Mechanical Properties of Primary and Immortal Fibroblasts in Cell Bi-Layers

Immortalized cells are commonly used as analogs for primary cells in many cell mechanics, tissue engineering, and biochemical assays. However, it is not well-established whether immortal cell lines can mimic the behavior of primary cells in more physiological (three-dimensional) environments. For this project, we investigate the mechanical properties of primary cardiac fibroblasts (CFs) and 3T3 transformed fibroblasts when cultured in cell bi-layers by comparing the cellsʼ viscoelastic properties.Many cellular and tissue processes depends critically on the viscoelastic properties of the cell (1,2). Additionally, changes in a cellʼs mechanical properties are correlated with some disease states (3). Particle tracking microrheology (PTM) is an ideal technique for measuring the passive, internal viscoelastic properties of cells in more physiological constructs, since it does not require direct contact with the cells. We found that the top layer of 3T3 cells in the bi-layer was significantly stiffer than the bottom layer, while CFs did not exhibit any significant difference between layers. These data suggest that 3T3 cells may exhibit different cytoskeletal behavior in 3D culturing scenarios compared to primary fibroblasts.