The story starts back in the 1950s, when some particularly adventurous scientists decided to look for a fountain of youth by surgically attaching the blood vessels of young mice to elderly ones. The process, which they called parabiosis, resulted in younger-looking cartilage in the elderly mice.
Now, scientists know that stem cells are responsible for the growth of new tissue, which keeps organs acting "young" — that is, working efficiently. Studies from the early 2000s found that old mice and young mice had similar numbers of stem cells, but those cells were inactive in the older subjects.
Scientists then set about looking for the compound that caused stem cells to contribute to new tissue growth in younger bodies. Research at Harvard discovered that when older mice were injected with a protein called GDF11 — which is common in the blood of younger animals, but not in older ones — their hearts showed signs of rejuvenation.
The story doesn't stop there, according to three new studies published this month. The first, which was conducted by the same Harvard researchers who did the GDF11 research, found that GDF11 injections into the skeletal muscle of older mice activated stem cells in the muscle, which gave the mice greater strength and endurance. The second study, conducted by the same Harvard team, found that both parabiosis and GDF11 injections contributed to increased neuron growth and a better sense of smell in the older mice.
The third study, which was conducted by researchers at Stanford and published in the journal Nature Medicine, backed up the Harvard team's assertion that young blood can rejuvenate the brains of older animals. In this experiment, the results showed that parabiosis resulted in increased connections between neurons in the hippocampus. And, the researchers found that injecting the older animals with plasma from the blood of younger ones resulted in dramatically improved results on memory tests.
Unsurprisingly, scientists are jumping up and down at the concept of treating animals with young blood to reverse the effects of aging. Experts are already talking about potentially using these principles for everything from arthritis to Alzheimer's. But, some are also expressing concern, since allowing stem cells to run rampant in our bodies could potentially cause our tissue cells to replicate too wildly. As UC Berkeley professor Irina Conboy told The New York Times, “It is quite possible that it will dramatically increase the incidence of cancer." Still, there's something pretty poetic (if a little bit creepy) about deriving youth from the blood of younger models. I smell a vampire franchise in here somewhere. (The New York Times)