Normal human cells have been dried out and revived eight days later using a trick evolved by a bacterium that can survive for centuries without water. The technique could have all sorts of medical uses.
Blood for transfusions could be stored for long periods, for example, or carried to remote disasters without having to be kept cool. Antibodies and vaccines would have an almost unlimited shelf life, making them easier to distribute in developing countries.
Desiccated medical supplies could even be sent on long space missions. And it should become possible to make cell-based biosensors to detect poisons such as nerve gas. “You could rehydrate them when you needed the sensor,” says Malcolm Potts of the Virginia Tech Center for Genomics in Blacksburg, who developed the technique.
Our cells usually die within seconds without water. But Potts and his colleague David Helm knew of a photosynthetic bacterium, or cyanobacterium, called Nostoc commune, that can survive such harsh conditions. N. commune lives on exposed rock surfaces, where it often dries out. When the rock gets wet again the cells come back to life, swelling up to form gel-like masses whose sudden appearances led to the popular names “star jelly” and “witches butter”.
N. commune survives by surrounding itself with a slimy substance called glycan, Potts says. “It forms a woolly overcoat for the cells.” Glycan is thought to protect cell membranes, as well as slowing the rate of drying.
So Potts and Helm tried mixing purified glycan with human kidney cells and drying them out at room temperature. When they rehydrated the cells 8 days later, half of the cells recovered and started dividing again, Potts told a meeting of Britain’s Society for Experimental Biology in Canterbury earlier this month. “It’s a breakthrough,” says Potts. “By applying the techniques we have found in cyanobacteria, we can dry out human cells. It’s very exciting.”
Alan Tunnacliffe of the Institute of Biotechnology at Cambridge University says he’s surprised the cells survived with only glycan to protect them, as it does not get inside the cells. “I am a little sceptical,” he says. “But if it does work, it is a major achievement.”
Last year, Fred Levine of the University of California in San Diego reported that he had revived dried human cells after 5 days (New Scientist, 19 February 2000, p 11). But this technique doesn’t work for normal cells-Levine’s team had to genetically modify the cells to make a sugar called trehalose, which protects cells against freezing and drying from the inside.
Other researchers have failed to repeat Levine’s results. But he insists the technique works. “We have been drying cells, putting them in a standard cardboard container, sending them [from California] to the East Coast and having them successfully rehydrated,” he says.
Potts and Helm hope that one day tissues and perhaps even organs could be dried out and revived. But this won’t be achieved with glycan alone, Potts says. “In the end it’s bound to require a combination of different approaches.”
Author: Joanna Marchant
New Scientist issue: 21st April 2001
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Contact: Claire Bowles
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