Cells interact with their local environment to communicate and respond to foreign, potentially harmful objects. Membrane receptors can respond to external stimuli by undergoing conformational change or by reorganizing. These phenomena can initiate signaling cascades that are crucial for vital biological processes, such as the immune response. Because of this sensitivity to external stimuli, it is challenging to immobilize cells for imaging without causing them to respond. We set out to develop a sensitive imaging platform that is minimally perturbative to cells by combining light-sheet microscopy and hydrogel suspension.
The cover for the May 8 issue of the Biophysical Journal is an artistic rendering of how surfaces can influence membrane protein dynamics in lymphocytes. A red T cell interacts with the surface and spreads out due to adhesion. A green T cell is suspended in an agarose hydrogel that allows the cell to retain its natural shape. The difference between these cells is visualized using reflection to indicate that the green cell is floating. For both cells, real tracking data is rendered as thick glowing lines. The red tracks on the adhered cells are immobile due to the interaction with the surface, while the green tracks on the suspended cell undergo free diffusion. The light sheet, which is used to image these dynamics, is also depicted by a cyan glow. Where it overlaps one of the green tracks, fluorescence is portrayed by the emission of a yellow glow. The membranes of the cells were created with displacement mapping using T cell electron microscopy data and the final image was rendered in SolidWorks.
This illustration highlights the dramatic influence that external factors can have on cells. There is a general need to develop minimally perturbative imaging methods to probe the native state of cells and to understand changes that occur during cellular processes such as recognition and activation, which rely on intercellular interactions.
- Aleks Ponjavic, James McColl, Alexander Carr, Ana Mafalda Santos, Klara Kulenkampff, Anna Lippert, Simon Davis, David Klenerman, Steven Lee