Can Blood from a Younger Mouse Rejuvenate Ailing Older Mice?

Some scientists think they have discovered the fountain of youth - but there's still a great deal of controversy and mystery.

The more that researchers attempt to study a process known as "parabiosis", the more questions they have. Frequently studied in mice, parabiosis entails an exchange of blood between two animals. Several recent studies have focused on an older mouse's response to blood from a younger mouse.

A new study published in the latest edition of the journal Nature Communications shows that blood from a younger mouse helped bone fractures in older mice heal more quickly. Despite the aging mice's bodies' decreased ability to rebound from injury as quickly, older mice infused with young blood healed at similar rates to younger mice.

Scientists aren't exactly sure why the young blood was so effective in healing bone fractures, although they believe it could somehow be related to "hormones, small molecules, minerals or factors" produced by the mice's red blood cells. They did, however, identify the protein beta-catenin as somehow being related to the process.

According to Sara Reardon at Nature, a 2013 study from Harvard University seemed to offer another explanation, identifying a protein, GDF11, which becomes less abundant in a mouse's blood as it ages. An infusion of GDF11-rich blood bolstered the mouse's ability to regenerate muscle cells.

Subsequent studies attempting to recreate the 2013 results, however, showed completely contradictory results: increased amounts of GDF11 in an old mouse's blood severely inhibited its ability to recover from an injury.

Despite the myriad of conflicting information, researchers at various institutions are continuing full speed ahead investigating whether or not parabiosis could be a viable treatment for humans, and the practice has support throughout the medical community:

"We argue that parabiosis is a technique that should enjoy wider acceptance and application, and that policies should be revisited especially if one is to study complex age-related, chronic disorders," said the National Institutes of Health in a recent report.