Gel to trick worn-out knees into repairing themselves
AJAB of gel that triggers the body’s own repair process could be a new treatment for arthritis of the knees. The gel contains special signalling compounds and, when injected into the damaged area, it acts like a homing beacon, attracting cells that can then turn into new tissue.
Osteoarthritis occurs when cartilage — a tough but slippery tissue that coats the ends of the bones in our joints — becomes rougher and thinner. Sometimes holes form in it, allowing bone to rub on bone.
Unlike other tissue, cartilage does not have its own blood supply and so does not heal itself efficiently.
Researchers at Iowa University in the U. S. developed the gel after they discovered that cartilage contains a type of cell known as a precursor cell.
These are stem cells (which have the capacity to develop into any type of cell in the body) that have already committed to becoming a particular sort — in this case, cartilage. However, they have not yet fully developed into that tissue.
THE same researchers also identified that these cartilage precursor cells react to natural signalling compounds in the blood. One of these signalling compounds — stromal derived factor 1 (known as SDF1) — acts like a homing beacon for the precursor cells, drawing them out of the surrounding healthy tissue and into the damaged area where they can form new cartilage.
In laboratory studies, the Iowa team injected a gel made with SDF1 into holes in cartilage and the precursor cells moved towards the SDF1 signal.
Growth factors that had been added to the gel then caused the precursor cells to grow into cartilage that repaired the holes.
By comparison, when a placebo gel was used, very few cells migrated into the site over the 12-day test.
‘The new cartilage integrates seamlessly with the undamaged tissue,’ say the researchers. ‘ It has normal concentrations of proteoglycans — proteins that make tissue tough and resilient — and good structural properties, and looks like normal cartilage.’
They believe that the gel could be a viable alternative to total knee replacement, which currently is the only cure for arthritic knees.
The researchers added that all the components of the gel are individually approved for human use as part of other treatments, so approval for the therapy for knee arthritis could be swift — with use in patients in less than five years. Further trials are being planned.
Professor Anthony Hollander, head of the Institute of Integrative Biology at the University of Liverpool and an expert in tissue engineering, said: ‘It is an interesting idea to use a gel to deliver the chemical signals right into the middle of a cartilage lesion.
‘ It could be a relatively cheap solution to a huge problem and be used widely if it proves to be effective. But much more research is needed.’
MEANWHILE, artificial knee joints that are custom-made for an individual patient are being compared to standard replacement joints in a clinical trial at the University of Tennessee.
normally, a replacement joint is selected by a surgeon from a range of standard sizes.
The custom fit knee replacement, known as Conformis, is based on a CT scan and modelled to their specific measurements.
Around 100 patients who had the Conformis implant or an offthe- peg replacement will be observed six months after surgery as they perform tasks such as standing up from a chair and walking upstairs.
X-rays showing how a dye moves in the joint will also be taken.
The researchers want to see if the custom-made joints move more like a normal knee, which they say might have implications for how quickly the implant wears out. Currently, a knee replacement lasts around 15 years.