Forces play an essential role in the lives of many cells. Cells move around and maintain or change their shape by exerting forces. To understand how cells generate and respond to forces, a setup is...Show moreForces play an essential role in the lives of many cells. Cells move around and maintain or change their shape by exerting forces. To understand how cells generate and respond to forces, a setup is required to apply forces on a cellular scale. We constructed a magnetic tweezer which allows us to produce magnetic fields inside a cell. We then administered paramagnetic beads to the cells, which they phagocytose. The magnetic fields generated by the tweezer couple to the paramagnetic bead, pulling the bead in the direction of the tweezer. Using this technique, we demonstrate that a mouse embryonic fibroblast has both an elastic and a plastic response to being repeatedly pulled on, consistent with existing literatuture.Show less
Most vital processes in our body including tissue formation, wound healing and immune response are dependent on directed cell migration, which is mediated by chemical and mechanical stimuli....Show moreMost vital processes in our body including tissue formation, wound healing and immune response are dependent on directed cell migration, which is mediated by chemical and mechanical stimuli. Dysfunctions in directed migration can have severe consequences, such as tumor formation and metastasis. We studied the combined effect of both chemical and topographical stimuli on the model organism Dictyostelium discoideum, which exhibits amoeboid migration similar to that of higher eukaryotes. A chemotactic gradient was introduced by the diffusion of cyclic adenosine monophosphate (cAMP) in a microfluidic chamber and a topotactic gradient was established by use of a polydimethylsiloxane (PDMS) micro-pillar array of variable pillar density. Establishing both gradients in a quasi-3D environment mimics a controllable natural setting that D. discoideum cells encounter during the aggregation competent state. We then observed live cell migration of 2000 cells in different configurations of the combined gradients using spinning disk confocal fluorescence microscopy. We distinguished directed cellular runs from non-directed random migration through high resolution motion analysis. This analysis helped characterizing the combined chemotactic and topotactic effects on cell migration. We found that different configurations of both gradients, individually and combined, can increase or suppress cell velocity and amplify or weaken directionality in migration.Show less
