The naked mole rats they can reproduce throughout their lives because do not stop producing eggswhich calls into question that female mammals have a finite ovarian reserve, as suggested by a new study that analyzes the fertility of this animal.
The research, published in Nature Communications, is coordinated by Miguel Brieno-Enriquezfrom the University of Pittsburgh (USA), and sheds new light on the processes that give these rodents what seems like eternal fertility, findings that could lead to new therapies for people.
Brieño-Enríquez recalled, in a university statement, that naked mole rats or shaved rats are “the strangest mammals“. They are the longest-lived rodents, they almost never suffer from cancer, they do not feel pain like other mammals, and only the queen can have young.
The most amazing thing for the researcher is that they never stop reproducing, that is, do not experience decreased fertility as they age, so the team wanted to understand the causes.
In most mammals, including humans and mice, females are born with a finite number of ovuleswhich are produced in the womb by a process called oogenesis, and are depleted over time, so fertility declines with age.
Conversely, naked mole rat queens may reproduce to an old agewhich suggests that these rodents have special processes to preserve their ovarian reserve and prevent fertility decline.
Brieño-Enríquez explains that there are three possibilities of how she does it: being born with many ovules, that not so many ovules die, or that they continue to be created after birth. The team found evidence of each of these three processes.
How the test was carried out
The researchers compared mouse and mouse ovaries at different stages of development. Despite their similar size, mice live at most four years and begin to show decreased fertility at nine months, while naked mole-rats have a life expectancy of 30 years or more.
Female naked mole rats have an “exceptionally large number of ova” compared to mice and the death rates of these cells are lower, the statement added.
For example, at eight days old, a female naked mole rat has an average of 1.5 million eggs, about 95 times more than mice of the same age.
Furthermore, according to the study, oogenesis occurs after birth in naked mole-rats. Egg precursor cells were actively dividing in 3-month-old animals, and were found in 10-year-old animals, “suggesting that oogenesis could continue throughout their lives.”
For the study’s lead author Ned Place, from Cornell University (USA), this finding is “extraordinary”, It “defies the dogma established nearly 70 years ago that female mammals are endowed with a finite number of ova before or shortly after birth, with no additions to the ovarian pool thereafter.”
The female shaved mouse, unlike bees or ants, is not born a queen, but when she dies or is removed from the colony, subordinates compete to take their place and reproductively activate, explains Brieño-Enríquez.
To better understand this process, the researchers removed three-year-old females from the colony to trigger their reproductive activation and compared these new queens with subordinates.
Thus, they verified that the non-reproductive subordinates had ovule precursor cells in their ovaries, but that they began to divide only after the transition to queen.
“This is important because if we can figure out how they do it, we could develop new drug targets or techniques to improve human health“, says Brieño-Enríquez in the same note.
Although humans live longer and longer, menopause continues to occur at the same age. “We hope to use what we are learning from the naked mole rat to protect ovarian function later in life and prolong fertility.