It's half time, bring on the hydrogel

A torn cartilage can be very serious, but the road to recovery may soon be shorter as a result of work on hydrogels by US researchers.

The common sports injury is actually damage to a part of the knee known as the meniscus, which consists of tough cartilage and acts to distribute body weight evenly across the knee. The meniscus can be damaged if the knee is both bent and twisted at the same time. If this damage is severe enough, then surgery is often the only option for treatment.

A potential alternative form of treatment would be to introduce a hydrogel into the knee to support the damaged meniscus and promote the formation of new cartilage, and a number of research groups have studied various hydrogels for this purpose. Now, researchers from the Massachusetts Institute of Technology (MIT), Cambridge, and Harvard Medical School, Boston, have carried out a detailed investigation into the properties of one of the most promising of these hydrogels, which is based on hyaluronic acid (HA).

The advantage of HA is that it is a natural polysaccharide that already plays a role in various wound-healing processes in the body. To create their hydrogel, the researchers combined HA with the photoreactive compound methacrylic anhydride to produce methacrylated HA (MeHA), and then mixed this with the photosensitive compound poly(ethylene glycol) dimethacrylate. When this liquid mixture is exposed to ultraviolet light, it polymerises to form the hydrogel.

After discovering that an excess of MeHA in the hydrogel makes it less able to support tissue cells, the researchers were able to create a hydrogel that could support encapsulated cartilage-producing cells known as chondrocytes. They tested this hydrogel on mice and discovered that, over three months, the hydrogel generated progressively higher amounts of healthy new cartilage.

’Using a patient’s own cartilage-producing cells, our goal is to place the cells into our new gel and inject them into the injury site so that cartilage grows where it is needed,’ explains lead researcher Jason Burdick of MIT.

Jon Evans