A team of researchers from Harvard Medical School has found evidence of human and mouse germ cells restoring their biological age. In their article published in the journal Science Advances, the group describes their study of the aging process in germ cells and what they discovered during the research.
How we thought biological age determination worked ...
As animals age, all the cells in their body replicate repeatedly. As the process continues, replication errors and other external factors (such as exposure to pollutants) lead to a gradual decay of cellular quality, which is all part of the natural aging process.
... and what the research found
In this new effort, the researchers found evidence showing that germline cells have a mechanism to restore this process, allowing offspring to reset their aging clocks and biological age.
Germ cells transmit genetic material from parent to offspring during the reproductive process. For many years, scientists have wondered why these cells don't inherit their parents' age. And for many years they thought cells were ageless, but recent work has shown that they do indeed age. So this raised the question of how offspring are able to start their life with fresh cells.
To find out, the researchers used molecular clocks to monitor the aging process of mouse embryos. These watches were developed to measure changes epigenetics in the cells. The researchers used them to continually compare the biological age of embryos (how many years appear to be based on reactions to epigenetic changes) with their chronological age. They found that the biological age of mouse embryos remained constant during initial cell division after an egg was fertilized. But then, about a week after the embryo attached itself to the uterus, the biological age of the embryos dropped. This finding suggested that some mechanism had reset the embryo's biological clock to zero.
The team then turned their attention to the biological age of human embryos
They have not been able to monitor aging in human embryos (due to well-known ethical limitations) but have found evidence that human embryos also "reset" their biological age. Next step? Continue to look for the mechanism behind the recovery process.