Quantifying cell and tissue mechanics
Tissues change their mechanical properties during development, disease, and wound healing, but under normal conditions the elastic moduli of healthy tissues from organisms at the same stage of development are tightly controlled. Cells in culture respond strongly to changes in substrate or matrix stiffness that span the range from healthy to diseased organs, and matrix stiffness can have as profound an effect on cellular phenotype as chemical stimuli. Because the cell’s internal cytoskeleton as well as the extracellular matrix are composed of stiff or semi-flexible polymers, the physics of rigid polymer networks is often used as a guide towards understanding the mechanical responses of tissues. However, direct measurements of tissues subjected to the large compressive and shear strains they encounter in vivo reveal that the nonlinear elastic responses of tissues often differ fundamentally from the responses of purified polymer networks. How the mechanics of a tissue that is characterized by densely packed cells encapsulated within a polymer matrix change when specific elements of this composite material or altered suggests that tissue mechanics emerges from a complex interaction between structurally disparate materials that cannot be accounted for entirely by current simplified models.
Bio
Paul Janmey is professor of physiology, physics, and bioengineering at the Institute of Medicine and Engineering at the University of Pennsylvania. He received his Ph.D. in physical chemistry from the University of Wisconsin and completed his postdoc at the Hematology-Oncology Unit at Massachusetts General Hospital.
Dr. Janmey’s research interests include the interaction between cytoskeletal and extracellular matrix stiffness, effects of substrate mechanics on cell structure and function, phosphoinositide signaling for actin assembly, fibrin-based materials for wound healing, and intermediate filament assembly and mechanics.