You don’t need a major blood transfusion to regain your youth, just add some water to the blood?

Studies have found that thinning the blood can rejuvenate both the body and the brain, but its application needs further demonstration.

Author: Xu Sijia, Kyoto University School of Medicine, Japan

Editor | Gao Peiwen

The stories of vampires are well-known to everyone. They are beautiful and elegant, and they stay young forever by sucking or bathing in blood. While they are horrifying, they also make people curious about the actual power of blood.

In the past, people have discovered that after old mice and young mice shared blood, cell tissues regained vitality - plasma exchange can indeed reverse the aging of the body, and it is inferred that only plasma from young individuals has this effect.

But scientists recently discovered that the key may not be the supplementation of certain "youthful substances", but the dilution of some harmful substances related to aging and disease in the original plasma (Aging, 2020).

How do they prove this? Can we become younger by adding some water to the blood?

Plasma: The "Yellow River" that carries life

Blood is composed of cellular components (such as red blood cells, white blood cells, platelets, etc.) and plasma. Under normal circumstances, blood will coagulate when exposed to air. After adding anticoagulants, the cells and plasma in the blood can be separated in vitro.

Plasma is a pale yellow liquid that carries blood cells like a river, transporting various substances needed for life activities, including metabolic waste and pathogenic factors.

Plasma dilution: more than just adding water

The researchers used normal saline and 5% albumin to make a "neutral plasma" and used it to replace half of the plasma in the mice's bodies. They found that it can not only effectively repair muscle strain in elderly mice, but also reduce fatty liver and liver fibrosis.

The repair activity of these mice is not inferior to that of young mice, or even higher. Since the composition of neutral plasma is very simple, the researchers believe that the dilution factor of plasma plays a key role.

Why use albumin solution for this study instead of just water?

Because real plasma contains inorganic salts such as sodium chloride and about 5% albumin in addition to water. Inorganic salts constitute the crystal osmotic pressure of blood. Too high a concentration will cause blood cells to dehydrate and die, while too low a concentration will cause them to swell and burst after absorbing water. Macromolecules such as albumin play an important role in constituting the colloidal osmotic pressure of blood and retaining water in blood vessels.

Albumin is mainly produced in the liver. Therefore, some patients with liver failure cannot synthesize enough albumin, which causes the blood colloidal osmotic pressure to decrease. It is easier for water and inorganic salts to leave the blood vessels and enter the abdominal cavity, forming ascites.

Under normal circumstances, the concentration of albumin does not change much with age, so the infusion of normal saline containing 5% albumin is to make up for the albumin lost in the replaced plasma and to reduce the fluctuation of blood osmotic pressure, so that a "plasma dilution" effect that is closer to the physiological state can be observed.

Plasma "adds water" to enhance the vitality of the body and brain

Studies have found that after neutral plasma replacement, the body's ability to repair itself becomes stronger.

The researchers divided 18-month-old mice (equivalent to 56 years old in humans) into two groups, replaced half of the plasma in the mice with plasma from other elderly mice (mice of the same age) in one group and neutral plasma in the other group. The next day, a drug with muscle-dissolving effect (muscle destruction) was injected locally into the legs of the mice.

After 5 days, muscle tissue from the injection site was taken for comparison. The results showed that the muscles of mice after plasma dilution had stronger recovery ability and more muscle regeneration proteins were synthesized in the cells.

In addition, plasma dilution can stimulate the new generation of neurons in the brain.

The subgranular area of ​​the dentate gyrus of the mammalian hippocampus (a specific brain area) is distributed with neural progenitor cells that have the potential for self-proliferation and differentiation. The new neurons generated here determine the ability of learning and memory, and participate in emotional regulation. This function usually gradually declines with age.

The study found that the number of new neurons in the young mice in the partial neutral plasma replacement group was 10 times that of the plasma replacement group of the same age. Even in old mice, more active nerve cell proliferation was observed after plasma dilution.

In addition, the study found that neutral plasma exchange can effectively reduce the concentration of pro-inflammatory proteins that fuel age-related diseases such as chronic inflammation.

By comparing the changes in proteins in the plasma of mice in the plasma dilution group and humans after plasma exchange treatment, the researchers also found that as the inhibitory substances accumulated in the body due to aging were diluted, the body's regulation of cell division and immune response seemed to be restarted, and the body seemed to be injected with new vitality.

Even better, because the regulation of physiological functions is often up and down, and horizontally related, these changes gradually spread to more organs like waves and can last for a long time.

Providing new ideas for delaying aging and resisting diseases

In fact, plasma exchange technology has long been used in clinical treatment.

Some patients have abnormal immune function, and a large number of harmful antibodies are produced in the body, which attack healthy tissues. Another example is hereditary hyperlipidemia, which impairs the cholesterol metabolism function of patients. A large amount of cholesterol accumulates in the blood vessels at a young age, leading to early onset of cardiovascular and cerebrovascular diseases.

For these difficult diseases, when drug responses are inadequate, plasma exchange may delay progression.

Technically, it is not complicated. Usually, a thick vein is taken from the patient's neck or thigh and inserted into a blood collection tube. The blood is then drawn into a machine with anticoagulants added. The blood cells and plasma are then separated, and the harmful substances that cannot be metabolized in the patient's plasma are filtered out. The plasma or albumin donated by normal people is then added and then transfused back into the human body.

Each time usually takes several hours and can replace 2 to 3 liters of plasma.

One of the important complications of plasma exchange is the risk of allergy and infection caused by allogeneic blood products.

Therefore, if young plasma is no longer necessary, the idea of ​​plasma dilution alone can be used to improve human function, resistance and age-related diseases. This will not only reduce the use and risks of blood products, but will also be of great significance for understanding the mechanism of aging and increasing human life expectancy.

However, scientists still need to accumulate more evidence for this.

Right now, instead of looking forward to a "major change", it is better to drink more water, exercise regularly, and maintain your health to the best of your ability every day.

References

1. Conboy IM,Conboy MJ, Kiprov D, et al. Rejuvenation of three germ layers tissues by exchanging old blood plasma with saline-albumin[J]. Aging, 2020, 12(10):8790-8819.

2. Castellano JM, Mosher KI, Abbey RJ, et al. Humanumbilical cord plasma proteins revitalize hippocampal function in aged mice[J]. Nature, 2017, 544(7651): 488-492.

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