In a ground-breaking study, scientists have found that injecting young mice with blood can increase the lifespan of elderly mice by 6-9%. This result, equivalent to an extra six years of life for humans, suggests that the blood of young mice contains compounds that promote longevity. While it is still unclear how this research can be applied to humans, it opens up new possibilities for the treatment of aging.
The practice of joining animals together, known as parabiosis, has a long history in scientific research. In the 19th century, French scientists connected the blood vessels of two rats to demonstrate that they shared a common circulatory system. This pioneering experiment led to the discovery that substances administered to one rat could affect the other, indicating that their bodies were interconnected.
In the 1950s, Clive McKay and his colleagues at Cornell University used parabiosis to study the aging process. By pairing young and old rats, they noticed that the cartilage in the old rats looked more youthful. This suggested that the young animals had factors in their blood that could reverse or slow down the aging process.
In recent years, parabiosis research has experienced a second wind. Modern techniques have allowed scientists to study the effects of shared blood flow between animals of different ages in more detail. These studies have shown that old mice have rejuvenated muscles and brains, while young mice show signs of accelerated aging.
The preliminary results of the parabiosis studies have prompted some doctors to suggest injecting blood plasma from young mice as a potential treatment for age-related diseases. However, in 2019, the Food and Drug Administration issued a warning against such a treatment, citing a lack of proven clinical benefit and potential harm.
Dr. James White and his colleagues at Duke University School of Medicine refined the parabiosis procedure in mice to better understand the anti-aging effect. They increased the duration of the bond between old and young mice to three months, twice as long as in previous experiments. After disconnecting the mice, they monitored the animals to determine how this would affect their lifespan.
The results of Dr. White’s study were striking. Not only did the older mice live longer, but their aging process appeared to have changed. Molecular markers in the blood and liver, which serve as indicators of biological age, showed that the old mice were “rejuvenated” compared to untreated mice of the same age. This suggests that the infusion of young blood altered their aging trajectory.
Interestingly, the young mice in the study also showed changes. They aged rapidly when paired with the old mice, but returned to their normal state after separation. This suggests a complex interaction between young and old blood and raises further questions about the mechanisms underlying these effects.
A glimpse into the future
The study, published in Nature Aging, provides valuable insight into the potential benefits of infusions of young blood. Although the study is at an early stage, it offers hope for the development of new treatments for aging in the future.