One of life's great mysteries is how aged parents produce youthful children. Our cells show signs of age as a result of the accumulation of damage caused by the environment and the boAdy's metabolism (新陈代谢), and yet they can combine to produce a baby biologically younger than its parents. This has led biologists to suggest that the germline (生殖细胞) are immune to ageing, which could lead to ways of curing age-related diseases.
But recent research shows that not only does the germline age, but that ageing starts even as embryos develop in the uterus (子宫), much sooner than we thought. "Then the question is, if ageing begins earlier, when does it actually begin?" says Vadim Gladyshev at Brigham and Women's Hospital in Boston.
Gladyshev and his colleagues looked at the changes in cells and tissues from the start of mouse development. The team found that this measure of ageing began to decrease when the early embryo formed into a hollow ball and reached its lowest point after it had been fixed in the uterus. It then increased again as development progressed. The team also looked at data on human embryos, and found signs of a similar pattern at work, although ethical restrictions on growing human embryos beyond 14 days in the lab mean the team was unable to study every stage of development. The discovery points to a refreshing mechanism (机制) that rolls back ageing to a minimum point from which a new individual can begin life, says Gladyshev.
Ageing can also be changed in adult cells by reprogramming them into more immature cells. However, this also makes the cells lose their specialised adult functions, making it less useful as a way to repair age-related damage. Gladyshev hopes that further study will help reveal whether it is possible to separate these two processes." This discovery is exciting, since it suggests a potential, naturally occurring refreshment that resets the biological time of germ cells during the first days of development," says Belmonte at the Salk Institute in California.
