Résumé
We attempted to estimate in living adherent epithelial alveolar cells, the degree of structural and mechanical heterogeneity by considering two individualized cytoskeleton components, i.e., a submembranous "cortical" cytoskeleton and a "deep" cytoskeleton (CSK). F-actin structure characterizing each CSK component was visualized from spatial reconstructions at low and high density, respectively, especially in a 10-μm-cubic neighborhood including the bead. Specific mechanical properties (Young elastic and viscous modulus E and η) were revealed after partitioning the magnetic twisting cytometry response using a double viscoelastic "solid" model with asymmetric plastic relaxation. Results show that the cortical CSK response is a faster (τ ^sub 1^≤ 0.7s), softer (E^sub 1^: 63-109 Pa), moderately viscous (η^sub 1^: 7-18 Pa s), slightly tensed, and easily damaged structure compared to the deep CSK structure which appears slower (τ^sub 2^ 1/2 min), stiffer (E^sub 2^: 95-204 Pa), highly viscous (η^sub 2^: 760-1967 Pa s), more tensed, and fully elastic, while exhibiting a larger stress hardening behavior. Adding drug depolymerizing actin filaments decreased predominantly the deep CSK stiffness. By contrast, an agent altering cell-matrix interactions affected essentially the cortical CSK stiffness. We concluded that partitioning the CSK within cortical and deep structures is largely consistent with their respective functional activities. © 2003 Biomedical Engineering Society. PAC2003: 8716Ka, 8716Ac, 8380Lz[PUBLICATION ABSTRACT]