After 70 years old, the secret of blood aging is revealed
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Since ancient times, "death" has been a topic that people are reluctant to mention. In traditional Chinese culture, all words related to the word "death" will find another way to replace them. Everyone is afraid of death, but everyone will die, and aging is the prelude to death.
Baidu Encyclopedia defines aging as follows: "Aging refers to the phenomenon that the body's physiological and psychological adaptability to the environment is progressively reduced and gradually tends to death." a gradual process of accumulation". When the body's adaptability is reduced to a certain level, when the molecular cells are damaged to a certain level, there will be a cliff-type aging, and this age is 70 years old.
Although studies have found that people's bodies age rapidly after the age of 70, the mechanism is not clear. In order to solve this mystery, scientists from the Wellcome Sanger Institute in the UK and the Wellcome-MRC Cambridge Stem Cell Institute have teamed up to complete a study recently. They analyzed the whole genomes of 3,579 blood stem cells in 10 individuals ranging in age from newborns to older adults.
It was found that adults under the age of 65 produced blood cells from 20,000 to 200,000 stem cells, each contributing roughly the same amount, and most of them belonged to clonal hematopoiesis. In contrast, the source of blood cells in the elderly over the age of 70 has dropped significantly, and even only differentiated from 10 to 20 stem cells.
After further analysis, it was found that these "highly active" stem cells often accumulate a large number of mutations, and due to the process of somatic mutation, the number will be further expanded, and eventually occupy the dominant position of the human bone marrow, resulting in an irreversible decrease in the diversity of the blood cell population in the elderly, and Disrupts the production of normal functioning mature blood cells.
These findings led the team to propose a model in which age-related changes in blood production stem from somatic driver mutations that cause clonal stem cells to dominate the bone marrow of older adults, where they follow in many other tissues of the body. increase with age.
Specifically, clones driven by mutations in DNMT3A expanded rapidly in young adults and slowed down in older adults. TET2 mutation-driven clones grow uniformly throughout a person's life, but after age 75 they are more common than dnmt3a-mutated clones. Additionally, clones with mutations in the splicing genes U2AF1 and SRSF2 expanded only later in life and exhibited some of the fastest growth.
The study shows for the first time that mutations that accumulate gradually throughout life can lead to dramatic changes in the number of blood cells in old age. This change precisely reflects why the body ages rapidly after the age of 70.