Elastic Modulus Versus Cell Packing Density in MDCK Epithelial Monolayers

TL;DR

This study examines how the elastic modulus of MDCK epithelial monolayers varies with cell packing density, revealing a decrease at low densities and a plateau at high densities, which informs tissue mechanics understanding.

Contribution

It provides the first multi-cellular scale measurement of tissue elasticity in relation to cell density in MDCK monolayers, using micro-indentation techniques.

Findings

Elastic modulus decreases with increasing cell density at low densities.

Elastic modulus plateaus at high cell densities.

Results inform understanding of tissue mechanics and collective cell behavior.

Abstract

The elastic moduli of tissues are connected to their states of health and function. The epithelial monolayer is a simple, minimal, tissue model that is often used to gain understanding of mechanical behavior at the cellular or multi-cellular scale. Here we investigate how the elastic modulus of Madin Darby Canine Kidney (MDCK) cells depends on their packing density. Rather than measuring elasticity at the sub-cellular scale with local probes, we characterize the monolayer at the multi-cellular scale, as one would a thin slab of elastic material. We use a micro-indentation system to apply gentle forces to the apical side of MDCK monolayers, applying a normal force to approximately 100 cells in each experiment. In low-density confluent monolayers, we find that the elastic modulus decreases with increasing cell density. At high densities, the modulus appears to plateau. This finding will help guide our understanding of known collective behaviors in epithelial monolayers and other tissues where variations in cell packing density are correlated with cell motion.