New study has identified the “ground zero” of ageing, providing insights into a natural rejuvenation event.
Until now it has remained a mystery how germline cells seem to be immune to the passage of time, compared to the rest of cells in our body, which age and accumulate damage. Now, a new study suggests that the key to youthful cells might be like a reset button.
Researchers from Harvard University in the USA have shown that the age of mouse embryo cells resets about one week into development. This point in their development pathway is considered the “ground zero” of ageing, the lowest biological age an organism has during its life.
“Our study uncovers a natural rejuvenation event during embryogenesis and suggests that the minimal biological age (ground zero) marks the beginning of organismal ageing,” the authors said in their report.
The research was led by Professor Vadim Gladyshev, from Harvard Medical School, in Boston, Massachusetts in the USA. “The identification of a rejuvenation event during embryogenesis leading to ground zero may allow to identify mechanisms that could be activated in some cells in adult tissues thereby making them younger”.
About the study
DNA sequences are covered with small marks, called epigenetic modifications, which have a role regulating the expression of genes. Advanced sequencing methods and statistical analyses have been able to identify specific patterns of these epigenetic modifications on stretches of DNA, which can pinpoint the biological age of the cells and tissues.
In this new study, researchers tracked these epigenetic modifications, called “epigenetic clocks”, on mouse embryos across their development to better understand the ageing process.
Researchers found that, on average, the epigenetic age of mouse fertilized eggs, called zygotes, was not zero. Instead, embryos showed a reduction in age up to approximately the seventh day. This pointed to the existence of a “ground zero”, a point from where cells started to age.
The researchers also studied previous data from human embryos and found that by the 6th week of development, embryos age, suggesting that the ground zero has been achieved earlier.
Previously, rejuvenation of cultured adult cells was achieved by expressing four genes, known as Yamanaka factors, which converted adult cells into embryo-like cells.
What this new study found, however, is that there is also a natural rejuvenation process that works during development. “This discovery could lead to a better understanding of how rejuvenation works and how it may be used to force any cell to rejuvenate. If this can be achieved in many cells in the body, it may be expected that the biological age of the organism will be reduced, leading to a longer and heathier life,” Prof Gladyshev said.
Overall, the findings of this study offer a new perspective on how ageing works and when it begins, and may, one day, help rejuvenate ageing cells in adult organisms.