Eternal youth has been chased by mankind for thousands of years, and so far, our efforts to turn back the clock have remained fruitless. But we seem to be getting closer — humans are living longer than ever before through advancements in public health, nutrition, and medicine. We are learning more and more about what makes our bodies tick, so is it only a matter of time before we finally discover that fountain of youth?
One unexpected potential source of age reversal has been toyed with for decades, but only recently investigated as a potential treatment for humans: young blood. It sounds morbid, but a number of animal studies have found that something in the blood of young rodents helps rejuvenate the bodies and minds of their elderly counterparts. Once worn-out stem cells leap into action, producing shiny new tissue in the heart, muscle, and brain.
Although young blood seems to be a youth elixir for rats and mice, its effects on humans is still a question mark — but not for long. The first young-blood clinical trial is currently underway at Stanford University, attempting to treat elderly patients suffering from Alzheimer's disease using transfusions from donors under 30 years old.
“When we are speaking about reverse aging, we are not aiming towards immortality," said DLDsummer15 speaker Dr. Shai Efrati, director of the Sagol Center for Hyperbaric Medicine and Research at Assaf Harofeh Medical Center in Israel. “What we want is a good quality of life — we want to go down with our heads up, and that is our mission." The reason why aging occurs is still unclear, although its effects are unmistakable and seemingly unstoppable. But some researchers are starting to reframe aging as a complex disease — in other words, a condition that can be manipulated — rather than just an inevitable end.
Efrati discussed the conditions necessary to wind the body's clock back and his own efforts to do so in his DLDsummer15 talk, “Reverse Aging". His own research focuses on hyperbaric oxygen therapy (HBOT), which involves breathing pure oxygen in a chamber with increased air pressure to deliver more oxygen to the bloodstream. The extra oxygen has the ability to spur previously dormant neurons into activity.
“There is anti-aging, when we want to stop it, and there is reverse aging," he said. “When we are speaking about reverse aging, it means that we need to do regeneration." The idea that young blood may have regenerative benefits dates back to the 1950s with a series of papers by Cornell University researcher Clive McCay, including one titled “Experimental Prolongation of the Life Span." McCay used an age-old technique called parabiosis, first described in the 1800s but largely ignored for the next century. This Frankenstein-like technique involves stitching together flaps of skin from the sides of two rats to conjoin their blood supplies.
When McCay connected an old rat with a young one in his experiments, termed heterochronic parabiosis, he found evidence of benefit to the older rat's lifespan and tissue function. However, his studies were small and largely anecdotal.
Recently, heterochronic parabiosis as a method of investigating the aging process is experiencing a revival. Studies from the last decade have seen that a shared blood supply appears to rejuvenate stem cell activity in elderly animals, but slow down regeneration in the young. These results hinted that something in young blood has an age-reversing effect, and vice versa.
Then in 2014, three landmark papers were published simultaneously that gave us the best evidence so far that young blood may contain a fountain of youth. They also moved away from heterochronic parabiosis to more real-world therapies that aging humans could one day adopt. Two of the studies focused on a specific protein found in blood, growth differentiation factor 11 (GDF-11), that declines in concentration with age. Treatment with pure GDF-11 injections gave a similar stem cell boost in muscle tissue to that seen with heterochronic parabiosis, and older mice were able to outperform controls on strength and endurance tests.
The third study out of Stanford University used injections of whole young blood without focusing on a particular protein, but witnessed the same type of enhancements. After treatment, the old mice had better memory recall and experienced a reactivation of neural stem cells in the hippocampus.
Although these results seem promising, what works in controlled experiments on mice don't always prove effective in humans. And there's no telling how long these age-reversing perks would last in people, either. For mice, the youthful boost seemed to last only for a few weeks after the initial GDF-11 or young-blood injection.
These questions don't have answers yet, but researchers are determined to find out. October of last year marked the beginning of the first young-blood clinical trial at Stanford, where patients with Alzheimer's disease will be given transfusions of blood plasma from volunteers under 30 years old. Stanford neuroscientist Tony Wyss-Coray has also launched a startup company, Alkahest, to focus on young-blood treatment applications that already has investors clamoring.
The study is still in the recruiting phase, but Wyss-Coray ultimately hopes to see improvements in subjects' cognitive function. Any method to successfully reverse aging, whether it be young-blood injections, a drug of some kind, or the HBOT that Shai Efrati has been researching, has the potential to transform medicine as we know it. Advanced age is a risk factor for the many diseases humans die from today — heart disease, cancer, stroke, etc. — so finding a sort of catch-all therapy could truly be revolutionary.