Large doses of young exosomes, delivered intravenously, have been shown to have extraordinary rejuvenation power in rats. We have known this for 5 years, but translation to human trials has been slow, not for technical reasons but because of trade secrets and intellectual property law and the inability to guarantee that he who funds the translation research will profit from the finished product.

In the interim, a cottage industry has developed around a weaker human therapy based on the technique that is so successful in rats. Plasma infusions are a well-developed, safe and approved procedure for trauma injury and other applications. It has been adapted by clinics in Texas as an anti-aging therapy. For some tens of thousands of dollars, an old person can buy two liters of blood plasma from a guaranteed healthy young donor. 

For those with the money to spend, the limit of two liters comes about because the volume of the body’s circulatory system can be stretched only so much. Putting extra fluid into the system, with extra pressure on the arterial walls, can be dangerous. Typically, one liter of blood plasma can be removed and two added, for a net volume increase of one liter. (An adult might have 5 liters total, so this amounts to a 20% expansion of the blood volume.)

Some people report good results from this procedure, but no one has been restored to youthful appearance, health, endurance, and learning potential comparable to the rats in the laboratories of Harold Katcher or Xi Chen. I’m guessing this is because the exosome dosages in these rat experiments were far larger than the ~35% replacement that is achieved in the Texas clinics. I believe that Katcher and Chen both used exosome infusions large enough to overwhelm the reservoir of old exosomes in the blood of the old rat. 

Proposal for infusing larger plasma doses in human trials

Blood plasma is 90% water. If it is the water volume that limits the dosage of young plasma, an obvious work-around is to concentrate the exosomes and other plasma ingredients before infusion. Freeze dried plasma is already a well-developed technology, in use for 80 years. Under a vacuum, the plasma is evaporated and the evaporation lowers the temperature. Over the course of 10-20 hours, almost all the water is removed, and the plasma is reduced to a slurry.

This technique has been developed for the convenience of long-term storage only, so that, in hospitals, plasma is routinely reconstituted to full strength before administration. But by adding less water, the plasma could be reconstituted at triple strength or more. In this way, a much larger dosage of young plasma could be infused in the old patient.

Refinements

Platelets are miniature cells responsible for blood clotting. It will be necessary to remove platelets from the plasma, because blood with 3 or 4 times the healthy concentration of platelets poses a danger of clotting, heart attack, and strokes. It may be advisable to remove albumen and some other elements of the plasma to keep their concentration within normal limits. 

There is an experimental anti-aging clinic in California, where old blood plasma is removed and replaced with albumen. It probably makes sense to remove old exosomes as we add young exosomes

We do not yet know

The principal uncertainty is whether the young exosomes are able to reprogram the body’s epigenetics, with a result that is self-sustaining. If we are lucky, then the reprogrammed body will produce its own young exosomes; if we are unlucky, then infusions of young exosomes will have to be repeated, perhaps as often as the blood turns over, which is a few months; if we are very unlucky, then the infusions will have to be repeated as often as exosomes are cleared from the blood, which is less than one day, and the treatment becomes completely impractical.

But results with rats suggest that the rejuvenation has some staying power.