Instant stem cells - just add water
Dried cells could aid remote medicine.
19 December 2003
HELEN PEARSON

 
Cell membranes crack if they are overly parched.
 
 
 

Researchers are honing a technique to create dried stem cells that can be revived just by adding water. The 'instant' cells might make mobile therapies for remote regions or the battlefield.

Because some stem cells can make fresh bone, muscle or blood, doctors hope to use them to repair tissues. But, like transplant organs kept on ice, their shelf life will be limited without an easy way to store and transport them.

Today researchers save stem cells by freezing them in expensive vats of liquid nitrogen at -140 ºC. To stop damaging ice crystals forming inside the cells, they bathe them in a toxic chemical such as dimethylsulphoxide. This must be washed off before cells can be used.

Air drying

Several scientists are looking for a way to air-dry cells, comparable to the technique that turns grapes to raisins. Dried stem cells might be stored in portable packets that can be ripped open and their contents mixed with water at the scene of an accident, says Ann Oliver of the Center for Biostabilization at the University of California, Davis.

Oliver dreams of plastering desiccated stem cells onto a bone-shaped matrix and then adding water and growth proteins to trigger the cells to divide and form new bone, ready for a transplant. "It's a pie-in-the-sky goal," she admits.

In their latest advance, Oliver and her colleagues dried out mesenchymal stem cells, sucked from bone marrow. After drying, less than 40% of the cells was water. When rehydrated immediately afterwards, up to half grew and divided, Oliver revealed at this week's American Society for Cell Biology meeting in San Francisco.

Her team soaked the stem cells in an anti-freeze sugar called trehalose. This sugar sloshes around in organisms that survive dehydration, such as brine shrimp, baker's yeast and certain drought-resistant resurrection plants. Adding a second protective compound called arbutin boosted cell survival further.

Researchers have used trehalose before to preserve other cells. The real breakthrough, says Fred Levine of the University of California, San Diego, will come when cells can be revived after several weeks on the shelf. Levine says his group are achieving similar results as Oliver's, also with mesenchymal stem cells.

What's more, 80-90% of rehydrated cells must be revived before the technique can be put into practice, says Mark Pittenger of Osiris Therapeutics in Baltimore, Maryland, whose company works with Oliver. "It's unclear when it'll come along," he says.

Wet ones

Dehydration must remove as much water as possible so that cells' metabolism is halted, otherwise they churn out waste that poisons their surroundings. But cell membranes crack if they are overly parched. Researchers are experimenting to strike the right balance.

Oliver and her team used a similar technique to dry and store blood platelets for transfusions for up to two years, without causing them any obvious harm. Transferring the technique to stem cells is tricky because, unlike platelets, they have nuclei that must be perfectly preserved.