Hydrogel Shows Promise as Treatment for Arthritic Joints
/By Pat Anson, PNN Editor
An experimental hydrogel that helps regenerate bone and cartilage tissue is showing promise as a treatment for arthritic joints, according to new research by Chinese and Canadian scientists. The gel is biodegradable and mimics the articular cartilage found in knee and hip joints.
In tests on laboratory animals, researchers say the gel showed signs of repairing articular cartilage 12 weeks after being implanted in rabbits, with no gel remaining and no rejection by the animals’ immune systems, according to findings published in the journal Nature.
Further animal testing is needed, but if the hydrogel proves useful in human trials, it could be used someday as an alternative to knee and hip replacement surgery. About one in four adults in the United States have some form of arthritis, which causes thinning of cartilage and progressive joint damage. Many resort to risky joint repair and replacement procedures.
“Cartilage is tricky,” says senior author Dr. Hongbin Li, a professor in the University of British Columbia’s department of chemistry. “Articular cartilage repair represents an important medical challenge because naturally speaking, it doesn’t repair itself.”
A delicate balance is needed to make biodegradable cartilage implants tough and stiff enough to support muscle-bearing tissues. They can’t be too stiff, or they’ll break when bent too far. Conversely, if they are too soft, they may not be useful in a joint.
In animal studies, researchers say a stiffer version of the gel had better results than a softer version, because it formed a scaffold that was more compatible with bone and cartilage tissue. That provided a physical cue to the body for tissue regeneration.
Dr. Linglan Fu holding the hydrogel
“This just shows how complex this area of research is, and the need to take into account the many different physical and biochemical cues and factors when designing these scaffolds,” says co-author Dr. Qing Jiang, a professor and surgeon at Nanjing University.
The research team used a new approach to stiffen biomaterials in the gel without sacrificing toughness, by physically entangling the chains of a protein.
“These entangled chains can move, which allows energy, for instance, the impact from jumping, to be dissipated, just like shock absorbers in bikes. In addition, we combined this with an existing method of folding and unfolding proteins, which also allows for energy dissipation,” says first author Dr. Linglan Fu, who conducted the research as a doctoral student at UBC’s department of chemistry.
The resulting gel is tough, able to resist slicing with a scalpel, and is more stiff than other protein-based hydrogels. Its ability to resist compression was among the highest achieved by any such gel, according to researchers, who say it compared favorably with actual articular cartilage. The gel was also able to rapidly recover its original shape after compression, as real cartilage does.
Researchers at Duke University are also working on an experimental hydrogel to replace damaged knee cartilage. The gel is made with thin sheets of cellulose fibers infused with a water absorbing polymer, creating a Jello-like material that is surprisingly strong. The cellulose fibers act like the collagen in natural cartilage, giving the gel strength when pulled or stretched.
