Biophysical Society Thematic Meeting

Mechanobiology of Disease

Tuesday Speaker Abstracts

Mechanobiology of Epithelial-to-Mesenchymal Transition in Confined Environments

Amit Pathak

Washington University in St. Louis, St. Louis, MO, USA.

Epithelial cells disengage from their clusters and become motile by undergoing epithelial-to-

mesenchymal transition (EMT), an essential process for fibrosis and tumor metastasis. Growing

evidence suggests that high extracellular matrix (ECM) stiffness induces EMT. However, very

little is known about how various geometrical parameters of the ECM might influence EMT. We

have adapted a hydrogel-microchannels based matrix platform to culture epithelial clusters in

ECMs of tunable stiffness and confinement. We report that epithelial clusters undergo EMT to a

greater degree in more confined ECM settings. Surprisingly, cell clusters residing in soft ECMs

exploit this confinement-sensitive EMT better than those in stiff ECMs. Upon pharmacological

inhibition of microtubules, cells lose the ability to polarize their cytoskeleton in response to

ECM confinement, which in turn disables the confinement-sensitive EMT. Disruption of cell-

ECM adhesions blunts the influence of ECM stiffness on EMT. To gain quantitative insights into

relative contributions of subcellular and extracellular features to the ECM-dependent EMT, we

simulated our experimental findings through a novel computational model that combines

mechanics-based cellular features into a multi-cell network under varied ECM properties. Our

model is based on cooperative operation of cell-ECM adhesions, protrusion dynamics, and

actomyosin forces, which collectively dictate the state of cell-cell junctions in each cell of a

given epithelial cluster. The model also accounts for the stiffness and the geometry of the ECM

surrounding the mutli-cell network. Taken together, our experimental and computational results

reveal that ECM confinement alone can induce EMT, even in soft tissue contexts that otherwise

maintain epithelial integrity in unconfined environments. These findings highlight that

topographical structure and mechanical stiffness of the tissue microenvironment can both

independently regulate EMT, which brings a fresh perspective to the current understanding of

microenvironment-dependent dissemination and invasion of cancer cells through confined spaces

around tumor.