Chuong's team did not see a similar hair regrowth reaction when it plucked the same number of hairs spread over a larger area. If the plucking pattern exceeded six millimeters in diameter, for example, hairs did not regenerate at all—even after 30 days. Higher-density plucking from circular areas with diameters between three and five millimeters, however, triggered the regeneration of between 450 and 1,300 hairs, including ones outside of the plucked area. The team also detected elevated levels of certain chemicals that suggest the cells were “talking” amongst themselves. “Chemical communication between mammalian cells has obviously been reported before but the novelty here is about space and crowding,” says Vanessa Sperandio, a professor of microbiology and biochemistry who focuses on quorum sensing at The University of Texas Southwestern Medical Center. “There is a relationship here with thresholds that no one has seen before,” says Sperandio, who was not involved with the study. …show more content…
Collectively, these clues all suggest neighbor cells’ signaling had some importance.

In bacteria it has been widely documented that communication hinges on quorum sensing. When there are only a few bacteria, they will not meet the threshold for action. But once their concentration is high—which they can sense from a greater number of signaling molecules around them—they can and will take collective action. Quorum sensing in animal cells, Chuong says, could similarly help the body decide whether to ignore small irritations or take collective action. “I think quorum sensing would help an organ respond collectively so it could deal with outside stimuli in the most effective and efficient way,” he