Cell Cycle Phases, Their Effect on Cell Mechanical Properties, and the Impact on Candida-Host-Cell Interactions.

Cell mechanics is essential in many biological phenomena such as cell division and migration. Further, cell mechanobiological measurements can distinguish between healthy and diseased cells; thus, investigations of cell mechanics have led to the development of tools to study the elasticity and the viscosity of cells. Cell mechanics can be affected by factors such as cell morphology, cytoskeletal remodelling, and cell intrinsic factors, and these are important in understanding disease progression. Here, we use an atomic force microscopy (AFM)-microrheology with a colloidal probe for a dynamic mechanical analysis of host cell elasticity and viscosity at 6 frequencies ranging from 1 to 200 Hz. Epithelial cells exhibit a more "liquid-like" behavior as the frequency increases, whereas cancerous cells transition into this viscous, fluid-like state at lower frequencies (48 and 63 Hz) compared to normal cells (92 Hz). Cell mechanical measurements inherently exhibit heterogeneity due to physical factors, such as cell shape and the position of the probe on the cell surface. In addition to this physical variability, biological parameters─notably the cell cycle phases─also contribute to mechanical heterogeneity. In this study, we specifically investigated the influence of cell cycle phases on the cell mechanical properties. Using chemically synchronized normal and cancerous cells in different phases of the cell cycle shows that the actin cytoskeleton undergoes rapid reorganization as the cell cycle progresses. Results show that as actin becomes disorganized, the elastic moduli decreases and the loss tangent is larger coupled with a lower phase shift frequency. Cells in the G1 and S phase had the lowest elastic moduli (G') meaning they were softer than cells in the G2/M phase. During disease onset, the pathogen adheres and invades the host, a process that leads to cytoskeleton arrangement and thus changes in cell elasticity, and thus, to understand the impact of the cell cycle on host invasion, we probed the interaction of Candida albicans with HeLa, HCT 116, and HaCaT cells using AFM in the single-cell force spectroscopy mode. There was a significant increase in force of interaction during the S phase which could be attributed to the disorganized cytoskeleton. This shows the importance of cytoskeletal organization and cell cycle phase in cell mechanical properties and pathogen-host interaction.