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. 鈥淵ou could rehydrate them when you needed the sensor,鈥� says Malcolm
Potts of the Virginia Tech Center for Genomics in Blacksburg, who developed the
technique.
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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 鈥渟tar jelly鈥� and 鈥渨itches butter鈥�.
N. commune survives by surrounding itself with a slimy substance called
glycan, Potts says. 鈥淚t forms a woolly overcoat for the cells.鈥� 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鈥檚 Society for Experimental Biology in Canterbury earlier this
month. 鈥淚t鈥檚 a breakthrough,鈥� says Potts. 鈥淏y applying the techniques we have
found in cyanobacteria, we can dry out human cells. It鈥檚 very exciting.鈥�
Alan Tunnacliffe of the Institute of Biotechnology at Cambridge University
says he鈥檚 surprised the cells survived with only glycan to protect them, as it
does not get inside the cells. 鈥淚 am a little sceptical,鈥� he says. 鈥淏ut if it
does work, it is a major achievement.鈥�
Last year, Fred Levine of the University of California in San Diego reported
that he had revived dried human cells after 5 days
(快猫短视频, 19 February 2000, p 11).
But this technique doesn鈥檛 work for normal cells鈥擫evine鈥檚
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鈥檚 results. But he insists the
technique works. 鈥淲e have been drying cells, putting them in a standard
cardboard container, sending them [from California] to the East Coast and having
them successfully rehydrated,鈥� he says.
Potts and Helm hope that one day tissues and perhaps even organs could be
dried out and revived. But this won鈥檛 be achieved with glycan alone, Potts says.
鈥淚n the end it鈥檚 bound to require a combination of different approaches.鈥