Cellular aging: from physiology to pathology
Dr. Manuel Serrano and his colleagues from the Spanish National Cancer Research Center claim that the term "physiological cell aging" (English cellular senescence) incorrectly describes the phenomenon for which it is used. He does not insist on changing terminology, but advocates changing traditional views on the physiological aging of the cell, which, first of all, is a mechanism for removing unnecessary cells, but can also act as a "double-edged sword" for the body.
More than 50 years ago, Leonard Hayflick and Paul Moorhead established that after a certain number of divisions, cells grown in culture cease to proliferate. They called this phenomenon physiological aging of the cell and suggested that it could be the cause of aging of the body. However, a recent study conducted with the active participation of Serrano, who is one of the leading experts on the physiological aging of cells in the world, showed that this landmark observation shed light on only part of the picture.
Today we understand that the relationship between the physiological aging of the cell and the aging of the body is similar to the relationship between firefighters and a fire: despite the fact that there are many firefighters on the fire, their presence is not the cause of the fire, but an attempt to extinguish it. By analogy, the mechanism of physiological aging is activated in the presence of damage to prevent its spread and subsequent restoration of the affected tissue. In an aging organism, as well as in certain diseases, this process does not reach its logical conclusion, leaving a large number of cells in the tissues in the phase of physiological aging. Thus, the physiological aging of cells is part of the aging problem, not its cause.
It is known that the program of physiological aging is triggered in cells in response to stimuli such as activation of oncogenes, absence or defective functioning of antitumor genes and shortening of telomeres. All these stimuli damage cells and in this context, physiological aging is a protective mechanism.
Moreover, the authors have recently established that the physiological aging of the cell is involved in a process that is extremely important for the body and directly opposite to aging – development. As the embryo grows, it needs to remove or rearrange physiological structures, and the genetic mechanisms used for this are similar to the mechanisms of physiological aging.
Based on this, a new vision of the issue was formulated, according to which the physiological aging of a cell is a physiological mechanism, the purpose of which is to destroy unnecessary cells and regenerate tissue, and the resulting tissue may differ from the original one.
Such a revision of the question indicates a number of diseases in which the physiological aging of the cell can have both positive and negative effects. For example, in cancer, the physiological aging of cells can stop the growth of a tumor, and in atherosclerosis – the formation of plaques on the walls of blood vessels. On the other hand, in obesity and diabetes mellitus, it contributes to the progression of the disease by increasing the resistance of tissues to insulin and stimulating inflammatory processes.
Therefore, from the point of view of the clinic, specialists, depending on the situation, should develop both therapeutic directions: both suppression and stimulation of physiological aging of cells.
There is also another unanswered riddle – birthmarks. It is known that they are clusters of cells in the phase of physiological aging. The reason why they are not destroyed remains to be seen.
Article by Daniel Munoz-Espin et al. Cellular senescence: from physiology to pathology is published in the journal Nature Reviews Molecular Cell Biology.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Centro Nacional de Investigaciones Oncologicas: Senescence: a misnamed double-edged sword.
16.07.2014