How the study worked

The investigation combined several approaches: analyses of extracellular vesicles, cell culture experiments, mouse studies of aging-associated osteoarthritis, and a human exercise intervention.

In the human part of the study, older adults completed a structured aerobic exercise program. The researchers collected blood samples before the program began and again after three months of training. From these samples, they analyzed how aerobic exercise altered the molecular contents of circulating EVs, then tested the biological effects of these exercise-derived vesicles on cartilage cells and joint tissues in the laboratory. The team also identified and tested specific molecules that became enriched inside EVs after training.

Exercise reshapes the cargo

The results showed that moderate-intensity exercise significantly changed the molecular cargo of circulating EVs in ways that promoted cartilage health and tissue resilience. When researchers applied EVs collected after exercise to knee joint tissue in the lab, the vesicles improved the health of cells and cartilage tissue.

Among the molecular signals that increased after exercise, one stood out: microRNA-29. MicroRNAs are short stretches of genetic material that help regulate how genes are expressed inside cells. When the researchers delivered microRNA-29 directly to aged, osteoarthritic joints, the treatment restored more youthful characteristics in cartilage cells and reduced features associated with joint degeneration.

That result suggests microRNA-29 acts as a key mediator of exercise's protective effects on cartilage.

What comes next

The findings remain preliminary in several respects. The researchers demonstrated the effects in cell cultures, in mice, and in blood samples from older adults following a three-month exercise program — not yet in a clinical treatment tested on patients. How a therapy based on EVs or microRNA-29 would work in practice, at what dose, and for whom remains to be established.

Still, the discovery opens a path toward new osteoarthritis treatments, including therapies that use EVs or their molecular cargo directly. The researchers say such strategies could be especially valuable for people who cannot get sufficient physical activity because of pain, disability or other health limitations. The work also illustrates how regenerative medicine can be paired with traditional rehabilitation principles.

The team anticipates that this research will help guide the design of clinical programs aimed at maximizing the biological responses associated with joint protection and tissue health.

As physical therapists, Iijima and Ambrosio are driven by a simple but important question: why, and how, does exercise work? Much remains to be learned about why exercise ranks among the most effective treatments for a wide range of musculoskeletal conditions. This study represents one step forward in that effort.

Publication details: Hirotaka Iijima et al, "Exercise enhances aged chondrocyte health through microRNA-29-enriched extracellular vesicles," Nature Aging (2026). DOI: 10.1038/s43587-026-01225-9