Hydrodynamics and multiscale order in confluent epithelia

Armengol-Collado, Josep-Maria; Carenza, Livio Nicola; Giomi, Luca

doi:10.48550/arxiv.2202.00651

Cited by 5 publications

(8 citation statements)

References 45 publications

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“…Our work paves the way for a deeper understanding of cell intercalation and other remodelling events in epithelial layers, where small-scale hexatic order (i.e. p = 6) has been recently discovered [64,65].…”

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confidence: 77%

Passive self-propulsion and enhanced annihilation of $p-$atic defects

Krommydas¹,

Carenza²,

Giomi³

2022

Preprint

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We investigate the effects of hydrodynamics on the motion of topological defects in p−atic liquid crystals: i.e. two-dimensional liquid crystals characterised by p−fold rotational symmetry. Using numerical simulations and analytical work, we demonstrate the existence of a generic passive self-propulsion mechanism for defects of winding number s = (p − 1)/p and arbitrary p values. Remarkably, whereas this mechanism is not unique to nematics (i.e. p = 2), nematics are the only type of liquid crystals where passive self-propulsion is thermodynamically stable. Furthermore, we find that hydrodynamics can accelerate the annihilation dynamics of pairs of ±1/p defects and that this effect increases with p before approaching a plateau.

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confidence: 77%

Passive self-propulsion and enhanced annihilation of $p-$atic defects

Krommydas¹,

Carenza²,

Giomi³

2022

Preprint

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“…In this article, we explored the multiscale structure of in vitro layers of MDCK-II cells, with the goal of unveiling how the mechanical and biochemical properties of the monolayers and the substrate affect the crossover between hexatic and nematic orientational order. Such a remarkable example of multiscale organization in living matter has been recently identified by means of numerical simulations and experiments 30,31 , and has been conjectured to contribute to the biophysical versatility of epithelial tissues, whose tasks range from organism-wide morphogenetic migration to collective metastatic invasion under strong confinement. By comparing the behavior of two different cell lines -MDCK WT and the mesenchymallike MDCK E-cad KO cells -we showed that the existence of hexatic order crucially relies on E-cadherin-mediated intercellular adhesion, whose lack on MDCK E-cad KO cells rendered the cellular shape significantly elongated, hence prone to form nematic phases.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…Previous numerical studies suggested that, as other twodimensional assemblies of equally-sized isotropic building blocks, epithelial layers resemble hexatic liquid crystals: anisotropic fluids featuring quasi-long-ranged 6−fold orientational order [27][28][29] . More recently, this picture has been further elaborated by experimental 30 and theoretical 31 studies, which indicated that certain epithelial layers feature, in fact, a unique combination of nematic and hexatic order, with the former being dominant at large and the latter at small length scale. These two types of liquid crystal order crossover at intermediate length scales -corresponding roughly to clusters of a dozen cells for MDCK GII on non-coated glass 30 -where the local hexagonal structure inherited from the shape of individual cells is gradually replaced by the uniaxial arrangement caused by clustering of cells into chain-like assemblies.…”

Section: Introductionmentioning

confidence: 97%

“…It has been speculated that the specific magnitude of such a hexanematic crossover scalehereafter referred to as R × -could affect the strategy of epithelial layers with respect to collective migration 31 . Depending on the length scale, L, at which it is confined, an epithelial layer could select among the different motility modes at its disposal.…”

Section: Introductionmentioning

confidence: 99%

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Hexanematic crossover in epithelial monolayers depends on cell adhesion and cell density

Eckert

Ladoux

Giomi

et al. 2022

Preprint

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During tissue folding in developmental processes and monolayer migration in wound healing, epithelial cells undergo shape changes and move collectively. Recent experimental and numerical results suggested that these processes could leverage on the existence of both nematic (2--fold) and hexatic (6--fold) orientational order coexisting at different length scales within the same epithelial layer. Yet, how this remarkable example of multiscale organization in living matter is affected by the material properties of the cells and their substrate is presently unknown. In the current article, we experimentally address these questions in monolayers of Madin-Darby canine kidney cells (MDCK-II) having various cell density and molecular repertoire. At small length scales, confluent monolayers are characterized by a prominent hexatic order and nearly vanishing nematic order, independently on the presence of E-cadherin, the monolayer density, and the underlying substrate stiffness. All three properties, however, dramatically affect the organization of MDCK-II monolayers at large length scales, where nematic order becomes dominant over hexatic order. In particular, we find that the length scale at which nematic order prevails over hexatic order -- here referred to as hexanematic crossover scale -- strongly depends on cell-cell adhesions and correlates with the monolayer density. Our analysis sheds light on how the organization of epithelial layers is affected by the material and mechanical properties, and provides a robust approach for analyzing the tissue composition towards understanding developmental processes.

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Hydrodynamic theory ofp-atic liquid crystals

2022

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We formulate a comprehensive hydrodynamic theory of two-dimensional liquid crystals with generic p-fold rotational symmetry, also known as p-atics, of which nematics (p = 2) and hexatics (p = 6) are the two best known examples. Previous hydrodynamic theories of p-atics are characterized by continuous O(2) rotational symmetry, which is higher than the discrete rotational symmetry of p-atic phases. By contrast, here we demonstrate that the discrete rotational symmetry allows the inclusion of additional terms in the hydrodynamic equations, which, in turn, lead to novel phenomena, such as the possibility of flow alignment at high shear rates, even for p > 2. Furthermore, we show that any finite imposed shear will induce long-ranged orientational order in any p-atic liquid crystal, in contrast to the quasi-long-ranged order that occurs in the absence of shear. The induced order parameter scales like a nonuniversal power of the applied shear rate at small shear rates.

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Hydrodynamics and multiscale order in confluent epithelia

Cited by 5 publications

References 45 publications

Passive self-propulsion and enhanced annihilation of $p-$atic defects

Passive self-propulsion and enhanced annihilation of $p-$atic defects

Hexanematic crossover in epithelial monolayers depends on cell adhesion and cell density

Hydrodynamic theory ofp-atic liquid crystals

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