For people suffering from cartilage-related joint problems, one wrong move can send pain shooting through a leg, generate an uncomfortable clicking sensation or even lock up the joint entirely. To make matters worse, these problems don’t get better on their own.

“Unlike most tissues in the body, cartilage has an uncanny inability to heal itself,” says Kyriacos Athanasiou, distinguished professor of Orthopaedic Surgery in the School of Medicine and chair of the Department of Biomedical Engineering in the College of Engineering.

Cartilage just isn’t designed to regenerate. The tissue has few cells, even fewer regenerative stem cells, and no blood flow. In addition, articular cartilage, the tissue between joints, is under severe strain.

“The cartilage in your knee experiences pressure that would be the equivalent of an elephant, standing on one leg, on top of your knee,” says Athanasiou.

As a result, cartilage in the knees, shoulders and hips wears out. But the tissue can be found throughout the body. The cartilage that cushions the temporomandibular joint, which connects the jaw to the skull, can also cause problems, creating a painful temporomandibular joint disorder (TMD).

Making a replacement

Because cartilage doesn’t regenerate, Athanasiou and colleagues are investigating ways to create new tissue. Using both stem cells and non-articular cartilage from the ribs, the researchers have produced tissue that replaces damaged cartilage.

“We have developed a process that allows us to engineer biomimetic cartilage,” says Athanasiou. “In other words, this tissue looks and behaves like the real thing.”

This new bioengineered material could have an enormous impact on millions of people who have join pain due to arthritis, injury or other causes, but who may no longer need prosthetic joint replacements.

The biological alternative is a big leap forward in cartilage engineering. Previous attempts produced only small amounts of tissue, and therefore could be used to treat only minor injuries.

“Up to this point, we’ve been able to correct only small lesions, about one or two centimeters,” says Athanasiou. “Now we can make large pieces.”

Equally important, because the lab is creating cartilage out of stem cells derived from a patient’s own skin, the body won’t react to the transplant as foreign, reducing the chance of rejection.

Solving TMD

As important as engineered cartilage is as an alternative to knee or hip replacements, it would be life altering for those suffering from TMD.

“One in four people has this condition,” says Athanasiou. “It’s very painful, but most don’t seek treatment because we simply don’t have a good solution.”

The problem is in how the cartilage disc is attached. Athanasiou likens it to a trampoline. “It’s a membrane that has no integrity on its own. It’s like a piece of loose cloth. But if you attach the membrane, it becomes a powerful surface.”

Athanasiou believes their engineered cartilage could be the solution. Once attached, it could provide relief for those suffering from TMD.

Adding bone

The lab’s efforts are not limited to cartilage; they are also engineering new bone. To some degree, this was born of necessity, as the researchers needed a bone substrate to grow cartilage. A collaboration with the UC Davis School of Veterinary Medicine produced even more promising results.

When a 10-year-old Münsterländer dog lost part of its jaw to cancer, two veterinary surgeons and Athanasiou lab postdocs found a novel solution: use a growth factor called bone morphogenetic protein to attract stem cells and generate new bone. The procedure worked, allowing the dog to eat normally and enjoy his favorite chew toys.

This ability to create new bone and cartilage is drawing a lot of attention. The California Institute for Regenerative Medicine awarded a grant to Athanasiou’s lab to accelerate the research. Athanasiou is excited about the progress but cautious about getting these technologies to the clinic.

“For the first time, we can resurface an entire joint or engineer a whole meniscus,” says Athanasiou. “But there’s a lot more to do. It’s going to take some time before we can turn them into treatments.”