Change in the Number Distribution of Complex Shear Modulus of Single Cells by Actin Cytoskeleton Modifications Measured by Atomic Force Microscopy

Abstract

The rheological properties of living cells strongly depend on their cytoskeletal structures, which are composed of polymer networks and responsible for fundamental cellular functions. In particular, the actin network plays a major role in determining the rheological properties of living cells. In order to elucidate how the rheological properties of individual cells are affected by actin filamentous structures, we measured the number distribution of complex shear modulus of single cells, which were treated by actin modification drugs and cultured on microarray substrates, by atomic force microscopy. A force modulation mode experiment was employed to measure the complex shear modulus of single cells in a frequency range of 2-200Hz. When the cells were treated with actin-stabilizing drug, jasplakinolide, and actin-disrupting drug, cytochalasin D (CD), the storage modulus G’ and loss modulus G” increased and decreased, respectively. The changes in G” were smaller comparing to those in G’. The moduli exhibited a weak power-law dependence on frequency [1], whereas the increasing and decreasing of G’ and G” were accompanied by a decreasing and increasing power-law exponent respectively. Furthermore, their corresponding logarithmic standard deviation σ showed a slight change in the case of jasplakinolide treatment whereas it became small and attained a constant value at higher frequencies in CD treatment [2]. The results indicated that individual differences of cell rheology enhanced as actin cytoskeletal structures were stabilized. Furthermore, it was implied that the observed frequency dependence of σ was attributed to a frequency susceptibility of actin filaments.[1] B. Fabry et al., Phys. Rev. E., vol. 68, pp. 041914-041917, 2003.[2] S. Hiratsuka et al., Ultramicroscopy, vol. 109, pp. 937-941, 2009.