Young blood: the data was not confirmed
Exactly one week after the publication of data on the rejuvenation of elderly mice using injections of blood plasma of young people, the authors of the hypothesis of "young blood" stated that they were unable to confirm the results of their early experiments.
Researchers at the University of California at Berkeley, working under the guidance of Associate Professor Irina Conboy, have demonstrated that the condition and ability to repair tissue damage in young mice deteriorate significantly when replacing half of their blood volume with the blood of old animals. At the same time, the data obtained as a result of the work refute the theory of the rejuvenating effect of young blood.
In 2005, the authors published their data indicating the rejuvenation of old mice, whose circulatory system was surgically connected to the circulatory system of young animals in such a way that the mixing of young and old blood was ensured. Despite the ambiguity of the mechanisms underlying this rejuvenation, when covered in the media, the revealed phenomenon was presented as the ability of young blood to reverse the aging process. Over the years since then, researchers have spent millions of dollars studying the potential use of young blood in clinical practice, for example, for administration to elderly people.
Blood transfusion is a widely used procedure in medicine, however, frequent transfusions or the introduction of a large volume of donated blood or its components can lead to the development of adverse reactions caused by genetic differences between donors and recipients. These adverse reactions are of the nature of immune rejection and can lead to the development of insufficiency of various organs.
While the experimental model used in 2005, known as parabiosis, demonstrated the possibility of eliminating some aspects of aging, it does not allow controlling the process of blood metabolism, which is necessary for a deeper study of the mechanisms of the influence of young blood on the aging process.
In conditions of parabiosis, in addition to blood exchange, animals receive all internal organs for joint use, including the lungs, heart, liver, kidneys, as well as the thymus and other immune organs. The effects of blood mixing appear only a few weeks or even months after the surgical connection of animals, while the exact time intervals of this process are unknown, as well as the degree of blood mixing.
In their new work, researchers have developed an experimental technology for blood exchange between animals without surgically connecting their circulatory systems. It allows you to control blood flow and accurately assess the reaction of old animals to young blood and vice versa. The new system implies the possibility of connecting and disconnecting mice at the request of researchers, which eliminates the influence of "common" organs or any other adaptation to surgical connection.
A snapshot from an article in Nature Communications
One of the most unexpected observations made during the study was the rapid manifestation of the influence of blood on the condition and ability to repair many tissues, including muscles, liver and brain. These effects began to manifest themselves already about 24 hours after the blood exchange.
As part of the study, the authors repeated the experiments of 2005 using a new system. In each production, an old and a young animal exchanged blood until 50% of the blood in the body of each of them was replaced by the blood of a "partner". After that, the levels of various markers of aging were measured for each animal, such as the ability of liver cells to grow and the severity of fibrous and fatty degeneration of the liver, the formation of new neurons in the hippocampus – the region of the brain responsible for learning and memory – as well as muscle strength and the ability of muscle tissue to recover. In many of these experiments, improvements were either not observed in the young blood transfusions of old mice, or they were very poorly expressed compared to the animals of the control group. At the same time, young mice receiving old blood transfusion showed a marked deterioration in the condition of the listed tissues and organs.
The most significant data were obtained by analyzing the effect of blood on neurogenesis (formation of new neurons) in the hippocampus. In these experiments, young blood did not have a significant effect on the state of nerve stem cells of old mice, whereas in young mice that received old blood, there was more than a twofold decrease in the activity of the formation of new neurons compared to normal young animals.
The authors suggest that the previously observed positive effect of young blood on the state of the brain of old animals could be due to a decrease in the concentration of neurogenesis inhibitors contained in old blood due to the dilution of young blood. Currently, they are already searching for these molecules, the elimination or neutralization of which can form the basis of new methods for improving memory and cognitive function. In addition, they note that in the future it is necessary to conduct experiments to study in detail the factors that cause deterioration of the tissues and organs of young animals under the influence of old blood.
Article by Justin Rebo et al. A single heterochronic blood exchange reveals rapid inhibition of multiple tissues by old blood published in the journal Nature Communications.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on University of California – Berkeley: Young blood does not reverse aging in old mice, UC Berkeley study finds.
24.11.2016