Viscoelastic Finite-Element Modelling of Cell Deformation in an Optical Stretcher

In this paper, we discuss the results arising from using a finite-element model [1] of cell deformation to study the optical stretching [2,3] of normal and malignantly transformed fibroblast cells. The key feature of our model is the use of a constitutive viscoelastic fluid element [4] whose parameters are both spatially and temporally varying so as to mimic the experimentally-observed spatiotemporal heterogeneity of cellular material properties. First, we show that normal fibroblast cells can undergo active cellular response by increasing their cellular viscosity when optically stretched for loading times of between 0.2s and 2.5s. Second, we show that, under similar optical conditions, cells of a smaller radius will experience more stretching compared to cells of a larger radius. This may explain why malignantly transformed cells experience higher strains than normal cells. Third, we compute the extent of the propagation of stress in the cytoplasm, and show that, for malignantly transformed cells, the maximal stress does propagate into the nuclear region whereas for normal cells, the maximal stress does not. We discuss how this may impact the transduction of cancer signalling pathways.