Neuroscientist Tony Wyss-Coray, PhD, and his anything-goes grad student, Saul Villeda (now a PhD) decided to ignore the traffic light called the blood-brain barrier and charge full-speed ahead into a study, now published in Nature, of naturally occurring blood-borne substances that - however they do it - manage to make young brains act older. These substances, whose levels unfortunately rise with increasing age, appear to inhibit the brain’s ability to produce new nerve cells critical to memory and learning.
Wyss-Coray, Villeda, and their Stanford peers not only identified a half-dozen such substances in a mouse study but confirmed that they all rose in an age-related fashion in humans, too. One of the blood-borne chemicals, eotaxin, is well known as a signaling molecule that attracts immune cells called eosinophils to areas where it's being secreted. Eosinophils, in turn, have been implicated in allergy and asthma -- which is a whole other story, except for the consequence that drugs that block eotaxin's action are already in clinical trials for asthma.
One wonders - and you can be sure Wyss-Coray and Villeda are wondering, too - what would happen if one were to block four or five of these age-related substances' activity. Would we be able to produce more new brain cells in our 80s and 90s? Would we remember where we left the car keys?
Tom Rando, MD, PhD, one of the study's co-authors, had gotten the ball rolling five or six years ago when he demonstrated, using a technique later adopted by Wyss-Coray's group, that muscle stem cells are more robust if bathed in young blood. Another study, which I wrote about a year and a half ago, got similar results when looking at the effects of young versus old blood on the relative pep of blood-forming stem cells.
The possibilities are huge. As I wrote in a news release on this study:
The findings raise the question of whether it might be possible to shield the brain from aging by eliminating or mitigating the effects of these apparently detrimental blood-borne substances, or perhaps by identifying other blood-borne substances that exert rejuvenating effects on the brain but whose levels decline with age.
Wyss-Coray's group also learned that something in young mice's blood makes old brains act (or at least look) younger. They're now trying to identify some of these "rejuvenating factors" for further experiments directed at keeping our brains young. Stay tuned.