Rejuvenation science: Rewinding biological clock works for mice, not yet for humans

THE QUEST TO LIVE LONGER, fuller lives has captivated humanity for millennia. In lab mice, scientists have spent about a century studying the cellular damage that builds up in older animals and exploring ways to suppress the wear and tear. But around two decades ago, the goal posts changed. Rather than simply trying to slow the body’s decline, the field of “rejuvenation science” emerged to prevent age-related breakdown of cells and tissues even before diseases emerge — in essence, to rewind the biological clock.

This bold promise draws support from a set of curious experiments in mice. In one key study published in 2005, a team of Stanford researchers surgically connected a young mouse and old mouse so that the animals’ blood vessels form a single, shared circulatory system — a process known as “parabiosis.” The results were dramatic: The old mouse in these parabiotic pairs had younger-looking eyes and skin, and their tissues and cells looked youthful under a microscope and in lab dish assays.