Mechanical measurement of supracellular rigidity during two-dimensional epithelial jamming

by Dr. Lior Atia

Department of Mechanical Engineering, BGU

at Biological and soft-matter physics

Thu, 17 Nov 2022, 12:10
Sacta-Rashi Building for Physics (54), room 207

Abstract

All organ surfaces and body cavities are lined by a continuous multicellular layer comprised of epithelial cells that normally constitute a stationary cellular collective. Yet, this cellular collective can become migratory as evidenced by collective cellular motions that arise in key physiological events, such as cancer invasion, embryonic development, and wound healing. In these, a shift between a collective stationary state to a collective migratory state is widely described as an unjamming transition. Unjamming, or jamming, are conventionally examined in two-dimensional epithelia by cell density, cell shape, and by the unique manner in which constituent cells move. All of these visual traits allegedly indicate if cells collectively flow like a fluid or jam and rigidity like a solid. However, it is completely unknown if there exists a directly measured rheological property that mechanically indicates the emergence of a supracellular rigidity as the epithelial cells come to a halt. In this talk I will show how we have bridged this gap by constructing a magnetic tweezers (MT) system that thrust a thin ferromagnetic disk, functionalized and coated with adhesive proteins, and anchored to the apical part of about three thousand cells in a completely confluent two-dimensional epithelial monolayer. The MT pulls the disk and applies a controlled shear stress on the apical plane of the monolayer at different migratory stages. Our observations show how different features in the temporal shear response indicate the emergence of a supracellular rigidity of the epithelial layer in the vicinity of what is usually described as a jamming transition. These, and further observations I will show, suggest that migration and proliferation within the layer is tied to a long-range mechanical resistance to cellular rearrangements, and raise the hypothesis that the jamming and unjamming transitions play a pivotal role in tissue homeostasis, or lack of.

Created on 13-11-2022 by Feingold, Mario (mario)
Updaded on 13-11-2022 by Feingold, Mario (mario)