BIOE Seminar: Jeffrey Fredberg
Friday, May 3, 2019
9:00 a.m.-10:00 a.m.
A. James Clark Hall, Room 2132
Dr. Giuliano Scarcelli
Dr. Jeffrey Fredberg
Professor of Bioengineering and Physiology
Harvard T.H. Chan School of Public Health
Geometrical constraints during epithelial jamming
As an injury heals, an embryo develops, or a carcinoma spreads, epithelial cells systematically change their shape. In each of these processes cell shape is studied extensively, whereas variability of shape from cell-to-cell is regarded most often as biological noise. But where do cell shape and variability of cell shape come from? Here we report that cell shape and shape variability are mutually constrained through a relationship that is purely geometrical. That relationship is shown to govern processes as diverse as maturation of the pseudostratified bronchial epithelial layer cultured from either non-asthmatic or asthmatic donors, and formation of the ventral furrow in the epithelial monolayer of the Drosophila embryo in vivo. Across these and other epithelial systems, cell shape variability collapses to a family of distributions that is common to all. That distribution, in turn, is accounted for quantitatively by a mechanistic theory of cell-cell interaction showing that cell shape becomes progressively less elongated and less variable as the layer becomes progressively more jammed. These findings suggest a connection between jamming and geometry that spans living and inert jammed systems alike, and thus transcends system details. Although molecular events are needed for any complete theory of cell shape and cell packing –whether during embryogenesis, cancer invasion, or wound healing– evidence points to jamming behavior at a larger scale of organization as setting overriding geometrical constraints.