A new study in Cell Stem Cell, discusses ‘sex and stem cells’ or the “sexual dimorphism of longevity”, wherein most of supercentenarians are female, linking this to increased stem cell self-renewal and regeneration potential in females.
Of note, out of the 53 living supercentenarians – human individuals currently living over the age of 110 – 51 are female, and sexual dimorphism with respect to longevity is a characteristic of most mammals. This raises questions regarding the mechanisms driving the sexual dimorphism of longevity.
In this article Ben Dulken and Anne Brunet from the Stanford University Medical Scientist Training Program relate this phenomenon to increased stem cell self-renewal and tissue regeneration in female organisms.
It is known that most adult stem cell populations undergo an age-related decline, leading to dysfunctional tissue homeostasis.
Mentioned are several studies aiming to elucidate the mechanisms responsible for the sexual differences in lifespan and health, including the differential utilization of steroid hormones, estrogen and testosterone that have been proposed to contribute to lifespan.
Estrogen appears to play a major role, but signaling pathways that do not involve estrogen are also involved – interestingly, male eunuchs (castrated males) have been noted to live as much as 14 years longer than non-castrated males.
Of note, estrogen increases the proliferation of neural stem cells (NSCs) in a transient manner that fluctuates throughout the estrus cycle – NSC proliferation is highest during the proestrus phase of the estrus cycle, when estrogen levels are particularly high.
According to the authors, many questions remain unanswered regarding the effects of sex on stem cells, although the importance of sex as a variable in longevity is now well-established. This includes the fact that adult stem cells in non-sexual tissues are regulated in a sexually dimorphic manner and are responsive to the effects of sex hormones.