Stem cell capsules may help mend broken bones

French and Australian scientists have come up with a new way of delivering stem cells that could one day lead to a single injection to mend broken or diseased bones and joints.

"It is growth factor and stem cells in an injectable format. This would be used wherever you would like to regenerate bone," ABC Science quoted Dr Frank Caruso of the Centre for Nanoscience and Nanotechnology at the University of Melbourne, as saying.

For medical scientists, bone and joint problems are particularly challenging because bone cells sometimes don't heal themselves very well.

That's why researchers are exploring ways to effectively transplant stem cells that will regenerate bones and joints.

Caruso and colleagues have designed a capsule made of synthetic polymers, which they have impregnated with growth factors that stimulate the differentiation of stem cells into bone cells.

He says the capsules are very tiny - ranging from about 100 nanometres to tens of microns.

The researchers have then combined these capsules with embryonic stem cells in a matrix of alginate gel. They injected the mixture into lab animals and showed they can stimulate bone regrowth.

Caruso says the development may lead to treatments in 5 to 10 year if ongoing experiments prove positive.

He says that the team plans to engineer the capsule to control the release of the growth factors, which might otherwise be quickly degraded by the body, avoiding the need for multiple injections.

"The aim is to have a one-dose therapy," he said.

The findings have been published in the Proceedings of the National Academy of Sciences.