Mapping the subcellular mechanical properties of live cells in tissues with fluorescence emission–Brillouin imaging

Mechanical properties of cells and the matrix that surrounds them contribute to cell shape, control cell migration, and regulate cell growth. Elsayad et al. engineered a microscope system that integrated fluorescence emission detection with detection of a light-scattering process called the Brillouin frequency shift and called the method fluorescence emission–Brillouin scattering imaging (FBi). With this optical approach, the authors showed that the mechanical properties of live plants can be visualized at the submicrometer scale and demonstrated that this approach can be used to investigate regulatory events that alter cellular and extracellular mechanical properties of living cells within tissues. This work also revealed that the cytoplasm near the cell membrane and the extracellular matrix are regions of locally increased stiffness and showed that the sides parallel to the growth axis of an expanding plant hypocotyl, but not root, cells are “stiffer” than the sides perpendicular to the growth axis. Thus, FBi is another tool in the microscopy toolkit for exploring properties of cells and tissues.