Diluting Blood to Fight the Effects of Aging?

Studies in mice suggest that neutral blood exchange could be useful to prevent tissue aging

How vampires stay young

The vampires in many folk tales share a few characteristics, among them immortality and a taste for blood. Actually, these two might be linked, as we’ll see below.

Another interesting commonality is that vampires seem to prefer young victims, sinking their canines into necks belonging to people in the prime of their life.

This is, of course, because it makes for a greater, more dramatic story.

But the imaginary bloodsucking night people might be on to something.

In mice, heterochronic parabiosis (connecting the vascular systems of a young and an old mouse) has been shown to aid tissue regeneration, support the immune system, replenish the stem cell stores, and keep the central nervous system firing on all neuronal cylinders.

As you can imagine, some companies smelled potential profits and offered young plasma transfusions. The price tag fluctuates between several thousand to hundreds of thousands of US dollars, which makes one question the motives of the providers.

Furthermore, parabiosis is not without its question marks. In some studies, the parabiosed mice died without apparent reason (possibly immune rejection). Sometimes the negative effects on the younger mouse are a lot worse than the small positive effects on the old mice. And so on.

There is definitely potential here, but right now the FDA warns against young blood transfusions in humans for the sake of mitigating aging:

…we’re concerned that some patients are being preyed upon by unscrupulous actors touting treatments of plasma from young donors as cures and remedies. Such treatments have no proven clinical benefits for the uses for which these clinics are advertising them and are potentially harmful…The promotion of plasma for these unproven purposes could also discourage patients suffering from serious or intractable illnesses from receiving safe and effective treatments that may be available to them.

So, maybe back off from the vampire solution for now.

Dilution solution?

In the same way that there might be factors in young blood that promote health, there might be factors in old blood that do the opposite (such as molecules that help cancer spread).

What if we dilute the old blood, reducing the concentration of these age-related molecules?

A pair of recent studies (study one, study two) tried exactly that.

By replacing half of the blood plasma in old mice with a saline solution containing 5% albumin (a common blood protein), the authors achieved:

…to meet or exceed the rejuvenative effects of enhancing muscle repair, reducing liver adiposity and fibrosis, and increasing hippocampal neurogenesis in old mice, all the key outcomes seen after blood heterochronicity.

No need to suck young people’s blood, apparently.

This procedure, called neutral blood exchange (NBE), also allowed:

…old mice [to] perform much better in novel object and novel texture (whisker discrimination) tests after a single NBE, which is accompanied by reduced neuroinflammation…

The hypothesized mechanism behind these impressive results is that diluting the blood this way gets rid of some of the SASP molecules. SASP is the abbreviation of ‘senescence-associated secretory phenotype’, or the molecules secreted by senescent cells that promote aging in healthy nearby cells. Beyond SASP, it is possible that the removal of a significant amount of signaling proteins through dilution ‘resets’ certain signaling pathways.

Caution: do not try this at home.

Mice are not human. More research needed.

However… therapeutic blood exchange (TPE), which could be seen as an enhanced NBE in which the patients own blood is ‘scrubbed clean’ of detrimental factors and then returned is being investigated in humans:

Current multicenter trials are being conducted to further investigate the efficacy of TPE in treating Alzheimer’s disease.

Overall:

…this work supports the paradigm that diluting and resetting to health and youth systemic signaling milieu promotes the “young” determinants of tissue health, rejuvenating the brain (and in fact, all tissues and parameters that were studied up-to-date).

Rather than sucking someone else’s blood, the key to a long life may be getting your blood cleaned from time to time.