Cell-migration in two-state micropatterns

Migrating cells are key players during development and immune response, and also in cancer metastasis. Cells actively adapt their mode of migration to constraints imposed by their microenvironment. To provide standardized and tunable microenvironments for the study of cell organization and migration, micropatterning techniques were developed. Micropatterning allows the controlled deposition of cell-adhesive proteins in defined geometries on a surface while rendering the surrounding areas cell-repellent. The spreading dynamics of cells on micropatterns has previously been successfully modelled and several theoretical models exist for cell migration on homogeneous substrates. In contrast, little is known about the dynamics of cells in confining microenvironments. In particular, it is an open question how the dynamics changes as a function of the geometry of the confinement. In this thesis, I developed an artificial micrometre-scale two-state system for the study of cell migration in confinement. Furthermore, I identified several geometric determinants affecting the migration dynamics and quantified their effect. The micropatterned system consists of two cell-sized adhesion sites at either end of a connecting stripe. MDA-MB-231 human breast cancer cells, and several other cell lines, responded to the dumbbell-like geometry by migrating back and forth between the adhesion sites. The migration can be characterized by direct readouts from the cell trajectories such as accelerations, dwell times and occupation probabilities. In collaboration with the Broedersz group, we found a novel theoretical description for cell migration in confinement that is entirely based on short-timescale readouts. We showed that the cell migration in the two-state micropattern is captured by a stochastic equation of motion consisting of a deterministic and a stochastic term. Both terms were inferred from the data and a good agreement between model prediction and experimental data was found. In particular, we established that highly metastatic MDA-MB-231 breast cancer cells and non-tumourigenic MCF10A breast epithelial cells have distinct deterministic dynamics on two-state patterns with a bridge width of 7.2 μm. The two-state setup was further used to systematically probe the influence of geometrical cues presented to the cells within the micropatterns. Thus, the migration dynamics of cells was found to be sensitive to bridge length and width, adhesion site area and adhesion site orientation. Specifically, the escape rates of cells from differently shaped adhesion sites were determined. For isotropic shapes, it was found that the escape rates linearly depend on adhesion site area only. When adhesion sites extend significantly into the direction orthogonal to the micropattern’s bridge, cell polarisation on the adhesion sites biases occupation probabilities. Consequently, the two-state system is a suitable assay to study cell dynamics as a function of the confining microenvironment. In this particular confinement, cells have to deform in order to transition between the two adhesion sites. As cell lines of different metastatic potential exhibit different dynamic behaviour, the measured escape dynamics may possibly be connected to clinical parameters like invasiveness.