Need a new knee or hip? Grow it yourself, research promises

PEOPLE with knee or hip problems could in future "grow" their own replacement joints using their own stem cells, scientists said today.

A team of experts has, for the first time, shown it is possible to grow joints inside the body which have a full range of movement and can bear weight.

The joints could potentially last longer than commonly-used artificial joints, saving elderly patients from having to undergo gruelling operations to replace those that have worn away.

The pioneering study was carried out on rabbits but researchers believe it paves the way for a future where people grow their own bone and cartilage.

Professor Jeremy Mao and his team at Columbia University Medical Centre in New York led the study with colleagues from the University of Missouri and Clemson University in South Carolina.

They used a computer to help create artificial scaffolds that were anatomically the same size and shape as rabbit hip joints.

The scaffolds were infused with a growth factor and implanted into ten rabbits after their own hip joints had been removed.

Attracted by the growth factor, their own stem cells went to the location of the missing joint and regenerated cartilage and bone in two separate layers. Three to four weeks after surgery, the rabbits had fully regained movement and could bear weight just as well as animals that had never undergone surgery.

The rabbits had grown the joints using their own stem cells, instead of relying on an injection of stem cells into their body.

This is the first time scientists have regenerated a limb joint using either harvested stem cells or an animal's own stem cells.

The study was published online in the Lancet medical journal.

Prof Mao said: "This is the first time an entire joint surface was regenerated with return of functions, including weight-bearing and locomotion.

"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. Several scientific and regulatory issues must be dealt with prior to patient applications."

Prof Mao said recovery in human patients may be more complex because they only have two legs to bear weight, rather than four.

"Also, patients may have pre-existing conditions and medication that could affect joint regeneration, and this is clearly difficult to replicate in a study using animal models," he said.

"However, human patients would benefit from post-operative rehabilitation."

Data suggests that many patients now undergoing joint replacements will outlive their replacement joint. They will then need another operation in old age to replace it, potentially without much bone left to support another joint.

In an accompanying comment article, Dr Patrick Warnke from Bond University in Australia, said the research offered a "promising insight" into the future for patients.

However, he warned that not everyone would have the same capacity for natural regeneration, for example elderly people with diabetes.