Scientists have known for some time that the four genes, which are known collectively as the Yamanaka factors, could turn adult cells back to their stem cell state, where they can grow into any part of the body.
But it was always feared that allowing that to happen could damage organs made from the cells, and even trigger cancer.
However, it was discovered that stimulating the genes intermittently reversed ageing, without causing any damaging side effects.
In mice with a premature ageing disease, the treatment countered signs of ageing and increased their lifespan by 30 per cent. If it worked similarly in humans it could allow people to live until more than 100 years old. In healthy mice it also helped damaged organs to heal faster.
"In other studies scientists have completely reprogrammed cells all the way back to a stem-cell-like state," says co-first author Pradeep Reddy, also a Salk research associate.
"But we show, for the first time, that by expressing these factors for a short duration you can maintain the cell's identity while reversing age-associated hallmarks."
The breakthrough could also help people stay healthier for longer. The ageing population means that the risk of developing age-related diseases, such as dementia, cancer and heart disease also rises. But if the body could be kept younger for longer then it could prevent many deadly diseases for decades.
This article was originally publish by The Telegraph.