Japanese research team visualizes cellular metabolic changes during fracture healing using hyperpolarized MRI

On August 21, 2026, Gifu Pharmaceutical University and Gifu University announced that a multi-institutional Japanese research team successfully visualized changes in the redox state of skeletal progenitor cells during fracture healing in living mice using hyperpolarized magnetic resonance imaging technology. The findings were published online on August 15, 2026, in the British academic journal *npj Imaging*.

The study was led by Takuya Kubo, a graduate student in the Department of Pharmacology at Gifu Pharmaceutical University, Professor Eiichi Hinoi, and related research teams at Gifu University, in collaboration with the University of Tokyo, Osaka University, the Research Institute of National Rehabilitation Center for Persons with Disabilities, and other institutions.

After a fracture occurs, a tissue called a "callus" forms at the fracture site, and multiple cell types participate in the repair process. Among them, skeletal progenitor cells can proliferate and differentiate into chondrocytes and osteoblasts, serving as an important cellular basis for fracture repair. Existing X-ray and CT examinations primarily observe structural changes such as bone morphology and bone mass, but in the early stages of fracture healing, it is difficult to accurately assess repair progress using structural imaging alone.

In this study, the researchers combined hyperpolarized MRI technology capable of reflecting redox states—namely in vivo dissolution dynamic nuclear polarization MRI (DNP-MRI)—with a contrast-enhancing probe that reacts with reactive oxygen species, to observe callus formation and metabolic changes in a mouse fracture model.

The results showed that, compared with healthy unfractured bone, the probe signal at the fracture site declined more rapidly, indicating enhanced local redox activity. This activity peaked on day 3 after fracture; remained at elevated levels on days 7 and 14; and subsequently declined on days 21 and 28 as bone remodeling progressed.

The research team further analyzed skeletal progenitor cells at the fracture site and found that, compared with similar cells derived from healthy bone, these cells exhibited higher redox activity accompanied by more mitochondrial-derived reactive oxygen species. The researchers believe this indicates that DNP-MRI can capture cellular activity and in vivo redox dynamics during fracture healing.

These findings provide a new imaging approach for early assessment of fracture healing and contribute to a deeper understanding of bone regeneration mechanisms. The research team stated that this technology holds future potential for fracture healing assessment, bone regeneration research, and the development of diagnostic and therapeutic methods for skeletal diseases.