Hip hope from stem cell technique

US researchers have developed a promising new technique that might one day enable doctors to regrow broken or diseased joints in patients.

Writing in the The Lancet, US researchers say they have regrown the forelimb thigh joint of rabbits using their own stem cells.

Scientists say they have shown "proof of principle" for the technique which could replace hips

It was the first time an entire joint surface had been regenerated with the return of functions, they said.

The research could benefit patients with damaged hips, shoulders or knees.

The team removed the limbs from 10 rabbits and replaced them with an artificial limb-shaped skeleton.

This was soaked with chemicals which attract bone and cartilage stem cells.

Four weeks later the rabbits had regrown their joints and were able to move normally.

"This is the first time an entire joint surface was regenerated with return of functions including weight bearing and locomotion," said Professor Jeremy Mao of Columbia University Medical Center, New York.

"Regeneration of cartilage and bone both from the host's own stem cells, rather than taking stem cells out of the body, may ultimately lead to clinical applications. In patients who need the knee, shoulder, hip or finger joints regenerated, the rabbit model provides a proof of principle," he said.

Researchers have artificially grown a range of tissue on scaffolding using stem cells for many years, but these have been grown in laboratories. The lab grown tissue has been quite small and has had no veins or arteries to supply them with blood.

More recently, however, several groups of researchers have successfully grown tissue inside animals, where blood vessels naturally form as the tissue grows.

The US group is the latest to have shown that this is a promising technique - and is the first to have grown a large amount of good quality bone and cartilage into successful working joints.

'Too old'

According to Professor Patrick Warnke, a stem cell researcher and plastic surgeon at Bond University in Australia, there is technically no reason why trials should not begin on human patients, for example as an alternative to hip replacements.

But he said there were ethical issues to be considered before beginning clinical trials.

"A hip replacement would definitely cure any potential recruit to any clinical trial. On the other hand you have an experimental treatment that may turn out to be a better option - but may not work at all," he said.

If human trials were to be approved they would not be suitable for very old patients, according to Professor Warnke.

"It would take months of movement, physiotherapy and bed rest for the joint to grow which would be much too long for older people. They would be better off with a normal hip replacement when they can walk out of the hospital after the procedure."

Professor Molly Stevens of Imperial College London said: "Growing large areas of tissue is a massively important clinical goal.

"This is the latest study to have shown that there are stem cells in the body that can be harnessed to grow bone and tissue if they are given the right sort of signals."