Diluting blood plasma rejuvenates tissue, reverses aging in mice
Plasma exchange could be the key to unlocking the body's regenerative capacities

Date:
June 15, 2020
Source:
University of California - Berkeley
Summary:
A new study reveals that replacing half of the blood plasma
with a mixture of saline and albumin reverses signs of aging
and rejuvenates muscle, brain and liver tissue in old mice. The
research team is currently finalizing clinical trials to determine
if a modified plasma exchange in humans could be used to treat
age-associated diseases and improve the overall health of older
people.



FULL STORY ==========================================================================
In 2005, University of California, Berkeley, researchers made the
surprising discovery that making conjoined twins out of young and old
mice -- such that they share blood and organs -- can rejuvenate tissues
and reverse the signs of aging in the old mice. The finding sparked
a flurry of research into whether a youngster's blood might contain
special proteins or molecules that could serve as a "fountain of youth"
for mice and humans alike.


==========================================================================
But a new study by the same team shows that similar age-reversing effects
can be achieved by simply diluting the blood plasma of old mice --
no young blood needed.

In the study, the team found that replacing half of the blood plasma
of old mice with a mixture of saline and albumin -- where the albumin
simply replaces protein that was lost when the original blood plasma
was removed -- has the same or stronger rejuvenation effects on the
brain, liver and muscle than pairing with young mice or young blood
exchange. Performing the same procedure on young mice had no detrimental effects on their health.

This discovery shifts the dominant model of rejuvenation away from young
blood and toward the benefits of removing age-elevated, and potentially harmful, factors in old blood.

"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," said Irina Conboy, a professor of bioengineering at UC Berkeley who is the first
author of the 2005 mouse-joining paper and senior author of the new
study. "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." In humans, the composition
of blood plasma can be altered in a clinical procedure called therapeutic plasma exchange, or plasmapheresis, which is currently FDA-approved in
the U.S. for treating a variety of autoimmune diseases. The research team
is currently finalizing clinical trials to determine if a modified plasma exchange in humans could be used to improve the overall health of older
people and to treat age-associated diseases that include muscle wasting, neuro-degeneration, Type 2 diabetes and immune deregulation.



==========================================================================
"I think it will take some time for people to really give up the idea that
that young plasma contains rejuvenation molecules, or silver bullets, for aging," said Dobri Kiprov, a medical director of Apheresis Care Group and
a co-author of the paper. "I hope our results open the door for further research into using plasma exchange -- not just for aging, but also
for immunomodulation." The study appears online in the journal Aging.

A molecular 'reset' button In the early 2000s, Conboy and her husband
and research partner Michael Conboy, a senior researcher and lecturer in
the Department of Bioengineering at UC Berkeley and co-author of the new
study, had a hunch that our body's ability to regenerate damaged tissue
remains with us into old age in the form of stem cells, but that somehow
these cells get turned off through changes in our biochemistry as we age.

"We had the idea that aging might be really more dynamic than people
think," Conboy said. "We thought that it could be caused by transient and
very reversible declines in regeneration, such that, even if somebody is
very old, the capacity to build new tissues in organs could be restored
to young levels by basically replacing the broken cells and tissues
with healthy ones, and that this capacity is regulated through specific chemicals which change with age in ways that become counterproductive."
After the Conboys published their groundbreaking 2005 work, showing that
making conjoined twins from the old mouse and a young mouse reversed
many signs of aging in the older mouse, many researchers seized on the
idea that specific proteins in young blood could be the key to unlocking
the body's latent regeneration abilities.



========================================================================== However, in the original report, and in a more recent study, when blood
was exchanged between young and old animals without physically joining
them, young animals showed signs of aging. These results indicated that
that young blood circulating through young veins could not compete with
old blood.

As a result, the Conboys pursued the idea that a buildup of certain
proteins with age is the main inhibitor of tissue maintenance and repair,
and that diluting these proteins with blood exchange could also be the mechanism behind the original results. If true, this would suggest an alternative, safer path to successful clinical intervention: Instead
of adding proteins from young blood, which could do harm to a patient,
the dilution of age-elevated proteins could be therapeutic, while also
allowing for the increase of young proteins by removing factors that
could suppress them.

To test this hypothesis, the Conboys and their colleagues came up with
the idea of performing "neutral" blood exchange. Instead of exchanging
the blood of a mouse with that of a younger or an older animal, they
would simply dilute the blood plasma by swapping out part of the animal's
blood plasma with a solution containing plasma's most basic ingredients:
saline and a protein called albumin. The albumin included in the solution simply replenished this abundant protein, which is needed for overall biophysical and biochemical blood health and was lost when half the
plasma was removed.

"We thought, 'What if we had some neutral age blood, some blood that
was not young or not old?'" said Michael Conboy. "We'll do the exchange
with that, and see if it still improves the old animal. That would mean
that by diluting the bad stuff in the old blood, it made the animal
better. And if the young animal got worse, then that would mean that that diluting the good stuff in the young animal made the young animal worse."
After finding that the neutral blood exchange significantly improved the
health of old mice, the team conducted a proteomic analysis of the blood
plasma of the animals to find out how the proteins in their blood changed following the procedure. The researchers performed a similar analysis
on blood plasma from humans who had undergone therapeutic plasma exchange.

They found that the plasma exchange process acts almost like a molecular
reset button, lowering the concentrations of a number of pro-inflammatory proteins that become elevated with age, while allowing more beneficial proteins, like those that promote vascularization, to rebound in large
numbers.

"A few of these proteins are of particular interest, and in the future,
we may look at them as additional therapeutic and drug candidates," Conboy said. "But I would warn against silver bullets. It is very unlikely that
aging could be reversed by changes in any one protein. In our experiment,
we found that we can do one procedure that is relatively simple and FDA-approved, yet it simultaneously changed levels of numerous proteins in
the right direction." Therapeutic plasma exchange in humans lasts about
two to three hours and comes with no or mild side effects, said Kiprov,
who uses the procedure in his clinical practice. The research team is
about to conduct clinical trials to better understand how therapeutic
blood exchange might best be applied to treating human ailments of aging.

This work was supported by the National Institutes of Health under grants
R56 AG058819, R01 EB023776, R01 HL139605; by an Open Philanthropy Project award; and by the National Institutes of Health T32 and Cooke fellowships.


========================================================================== Story Source: Materials provided by
University_of_California_-_Berkeley. Original written by Kara Manke. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Melod Mehdipour, Colin Skinner, Nathan Wong, Michael Lieb, Chao Liu,
Jessy Etienne, Cameron Kato, Dobri Kiprov, Michael J. Conboy,
Irina M.

Conboy. Rejuvenation of three germ layers tissues by exchanging
old blood plasma with saline-albumin. Aging, 2020; DOI:
10.18632/aging.103418 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200615115724.htm

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