Cells in the "bottleneck"

Rapid decrepitude was associated with impaired growth of new blood cells

Sergey Vasiliev, Naked Science

Many people remain healthy and active even after 60 years. However, with the transition to the next ten, there are dramatically fewer of them: at this age, the body is rapidly getting old. Recent studies show that such changes may be associated with a catastrophic violation of hematopoiesis — the production of new blood cells, which occurs in old age. Perhaps something similar happens with other organs and systems, suggest the authors of a new article published in the journal Nature (Mitchell et al., Clonal dynamics of haematopoiesis across the human lifespan).

An international team of scientists was led by Peter Campbell from the Cambridge Stem Cell Institute. Biologists examined blood samples taken from representatives of different age groups — from infants to 80-year-olds. Screening of the erythrocytes and leukocytes contained in them showed that for most of their lives they represent a wide range of populations that are generated by a multitude — from 20 thousand to 200 thousand — of stem cells operating in the bone marrow.

However, after about 65 years of age, something unexpected happens to them, and the descendants of a small number of stem cells begin to dominate the populations. About half of the red and white blood cells in humans in the last period of life are produced by only a couple dozen clones of stem cells. The diversity of the blood cell population is falling catastrophically.

Scientists attribute this to the occurrence of mutations that occur throughout life, including in stem cells. Most of these mutations are neutral and do not affect anything, but occasionally there may be those that allow the stem cell to develop and divide slightly faster than the rest. At first, this is almost imperceptible: only over time the difference accumulates, and such cells begin to dominate blood production. And the monotony of cell populations leads to a decrease in their "quality" and the development of many diseases.

Perhaps, in old age, such processes occur not only in the blood. Peter Campbell and his colleagues suggest that cell populations in other organs and tissues, from the skin to the liver, degrade in a similar way. Scientists intend to test this in future experiments, but for now they remind that many bad habits and unhealthy lifestyle contribute to the accelerated accumulation of mutations and thereby premature senility.

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