Young blood transfusion

Research

Experiments beginning in the 1950s in the Cornell University lab of Clive McCay on pairs of old and young rodents placed into parabiosis provided some evidence, albeit limited and "largely anecdotal", that the circulation of blood from young mice increased both the longevity and the tissue function of old mice. After decades in which relatively little work on parabiosis in aging was done, the work was revived by researchers at Stanford University and the University of California at Berkeley. Parabiosis experiments are difficult to generalize, as the circulatory systems of the mice are fully joined and it is unclear whether the benefits come from the sharing of blood or the older mouse's access to the younger mouse's organs.

A study conducted at UC Berkeley found that when delivered alone, blood from older mice was more inhibitory to the regenerative capacities of younger mice than blood from younger mice was beneficial to older ones, and that the benefit of young blood in older mice was less than had been observed when older mice were subjected to parabiosis. Replacing plasma of old mice with saline and albumin from young mice was sufficient to rejuvenate brain, liver, and muscle. A 2020 review of plasma components that change with age identified several candidate anti-aging and pro-aging factors.

In experiments like this, researchers found that some of the parabiosed died quickly (11 out of 69 in one experiment) for reasons the scientists could not explain, but described as possibly some form of immune rejection; most such cases were the young parabiont. Amy Wagers, a researcher who coauthored several mouse studies on young blood transfusion, has said that her papers do not provide a scientific basis for some of the existing human trials.

A review of studies on donor age for whole blood transfusions reported that blood from donors under the age of 20 years, when compared to donors aged 20–60 years, resulted in a modestly higher risk of death in the recipients. However, other studies have found no effect of age. Research on blood transfusion outcomes has been complicated by the lack of careful characterization of the transfusion products that have been used in clinical trials; studies had focused on how storage methods and duration might affect blood, but not on the differences among lots of blood themselves.

Another approach to achieving "younger" blood is to rejuvenate blood-producing stem cells in the bone marrow. A 2023 study reported that the existing rheumatoid arthritis drug anakinra blocked IL-1B in elderly mice and returned those cells to a more youthful state.