Extracellular matrix stiffness influences tissue growth and changes in function by modulating cell contractility. For example, as stiffness increases in connective tissue, the cells of a normal breast duct (panel 1, left) start to behave aberrantly, causing the structure of the duct to degrade (panel 2, center), as the uncontrolled cell growth of duct-lining cells invade the duct tube (panel 3, right).

Credit: Matthew Naszek, University of Pennsylvania School of Medicine; Cell Press