Cell motility in a compressible gel (Vol. 51, No. 1)

Actomyosin droplet with superimposed velocity field.

Cell motility is crucial to biological functions ranging from wound healing to immune response. Spontaneous movement and deformation are physically driven by the cell cytoskeleton.

The cytoskeleton consists of protein filaments and motors which constantly consume chemical energy (ATP) and convert it to work. In particular, actin filaments interact with myosin motors to generate contraction forces in the cell, which drive cell motion and division. Most of the research has focused, both experimentally and theoretically, on cell migration on a two-dimensional substrate (crawling), providing a detailed outline of some basic migration mechanisms. However, some cells, such as breast tumor cells, can also “swim” in a straight line inside a 3D tissue or a polymeric fluid, in the absence of substrates. The authors present a minimal model for pattern formation within a compressible actomyosin gel, which is numerically solved both in 2D and 3D. Contractility leads to the emergence of an actomyosin droplet within a low-density background. This droplet then becomes self-motile for sufficiently large motor contractility. Simulations also show that compressibility has the effect to facilitate motility, as it decreases the value of the isotropic contractile stress beyond which the droplet starts to move.

G. Negro et al, Hydrodynamics of contraction-based motility in a compressible active fluid, EPL 127, 58001 (2019)