In 2005, researchers at the University of California made a remarkable discovery. Joining together old and young mice so that they shared the same blood – a technique called parabiosis – reversed signs of ageing in the old mice. Ever since, researchers have been searching for proteins contained within young plasma that might be responsible for this rejuvenating effect. Notably, a paper last month reported that a proprietary plasma fraction could reduce the epigenetic age of rats by over 50%.
Now, the same team that produced the 2005 research have thrown a spanner in the works by showing that age-reversing effects can be achieved simply by diluting the blood. They replaced half of the blood plasma of old mice with a mixture of saline and ( replaces the protein that was lost when the blood is was removed). They found that that the rejuvenation effects on the brain, liver and muscle were the same or stronger than parabiosis or young blood.
This discovery seems to suggest that the effect of blood on ageing could be less related to beneficial factors in young blood, and more due to harmful factors in old blood. Professor Irina Conboy, first author of the 2005 study, explains:
There are two main interpretations of our original experiments: The first is that, in the mouse joining experiments, rejuvenation was due to young blood and young proteins or factors that become diminished with aging, but an equally possible alternative is that, with age, you have an elevation of certain proteins in the blood that become detrimental, and these were removed or neutralized by the young partners. As our science shows, the second interpretation turns out to be correct. Young blood or factors are not needed for the rejuvenating effect; dilution of old blood is sufficient.”Diluting blood plasma rejuvenates tissue, reverses aging in mice: Plasma exchange could be the key to unlocking the body’s regenerative capacities. (2020). Retrieved 16 June 2020, from https://www.sciencedaily.com/releases/2020/06/200615115724.htm#:~:text=A%20new%20study%20reveals%20that%20replacing%20half%20of%20the%20blood,liver%20tissue%20in%20old%20mice.
Analysing the proteins in the blood of these animals, researchers found that the exchange process reduced the levels of a number of inflammatory proteins that increase with age, while also allowing some beneficial proteins to rebound.
An FDA approved procedure called therapeutic plasma exchange exists and can alter plasma composition in humans. Clinical trials will investigate whether a modified plasma exchange could treatin humans, including muscle wasting, neurodegeneration, type 2 diabetes and immune deregulation.
Diluting blood plasma rejuvenates tissue, reverses aging in mice: https://www.sciencedaily.com/releases/2020/06/200615115724.htm#:~:text=A%20new%20study%20reveals%20that%20replacing%20half%20of%20the%20blood,liver%20tissue%20in%20old%20mice.
Rejuvenation of Aged Progenitor Cells by Exposure to a Young Systemic Environment: DOI: 10.1038/nature03260
Rejuvenation of three germ layers tissues by exchanging old blood plasma with saline-albumin: https://doi.org/10.18632/aging.103418
Reversing age: dual species measurement of epigenetic age with a single clock: https://doi.org/10.1101/2020.05.07.082917