Researchers at Stanford Medicine have discovered a novel treatment that may regenerate damaged knee cartilage and prevent osteoarthritis, offering a potential alternative to joint replacement surgery. The breakthrough, demonstrated in older mice, involves blocking a protein that contributes to age-related tissue degeneration.
This new approach focuses on the protein 15-PGDH, described as a gerozyme—an enzyme that becomes more abundant with age and leads to a decline in tissue function. In previous research, blocking 15-PGDH in young mice led to increased muscle mass, endurance, and regeneration of bone, nerve, and blood cells. These tissues healed by activating specific stem cells to multiply and differentiate. However, cartilage tissue appears to regenerate differently, by altering gene activity rather than relying on stem cell recruitment.
When older mice were treated with a small molecule drug designed to inhibit 15-PGDH, their knee cartilage thickened, and the cells produced hyaline cartilage—the smooth articular cartilage crucial for healthy joint movement. "The effects were remarkable," said Nidhi Bhutani, a senior study author. This cartilage regeneration occurred without the need to recruit stem cells, a finding that surprised the research team.
Preventing Osteoarthritis After Injury
The researchers also investigated the treatment's effectiveness in preventing osteoarthritis following traumatic knee injuries. Approximately half of individuals who suffer a knee injury go on to develop osteoarthritis. In the study, mice treated with the 15-PGDH inhibitor twice weekly for four weeks showed a reduced likelihood of developing arthritis compared to untreated mice, who developed the condition within four weeks.
The treatment appears to revert cartilage to a more youthful biological state. Further analysis of human osteoarthritis cartilage samples treated with the inhibitor revealed a decrease in 15-PGDH proteins and reduced activity associated with cartilage degradation after one week, accompanied by articular cartilage regeneration.
"It's clear that a large pool of already existing cells in cartilage are changing their gene expression patterns," Bhutani explained. "And by targeting these cells for regeneration, we may have an opportunity to have a bigger overall impact clinically."
While these findings are based on mouse models, an oral version of the 15-PGDH inhibitor has been developed and found safe in humans for treating age-related muscle weakness. Further clinical trials are necessary to confirm the safety and efficacy of this treatment specifically for cartilage regeneration in humans.