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.
Las naked mole rats They can reproduce throughout their lives 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, which is published in ‘Nature Communications’, is coordinated by Miguel Brieo-Enrquez, from the University of Pittsburgh (USA), and sheds new light on the processes that give these rodents what appears to be an eternal fertility, findings that could lead to new therapies for people.
Brieo-Enrquez recalled, in a university statement, that naked or shaved mice they are “the strangest mammals”. Are the longest-lived rodents almost never get cancer, they do not feel pain like other mammals and only the queen can have young.
The most astonishing thing for the researcher is that they never stop reproducing, that is, they do not suffer a decline in fertility as they age, which is why the team wanted to understand the causes.
In most mammals, including humans and mice, females are born with a finite number of eggs, which are produced in the uterus by a process called oogenesis, and are depleted over time, so fertility declines with age. age.
In contrast, naked mole-rat queens can reproduce to a very old age, suggesting that these rodents have special processes to preserve their ovarian reserve and prevent fertility decline.
Brieo-Enrquez explains that there are three possibilities for how she does it: being born with many ova, that not so many ova die, or that they continue to be created after birth. The team found evidence of each of these three processes.
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 “exceptionally large numbers of ova” compared to mice, and the mortality 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”, as it “challenges the dogma established almost 70 years ago, according to which 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, the subordinates compete to take her place and become reproductively active, explains Brieo-Enrquez.
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 egg precursor cells in their ovaries, but that they began to divide only after the transition to queen.
“This It is important because if we can find out how they do it, we could develop new drug targets or techniques to improve human health,” says Brieo-Enrquez 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.”
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