When people have knee arthritis, cartilage cushioning the joint progressively breaks down. Now an early study hints at a possible solution: replacing it with cartilage from the nose.
Researchers tested the approach in just two patients with knee arthritis, and said much work lies ahead.
But the initial findings, published Sept. 1 in Science Translational Medicine, indicate that nose cartilage cells can be safely used to generate replacement cartilage for the knee.
And months after the procedure, the two patients were reporting less pain and better knee function.
Whether that relief can be credited to the replacement cartilage is unclear, however.
"We are very far from possibly claiming efficacy," said researcher Ivan Martin, a professor at the University of Basel in Switzerland.
Further studies, he said, are needed to rigorously test the procedure as a treatment for knee osteoarthritis.
Osteoarthritis refers to the common "wear-and-tear" form of the arthritis where joint cartilage -- the protective tissue at the ends of bones -- gradually deteriorates. Over time, that causes changes to the bone itself, leading to inflammation, joint stiffness and pain.
There are treatments for knee arthritis, such as physical therapy and cortisone injections, but no way to halt its progression. At some point, joint replacement surgery might be needed.
Right now, there are ways to repair some degree of cartilage damage in the knee -- including moving cartilage from a non-weight-bearing part of the knee to fill in the defect in the injured cartilage.
But those treatments are used when there is a limited area of cartilage damage, such as a tear from a sports injury, explained Dr. Andreas Gomoll, an orthopedic surgeon who was not involved in the study.
Gomoll, who is based at the Hospital for Special Surgery in New York City, explained it this way: If a road has a single pothole, but the pavement around it is sound, you can simply fill in the pothole. But if the road is riddled with pot holes, that won't work.
Knee osteoarthritis is akin to the latter scenario, Gomoll said.
Beyond that, he explained, the arthritic knee is full of inflammation, which would expose any transplanted cartilage to a "toxic environment."
For the new study, Martin's team looked at whether cartilage cells from the nose could stand as a possible alternative. Research has suggested the cartilage there has a greater regenerative capacity and may be more adaptable to harsh conditions. It's also easy to remove cells from the nose.
The researchers started in the lab. First, they used nasal chondrocytes (cartilage cells) to grow new cartilage, which they then exposed to inflammatory factors similar to what's found in arthritic knees. The cartilage held up -- and even seemed to quiet the "inflammatory profile" of cells from arthritic joints.
Next, the researchers showed that the transplanted cartilage could be successfully integrated into the arthritic joints of lab animals.
Then came the two patients with knee osteoarthritis. Both patients, in their 30s, had knee pain and other symptoms that were not responding to non-surgical therapies.
The patients underwent an osteotomy, a surgical procedure where bones of the knee joint are cut and realigned to relieve pressure on the damaged area of cartilage. They also received replacement cartilage made from their own nasal cells.
MRI scans later showed that the nasal cartilage had filled in the defects in the patients' knee cartilage. And three to 14 months after the procedure, the patients were reporting less pain and better knee joint function.
Gomoll cautioned, however, that the symptom relief could have been from the osteotomy.
Martin agreed that it's unclear whether the nasal cartilage itself was an effective treatment. He said larger studies are needed not only to prove its effectiveness, but also to figure out which patients are good candidates.
Gomoll said it will be interesting to see whether nose cartilage does indeed "know a few tricks" that allow it to thrive in the arthritic knee.
He also cautioned that osteoarthritis is more complicated than simply a cartilage defect. There is inflammation and damage to other joint structures. Plus, there are patient factors that contribute to the condition, Gomoll said -- such as being overweight or "bow-legged" (as the two study patients were), and even genetics.
Because of that complexity, Martin does not see nasal cartilage as a magic bullet. "Ultimately, I believe combination therapy will be required," he said.
Physical therapy, Martin added, would be essential, to help prevent the new cartilage from deteriorating, as the "native" cartilage did.
The American Academy of Orthopaedic Surgeons has more on knee arthritis.
SOURCES: Ivan Martin, PhD, professor, department of biomedicine, University of Basel, Switzerland; Andreas H. Gomoll, MD, associate attending orthopedic surgeon, Hospital for Special Surgery, and associate professor, orthopedic surgery, Weill Cornell Medical College, New York City; Science Translational Medicine, Sept. 1, 2021, online