Scientists have successfully extended the lives of mice by systematically reprogramming their cells. After the experiment, the animal's cellular age was reversed and their lifespan increased from 18 to 24 weeks.

Past studies conducted in-vitro in the lab had already shown that reprogramming adult cells into pluripotent cells – cells that can differentiate into any cell types that make up the human body – reversed the ageing process.

However, this had not been directly demonstrated in-vivo, in a living organism. All previous efforts had ended in mice developing tumours and dying. The new study, published in the journal Cell, constitutes the first report of cellular reprogramming extending the lifespan of a live animal.

The scientists, from the Salk Institute in the US, came up with a partial cellular reprogramming approach designed to avoid the development tumours. Like other researchers had done before them, the team reprogrammed the mice's cells by inducing the expression of four genes commonly referred to as the Yamanaka factors in these cells.

With this method, it normally takes two to three weeks for cells to reach pluripotency. The originality of this study however is that the scientists conducted reprogrammed the cells, but over two to four days only.

cellular ageing
This cartoon depicts turning back the ageing clock through cellular reprogramming Juan Carlos Izpisua Belmonte Lab /Salk Institute

The result was that their reprogrammed cells did not reach pluripotency, but that they were nevertheless rejuvenated by the process. Cellular and physiological signs of ageing were attenuated, and this happened without the mice developing any tumours. More impressive perhaps, the lifespan of the mice increased by 30%.

The scientists' reprogramming method was applied to all of the mice's cells and this resulted in improvement for a number of organs. Tissue from skin, spleen, kidney and stomach all improved appearance when examined under a microscope. The cardiovascular system also showed improvements in structure and function.

Today, age remains one of the most important risk factors in a number of diseases, including cardiovascular diseases. With this study, scientists add another piece to the puzzle to understand the ageing process and how it can be reversed to protect people from age-related illnesses.