Age by extracellular DNA

Age differences in DNA fragments in blood were found

Dmitry Mazalevsky, Naked Science

Scientists have identified differences in DNA fragments found in the bloodstream associated with age and human health. They are called extracellular DNA (cfDNA), and specialists can use the differences to determine the difference between biological and chronological age.

In their work, the researchers extracted cfDNA from blood samples of people aged 20 and 70 years, as well as among healthy and unhealthy centenarians (people whose age exceeds 100 years). A team of scientists led by Nicola Neretti, an employee of Brown University (Rhode Island, SS), found differences in how DNA was organized in each of the four groups. The results of the study are published in the journal Aging Cell (Teo et al., Cell‐free DNA as a biomarker of aging).

The researchers used cfDNA sequencing combined with sophisticated computational analysis to reconstruct the arrangement of nucleosomes in different regions of the genome — both in places that are usually open to gene expression, and where they are usually densely packed. In the course of their work, they found that nucleosomes — the structural part of the chromosome — were well located in the DNA of volunteers in their 20s, but were less regular in older groups, especially among unhealthy centenarians. 

According to Neretti, cfDNA is something like a message in a bottle that captures how a cell looked, epigenetically speaking, before it died. Many cellular mechanisms are involved in maintaining the distance between nucleosomes, but these components may decrease with age. Nucleosomes themselves do not decay and do not become denser, and changes in their organization, in turn, lead to changes in the availability of various parts of the genome, which provokes the appearance of even more errors, including the release of usually blocked genetic elements called transposons.

The team found a decrease in cfDNA signals at the beginning of two common transposons with increasing age. This suggests that these transposons are more free in unhealthy centenarians and people over 70 years old and, thus, are more likely to be embedded in the genome, causing genetic disorder.

In the future, scientists want to try to track the same processes in people over 20 and 30 years old to find out how each individual's epigenome changes, as well as the rate of this change with age. In their opinion, a large study can reveal the connection of epigenomic differences with health, lifestyle or diets and more accurately determine the difference between the biological and chronological age of a person.

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