Scientists at the University of Cambridge have developed an experimental treatment that helped damaged mouse hearts recover after a heart attack, offering a possible route towards therapies that could one day repair injured human heart muscle.
The modified mRNA treatment encourages adult heart muscle cells to divide again. It improved pumping function in mice following experimentally induced heart attacks, according to research published on 9 November 2026 in the peer-reviewed journal Nature Cardiovascular Research. The treatment has not yet been tested in human patients.
What the Cambridge researchers found
A heart attack interrupts the blood supply to part of the heart, killing muscle cells. Unlike many other tissues, the adult human heart has very little ability to replace those lost cells. The result can be permanent scarring and, in some patients, heart failure.
The researchers developed a modified messenger RNA (mRNA) treatment that briefly activates two proteins, Myc and cyclin T1, involved in stimulating cell growth and division. The experimental treatment was injected into the hearts of mice shortly after a heart attack.
At 28 days, mice given the treatment had better heart pumping function than those given a control injection. In the study’s direct mRNA treatment experiment, the decline in left ventricular ejection fraction was approximately 26 percentage points in treated mice, compared with 37 percentage points in controls. Ejection fraction measures the proportion of blood the left ventricle pumps out with each contraction.
The researchers also found evidence of heart muscle cell division and increased muscle tissue. Importantly, the direct mRNA experiment did not demonstrate a significant reduction in scar size, so the results should not be interpreted as full reversal of heart attack damage. The University of Cambridge said improvements in heart function were still evident at follow-up assessments including 12 weeks.
Why the treatment is potentially significant
Existing medicines and procedures can help manage heart disease, improve blood flow and reduce the risk of further injury. However, replacing heart muscle that has already died remains a major challenge.
Dr Catherine Wilson, a co-senior author at Cambridge’s Department of Pharmacology and Gurdon Institute, said: “We’re not just treating the symptoms of heart failure – this approach could help the heart to repair itself.”
The research was conducted by scientists from the University of Cambridge, QIMR Berghofer Medical Research Institute and AstraZeneca, with further work supported by the British Heart Foundation.
What the research does not yet prove
This is early-stage animal research, not an available treatment for heart attack patients. The findings do not show that the approach is safe or effective in people, and the animal experiments involved relatively small groups.
Safety is particularly important because making heart cells divide can have unwanted effects. The paper reports that sustained, widespread activation of the same growth programme was harmful and caused rapid deaths in one mouse model. Researchers therefore explored short-lived, localised activation to limit that risk. No adverse effects were reported in the localised mRNA experiments, but that is not proof of long-term safety.
The experimental delivery method also involved injections directly into the heart. Before any use in patients, the team must refine the treatment, establish how it could be delivered safely and test it in larger animal studies. Human clinical trials would be needed before any claim of benefit for patients could be justified.
Watch: Cambridge explains the discovery
In the University of Cambridge’s video, researchers including Dr Catherine Wilson and Dr Aleksandra Boikova explain how the treatment is intended to restart the heart’s limited capacity for regeneration.
Sources
- University of Cambridge: Experimental treatment promotes repair after heart attack damage in animal study (9 November 2026)
- Boikova et al., Nature Cardiovascular Research: A transient modified mRNA encoding Myc and cyclin T1 improves cardiac function after myocardial injury (9 November 2026)
- Nature Cardiovascular Research: A regenerative pulse for the injured heart (commentary, 9 November 2026)
