Scientists talked about changes in the brain in people over 50 years old
Scientists have discovered a large-scale brain restructuring that begins in middle age and is especially noticeable in the period from about 50 to 75 years. At this time, immune cells change, the cells that support the protective barrier of the brain weaken, and the three-dimensional organization of the genome becomes less orderly. About how aging rebuilds the brain at the cellular and genetic levels, see the "Izvestia" material.
What happens to the brain after 50 years
The researchers studied how the regulation of genes and the spatial organization of the genome change with age in cells of the hippocampus, an area of the brain that plays an important role in learning and memory. To do this, the scientists used modern methods of analyzing individual cells and examined brain samples from people of different ages. The work was published in the journal Science.
One of the most noticeable periods of change was the age from about 50 to 75 years. At this time, the number of microglia, immune cells in the brain that form during embryonic development, was sharply reduced. At the same time, they were increasingly replaced by cells with molecular characteristics similar to immune cells found in the blood.
According to scientists, this casts doubt on the idea that microglia formed in the early stages of development persist in the human brain throughout life. Although microglia are crucial for maintaining brain homeostasis, the new cells showed more pronounced signs of inflammatory activity. The researchers suggest that such a restructuring may be related to chronic inflammation in the aging brain.
How the immune cells of the brain change
Microglia perform the functions of immune defense in the brain and are involved in maintaining its normal state. The researchers found that not only the number of these cells changes with age, but also their origin and molecular characteristics.
The cells that replace part of the embryonic microglia have features characteristic of immune blood cells. In addition, they exhibit more pronounced inflammatory characteristics. Scientists believe that this may contribute to the maintenance of chronic inflammation in the brain as we age.
Bing Ren, PhD, one of the authors of the study, Scientific director and CEO of the New York Genomic Center
When these cells fail to perform their vital functions, toxic substances accumulate that can trigger inflammatory processes that contribute to the development of neurodegenerative diseases.
The researchers also found a significant reduction in cell populations that help maintain the blood-brain barrier. This system protects the brain from potentially harmful substances circulating in the blood. Thus, age-related changes affect several components of the brain's defense system at once, from immune cells to mechanisms that separate nervous tissue from the bloodstream.
Why does the brain's defenses weaken
The changes affected not only immune cells. Scientists have discovered a reduction in cell populations involved in maintaining the blood-brain barrier. At the same time, they recorded changes in the work of the genome in several types of brain cells at once.
Inside the cell, DNA is not randomly located in the nucleus. It develops into a complex three—dimensional structure that helps regulate the activity of genes - to determine which ones should be turned on or off. The study showed that with age, this spatial organization becomes less orderly. According to scientists, the deterioration of the genome structure may be one of the fundamental signs of brain aging.
Nathan Zemke, Director of the Department of Single-cell Genomics at the Center for Epigenomics at the University of California, San Diego
This work represents an important step forward in understanding how aging alters the human genome in brain cells. These results demonstrate the urgent need to study gene regulation and genome organization in order to gain a mechanistic understanding of the aging process.
How aging rearranges the genome
Scientists have concluded that age-related changes in the brain cannot be described as a simple gradual deterioration of its functioning. According to the study, immune cells, the vascular system, neurons, and the organization of the genome are being rebuilt simultaneously.
Xiangmin Xu, Ph.D., professor and director of the Center for Neural Circuit Mapping at the University of California, Irvine and co-author of the study
It is important to note that this study shows that aging is not just a gradual deterioration, but a coordinated and dynamic restructuring of the immune, vascular, and neural systems.
The researchers believe that the findings may help to better understand why the risk of neurodegenerative diseases, including Alzheimer's disease, increases with age. The work also opens up the possibility of searching for potential targets aimed at maintaining the normal functioning of brain cells and neural connections throughout life.
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