Young blood may provide the key to youth, according to three studies released Sunday.
An infusion of blood from a younger mouse can reverse the effects of aging in older mice, researchers from the Harvard Stem Cell Institute and Stanford University School of Medicine found in three separate studies. They believe the findings have the potential to eventually help treat age-related conditions like Alzheimer's disease in humans.
"There are factors present in blood from young mice that can recharge an old mouse's brain so that it functions more like a younger one," Stanford researcher Tony Wyss-Coray said in a statement.
In the Stanford study, researchers were able to restore mental capabilities in older mice by giving them infusions of plasma from young mice. In these mice, the region of the brain responsible for forming certain types of memories, called the hippocampus, more closely resembled younger mice than other mice their age, according to the study.
The older mice who received the infusions also performed significantly better on tests that measured their memory and speed, according to the study. The opposite also held true - when younger mice received infusions from older mice, their performance levels decreased.
"We've shown that at least some age-related impairments in brain function are reversible. They're not final," said Stanford lead author Saul Villeda in a statement.
Similarly, the studies from Harvard found protein from the blood of younger mice can improve heart, brain and skeletal muscle function in older mice. After receiving the protein, the sense of smell in older mice also improved, according to the study.
Harvard researchers introduced the protein GDF11, which is also found in human blood, into older mice by both injection and by circulating the blood of younger mice through the older mice. Increasing the amount of GDF11 in older mice has improved the function of every organ system studied so far, according to researchers.
"This should give us all hope for a healthier future," said HSCI co-director Doug Melton in a statement. "We all wonder why we were stronger and mentally more agile when young, and these two unusually exciting papers actually point to a possible answer: the higher levels of the protein GDF11 we have when young. There seems to be little question that, at least in animals, GDF11 has an amazing capacity to restore aging muscle and brain function."
All of the researchers said it is not yet clear whether young blood would affect older humans in the same way, but they plan to continue researching. Researchers from the Harvard studies said they expect to start human clinical trials for GDF11 within three to five years.
"It isn't out of question that GDF11 might be capable of slowing some of the cognitive defects associated with Alzheimer's disease, a disorder whose main risk factor is aging itself," said Harvard researcher Lee Rubin in a statement.
The Harvard studies were published online in the journal Science. The study from Stanford was published in Nature Medicine.