Scientifically Speaking | Young “brain juice” helps to rejuvenate old brains

In the study, researchers at the Stanford University School of Medicine, tested whether an infusion of young mouse cerebrospinal fluid improved memory in old mice. It did.

As we get older, our ability to form and store memories begins to diminish. Our backs start to hurt, our eyesight gets worse, and we lose bone density and muscle mass. Through a combination of good genes that we inherit and good practices like eating well, exercising regularly, getting adequate sleep, and keeping stress levels low we can slow the effects of ageing. But we can’t stop ageing altogether. Wouldn’t it be great if the mental and physical frailty associated with ageing could be reversed?

Researchers found that genes associated with the production of a substance called myelin were very active in certain cells of the brain in old mice that received young cerebrospinal fluid. (Getty Images/iStockphoto)

Anti-ageing is a multi-billion-dollar research area that is still in its infancy because the biological mechanisms by which we age are only now coming into view. Studying ageing in populations is difficult because it is hard to design precise experiments on people. People live for many decades and do many things at once; parsing out what activities are responsible for slowing or speeding up ageing is difficult.

Fortunately, we can turn to model organisms like mice, which mimic many (but not all) of the processes of ageing that we see in humans. Mice live short lives and can be subjected to experimental surgical procedures in controlled environments.

In a column I wrote in December, I mentioned research that had been published in scientific journals that had shown that there were youthful factors and signals in the blood and faeces of young mice that could rejuvenate some of the signs of ageing in older ones. Now, scientists have shown in a research article published in Nature on May 11 that cerebrospinal fluid which surrounds the brain also has rejuvenating properties.

In the study, researchers led by Tal Iram and Tony Wyss-Coray at the Stanford University School of Medicine, tested whether an infusion of young mouse cerebrospinal fluid improved memory in old mice. It did. Old mice (18 months old) that received cerebrospinal fluid from young adult mice (10 weeks old) were able to perform better in a task that tested the recollection of fearful memories than old mice that did not.

How does the young cerebrospinal fluid exert its rejuvenating effects? Researchers found that genes associated with the production of a substance called myelin were very active in certain cells of the brain in old mice that received young cerebrospinal fluid. Myelin is a fat and protein-containing insulating layer around nerve fibres in the brain. It allows strong electrical signals to pass through neurons in the brain.

In 2020, three research groups separately showed that myelin formation is necessary for memories to be formed and later for memory retrieval. One group published an article in Nature Neuroscience showing that myelin formation occurs actively in young mice but slows down in older mice. This lack of myelin formation is associated with memory defects. What the more recent work shows is that by using young cerebrospinal fluid this cognitive decline can be reversed.

The scientists also found a factor in cerebrospinal fluid that is responsible for improved memory function. This protein, called fibroblast growth factor 17 has rejuvenating effects in mice.

Now, humans are not mice, but what is interesting from a human perspective is that we also have fibroblast growth factor 17. Further research will demonstrate what role this factor plays in dementia and whether drugs that target it help to alleviate memory loss. But we certainly have a better handle on the biological processes involved in memory formation and retrieval now.

Taken together all of these studies on factors in blood, faeces, and cerebrospinal fluid show that young animals are physiologically different from old animals, but at least some of the vitality of youth can be transferred.

At this point, you might be thinking about whether you should opt for transfusions of young biologics. Indeed, there are Silicon Valley startups that are looking into this. But it is too early to say if this will pan out as more than a fad.

Right now, transfusions of young biologics are not approved for use because we don’t know if they work in people. Still, if specific factors and how they work to create and store memories can be gleaned, there could be an opportunity for targeted treatments for dementia.

Anirban Mahapatra is a scientist by training and the author of a book on COVID-19. He’s writing a second popular-science book

The views expressed are personal