Mechanical assessment by magnetocytometry of the cytosolic and cortical cytoskeletal compartments in adherent epithelial cells.

This study aims at quantifying the cellular mechanical properties based on a partitioning of the cytoskeleton in a cortical and a cytosolic compartments. The mechanical response of epithelial cells obtained by magnetocytometry - a micromanipulation technique which uses twisted ferromagnetic beads specifically linked to integrin receptors - was purposely analysed using a series of two Voigt bodies. Results showed that the cortical cytoskeleton has a faster response ( approximately 1 s) than the cytosolic compartment ( approximately 30 s). Moreover, the two cytoskeletal compartments have specific mechanical properties, i.e., the cortical (resp. cytosolic) cytoskeleton has a rigidity in the range: 49-85 Pa (resp.: 74-159 Pa) and a viscosity in the range 5-14 Pa.s (resp.: 593-1534 Pa.s), depending on the level of applied stress. Depolymerising actin-filaments strongly modified these values and especially those of the cytosolic compartment. The structural relevance of this two-compartment partitioning was supported by images of F-actin structure obtained on the same cells.