Rabbits were able to regrow a leg joint using their own stem cells, say scientists exploring the cells' potential to replace artificial joints in human patients.

Researchers removed the forelimb thigh joint from 10 rabbits and then coaxed the animals' stem cells to regenerate the bone and cartilage .

It’s the first time an entire joint surface has been regenerated with return of functions including weight bearing and locomotion, said study author Professor Jeremy Mao of Columbia University Medical Center in New York.

The experiment is described in Thursday's online issue of the journal The Lancet.

For the study, Mao and his colleagues removed the limbs from 10 rabbits that then received an artificial limb-shaped skeleton soaked in growth factors to attract bone and cartilage stem cells.

Another 10 rabbits received the limb implant without the growth factor, known as growth factor beta-3, but they were not able to move as well as the animals in the first group, the researchers reported.

Three other rabbits whose joints were surgically damaged and not repaired had a permanent limp.

The findings represent a proof of principle for patients who need a knee, shoulder, hip or knee joint regenerated, the researchers said, noting that scientific and regulatory issues remain.

Bioreactor 'renaissance'

Human patients may also have other conditions and medications that could affect the regeneration of their joints, which the animal models did not face.

Since humans use two legs rather than four like rabbits, people might need to be on bed rest for longer periods than the animals.

In a journal editorial accompanying the study, Dr. Patrick Warnke, a stem cell researcher and plastic surgeon at Bond University in Gold Coast, Australia, described the work as "a renaissance of use of the host as a bioreactor."

But he added not all patients would be able to regenerate tissues the same way, such as elderly people with diabetes who might benefit from standard metal joint replacement.

The recovery period of immobility while the joint regenerates would also be risky, Warnke said.

Warnke suggested cultivating the joint replacement inside a patient's muscle joint and then transplanting it to where needed to reduce regeneration time.

Metal joints last about 10 to 15 years. Demand for replacement joints is expected to grow as the population ages.

The study was funded by New York State Stem Cell Science and the U.S. National Institutes of Health.