Using a new technique which takes adult cells back to their embryonic form, US researchers at the Salk Institute in California, showed it was possible to reverse ageing in mice, allowing the animals to not only look younger, but live for 30 per cent longer.

The technique involves stimulating four genes which are particularly active during development in the womb. It was also found to work to turn the clock back on human skin cells in the lab, making them look and behave younger.

"Our study shows that ageing may not have to proceed in one single direction," said Dr Juan Carlos Izpisua Belmonte, a professor in Salk's Gene Expression Laboratory. "With careful modulation, aging might be reversed.

"Obviously, mice are not humans and we know it will be much more complex to rejuvenate a person. But this study shows that ageing is a very dynamic and plastic process, and therefore will be more amenable to therapeutic interventions than what we previously thought."