101 Facts About Ageing #19: Reversal Of Ageing Occurs Naturally In Human Cells

As Daniel Patrick Moynihan, an American sociologist, politician, and diplomat once said: “Everyone is entitled to his own opinion, but not his own facts”. And we wholeheartedly agree. A shared set of facts is the first step to building a better world with longevity for all. In that spirit, we are creating a series that covers 101 indisputable facts about ageing, health and longevity.

The offspring of two 30 year-olds is not born with a biological age 30 – they will not inherit all of the age-related cellular changes that have occurred in the cells of their parents. Upon formation of the gametes – the sperm and egg cells that each contribute half of the new organism’s chromosomes – most cellular changes associated with ageing are erased.

Our understanding of how this happens is still incomplete. Gametes are formed through a type of cell division called meiosis to produce daughter cells with half of the chromosomes necessary to produce a new organism. The process of age reversal during meiosis can be easily observed in yeast. Yeast cells can divide asexually to produce cells with their full complement of 16 chromosomes. Under these circumstances, age is inherited asymmetrically, producing an older mother cell and a younger daughter cell. Yeast cells can also divide by meiosis to produce spores carrying 8 chromosomes, which will then reproduce sexually to produce new yeast cells. Research has shown that when aged ‘mother’ yeast cells form spores, those spores are able to replicate just as many times as spores derived from young cells. These spores show no signs of the age-related cellular damage that was present in their parent cell.

This is not to say that parental age has no effect on the health of the progeny in humans. There is some evidence that maternal age is associated with shorter telomere length in the offspring, and some epigenetic alterations (changes to how the DNA is read, without altering the DNA code itself) may also be conserved. Both of these are thought to be important hallmarks of ageing.