The vampire treatment that 'rejuvenates' ageing hearts: Dose of young blood can reverse life-threatening thickening of organ Hormone GDF-11 reduces the size and thickness of older hearts Could be first treatment for diastolic heart failure which affects millions By Fiona Macrae and Rachel Reilly Scientists have discovered a protein that reverses the symptoms of ageing in the heart Dracula was on to something. Scientists have used a dose of young blood to rejuvenate ageing hearts. The vampire-like treatment reversed the life-threating thickening and stiffening of the heart that occurs with age. The work was done on mice but the researchers believe it will lead to the first drug to mend "broken hearts" in elderly men and women. Researcher Richard Lee, a professor at Harvard Medical School in the US, said: "We need to work as hard as we can, to figure out if this discovery can be turned into a treatment for heart failure in our ageing patients." The researchers began by "sewing together" two mice of different ages, allowing young blood to flow into the older animal's body, and vice versa. Within four weeks, the heart of the older animal went from being stiff and struggling to fill with blood to resembling that of the much younger creature. The research team then spent months trying to identify the revitalising component of the young blood and eventually hit upon a hormone called GDF-11. Levels of this hormone fall with age. Giving old mice jabs of the hormone helped rejuvenate their hearts, the journal Cell reports. Professor Lee said: "We are very excited about it because it opens a new window on heart failure. This is the coolest thing I have ever been part of. Similar experiments, in which the circulatory systems of two mice have been connected, have led to old brains being given a new lease of life. The researchers who did this have proposed giving people in middle-age regular jabs of blood drawn form 20-somethings. However, the Harvard team don't have such an radical approach. Their plan is to give GDF-11 as a drug and hope to test it on patients for the first time in four to five years. They also want to find out if the hormone can help revitalise other ageing body parts and tissues. Professor Amy Wagers, also of Harvard, said: "If some age-related disease are due to a loss of circulating hormone, then it's possible that restoring levels of that hormone could be beneficial. We are hoping that some day, age-related human heart failure might be treated in this way. Dr Shannon Amoils, of the British Heart Foundation, said: "As our population ages, the number of people living with heart failure is increasing and it's crucial we find new ways of treating the condition. This study in mice shows that a blood hormone found in young animals can combat some of the cell changes in aging heart muscle, opening up an intriguing avenue for future research. However, she added the work will not help tackle heart failure caused by heart attacks and disease - the most common form of the condition. The protein could helps millions of elderly people who suffer with diastolic heart failure, which increases the size and thickness of the heart The GDF-11 protein could prove to be the first effective treatment of diastolic heart failure. Professor Lee said: 'The most common form of heart failure in the elderly is actually a form that's not caused by heart attacks but is very much related to the heart ageing. 'It's really frustrating because we don't have any drugs to treat this.'