When Wagers and her colleagues attached the circulatory systems of young mice to old ones, they found strong evidence of a biological reversal of many characteristics of aging. Later, Dr Wagers and colleagues discovered that injecting only GDF11 in aged animals can reproduce many of the benefits of parabiosis.

“What they found is that the old animals exposed to young blood experienced a biological reversal of aging by many different measures. Their brains grow younger, their hearts grow younger, their lungs, their bones – all over their body. And interestingly, the young animals exposed to old blood have accelerated aging. So this is just really strong proof that circulating factors regulate aging,” said Allen.