scholarly journals Active forces in confluent cell monolayers

2021 ◽  
Author(s):  
Guanming Zhang ◽  
Julia Mary Yeomans
Keyword(s):  
Field Model ◽  
Collective Motion ◽  
Cell Monolayer ◽  
Phase Field Model ◽  
Topological Defects ◽  
Cellular Interactions ◽  
Cell Monolayers ◽  
Nematic Ordering ◽  
Active Turbulence ◽  
Confluent Cell

We use a computational phase-field model together with analytical analysis to study how inter-cellular active forces can mediate individual cell morphology and collective motion in a confluent cell monolayer. Contractile inter-cellular interactions lead to cell elongation, nematic ordering and active turbulence, characterised by motile topological defects. Extensile interactions result in frustration, and perpendicular cell orientations become more prevalent. Furthermore, we show that contractile behaviour can change to extensile behaviour if anisotropic fluctuations in cell shape are considered.

Unifying polar and nematic active matter: Emergence and co-existence of half-integer and full-integer topological defects

2022 ◽  
Author(s):  
Aboutaleb Amiri ◽  
Romain Mueller ◽  
Amin Doostmohammadi
Keyword(s):  
Continuum Model ◽  
Topological Defect ◽  
Topological Defects ◽  
Active Matter ◽  
Defect States ◽  
Cell Monolayers ◽  
Half Integer ◽  
Generic Framework ◽  
Active Turbulence ◽  
The Continuum

Abstract The presence and significance of active topological defects is increasingly realised in diverse biological and biomimetic systems. We introduce a continuum model of polar active matter, based on conservation laws and symmetry arguments, that recapitulates both polar and apolar (nematic) features of topological defects in active turbulence. Using numerical simulations of the continuum model, we demonstrate the emergence of both half- and full-integer topological defects in polar active matter. Interestingly, we find that crossover from active turbulence with half- to full-integer defects can emerge with the coexistence region characterized by both defect types. These results put forward a minimal, generic framework for studying topological defect patterns in active matter which is capable of explaining the emergence of half-integer defects in polar systems such as bacteria and cell monolayers, as well as predicting the emergence of coexisting defect states in active matter.

scholarly journals Re-Use of Caco-2 Monolayers in Permeability Assays—Validation Regarding Cell Monolayer Integrity

Pharmaceutics ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1563
Author(s):  
Cristiana L. Pires ◽  
Catarina Praça ◽  
Patrícia A. T. Martins ◽  
Ana L. M. Batista de Carvalho ◽  
Lino Ferreira ◽  
...  
Keyword(s):  
Culture Media ◽  
Lucifer Yellow ◽  
Cell Monolayer ◽  
Time Interval ◽  
Cell Monolayers ◽  
Morphological Studies ◽  
Confluent Cell ◽  
Vitro Model ◽  
Permeability Assay

Caco-2 monolayers are a common in vitro model used to evaluate human intestinal absorption. The reference protocol requires 21 days post-seeding to establish a stable and confluent cell monolayer, which is used in a single permeability assay during the period of monolayer stability (up to day 30). In this work, we characterize variations in the tightness of the cell monolayer over the stable time interval and evaluate the conditions required for their re-use in permeability assays. The monolayer integrity was assessed through TEER measurements and permeability of the paracellular marker Lucifer Yellow (LY), complemented with nuclei and ZO-1 staining for morphological studies and the presence of tight junctions. Over 150 permeability assays were performed, which showed that manipulation of the cell monolayer in the permeability assay may contribute significantly to the flux of LY, leading to Papp values that are dependent on the sampling duration. The assay also leads to a small decrease in the cell monolayer TEER, which is fully recovered when cell monolayers are incubated with culture media for two full days. When this procedure is followed, the cell monolayers may be used for permeability assays on days 22, 25, and 28, triplicating the throughput of this important assay.

scholarly journals Chiral stresses in nematic cell monolayers

Soft Matter ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 764-774 ◽  
Author(s):  
Ludwig A. Hoffmann ◽  
Koen Schakenraad ◽  
Roeland M. H. Merks ◽  
Luca Giomi
Keyword(s):  
Collective Motion ◽  
Topological Defects ◽  
Cell Monolayers ◽  
Microscopic Origin

