Unlike humans and other mammals, whose fertility declines with age, naked mole rats can reproduce throughout their remarkably long lives.
A new study published in the journal Nature Communications sheds light on the unique processes that give rodents what appears to be eternal fertility, results that could eventually point to new treatments for humans.
“Naked mole rats are the strangest of all mammals,” said study lead author Dr. Miguel Prieno-Enriquez, associate professor at the Magee Women’s Research Institute and the Department of Obstetrics, Gynecology, and Reproductive Sciences at the University of Pittsburgh School of Medicine. These are the longest-lived rodents, they never get cancer and do not feel pain like other mammals, they live in underground colonies, and only the queen can breed. stop having children, she will not experience a decrease in fertility as she grows older. And we want to understand how she does it.”
In most mammals, including humans and mice, females are born with a limited number of eggs, which are produced in the uterus through a process called oogenesis. Because this limited supply of eggs is depleted over time, some are released at ovulation, but most simply die and fertility declines with age.
In contrast, naked mole rat queens can breed into old age, suggesting that rodents have special processes to maintain ovarian reserve and prevent impaired fertility.
Prieno-Henriquez said: “There are three possibilities for how she does this: she is born with a lot of eggs, or many of these cells do not die, or she continues to produce more eggs after birth. My favorite hypothesis is that it uses a combination of all three.” “.
Of course, Reino-Henriquez and his colleagues found evidence for each of the three processes.
The team compared the ovaries of naked mole rats and different mice at different developmental stages.
Despite their similar size, mice live no more than four years and begin to show reduced fertility after nine months of age, while naked mole rats have an average lifespan of 30 years or more.
Whereas, they found that female naked mole rats had an exceptionally high number of eggs compared to normal mice, and that the mortality rate of these cells was lower than that of mice. For example, at 8 days of age, a female naked mole rat has an average of 1.5 million eggs, which is about 95 times more than females of the same age.
Notably, the study showed that oocyte production occurs after birth in naked mole rats. The oocyte progenitor complex was actively dividing in 3-month-old animals, and these progenitors were found in 10-year-old animals, indicating that oocyte formation can continue throughout life.
“This is an unusual finding,” said senior author Ned Bliss, professor at the College of Veterinary Medicine at Cornell University. “It challenges the almost 70-year-old dogma that female mammals are endowed with a finite number of eggs before or shortly after birth.” without any addition to the ovarian reserve afterwards.
Naked mole rats live in large colonies of tens to hundreds of individuals. Like bees or ants, colony members share tasks, including providing defense, digging tunnels, caring for young, and collecting food. The only dominant female in the colony can breed, and she suppresses other females in order to maintain her royal status.
“Unlike bees or ants, a female naked rat does not give birth to a queen,” Prieno-Enriquez explained. “When the queen dies or is removed from the colony, subordinate females compete to take her place and become reproductively active. Any one of them can become queen.”
To learn more about this process, the researchers removed three-year-old females from the colony to encourage reproduction and compared these new queens to subordinate females. They found that non-breeding subordinates had a progenitor egg complex in their ovaries, but the cells only began dividing after transitioning to queen status.
Prieno-Henriquez said: “This is important because if we can figure out how to do this, we can develop new drugs or technologies that will help human health. Even though people live longer, menopause still occurs in the same age”. “We hope to use what we’ve learned from the naked mole rat to protect ovarian function later in life and prolong fertility.”
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