistical mechanics is an important tool for understanding polymer electroelasticity because the elasticity of polymers is primarily due to entropy. However, a common approach for the statistical mechanics of polymer chains, the Gaussian chain approximation, misses key physics. By considering the nonlinearities of the problem, we show a strong coupling between the deformation of a polymer chain and its dielectric response; that is, its net dipole. When chains with this coupling are cross-linked in an elastomer network and an electric field is applied, the field breaks the symmetry of the elastomer's elastic properties, and, combined with electrostatic torque and incompressibility, leads to intrinsic electrostriction. Conversely, deformation can break the symmetry of the dielectric response leading to volumetric torque (i.e., a couple stress or torque per unit volume) and asymmetric actuation. Both phenomena have important implications for designing high-efficiency soft actuators and soft electroactive materials; and the presence of mechanisms for volumetric torque, in particular, can be used to develop higher degree of freedom actuators and to achieve bioinspired locomotion. FIG. 1. Dielectric elastomer actuator with dimensions of length in the ê1 and ê2 directions, and thickness t in the ê3 direction, where t : (a) undeformed configuration; (b) a voltage difference is applied across the electrodes on the top and bottom surfaces and, as a result, the actuator contracts across its thickness and expands in the plane orthogonal.

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Cells exploit a phase transition to mechanically remodel the fibrous extracellular matrix

Cited by 26 publications

References 70 publications

Collagen fibril assembly: New approaches to unanswered questions

Collagen fibril assembly: New approaches to unanswered questions

Percolation of collagen stress in a random network model of the alveolar wall

Nonlinear Statistical Mechanics Drives Intrinsic Electrostriction and Volumetric Torque in Polymer Networks

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