Could ‘young’ blood stop us getting old?

US biotech companies are working towards plasma therapies to tackle age-related diseases in humans

In the early 2000s a group of scientists at Stanford University, California, revived a grisly procedure used in the 1950s known as parabiosis. They paired living mice, young with old, peeled back their skin and stitched together their sides so the two animals shared the same blood circulatory system. A month later, they found signs of rejuvenation in the muscles and livers of the old mice. The findings, published in 2005, turned the minds of scientists, entrepreneurs and the public to the potential of young blood to rejuvenate ageing people. By 2016, enough interest had grown to prompt a US-based startup called Ambrosia to start offering pricey infusions of young plasma - the cell-free component of blood. The procedure came under fire from the US Food and Drug Administration early last year both for its lack of proven clinical benefit and for potential safety issues; Ambrosia closed, though it has recently reopened.

Meanwhile, a clutch of scientific startups are trying to discover the secrets of parabiosis and use them to tackle age-related disease. By identifying factors in plasma that change with age, they aim to create therapies that either supplement what's beneficial in young blood or to inhibit what's detrimental in old. One is even beginning to report early clinical trial results.