mRNA therapy ‘reawakens’ heart muscle cells after heart attack in mice

Researchers from the University of Cambridge, QIMR Berghofer Medical Research Institute and AstraZeneca report in Nature Cardiovascular Research (published 9 November 2026) an experimental treatment that prompted damaged heart muscle to regenerate — in mice.

The problem

Adult heart muscle cells do not divide, so cells lost in a heart attack — up to about a billion in a human heart — are never replaced. The damage can lead to scarring and heart failure; current treatments ease symptoms and slow progression but cannot regrow muscle.

The approach

The team injected a modified mRNA into the injured heart that temporarily switches on two proteins, Myc and Cyclin T1, prompting heart muscle cells to divide. Because the effect is short-lived and local, it is not expected to permanently alter heart cells, a design meant to reduce the risk of overgrowth.

Results in mice

• Echocardiography showed a stronger heartbeat and about 10% more blood pumped per beat than in mice given a mock treatment.
• The improvement persisted at 28 days and 12 weeks.
• No adverse effects were seen in the mice.

Co-senior author Catherine Wilson called the results “really exciting”. British Heart Foundation’s Bryan Williams said the work is “an important step forward” but noted it is in mice and at an early stage.

Limitations

This is a preclinical animal study. Mouse hearts differ from human hearts; the effect size is modest; long-term safety, dosing and delivery in people are unknown. The team says trials in larger animals and then in humans are needed. AstraZeneca was a research collaborator. This is not a treatment available to patients.