Young blood for old rejuvenates aging mice
Science may have discovered the 'elixir of youth' after years of study, but rather than coming from the waters of a mythical spring, the key to restoring youth may lie in the blood of the young.
The search for eternal youth is so compelling that it has appeared in many myths and legends of centuries past, and in more recent times has spent a significant amount of time beckoning to us from advertisements and commercials. However, leaving behind the myths and the marketing, science may now be on the right track, thanks to some recent research dealing with the blood of mice.
When the tissues in our bodies, or the bodies of any animal, become damaged - through injury or disease - it's stem cells that step up to replace them and rejuvenate those tissues. At one point, it was thought that we lost stem cells as we aged, and this lack of 'supplies' to repair our tissues is what caused us to age and eventually die. However, experiments determined that this was false. Aged tissues have just as many stem cells as young tissues. Looking for the fundamental difference here, researchers over the past decade or so have found that exposing damaged tissues from old mice to the blood from young mice allowed those tissues to heal faster. Somehow, the younger blood was activating more stem cells to repair the damages.
Since then, more experiments of this kind have shown that young blood can repair muscles, rejuvenate an aged heart, and even stimulate the growth of new neurons in the brain - especially in the area of the hippocampus, which is important in forming memories.
While some of these experiments simply dealt with injecting the old mice with blood from young ones, the researchers had to dip a bit further into the macabre to study this in the most effective way, using what's known as parabiosis. This is where they surgically join together a young mouse and an old mouse, so that their circulatory systems are linked. Last year, these experiments yielded some exciting results when the researchers reported that the heart of the older mouse of the pair had shrunk and become more like the heart of its younger companion. The key here was apparently a protein in the blood called GDF11, and when the researchers extracted that from the young mouse's blood and injected that protein into a different aged mouse, they saw the same results.
The video below was recorded in 2013, by Harvard researchers Richard Lee and Amy Wagers, when they reported their findings:
Now, in three different studies published just over the weekend, two research teams at Harvard and one working at Stanford University and the University of California San Francisco, have been expanding on all this previous work. Using similar methods, the Stanford and UCSF researchers confirmed the growth of new neurons in the brain for the older mice, as the blood from the younger mice flowed through their veins, which increased the cognitive abilities of the older mice. They also found that the reverse was true - the blood from the older mouse caused the younger mouse to suffer impaired cognitive abilities, as if it had aged.
Meanwhile the Harvard researchers that worked with the GDF11 protein last year, to rejuvenate the hearts of older mice, found that it had similar effects on skeletal and brain tissues, and a separate research team at the university observed the protein's effects on the sense of smell of the older mice. Transplanting the protein from young mice to old mice showed increased blood flow in the region of the mouse's brain that controls their olfactory sense, and this stimulated new nerve cells to grow, improving the sensitivity of their sense of smell to that of a younger mouse.
Applications for human rejuvenation?
While these are some exciting results, and they give hope not only for finding effective treatments for conditions related to aging, like Alzheimer's disease, heart disease, diabetes, etc., but also for aging itself, it's not clear yet if these will have direct applications for human medicine. Mice have very similar genetic and biological characteristics to humans, so studies using them as a model can provide a starting point for researchers to examine reactions, conditions and diseases in humans. So, as the work continues for these researchers, the focus will likely be to see if these factors in the blood of young mice also exist in the blood of humans, and if so, if they can be isolated for testing. So, it will still be some time before any of this advances to human applications, though, but there's promise, nevertheless.