These virtually blind, subterranean-dwelling rodents have already defied many biological norms, with their imperviousness to cancer, resistance to pain, little sign of declining with age, and being able to convert energy like plants do in low-oxygen settings. Now, a new study has shed light on how the female rodents – which live to more than 30 years – can continue giving birth throughout their twilight years.
“Naked mole-rats are the weirdest animals,” said lead author Dr Miguel Brieño-Enríquez, assistant professor at Magee-Womens Research Institute and the University of Pittsburgh School of Medicine’s Department of Obstetrics, Gynaecology and Reproductive Sciences. “They’re the longest-lived rodent, they almost never get cancer, they don’t feel pain like other mammals, they live in underground colonies and only the queen can have babies. But to me, the most amazing thing is that they never stop having babies – they don’t have a drop in fertility as they age.”
The team compared naked mole-rat ovaries with those of mice across different stages of development. While mice showed a drop in fertility from around nine months, with a lifespan of around four years, their similarly sized rodent counterparts did not. Most female mammals, including humans and mice, are born with a finite number of egg cells that deplete over time, increasingly hampering fertility. Mole-rats, however, appear to have special biological processes that preserve these cells and sustains their fertility throughout their entire life.
In the study, researchers also removed three-year-old non-breeding females from the colony to activate their reproduction. They soon discovered that these females had egg-precursor cells that began dividing, in preparation for their queen status and to become the breeding mole-rat. Unlike humans and other mammals, this process of oogenesis occurs postnatally in naked mole-rats, with egg-precursor cells dividing to form eggs cells in both three-month-old and 10-year-old animals.
“This is important because if we can figure out how they’re able to do this, we might be able to develop new drug targets or techniques to help human health,” said Brieño-Enríquez. “Even though humans are living longer, menopause still happens at the same age.”
In humans, oogenesis occurs at the embryonic stage of development, so the number of egg cells is capped at birth. One-to-two million egg cells decline to 300,000-500,000 by puberty and drop thereafter until menopause. While some are lost through ovulation, most die. Working out just how mole-rats preserve their egg cells – and even create more – throughout their long lives has the potential to forge new paths to reproductive therapies for humans.
“We hope to use what we are learning from the naked mole-rat to protect ovary function later in life and prolong fertility,” said Brieño-Enríquez.
The study was published in Naked Communications.
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