There currently are 53 supercentenarians ? people age 110 years and over, alive today; and 51 of them are female. Ben Dulken, from Stanford University (California, USA), and colleagues explored the potential underlying reasons why no other demographic factor comes remotely close to gender in predicting the likelihood of achieving such an advanced age. With consideration for current knowledge about stem cell behavior and gender, the researchers submit that there are key differences in regenerative decline between men and women: particularly involving the sex hormones estrogen and testosterone in modifying lifespan. Previous studies report that estrogen has direct effects on stem cell populations in female mice, from increasing the number of blood stem cells to enhancing the regenerative capacity of brain stem cells. Further, other recent studies suggest that estrogen supplementation may increase the lifespan of male mice. Observing that: ?Longevity differs between sexes, with females being longer-lived in most mammals, including humans. One hallmark of aging is the functional decline of stem cells,? the authors consider that: ?a key question is whether the aging of stem cells differs between males and females and whether this has consequences for disease and lifespan.?
It’s known that estrogen has direct effects on stem cell populations in female mice, from increasing the number of blood stem cells (which is very helpful during pregnancy) to enhancing the regenerative capacity of brain stem cells at the height of estrus. Whether these changes have a direct impact on lifespan is what’s yet to be explored. Recent studies have already found that estrogen supplements increase the lifespan of male mice, and that human eunuchs live about 14 years longer than non-castrated males.
More work is also needed to understand how genetics impacts stem cell aging between the sexes. Scientists have seen that knocking out different genes in mice can add longevity benefits to one gender but not the other, and that males in twin studies have shorter telomeres–a sign of shorter cellular lifespan–compared to females.
“It is likely that gender plays a role in defining both lifespan and healthspan, and the effects of gender may not be identical for these two variables,” the authors write. “As the search continues for ways to ameliorate the aging process and maintain the regenerative capacity of stem cells, let us not forget one of the most effective aging modifiers is gender.”