Patrick Cañadas

Mechanical model of cytoskeleton structuration during cell adhesion and spreading

The biomechanical behavior of an adherent cell is intimately dependent on its cytoskeleton structure. Several models have been proposed to study this structure taking into account its existing internal forces. However, the structural and geometrical complexities of the cytoskeletons filamentous networks lead to difficulties for determining a biologically realistic architecture. The objective of this paper is to present a mechanical model, combined with a numerical method, devoted to the form-finding of the cytoskeleton structure (shape and internal forces) when a cell adheres on a substrate. The cell is modeled as a granular medium, using rigid spheres (grains) corresponding to intracellular cross-linking proteins and distant mechanical interactions to reproduce the cytoskeleton filament internal forces. At the initial state (i.e., before adhesion), these interactions are tacit. The adhesion phenomenon is then simulated by considering microtubules growing from the centrosome towards transmembrane integrin-like receptors. The simulated cell shape changes in this process and results in a mechanically equilibrated structure with traction and compression forces, in interaction with the substrate reactions. This leads to a compressive microtubule network and a corresponding tensile actin-filament network. The results provide coherent shape and forces information for developing a mechanical model of the cytoskeleton structure, which can be exploitable in future biomechanical studies of adherent cells.

Divided media based simulations of tissue morphogenesis

Tissue morphogenesis is a key point remaining weakly understood in development biology. In particular, whatever the species considered (animals and vegetables), most of formed epithelial tissues show analogous cell polygonal distributions (Gibson 2009). Accordingly, one may wonder if there are invariant features governing this process. Among the numerous studies performed up today to answer this question, only few approaches including physical models have been developed (Graner et Glazier, 1993; Martinand-Mari et al., 2009). These models allow cellular reorganisation within tissues already formed but by considering only limited movements and without any growing cells, which does not exactly correspond to biological tissue morphogenesis.

NUMERICAL MODEL OF THE CYTOSKELETON STRUCTURATION DURING CELL SPREADING

The objective of this work is to propose a mechanical model and a numerical method devoted to the cytoskeleton (CSK) form-finding resulting from its structuration during cell spreading. It is now well assumed that the cell mechanics closely depends on its CSK architecture and on the tension and compression forces carried by its filaments. Several structural models have been therefore developed, especially those based on the tensegrity analogy. However, the observed topological and geometrical complexities of the CSK networks lead to difficulties for determining and using a realistic structure [Baudriller et al., 2006]. The presented method allows calculating such a complex architecture and the associated forces in the different CSK filaments of an adherent cell.