Painful arthritic knees could be treated by injections of a lubricating fluid that has the same effect as a natural version found in joints. The fluid allows the damaged joints to repair themselves and has been shown to boost cartilage regeneration in rats.
Osteoarthritis involves damage to cartilage, a rubbery tissue that caps the ends of bones. Scans of arthritic knees can show bits of cartilage inside the joint that have broken off from the main cartilage tissue.
This increases friction inside the joint, leading to a feedback loop that accelerates the damage, says Chuanbin Mao at the University of Oklahoma.
People can have surgery to remove the debris and smooth remaining cartilage, but this does not work very well and brings with it side effects for older people. Some experimental approaches involve injecting stem cells, often taken from the person’s blood or fat.
Mao, along with other researchers, focused instead on synovial fluid, the liquid inside joints.
Healthy joint fluid contains a large molecule called a lubrication complex, consisting of acid that produces feathery subunits called lubricin, as well as lipid subunits.
As both molecules join onto each other, the lubrication creates a watery layer on top of the cartilage, which reduces friction during joint movement.
In practice, this should considerably reduce the inflammatory pain caused by arthritis. In this preliminary study in rats, the results have been positive.
The study concluded that: “Biocompatible injectable lubricants that facilitate cartilage regeneration may offer a translational strategy for the treatment of early osteoarthritis.”
The scientists created an artificial version of the lubrication complex by binding another feathery molecule called PAMPS and a fatty substitute to the same hyaluronic acid backbone.
When applied to pieces of human cartilage, this reduced friction in the lab tests.
The researchers also injected the substance into rats with early arthritis in their leg joints.
After eight weeks, the rats’ joints looked close to normal when viewed under the microscope, calculated by a commonly used arthritis-grading scale.
“The cartilage seemed to have regrown”, said Mao.
“We found that lubrication can help tissue regeneration – that’s something new,” the scientist said.
In the near future, the researchers will attempt to try out the artificial fluid on larger animals with joints that are more similar to those of humans.
There is still further research to be done before this method can safely be used on people.