Injecting Idle Mice with Young Blood Made Them More Youthful

We are all familiar with the mental image of a mouse on a wheel running a marathon with itself in a paw-pounding action. Unsurprisingly, all that running is good for its health, leading to increased blood flow to the brain, which results in more neurons, improved navigation, and memory.

But what if you could take those benefits from the marathoner mice and give them to their couch-potato counterparts? Would that work? 

This enticing prospect was investigated in a new study published Wednesday in the journal Nature, in which researchers injected sedentary mice with blood plasma, the liquid that surrounds blood cells, from mice that ran for miles on wheels. Surprisingly, the sedentary mice then performed better on learning and memory tests, as if they had put in all those miles themselves.

And the researchers also discovered that the type of brain inflammation linked to Alzheimer’s and other neurological disorders was reduced in sedentary mice after receiving the young blood.

While these results with mice don’t necessarily translate to humans, this discovery could nevertheless advance muscle regeneration therapy for older people, and have significant ramifications for Alzheimer's research and beyond, according to a press release.

Enhancing learning and memory with ‘young blood’

This isn't exactly new since the recent study builds on decades of research demonstrating that when old mice are given blood from young mice, numerous cells and tissues regain their youthful appearance. However, until now, it remained unknown which young blood has these rejuvenating properties.

In a recent study, researchers from UPMC and the University of Pittsburgh researchers discovered that extracellular vesicles (EV) in mouse blood transmit instructions to muscle cells for a longevity protein called "Klotho." As mice grow older, the EVs appear to get weaker and transmit fewer instructions for the protein. However, when the researchers gave older mice younger mice's blood, their cells and tissue began to exhibit more youthful characteristics, such as increased muscle regeneration. However, when EVs were removed from the blood, the effect was diminished.

These findings could contribute to a better understanding of why the ability of muscles to regenerate diminishes with age.

“In one way, it [the study] helps us understand the basic biology of how muscle regeneration works and how it fails to work as we age," said senior author Fabrisia Ambrosio, Ph.D., director of rehabilitation for UPMC International and associate professor of physical medicine and rehabilitation at Pitt. "Then, taking that information to the next step, we can think about using extracellular vesicles as therapeutics to counteract these age-related defects.”

While much research is required, researchers hope that their findings may lead to novel treatments to help individuals maintain and improve their longevity as they age. 

"EVs may be beneficial for boosting regenerative capacity of muscle in older individuals and improving functional recovery after an injury," said Ambrosio. "One of the ideas we’re really excited about is engineering EVs with specific cargoes, so that we can dictate the responses of target cells."