Mechanical modeling of crawling cells

Pierre Recho 1
1 Mécanique du Vivant
LMS - Laboratoire de mécanique des solides
Abstract : The ability of most eukaryotic cells to crawl is essential for embryogenesis, immune response and wound healing while functional abnormalities of crawling can provoke different diseases including cancer. Artificial biomimetic machines mimicking eukaryotic cells are of interests as prototypes of versatile engineering devices operating autonomously at a nano-scale. A prototypical scheme of cell motility includes polymerization of actin network coupled with dynamic assembly of focal adhesions, myosin-driven contraction and, finally, the detachment of adhesive contacts followed by de-polymerization which closes the treadmilling cycle. The motor part of an eukaryotic cell is a layer of an active gel whose functions are controlled by complex chemical and mechanical processes. In particular, the coordinated movements of this gel resulting in crawling involve spatial and temporal self-organization at the cytoskeletal level and require a continuous supply of energy. While the molecular and biochemical basis of cell motility is basically known, the qualitative understanding of the mechanical interplay between different active components is still limited despite many recent attempts to construct comprehensive mathematical models. This manuscript aims at presenting an analysis of a simple and one dimensional model accounting for cell crawling. The first chapter is dedicated to optimization of speed and mechanical efficiency of crawling. Our analysis shows that the obtained optimal distribution of contractile stresses and the optimal friction distribution are in good agreement with the observed distributions. In the second chapter, we propose a mechanism of cell motility which places emphasis on contraction while ignoring actin treadmilling. At the basis of the model is contraction driven uphill diffusion destabilizing symmetric configuration and causing polarization. The morphological instability is due to spontaneous internal motion of the cytoskeleton which is generated by active cross-linkers and simultaneously transports them. By studying the simplest one dimensional problem we show that such internal flow can generate steady propulsion of a finite cell body. The model exhibits motility initiation patterns similar to the ones observed in experiments. In the last chapter we focus on actin treadmilling-based motility which allows the cell not only to self-propel but also exert forces on obstacles (to push) and carry cargoes (to pull). We use a minimal one dimensional model of the crawling cell to show that the pushing dominated force-velocity relation is controlled by the protrusion mechanism. Instead, the pulling dominated force-velocity relation is controlled by the protrusion mechanism only at small values of the force which is replaced by the contraction mechanism at sufficiently large forces.
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  • HAL Id : pastel-00801360, version 1

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Pierre Recho. Mechanical modeling of crawling cells. Biomechanics [physics.med-ph]. Ecole Polytechnique X, 2012. English. ⟨pastel-00801360⟩

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