Mechanical properties of cells and modelling of structural instabilities in tissues

[摘要] ENGLISH ABSTRACT : Cells have inherent mechanical properties that can be modelled physically. Statistical physicsapproaches permit the understanding of deformation dependence by modelling the various elements of the cytoskeleton and combining these with the constraints and physical propertiesof the cell membrane. When cells combine to form more complex structures, including, forexample, epithelial structures, the resulting structure also needs to be understood. We wish tounderstand the mechanical contribution to the elastic properties and stability of the cell withinthe tissue when branching actin cytoskeletal network emerge or grow and their structure, spatial organisation and orientational ordering geometrically constrained by the cell membrane.Based on a grand canonical ensemble formalism by Frisch et al. [1] and Müller-Nedebocket al. [2], we model the structure of branching actin networks of living cell cytoskeletal filaments when these are rigidly contained with geometrical confining regions. The formalismallows a thermodynamic equilibrium calculation of density and orientational order density forfillaments and branch points. We find distinct local orientation, order parameter and densityprofiles for network filament segments, as the degree of branching and the ratio of persistencelengths of the filaments to the confining region size are varied. These results suggest the roleof the confinement in the structural properties and organization of branching actin networksinside the confining region. We next investigated the contribution of the elastic properties ofthe networks to the elastic properties and stability of the cells within tissues by computing the free energies and forces of networks system. We find that tissue cells are stable againstcompression while cell under shear become unstable beyond a critical angle.

[发布机构] Stellenbosch University