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Young Blood And Rejuvenation: What We Know So Far

Posted on 4 October 2023

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One of the keys to reversing the ageing process could be flowing through your veins. There is growing scientific evidence that factors contained within blood plasma (the liquid that remains after blood cells have been removed) could regulate the ageing process, and many hope that these factors could be used to reverse or delay ageing in humans. This speculation isn’t unfounded – numerous animal studies over the past few decades have shown that old organisms can be rejuvenated by introducing blood plasma from younger organisms. Some people have put this animal evidence into immediate human practice – entrepreneur Bryan Johnson has made quite a few headlines for receiving young plasma donations from his son. In this article, we’re going to review the various methods of harnessing young blood, the evidence that has so far been produced, and whether putting this into practice in humans now is justified.

What’s Special About The Blood?

The blood is a tissue that links every organ in the body together and supplies every living cell with oxygen and nutrients. It also exposes them to many thousands of signalling molecules produced by distant cells. As organisms age, the balance of these molecules changes. The levels of harmful signalling molecules associated with ageing (like inflammatory factors) increase, while the levels of signalling molecules thought to be associated with youthfulness (such as klotho) decrease. Many different factors contribute to this shift, such as the ageing of the immune system leading to chronic inflammation across many tissues and the gradual disruption of gene expression.

Based on several decades of research, many scientists believe that either the removal of harmful factors or the addition of beneficial ones may enable us to slow down or reverse the ageing process. How can we go about doing this?

Tools Of The Trade

There is more than one way to therapeutically improve the ‘quality’ of factors within the blood plasma. Here’s an overview of the different methods that have been investigated.

Heterochronic parabiosis: Heterochronic parabiosis is when two live animals, one old and one young, have their circulatory systems joined together so that they share blood. This exposes the older animal to factors within the blood of the younger animal, and also allows the older animal’s blood to be detoxified by the young animal’s organs. It is from parabiosis experiments that the first truly exciting evidence about the role of blood in ageing emerged. When young mice are paired with old mice, the old mice are rejuvenated while the young mice appear to age more rapidly. 

Heterochronic parabiosis

Blood dilution: In blood dilution, a portion of the plasma is replaced with saline solution. This means that no beneficial factors are added but harmful factors are diluted. Research suggests that this may have similar benefits to parabiosis.

Blood donation: Blood donation is currently the only way in which humans routinely and safely undergo medical removal of harmful factors present in the blood. There is currently very little research concerning whether blood donation might be beneficial in humans.

Plasma transfusion: In plasma transfusion, plasma is taken from a young organism and injected into an older organism. This has the dual effect of diluting harmful factors and introducing beneficial factors present in the young plasma. 

Specific plasma fractions: Researchers have attempted to identify and isolate the specific components of the plasma that are beneficial so that they can be purified to enhance their therapeutic benefits. Much of the recent research focuses on exosomes, which are microscopic packages containing signalling molecules and genetic material. Exosomes are released by cells into the blood and mediate long-distance communication. Exosomes could be synthesised artificially if they are found to have rejuvenating effects.

The Evidence

Below, you can see a table summarising positive findings for each of these techniques. You’ll quickly notice that while many benefits have been demonstrated in animal models, the column for human evidence is sparse. That’s because very few human studies have been performed.

Therapy TypeMouse ModelsRat ModelsHuman Studies
ParabiosisLifespan extension
Reversal of epigenetic age
Improved cognitive function
Reduced Alzheimer’s disease pathology
No evidenceNot applicable
Blood DonationNo evidenceNo evidenceReduced perfluoroalkyl and polyfluoroalkyl levels in firefighter blood/plasma donors.
Blood DilutionBroad rejuvenating effects
Enhanced muscle repair and neurogenesis
Improved cognitive function
No evidenceNo evidence
Plasma TransfusionReduced Alzheimer’s disease pathology
Reversed age-related impairments in cognitive function
Protection against inflammation and oxidative stress
Improved health and extended mean lifespan
Clinical trials ongoing
Safe and well tolerated in Alzheimer’s patients
Specific Plasma FractionseNAMPT-containing extracellular vesicles extend lifespanLifespan extension (exosome fraction E5)
Reversal of biological age in multiple organs by young porcine plasma fraction (exosome fraction E5)
Clinical trials planned

To the best of our knowledge, there is only one human study to date that has demonstrated a benefit to manipulating the blood plasma. It was a randomised clinical trial of Australian firefighters who had elevated levels of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in their blood. The study found that those assigned to donate plasma regularly benefitted from a significant reduction in PFAS levels. This is a proof of principle that periodically removing blood plasma is a viable way of removing harmful molecules from the blood. However, we still don’t know if this would have a significant and lasting effect on blood factors associated with ageing, since most of these factors are continuously produced by the body’s own cells.

What about adding in ‘youthful’ factors, such as plasma transfusions from young people or deliveries of exosome fractions? Because of the way clinical trial approval operates, researchers cannot simply give people young blood transfusions just to see what happens – they need to be targeting a specific disease. Some such trials have been initiated, such as this one in Alzheimer’s patients, but are still in the very early stages in which safety validation is the primary goal.

On Private Clinics Offering Young Blood Transfusion

Some private health clinics have begun offering blood transfusions from young donors, with claims that this can treat various conditions and delay the ageing process. However, as we have just seen, these claims are not yet substantiated by human clinical trials. Moreover, while plasma transfusions are generally safe, they are not risk-free due to the possibilities of allergic reactions and other adverse events. This means that you are paying for a treatment that has no proven benefit and that may harm you.

So, are the likes of Bryan Johnson and those who seek the services of private clinics wrong? Not necessarily, but they are taking a gamble. When someone takes a gamble with their health, they should fully understand the stakes and the risks, but unless done as part of a clinical trial there’s no guarantee that such information will be properly communicated.

The study of factors in the blood related to ageing is an exciting field that could be our ticket to slowing down the ageing process. However, clinical trials are currently lacking, and we can’t yet say whether young blood transfusion benefits humans in any way.

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    Title image by Diana Polekhina, Upslash

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