We discuss the microscopic origin of chiral stresses in nematic cell monolayers and investigate how chirality affects the motion of topological defects, as well as the collective motion in stripe-shaped domains.

scholarly journals Active inter-cellular forces in collective cell motility

2020 ◽  
Vol 17 (169) ◽  
pp. 20200312
Author(s):  
Guanming Zhang ◽  
Romain Mueller ◽  
Amin Doostmohammadi ◽  
Julia M. Yeomans
Keyword(s):  
Field Model ◽  
Cell Sheet ◽  
Phase Field Model ◽  
Cell Junctions ◽  
Sharp Transition ◽  
Cell Sheets ◽  
Persistent Random Walk ◽  
Confluent Cell ◽  
A Cell ◽  
Cellular Forces

The collective behaviour of confluent cell sheets is strongly influenced both by polar forces, arising through cytoskeletal propulsion, and by active inter-cellular forces, which are mediated by interactions across cell-cell junctions. We use a phase-field model to explore the interplay between these two contributions and compare the dynamics of a cell sheet when the polarity of the cells aligns to (i) their main axis of elongation, (ii) their velocity and (iii) when the polarity direction executes a persistent random walk. In all three cases, we observe a sharp transition from a jammed state (where cell rearrangements are strongly suppressed) to a liquid state (where the cells can move freely relative to each other) when either the polar or the inter-cellular forces are increased. In addition, for case (ii) only, we observe an additional dynamical state, flocking (solid or liquid), where the majority of the cells move in the same direction. The flocking state is seen for strong polar forces, but is destroyed as the strength of the inter-cellular activity is increased.

scholarly journals Defects in Active Nematics – Algorithms for Identification and Tracking

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Dennis Wenzel ◽  
Michael Nestler ◽  
Sebastian Reuther ◽  
Maximilian Simon ◽  
Axel Voigt
Keyword(s):  
Data Analysis ◽  
Field Model ◽  
Statistical Data ◽  
Phase Field Model ◽  
Topological Defects ◽  
Reliable Data ◽  
Data Driven ◽  
Nematic Order ◽  
Microscopy Data ◽  
Multi Phase

Abstract The growing interest in active nematics and the emerging evidence of the relevance of topological defects in biology asks for reliable data analysis tools to identify, classify and track such defects in simulation and microscopy data. We here provide such tools and demonstrate on two examples, on an active turbulent state in an active nematodynamic model and on emerging nematic order in a multi-phase field model, the possibility to compare statistical data on defect velocities with experimental results. The considered tools, which are physics based and data driven, are compared with each other.

Processing Immunoperoxidase Labeled Cell Monolayers and Cryostat Sesctions For Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 714-715
Author(s):  
K. Chien ◽  
R. Van de Velde ◽  
I.P. Shintaku ◽  
A.F. Sassoon
Keyword(s):  
Cell Monolayer ◽  
Cell Types ◽  
Surface Antigens ◽  
Immunoperoxidase Method ◽  
Reaction Step ◽  
Hot Plate ◽  
Air Drying ◽  
New Approach ◽  
Cell Monolayers ◽  
Glass Slides

Immunoelectron microscopy of neoplastic lymphoma cells is valuable for precise localization of surface antigens and identification of cell types. We have developed a new approach in which the immunohistochemical staining can be evaluated prior to embedding for EM and desired area subsequently selected for ultrathin sectioning.A freshly prepared lymphoma cell suspension is spun onto polylysine hydrobromide- coated glass slides by cytocentrifugation and immediately fixed without air drying in polylysine paraformaldehyde (PLP) fixative. After rinsing in PBS, slides are stained by a 3-step immunoperoxidase method. Cell monolayer is then fixed in buffered 3% glutaraldehyde prior to DAB reaction. After the DAB reaction step, wet monolayers can be examined under LM for presence of brown reaction product and selected monolayers then processed by routine methods for EM and embedded with the Chien Re-embedding Mold. After the polymerization, the epoxy blocks are easily separated from the glass slides by heatingon a 100°C hot plate for 20 seconds.

MARMOT Phase-Field Model for the U-Si System

2016 ◽  
Author(s):  
Larry Kenneth Aagesen ◽  
Daniel Schwen
Keyword(s):  
Phase Field ◽  
Field Model ◽  
Phase Field Model
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