The female of the species Heterocephalus glaber, a strange, extraordinarily long-lived rodent, insensitive to certain kinds of pain, practically immune to cancer, and living in colonies with a queen like bees or ants, does not see its fertility decline with age, unlike what happens with the females of other mammals, including the human being. This challenges the dogma that mammalian females have a finite ovarian reserve.
Understanding the reason for this unlimited ovarian reserve could open the way towards the creation of treatments against human infertility.
The international team of Miguel Brieño-Enríquez, from the University of Pittsburgh in the United States, has carried out a study that provides new and revealing data on the unique processes that endow these females with their permanent fertility.
In colonies of Heterocephalus glaber, a species known by popular names such as the naked mole-rat or shaved mole-rat, only the queen is fertile.
Naked mole-rats live in colonies of several tens to several hundred individuals. Like bees or ants, the members of the colony share the tasks of defense, tunnel digging, brood care and food gathering. Only the dominant female in the colony can reproduce, and her influence prevents other females from reproducing, thus maintaining her queen status.
One female of Heterocephalus glaber. (Photo: UPMC)
Unlike bees or ants, the female Naked Mole-rat that will act as queen is not born queen. When the queen dies or disappears from the colony, subordinate females compete to take her place and become reproductively active. Any female can become queen.
In most mammals, including humans, females are born with a finite number of eggs, which are produced in the uterus by a process called oogenesis. As this limited reserve of eggs is depleted over time (some are released during ovulation, but most simply die), fertility declines with age.
In contrast, naked mole-rat queens can reproduce even in old age, demonstrating that they have special processes in place to preserve their ovarian reserve and prevent decreased fertility. There are three ways in which this can be achieved: being born with many more eggs, that very few eggs die, and that new eggs continue to be generated after the birth of the female.
Brieño-Enríquez and his collaborators have discovered that all three things occur in naked mole-rat queens.
In one of the experiments, it was found that subordinate females, those that are not fertile, have egg precursor cells in their ovaries and that only when a subordinate female becomes queen do those cells start dividing from then on.
The study is titled “Postnatal oogenesis leads to an exceptionally large ovarian reserve in naked mole-rats”. And it has been published in the academic journal Nature Communications. (Fountain: NCYT de Amazings)