“Heart of glass” may be more than just a metaphor

Jeffrey Fredberg is a professor of bioengineering and physiology at the Harvard School of Public Health. His primary research interest is asthma. Fredberg was intrigued by the plasticity of the smooth muscle cells that surround the lung’s airways, and which are impaired in asthma, so he and some colleagues began to probe the mechanical properties of the cells. Using a method they invented in 1992, in which magnetized beads stretch and pull at cultured cells, the researchers came up with a series of surprising measurements. “They did not fit any preconceived notions about how muscle cells should behave — or how any cells should behave,” Fredberg said. Perplexed, research associate and lead author Ben Fabry showed the data to a colleague, who handed him a paper on soft glasses, which include substances such as foam, slurries, and colloidal suspensions. Conceptually, the theory appeared to fit their observations of living cells. But the real surprise came when they crunched the numbers into the mathematical formulas. “Lo and behold, the theory fit our data perfectly,” said Fredberg. “We wondered if this is the grand unifying theory of cell mechanics.”