During the formation of tissues, cells organize collectively by cell division and apoptosis. The multicellular dynamics such systems is influenced mechanical conditions can give rise to rearrangements movements. We develop a continuum description tissue dynamics, which describes stress distribution flow field on large scales. In absence apoptosis, we consider behave as an elastic solid. Cell apoptosis introduce sources that, in general, are anisotropic. By combining number balance with...

Significance Collective cell motion is very important in many biological processes such as wound healing, embryogenesis, or cancer progression. Nevertheless, it not clear which parameters control the transition from freely moving single cells to collective jammed motion. In this article, we uncover complex dynamics a monolayer ages, where shown gradually slow down with time, while distance over displacements are correlated first increases drastically and then decreases. This change of...

Propulsion by cilia is a fascinating and universal mechanism in biological organisms to generate fluid motion on the cellular level. Cilia are hair-like organelles, which found many different tissues uni- multicellular organisms. Assembled large fields, beat neither randomly nor completely synchronously—instead they display striking self-organization form of metachronal waves (MCWs). It was speculated early that hydrodynamic interactions provide physical for synchronization motion. Theory...

The dynamics of a self-propelled Brownian sphere confined between two planar hard walls is investigated by computer simulations and analytic solutions the corresponding Fokker-Planck equation. It shown that an accumulation particles, often linked to hydrodynamic dipole interaction, can be already obtained from combination motion self-propulsion. surface excess calculated as function particle velocity, wall separation, translational rotational diffusion coefficients. In limits narrow channels...

Recent experiments have shown that spreading epithelial sheets exhibit a long-range coordination of motility forces leads to buildup tension in the tissue, which may enhance cell division and speed wound healing. Furthermore, edges these commonly show finger-like protrusions whereas bulk often displays spontaneous swirls motile cells. To explain experimental observations, we propose simple flocking-type mechanism, cells tend align their with velocity. Implementing this idea mechanical tissue...

The precise role of the microenvironment on tumor growth is poorly understood. Whereas in constant competition with surrounding tissue, little known about mechanics this interaction. Using a novel experimental procedure, we study quantitatively effect an applied mechanical stress long-term spheroid cell aggregate. We observe that 10 kPa sufficient to drastically reduce by inhibition proliferation mainly core spheroid. compare results simple numerical model developed describe cancer progression.

Sperm swimming at low Reynolds number have strong hydrodynamic interactions when their concentration is high in vivo or near substrates vitro. The beating tails not only propel the sperm through a fluid, but also create flow fields which interact with each other. We study interaction and cooperation of embedded two-dimensional fluid by using particle-based mesoscopic simulation method, multiparticle collision dynamics. analyze behavior investigating relationship between beating-phase...

Worm-like filaments that are propelled homogeneously along their tangent vector studied by Brownian dynamics simulations. Systems in two dimensions investigated, corresponding to adsorbed interfaces or surfaces. A large parameter space covering weak and strong propulsion, as well flexible stiff is explored. For strongly filaments, the free-swimming spontaneously form stable spirals. The propulsion force has a impact on dynamic properties, such rotational translational mean square...

In most instances, tumors have to push their surroundings in order grow. Thus, during development, must be able both exert and sustain mechanical stresses. Using a novel experimental procedure, we study quantitatively the effect of an applied stress on long-term growth spherical cell aggregate. Our results indicate possibility modulate tumor depending pressure. Moreover, demonstrate that cells located core spheroid display different response than those periphery. We compare simple numerical...

Sperm are propelled by bending waves traveling along their flagellum. For steering in gradients of sensory cues, sperm adjust the flagellar waveform. Symmetric and asymmetric waveforms result straight curved swimming paths, respectively. Two mechanisms causing spatially have been proposed: an average curvature buckling. We image flagella human tethered with head to a surface. The waveform is characterized fundamental beat frequency its second harmonic. superposition harmonics breaks symmetry...

The collective behavior of active semiflexible filaments is studied with a model tangentially driven self-propelled worm-like chains. combination excluded-volume interactions and self-propulsion leads to several distinct dynamic phases as function bending rigidity, activity, aspect ratio individual filaments. We consider first the case intermediate filament density. For high-aspect-ratio filaments, we identify transition increasing propulsion from state free-swimming spiraled nearly frozen...

Many biological microorganisms and artificial microswimmers react to external cues of environmental gradients by changing their swimming directions. We study here the behavior eukaryotic flagellated in linear viscosity gradients. Motivated near-surface motion many microswimmers, we consider flagellar two spatial dimensions. employ a model flagellum consisting semi-flexible filament with travelling wave spontaneous curvature generic aspects viscotaxis actively beating flagella. The propulsion...

We study the behavior of self-propelled nano- and micro-rods in three dimensions, confined between two parallel walls, by simulations scaling arguments. Our include thermal fluctuations hydrodynamic interactions, which are both relevant for dynamical at to micro-meter length scales. In order investigate importance we also perform Brownian-dynamics–like simulations. cases, find that rods display a strong surface excess geometries. An analogy with semi-flexible polymers is employed derive laws...

In this work, we model biological tissues using a simple, mechanistic simulation based on dissipative particle dynamics. We investigate the continuum behavior of simulated tissue and determine its dependence properties individual cell. Cells in our adhere to each other, expand volume, divide after reaching specific size checkpoint undergo apoptosis at constant rate, leading steady-state homeostatic pressure tissue. measure state microscopic parameters show that pressure, rather than...

Both, in their natural environment and a controlled experimental setup, microswimmers regularly interact with surfaces. These surfaces provide steric boundary, both for the swimming motion hydrodynamic flow pattern. effects typically imply strong accumulation of near While some generic features can be derived, details swimmer shape propulsion mechanism matter, which give rise to broad range adhesion phenomena have taken into account predict surface given swimmer. We show this minireview how...

Worm-like filaments, which are propelled by a tangential homogeneous force along their contour, studied as they push loads of different shapes and sizes. The resulting dynamics is investigated using Langevin simulations. effects size shape the load, propulsion strength, thermal noise systematically explored. propulsive hydrodynamic friction load cause compression in filament that results buckling instability versatile motion. Distinct regimes elongated curved beating filaments with...

Run-and-tumble dynamics is a wide-spread mechanism of swimming bacteria. The accumulation run-and-tumble microswimmers near impermeable surfaces studied theoretically and numerically in the low-density limit two three spatial dimensions. Both uni-modal exponential distributions run lengths are considered. Constant lead to {peaks depletions regions} density distribution particles surface, contrast {exponentially-distributed lengths}. Finally, we present universal law for large channel widths,...

Collective cell motion is observed in a wide range of biological processes. In tumors, physiological gradients nutrients, growth factors, or even oxygen give rise to proliferation. We show using fluorescently labeled particles that these drive velocity field resulting cellular flow multicellular spheroids. Under mechanical stress, the drastically reduced. describe results with hydrodynamic model considers only convection by flow.

Spontaneous segregation of run-and-tumble particles with different velocities in microchannels is investigated by numerical simulations. Self-propelled are known to accumulate the proximity walls. Here we show how fast expel slower ones from wall leading a segregated state. The mechanism understood as function particle velocities, density, or channel width. In presence an external fluid flow, two segregate due their fluxes. Promising applications can be found development microfluidic...