Some features of the mechanical response of living cells to large deformations
Résumé
Pulmonary cells are normally submitted to large deformations which can become critical in the pathological cases where cells are exposed to both chemical and physical aggressive stresses. These injuries affect among others cell membrane, cytoskeleton structure and cellular functions. The response of cells secondary to such large deformations remains to be understood, whereas the limits for cellular elastic behavior are still under debate. In order to explore these features, we have performed AFM tests which consist in indenting living cells with a long tip over almost the entire cell height (~10 μm). Preliminary results show that the cells exhibit a surprisingly high capability of adaptation without breaking. So, we question in the present study the reasons of such cellular adaptability to large deformations and, more particularly, what mechanical properties at different scales are behind such a specific cellular feature. To understand experimental data, we used two different mechanical models of the probe-cell interaction: a granular-like model and a continuous model. The granular-like model, in which local properties are controlled, represents the interdependence between functional sub-cellular structures and aims at considering the spatial reorganization of intracellular force distribution within the cytoskeleton. The continuous model, in which global properties are controlled, will be used as a basis for comparison since it aims to describe stress distributions assuming a homogeneous cytoplasm. We expect, with this comparative approach, being able to relate global to local mechanical properties and their range of validity before the apparition of cell injury.