Stanford scientists have identified a method to regrow cartilage in aging joints, offering a potential alternative to knee and hip replacement surgeries. In a series of experiments, researchers used an injection that blocks a protein linked to aging and observed the regrowth of healthy cartilage in the knees of older mice.
The treatment also prevented arthritis in mice with joint injuries similar to ACL tears, often seen in athletes.
The therapy works by targeting a protein called 15-PGDH, which breaks down prostaglandin E2, a molecule essential for tissue repair. Researchers previously found that blocking this protein improved muscle strength in older mice.
The same approach has now shown promising results in restoring joint cartilage, both in animal models and in human tissue samples collected during knee replacement surgeries.
A shift in osteoarthritis treatment strategy
The researchers explained that this marks a shift from current osteoarthritis treatments, which typically focus on managing pain or surgically replacing joints.
The new method addresses the root cause of cartilage loss and encourages natural tissue regeneration. Clinical trials are already underway to test an oral version of the drug for age-related muscle weakness.
Scientists just discovered a way to completely reverse osteoarthritis and prevent joint pain for the first time.
This treatment allows the body to regenerate cartilage on its own instead of requiring surgery, something previously thought to be impossible. pic.twitter.com/SdMPq8r7NP
— Pubity (@pubity) January 4, 2026
Dr. Helen Blau, professor of microbiology and immunology and director of the Baxter Laboratory for Stem Cell Biology, said the findings show adult tissue can regenerate without the involvement of stem cells. Blau noted that existing cartilage cells, called chondrocytes, began expressing genes tied to younger, healthier tissue after treatment.
Dr. Nidhi Bhutani, associate professor of orthopaedic surgery and co-senior author of the study, said the level of cartilage regrowth achieved was greater than seen with any previously tested therapy.
Stanford scientists regrow cartilage without stem cells
In aging joints, chondrocytes typically increase activity in genes related to inflammation and bone formation while reducing genes involved in cartilage maintenance. The treatment reversed this pattern.
In mice, the number of harmful chondrocytes dropped significantly, while beneficial ones linked to hyaline cartilage rose from 22 percent to 42 percent. The regrown tissue was confirmed to be functional cartilage, not a less effective type called fibrocartilage.
Human cartilage samples treated with the same compound for one week also showed early signs of regeneration. These samples came from patients undergoing total knee replacement due to osteoarthritis. Researchers reported a decline in damaging enzymes and an increase in markers linked to healthy cartilage.
Improved joint function and hope for clinical trials
In injury models, mice that received the treatment twice a week for four weeks were far less likely to develop osteoarthritis than untreated animals. Treated mice also moved more normally and placed more weight on the injured leg.
Blau explained that although prostaglandin E2 is often linked to pain, its slight increase at natural levels helps promote healing. Bhutani added that the results have shifted their understanding of tissue repair by showing that existing cartilage cells can be redirected toward regeneration.
The study was published in Science and included contributions from researchers at the Sanford Burnham Prebys Medical Discovery Institute. Funding came from the National Institutes of Health and several foundations. Some authors are listed on patent applications related to this work.
