Engineered Protein Hydrogel Shows Promise in Articular Cartilage Repair

Found in the knee and hip joints, articular cartilage plays a vital role in executing smooth joint movement. Once damaged, a person may experience pain, reduced bodily function, and arthritis.

One of the possible solutions to this problem is implanting artificial scaffolds created from proteins which will help in articular cartilage repair. The extent to which cartilage regenerates depends on the ability of the scaffold to imitate its biological properties. As experts try to make this possible, they constantly face the challenge of combining the properties of stiffness and toughness, which seem incompatible.

Since articular cartilage does not repair itself, finding a way to regenerate them remains an important challenge in medicine. A team of Canadian and Chinese scientists from the University of British Columbia (UBC) has proven that it is possible to bring together these properties of the biodegradable hydrogel.

Cartilage-like Protein Hydrogels

Unlike other organs in the human body, articular cartilage is more challenging to imitate. This is because the implant must possess mechanical properties such as ultrahigh compressive strength, toughness, stiffness, and fast recovery. In short, conventional implants made from proteins demonstrate a mismatch between what is needed by the cell and what is being provided. Such kind of cartilage does not repair itself as well as it could, according to Dr. Hongbin Li from the UBC Department of Chemistry.

Dr. Li and his colleagues developed a strategy for stiffening the protein hydrogel without altering its toughness. They made this possible by physically tangling the chains into the hydrogel network of folded elastomeric proteins. The resulting hydrogel shows toughness and can resist being sliced with a scalpel. It is also proven to be stiffer than other conventional protein hydrogels.

Its potential in resist compression has been the greatest breakthrough in such hydrogels, showing a favorable comparison with actual articular cartilage. Like natural cartilage, the hydrogel can quickly recover and return to its original shape after being compressed.

During the animal testing phase, rabbits demonstrated notable signs of articular cartilage repair just 12 weeks after being implanted with hydrogel. Interestingly, their bodies' immune systems did not show rejection of the implant. Moreover, bone tissue growth was also similar to healthy tissue.

How Does Articular Cartilage Damage Affect a Person?

Articular cartilage refers to the smooth, white tissue covering the end of bones where they come together to form joints. Since this tissue does not have direct access to the blood supply, it has less capacity to repair itself once damaged.

People of all ages can be affected by damage in articular cartilage, which can result from trauma such as accidents, mechanical injury, or degenerative joint disease. A person with articular cartilage damage experiences symptoms in common such as pain, stiffness, and swelling. In some cases, the patient may have joint locking that can lead to a reduced range of movement.

Conservative treatments for articular cartilage damage include anti-inflammatory medicine, corticosteroid injections, and physical therapy. If the damage is left untreated, it can progress into osteoarthritis. This condition is characterized by worn-out articular cartilage that eventually exposes the underlying bone. At this point, the patient may undergo joint replacement surgery.