Collective cell motility

The course discusses some aspects of cell motility both at the individual cell level and at the collective level. The presentation is theoretical but the problems studied will be motivated by biological questions.  One of the main aspects of the course is to treat the cell itself and at a larger cell an assembly of cells as active matter and to discuss cell motility within the framework of active matter theory.

1-Introduction to cell motility: The first lecture gives a general introduction to single cell motility in two and three dimensions. It discusses the large scale motion of cells as a  persistent random walk and introduces briefly taxis phenomena.  The final part discusses the general physical principles of cell motion on a solid substrate

2-Keratocyte motion: Keratocytes are one of the most studied models of cell motility. They have a very flat shape containing mostly the actin-myosin cytoskeleton that can be considered as an active gel. This second lecture presents very simple models of keratocyte motions emphasizing in particular the relative roles of actin turn-over and of acto-myosin contractility. It also discusses the shape of moving cells. 

3-Spontaneous cell motion in cell monolayers: The third lecture considers collective cell motion in a confluent layer of elongated cells on a solid substrate. The cell layer is considered as an active nematic fluid. The lecture introduces the hydrodynamic theory of active nematics and shows how spontaneous flows can occur in the absence of imposed pressure gradients. If the activity is very large the layer reaches an active turbulent state.

4-Collective cell migration in an elastic matrix: During metastasis cancer cells migrate collectively through conjonctive tissues that can be considered as elastic media. Experiments in particular by P. Friedl have shown that there exist several types of migration patterns. The lectures presents a hydrodynamic theory of the cells migration in an elastic medium by considering them as an active polar fluid permeating through an elastic gel, and discusss the stability of a unifomly moving pattern. It also presents  a more microscopic model where the cells remodel the matrix both by secreting and degrading it.