Influence of Cell Confluency on Mechanical Properties of Breast Cells

Abstract

The mechanical properties of cells play important roles in various cellular processes, including cell division, migration, differentiation, and human diseases. Therefore, measuring the mechanical properties of cells provides valuable insights into such processes. A significant body of research already exists, and it has been reported that the actin fibers of cells play a major role in determining the mechanical properties of cells. Actin fibers are highly dynamic and have different structures as cells interact with their microenvironment and neighboring cells. Most studies about cell stiffness have focused on single, isolated cells, and the influence of confluency on cell stiffness has been largely ignored, even though actin structures change significantly as cell-to-cell junctions are formed. In this study, we hypothesize that cell confluency significantly affects cell stiffness. To test this hypothesis, we investigated the mechanical properties and actin distribution of human mammary epithelial cells (HMECs) in three different states: isolated cells, sub-confluent cells, and mature epithelial layers. Our method combined force data from an atomic force microscope with actin density data gathered using fluorescence microscopy. Our results show that the stiffness of cells in epithelial layers increases fivefold, compared to both single and sub-confluent cells. These changes in stiffness are highly correlated with reorganized actin filaments as we observed that regions with higher actin density have higher Young's moduli. Cell-cell interactions strongly influence actin organization and cell stiffness.