A team of researchers at Stanford Medicine has identified a single protein that, when blocked, reverses age-related cartilage loss in joints and prevents osteoarthritis from developing after injury. The discovery, published in the journal Science, could fundamentally change how arthritis is treated and may one day make knee and hip replacements unnecessary for many patients.
The findings represent a long-sought breakthrough in a field where treatment options have remained stagnant for decades. Until now, no drug has been able to slow or reverse the underlying joint damage caused by osteoarthritis, with care limited to pain control and eventual surgical joint replacement.
The Protein at the Center of the Discovery
The Stanford team focused on a protein called 15-hydroxy prostaglandin dehydrogenase, or 15-PGDH. The researchers refer to it as a gerozyme, a class of proteins they identified in 2023 that increase with age and actively suppress the body’s ability to repair its own tissue.
In aged or injured mice, 15-PGDH levels rise sharply in the cartilage of joints. The protein interferes with prostaglandin E2 (PGE2), a molecule the body produces to repair tissue and reduce inflammation. By blocking 15-PGDH, the researchers were able to restore PGE2 signaling and trigger natural regenerative processes that the aging body suppresses.
“We were surprised,” said Dr. Helen Blau, director of the Baxter Laboratory for Stem Cell Biology at Stanford University School of Medicine and senior author of the study, in comments to KTVU FOX 2. “We were amazed to see that extent of regeneration of the cartilage.”
What the Study Found
In the experiments, researchers used a small-molecule inhibitor that blocks 15-PGDH activity. The drug was administered both systemically (through oral or whole-body delivery) and locally (through injection directly into injured joints).
The results were significant. In aged mice, knee cartilage that had previously thinned with age thickened across the joint surface. Animals that received the inhibitor moved more normally and placed more weight on injured legs than mice that received a control treatment. Mice given the control treatment had double the levels of 15-PGDH compared with uninjured mice and developed osteoarthritis within four weeks.
The treatment also showed promise in preventing osteoarthritis from developing after injury. In mice with knee injuries similar to ACL tears in humans, the inhibitor prevented the typical progression to osteoarthritis. According to the research, roughly 50 percent of people who suffer an ACL tear go on to develop osteoarthritis 10 to 20 years later, making this a particularly significant finding for athletes and people with prior joint injuries.
A New Mechanism of Tissue Regeneration
What surprised the researchers most was how the regeneration actually happens. In bone, nerve, and blood tissue, repair typically occurs through stem cell activation. Cartilage appears to work differently.
The Stanford team found that the treatment “reeducates” existing cartilage cells, called chondrocytes, by changing how their genes behave. Using single-cell RNA sequencing and multiplexed immunofluorescence imaging, the researchers identified that 15-PGDH inhibition decreased the population of hypertrophic-like chondrocytes (the kind associated with cartilage breakdown) and increased extracellular matrix-synthesizing articular chondrocytes (the kind that produce healthy cartilage).
In the published Science paper, the researchers described this as a previously underappreciated mechanism: “Cartilage regeneration appears to occur through gene expression changes in preexisting chondrocytes, rather than stem or progenitor cell proliferation.”
Why This Matters for Public Health
Osteoarthritis affects roughly one in five adults in the United States and costs an estimated $65 billion annually in direct health care expenses, according to figures cited by Stanford Medicine. Current treatments are limited to managing symptoms, with eventual joint replacement surgery for many patients.
The Stanford findings suggest a fundamentally different path: targeting the aging process itself rather than its downstream effects. The same research team has previously shown that blocking 15-PGDH boosts muscle mass and endurance in aging mice, and the protein has also been linked to regeneration in bone, nerve, and blood cells.
What Comes Next
The small-molecule inhibitor used in the Stanford research has already cleared Phase 1 safety testing for another age-related condition, which could accelerate the path to human trials for joint applications. The researchers say they are aiming to initiate clinical trials for cartilage regeneration, citing what Stanford described as “a significant unmet medical need.”
“This is a new way of regenerating adult tissue, and it has significant clinical promise for treating arthritis,” Blau said in the Stanford Report.
The study was authored by Mamta Singla, Yu Xin Wang, and colleagues at Stanford Medicine, the Sanford Burnham Prebys Medical Discovery Institute, and other institutions. Several of the authors, including Blau and co-author Nidhi Bhutani, are inventors on patent applications held by Stanford related to 15-PGDH inhibition, which are licensed to Epirium Bio. Blau is a co-founder of Epirium and holds equity in the company.
For the millions of Americans living with chronic joint pain, the findings offer something that arthritis research has produced rarely: the realistic prospect of regrowing what age and injury have worn away.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. The research described is based on studies conducted in mice and human tissue samples; the treatment has not yet been approved for human use. Readers experiencing joint pain or symptoms of arthritis should consult a qualified healthcare provider for diagnosis and treatment options.
