Stem cells could repair joints

“Disabled people could soon re-grow damaged or diseased limb joints,” said the Lancet. The report said that the prospect of a new technique, using people’s own stem cells rather than transplanted ones “offers hope to millions suffering crippling pain”.

The study behind this news attempted to grow new cartilage in rabbits by drawing the rabbits’ own circulating stem cells to a scaffolding of bone-like substances implanted into their shoulder joints. To assess the technique the researchers then observed the rabbits’ movement and took samples from the joint to see if new cartilage had formed. The rabbits regenerated cartilage and were soon able to bear weight.

Stem cells

The real test of this technology will come if it is eventually applied to humans. While the researchers have tried growing cartilage to attach to artificial joints they say that regeneration of other tissues may also be possible with their technique. However, this type of research proceeds in small steps and so it is too soon to say if this could ever be a reliable alternative to a simple artificial hip replacement in humans.

Patients having joints replaced almost always want to know how long their artificial joint will last. But with ageing populations, and an increasing number of patients under 65 requiring replacement joints, there is a real danger many patients will outlive their replacement joint. These patients would then need another gruelling operation, at an advanced age, and yet without much bone left to support another metallic joint.

In this proof-of-concept study, Professor Mao and colleagues removed the forelimb thigh joint of 10 rabbits, and then implanted three dimensional biomaterial scaffolds infused with growth factor. The rabbits’ own stem cells were ‘homed’ by the growth factor to go to the location of the missing joint, and regenerated cartilage and bone in two separate layers. Just four weeks later, the rabbits were able to resume normal movements, similar to rabbits with normal functional joints. These rabbits had grown their own joint using their own stem cells, instead of stem cells harvested apart or outside of the host.

Prior to the work reported in this Lancet paper, no one has been able to regenerate a limb joint with either stem cells harvested or the host’s endogenous stem cells. Thus there are two new aspects to this work: 1) a limb joint regenerated for the first time with the animals involved resuming functions on the new joint; and 2) the regenerated limb joint being created from host’s own endogenous stem cells, not stem cells that are harvested and manipulated outside the host’s body.