Finding may impact understanding of mechanical facets of many diseases

An international team led by Jeffrey J. Fredberg, professor of bioengineering and physiology at the Harvard School of Public Health, has found that the cell modulates its mechanical properties in much the same way as a glassblower shapes fine glassware.

This new view of cellular functions sheds light on mechanical facets of phenomena as diverse as asthma, cancer, inflammation, and vascular disease. These findings appear in advance online from the July, 2005 issue of Nature Materials.

To fashion a work of glass, a glassblower must heat the object, shape it, and then cool it down. Fredberg and his colleagues have shown that the cell modulates its mechanical properties and changes its malleability in much the same way. But instead of changing temperature, the cell changes a temperature-like property that has much the same effect.

Using an array of novel nanotechnologies developed by the researchers at HSPH, Fredberg et al. discovered the basic physical laws that describe cell mechanical behavior. Previously, the classical model of cell mechanical behavior had pictured the cell as a viscous fluid core contained by an elastic cortical membrane, but their findings did not at all conform to that picture. The team's experiments show that the cell is a strange intermediate form of matter that is neither solid nor fluid, but retains features of both. Moreover, as the cell goes about its routine business of stretching, spreading, and contracting, it can vary that temperature-like property and control where it sits along the spectrum between solid-like and fluid-like states.

"These findings have important lessons for understanding the dynamics of structural proteins at a scale that is intermediate between the single molecule and integrative cellular function. This is a collective phenomenon of many molecules interacting in concert, and would disappear altogether in the study of one molecule interacting with another in isolation," said Fredberg. He continued, "The laws governing cell behavior bring together into one physical picture cell elasticity, viscosity, and remodeling, and give us a different way to think about the molecular basis of airway narrowing in asthma, vessel narrowing in vascular disease, wound repair, embryonic development, and cell invasion in cancer, all of which have important mechanical components. Perhaps most surprising of all, in addition to offering a different way to think about mechanisms of disease, these findings shed light upon the behavior of familiar inert condensed substances that remain poorly understood, including pastes, foams, emulsions, and granular materials."