Young blood. New Scientist sketches out the future of rejuvenation with experiments based on using young blood to keep old brains lively:
Disregarding vampire legends, the idea of refreshing old blood with new harks back to the 1950s, when Clive McCay of Cornell University in Ithaca, New York, stitched together the circulatory systems of an old and young mouse – a technique called heterochronic parabiosis. He found that the cartilage of the old mice soon appeared younger than would be expected.
It wasn’t until recently, however, that the mechanisms behind this experiment were more clearly understood. In 2005, Thomas Rando at Stanford University in California and his team found that young blood returned the liver and skeletal stem cells of old mice to a more youthful state during heterochronic parabiosis. The old mice were also able to repair injured muscles as well as young mice (Nature, doi.org/d4fkt5).
Once the researchers had ruled out the effect of reduced blood pressure on the older mice, they identified a protein in the blood plasma called growth differentiation factor 11 (GDF11) that appeared to fall with age. To see if it was linked to the rejuvenating effects, the team gave old mice with enlarged hearts daily injections of GDF11 for 30 days. Their hearts decreased in size almost as much as they had in the parabiosis experiments (Cell, doi.org/q2f).
A year later, the same team showed in mice that daily injections of GDF11 also increases the number of blood vessels and the number of stem cells in the brain – both factors known to improve brain function. A separate team led by Tony Wyss-Coray at Stanford performed similar experiments. His team injected blood plasma from young mice into old mice and showed an improvement in the old mice’s physical endurance and cognitive function (Nature Medicine, DOI: 10.1038/nm.3569).