Cells 'flock' to heal wounds

Like flocks of birds, cells coordinate their motions as they race to cover and ultimately heal wounds to the skin. How that happens is a little less of a mystery today.

Researchers once thought only the cells at the edge of a growing patch of wounded skin were actively moving while dividing cells passively filled in the middle. But that's only part of the picture. Rice University physicist Herbert Levine and his colleagues have discovered that the process works much more efficiently if highly activated cells in every part of the patch exert force as they pull their neighbors along.

There's a need to understand how cells cooperate to protect the site of a wound in the hours and days after injury, said Levine, who has introduced the first iteration of a computer model to analyse the two-dimensional physics of epithelial sheets. He hopes it will give new insight into a process with long-term implications not only for healing but also for understanding cancer, a prime motivator in his research since joining Rice under a grant from the Cancer Research and Prevention Institute of Texas.

A paper on the research by Levine, based at Rice University's BioScience Research Collaborative, and colleagues at the University of California at San Diego and in Germany and France appears today in the Proceedings of the National Academy of Science.

Levine and his colleagues create computer models of processes seen by experimentalists to flesh out the rules that govern biological systems. ''Here, we're combining experimental observations from single cells with general notions from the physics literature to create an integrated way of thinking about this multicellular system,'' he said.

The new models were prompted by a recent Harvard study showing ''that even in the middle of a sheet, cells were dynamically creating heads and tails and were actively moving rather than being passively carried along,'' Levine says. ''This data convinced us that we needed a different way to start to think about the problem.''