Collective and single cell behavior in epithelial contact inhibition

Abstract

Control of cell proliferation is a fundamental aspect of tissue physiology central to morphogenesis, wound healing, and cancer. Although many of the molecular genetic factors are now known, the system level regulation of growth is still poorly understood. A simple form of inhibition of cell proliferation is encountered in vitro in normally differentiating epithelial cell cultures and is known as "contact inhibition." The study presented here provides a quantitative characterization of contact inhibition dynamics on tissuewide and single cell levels. Using long-term tracking of cultured Madin-Darby canine kidney cells we demonstrate that inhibition of cell division in a confluent monolayer follows inhibition of cell motility and sets in when mechanical constraint on local expansion causes divisions to reduce cell area. We quantify cell motility and cell cycle statistics in the low density confluent regime and their change across the transition to epithelial morphology which occurs with increasing cell density. We then study the dynamics of cell area distribution arising through reductive division, determine the average mitotic rate as a function of cell size, and demonstrate that complete arrest of mitosis occurs when cell area falls below a critical value. We also present a simple computational model of growth mechanics which captures all aspects of the observed behavior. Our measurements and analysis show that contact inhibition is a consequence of mechanical interaction and constraint rather than interfacial contact alone, and define quantitative phenotypes that can guide future studies of molecular mechanisms underlying contact inhibition.EMT | growth regulation | mechanics | mitosis

Spatio-temporal morphology changes in and quenching effects on the 2D spreading dynamics of cell colonies in both plain and methylcellulose-containing culture media

“…In those models, contact inhibition sets in as the local cell density exceeds a certain critical value. Seemingly, this inhibition is caused by mechanical interactions and constraints that define cell phenotypes unable to undergo mitosis or crawl [42]. The increased colony heterogeneity in the gel medium makes the application of these models difficult.…”

Emergence of collective modes and tri-dimensional structures from epithelial confinement

“…We now turn to the later stages of these highly confined monolayers (t425 h). When the density reached a value of B10 6 cells cm À 2 , the increase in population within the monolayer drastically slowed down 19 ( Supplementary Fig. 1C,D).…”

“…1B). After 30 h, cell division slowed down but did not completely stop 19 ; the cells resulting from these divisions were apically extruded from the monolayer 20 ( Fig. 1c, Supplementary Fig.…”

Discontinuous fluidization transition in time-correlated assemblies of actively deforming particles

“…In contrast to externally driven systems (such as sheared materials), active matter is driven out of equilibrium at the scale of its microscopic constituents. Well-studied examples include biological tissues [3], bacterial suspensions [4] and active granular and colloidal particles [5][6][7][8].Epithelial tissues constitute a biologically relevant active system composed of densely packed eukaryotic cells [3,[9][10][11][12][13][14]. Such tissues display a surprisingly fast and collective dynamics, which would not take place under equilibrium conditions [10].…”