Young blood returns youth to the elderly
According to data obtained by scientists at Harvard University (Boston, Massachusetts), working under the guidance of Amy J. Wagers, the rejuvenating effect of blood is not at all an invention of the authors of stories about vampires. Researchers have demonstrated that the blood of young mice contributes to the rejuvenation of the hematopoietic system of elderly animals. The mechanism of this phenomenon, as well as its impact on health and life expectancy, is currently unknown.
During the experiments, the authors surgically connected the circulatory systems of two animals in such a way that the blood of young animals entered the vessels of old ones. The procedure restored youth to the hematopoietic cells of elderly mice, their total number decreased and they began to produce blood cells of various types in more adequate proportions. According to the authors, they observed an almost complete recovery of aging-associated changes in the behavior of blood stem cells.
These data, published in the January issue of the journal Nature in the article "Systemic signals regulate aging and rejuvenation of blood stem cell niches", together with similar results obtained earlier in work with muscle stem cells, indicate that the regenerative properties of stem cells are strongly influenced by environmental factors. The discovery of this fact has both positive and negative consequences for regenerative medicine.
As the body ages, it loses the ability to repair various tissues. The hematopoietic system is no exception: despite the increase in the number of hematopoietic cells inhabiting the bone marrow, their ability to give rise to blood cells of different types decreases. In addition, there is a violation of the quantitative ratio of emerging cells: the number of immune cells of B-lymphocytes decreases and the number of cells mediating inflammatory reactions increases.
According to one of the theories of aging, stem cells gradually wear out due to certain internal reasons. The results of earlier studies support this theory, but the data obtained by Wagers and other researchers indicate that the aging of stem cells is influenced by external factors. For example, the impact of some factors, currently not yet established, contained in the blood of young mice, restores the ability of muscle stem cells of the old organism to regenerate.
Apparently, the ability of hematopoietic cells to regenerate is mediated by osteoblasts – bone-forming stem cells, whose participation in regulating the activity of blood stem cells was demonstrated some time ago. The authors found that after interacting with osteoblasts of old animals, the hematopoietic stem cells of young mice begin to behave like cells of old animals. Conversely, young blood rejuvenates old osteoblasts, restoring their ability to stimulate hematopoietic cells.
To date, scientists have not yet been able to identify the molecules that cause this phenomenon. They believe that an important role in this mechanism belongs to the insulin-like growth factor-1 (IGF–1), a hormone that regulates the lifespan of many organisms. The authors demonstrated that the suppression of the activity of insulin-like growth factor-1 partially eliminates the signs of osteoblast aging. On the other hand, the suppression of the activity of this factor in muscle cells has the opposite effect. These facts indicate the versatility of the role of this hormone in the aging process
In the near future, the authors plan to study the effect of rejuvenation of the hematopoietic system on the health and life expectancy of animals. The blood of old animals contains fewer lymphocytes that protect the body from viruses and other pathogens, and more myeloid cells (neutrophils and macrophages) involved in the formation of age-associated inflammatory status of the body. Therefore, there are all prerequisites for the fact that the rejuvenation of the hematopoietic system as a whole has a positive effect on the state of the immune system, and, accordingly, on the body's resistance to infectious agents.
The data obtained by the authors are of great importance for regenerative medicine, especially for stem cell transplantation. They testify to the extreme importance of the microenvironment into which stem cells are transplanted. For example, if you take healthy young cells and inject them into an aging organism, its microenvironment can significantly reduce the therapeutic potential of the transplant.
About the similar work of Prof. See Zuev from the N.F.Gamalei Research Institute of Epidemiology and Microbiology in the article "The Blood Enemy of Youth".
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of TechnologyReview: Young Blood Reverses Signs of Aging in Old Mice.
29.01.2010