For as long as man has understood death, he's been hunting for the fountain of youth.
A few mice and thousands of experiments later, some scientists believe we are on our way. In the last year alone, several stories have broken surrounding the work of Thomas A. Rando, a professor of neurology at Stanford University School of Medicine, and his associates at Harvard. Rando is one of the pioneers in studies that may help produce treatments to reverse aging.
But Rando and his team's aspirations were born in another era: the 1950s. That was when Clive M. McCay, American gerontologist at Cornell University, experimented with conjoining old and young rats to see what their blood would do to each other. While McCay's work had its dark side ("If the two rats are not adjusted to each other," he wrote in the Bulletin of the New York Academy of Medicine, "one will chew the head of the other until it is destroyed"), it also yielded some surprising results.
After completing the procedure dubbed parabiosis, where rats were stitched together on the skin of their flanks, he found that "blood vessels grew and joined the rats' circulatory systems," according to The New York Times. That blood yielded cartilage in old rats that looked more youthful and presumably initiated some kind of rejuvenation. Conversely, the young mice with old blood showed accelerated rates of deterioration. The issue was they didn't know how, and by the 1970s the work surrounding blood transfusions was largely abandoned.
Enter stem cells.
It became clear in the early 2000s that stem cells actually weren't dying in aging tissue, but they just weren't receiving the signals they needed to. And that's where Dr. Rando came in.
Rando and his colleagues brought back Dr. McCay's experiments, joining old and young mice for five weeks before testing their muscles and tracking their progression. The results were both stunning and consistent: muscles in the old mice healed nearly identically to those of young mice.
That knowledge traveled with Amy J. Wagers, a member of Rando's team, all the way back to Harvard University, which is where we pick up the story and the latest breakthroughs.
Wagers and her colleagues have since identified a protein known as GDF11 that was common in the younger mice but scarce in old ones. After finding a way to isolate the protein, scientists began experimenting with injecting it into old mice. Even by itself, without the rest of the "young blood" with it, GDF11 rejuvenated the mice's hearts.
Teamed with this news was the work of another PhD — Dr. Saul Villeda — who, using the same conjoined mice experiment, helped discover that old mice who received young blood showed a "burst of brain cell growth in the hippocampus."
Just like Wagers, he was able to narrow down the effect of the blood to one protein. In his most recently published paper from July 2015, he identified it as B2M. And, just like how the old blood in young mice impaired their ability for growth, they found that when they injected B2M into young mice, it impaired their memory.
There are other dangers, too. According to Irina M. Conboy, a professor of bioengineering at University of California, Berkeley, waking up stem cells is a dangerous game.
"It is quite possible that it will dramatically increase the incidence of cancer," she told The New York Times. "You have to be careful about overselling it."
Still, these new discoveries could be the key to unlocking successful battles against Alzheimer's and heart disease. Obviously, the results in mice won't necessarily correlate to success in humans, but the concept itself has never felt more alive or more attainable.