Cell Crawling Assisted by Contractile Stress Induced Retraction

Abstract

Cell locomotion is a result of a series of synchronized chemo-mechanical processes. Crawling-type cell locomotion consists of three steps: protrusion, translocation, and retraction. Previous works have shown that both protrusion and retraction can produce cell movement. For the latter, a cell derives its propulsive force from retraction induced protrusion mechanism, which was experimentally verified by Chen (1979, "Induction of Spreading During Fibroblast Movement," J. Cell Biol., 81, pp. 684-691). In this paper, using finite element method, we take a computational biomimetic approach to study cell crawling assisted by contractile stress induced de-adhesion at the rear of the focal adhesion zone (FAZ). We assume the formation of the FAZ is driven by receptor-ligand bonds and nonspecific interactions. The contractile stress is generated due to the molecular activation of the intracellular actin-myosin machinery. The exerted contractile stress and its time dependency are modeled in a phenomenological manner as a two-spring mechanosensor proposed by Schwarz (2006, "Focal Adhesions as Mechanosensors: The Two-Spring Model," BioSystems, 83(2-3), pp. 225-232). Through coupling the kinetics of receptor-ligand bonds with contractile stress, de-adhesion can be achieved when the stall value of the contractile stress is larger than a critical one. De-adhesion at the rear end of the FAZ causes a redistribution of elastic energy and induces cell locomotion. Parametric studies were conducted to investigate the connection between the cell locomotion speed and stall stress, and receptor-ligand kinetics. Finally, we provide a scaling relationship that can be used to estimate the cell locomotion speed.