An Injection of Young Blood Improves Memory in Older Mice

Researchers are aiming for a clinical trial in humans next.


Sixteenth-century Hungarian countess Elizabeth Bathory is one of history’s most famous female serial killers. She tortured and killed scores of girls, often her own servants, in myriad horrible ways—sticking pins under their fingernails, even biting their flesh. But the less-verifiable rumor that has dogged her legacy is that she bathed in the blood of virgins, believing it would keep her youthful. It didn’t work. She died in 1614.

Fast-forward to the present, when modern medicine has extended our life expectancy considerably, without the use of young blood—until now.

While taking a dunk in a tub of O-neg is still not going to keep your skin from wrinkling, an intense new study published in Nature Medicine yesterday offers the possibility that introducing young blood to the inside of the body could keep the mind young. In the study, injections of blood from young mice significantly improved the memory of older mice.

Let’s quickly make all the responsible caveats one should when reporting on research that could easily be blown out of proportion: It’s just one study; it’s mice, not humans; more research is definitely necessary.

All that said, this is pretty cool.

To start, the California researchers connected the bodies of mice in pairs of two, sometimes two old mice, sometimes one old and one young—creating, essentially, conjoined twins. Then they looked at how thousands of different genes were expressed in the brain. When old mice were paired with young mice, they found that many of the genes that changed their expression in the old mice’s brains were located in the hippocampus—a part of the brain that is key to memory.

This wasn’t enough, though. They wanted to see if these observed changes in the brain would actually translate into behavioral changes, which is pretty hard to measure when two mice are stuck together. So in the next experiment, they injected three groups of older mice with saline, plasma from young mouse blood, or plasma from young mouse blood that had been denatured by heating it up.

“We found, indeed, that the mice that had young blood do better on memory tasks, which was consistent with the structural changes that we saw,” says Tony Wyss-Coray, co-author of the study and professor of neurology at Stanford University. Older mice injected with young blood improved their performance on memory-related tasks by 30 to 50 percent, he says.

The cooked blood, however, did not work, which led the researchers to believe that it’s one or several proteins in the young blood that are causing the beneficial effect. (Heat denatures proteins, changing their shape—this is what happens when you cook an egg—so proteins in the mouse blood, if they were indeed helping the older mice, would cease to work when heated).

Wyss-Coray explains to me that as organisms age, the proteins in their blood do change. There may be more or less of certain proteins at different ages. This was something he and his team researched, prior to embarking on this study.

The team just injected the blood into the mice’s veins—it didn’t have to be administered directly to their brains to work. “That’s the exciting aspect,” Wyss-Coray says, “because people get plasma transfusions all the time… There’s not a big hurdle to do a test like that.” And thanks to this relative ease, he says Stanford is currently pursuing a small clinical trial in humans, in which Alzheimer’s patients would be injected with plasma from young people. The trial is currently awaiting approval.

Though we can’t say for sure based on this study whether treatment with young plasma will be effective for humans, Wyss-Coray says that the structures at play in the brain are similar across species, so there’s reason to hope. Though the team saw results pretty quickly after injection—within hours at most—one thing that wasn’t addressed in this study is how long the effect lasts. It was weeks, at least, for mice, since that’s the length of time spanned by the study, but beyond that, we don’t know. Even if there is a similar effect in humans, it could be very temporary.

“It’s possible you get one good day out of it,” he says.

But in the face of Alzheimer’s, for which there is as yet no cure, the hope of one good day would not be nothing.