Superficial and deep changes of cellular mechanical properties following cytoskeleton disassembly

Abstract

The cytoskeleton, composed of actin filaments, intermediate filaments, and microtubules, is a highly dynamic supramolecular network actively involved in many essential biological mechanisms such as cellular structure, transport, movements, differentiation, and signaling. As a first step to characterize the biophysical changes associated with cytoskeleton functions, we have developed finite elements models of the organization of the cell that has allowed us to interpret atomic force microscopy (AFM) data at a higher resolution than that in previous work. Thus, by assuming that living cells behave mechanically as multilayered structures, we have been able to identify superficial and deep effects that could be related to actin and microtubule disassembly, respectively. In Cos-7 cells, actin destabilization with Cytochalasin D induced a decrease of the visco-elasticity close to the membrane surface, while destabilizing microtubules with Nocodazole produced a stiffness decrease only in deeper parts of the cell. In both cases, these effects were reversible. Cell softening was measurable with AFM at concentrations of the destabilizing agents that did not induce detectable effects on the cytoskeleton network when viewing the cells with fluorescent confocal microscopy. All experimental results could be simulated by our models. This technology opens the door to the study of the biophysical properties of signaling domains extending from the cell surface to deeper parts of the cell.

Impact of substrate elasticity on human hematopoietic stem and progenitor cell adhesion and motility

“…A decreased F-actin content or disruption of the actin cytoskeleton with cytochalasin D have been linked to decreased elastic moduli (Cai et al, 2010;Janmey et al, 1991;Kasas et al, 2005). Adrenergic stimulation of osteoblasts led to a decreased F-to G-actin ratio compared to untreated cells.…”

Research progress in quantifying the mechanical properties of single living cells using atomic force microscopy

“…When AFM tip indents the cells, the tip encounters different components of the cell, such as cell membrane, actin cytoskeleton, microtubules network, and cell nucleus [75], causing that the force curves can be divided into several segments and each segment responds to a particular region of the cell (e.g., cell cortex, cell center) [37]. In practice, force curves were fitted to the Hertz model which assumes a homogenous isotropic sample, causing that the mechanical changes at different depth of the cell are averaged [75]. Hence, frankly speaking, for the current approaches of analyzing the force curves, we do not know the elastic modulus calculated from the force curves responds to which part of the cell.…”

Probing nanomechanical properties from biomolecules to living cells

“…Various algorithms [1] and alternative analytical methods have been implemented in an attempt to overcome this limitation. In one such instance [44], the living cells were assumed to behave mechanically as multilayered structures. This assumption permitted the authors to identify superficial and deep effects which were associated with the disassembly of actin and microtubules, respectively.…”