Relationship Between Rheological Properties and Actin Filaments of Single Cells Investigated by Atomic Force Microscopy

We investigated how rheological properties of single cells are spatially correlated with actin filaments (F-actin) by atomic force microscopy (AFM). This was achieved by measuring the power-law rheological properties of mouse fibroblast cells adhered on micropatterned substrate by multi-frequency force modulation AFM in the combination of the immunofluorescent observation of F-actin. We observed that G(0), a scale factor of the modulus at a certain frequency, of cells was decreased as the F-actin was disrupted with a chemical treatment, showing that the spatial-averaged stiffness is associated with the F-actin formation, as observed in various cell types and microrheological methods. Interestingly, we found that G(0) measured in local locations within cells displayed a negative correlation with the corresponding F-actin density. The results indicate that the local cell stiffness is not necessarily correlated with the F-actin density, but rather depending on how network structures of F-actin are formed in local regions. (C) 2020 The Japan Society of Applied Physics