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Mar. 10th, 2004 09:52 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
novapsycheStudy disputes conventional theory of fertility
Scientists say they’ve found stem cells in mouse ovaries that apparently generate new eggs well into adulthood, challenging nearly a century of biological dogma about fertility in mammals — including humans.
If similar ovarian stem cells are found in women, researchers say it could lead to improved infertility and menopause treatments and possibly trigger a revolution in research into reproduction and women’s health.
[...] The idea that women are born with a fixed number of eggs, or oocytes, was first suggested nearly a century ago, and Tilly said the subject had not been seriously broached in more than 50 years.
Among humans, mice and other mammals, females gradually lose healthy follicles — the tiny envelopes in which eggs develop and then burst. In older women, eggs often are abnormal, leading to a decline in fertility.
But oocyte research in female fruit flies showed that simpler species remained fertile throughout their adult lives and their ovaries never completely lose their germ stem cells. Despite obvious differences, fruit flies, mice and even humans share many genes and basic biological functions.
Tilly and his colleagues measured the number of healthy and dying eggs in juvenile and adult female mice. Initially, they found that the eggs died at a low but steady rate.
However, once the female mice reached early adulthood, the number of dying eggs accelerated to about one-third of the estimated 3,000 or so total follicles in each ovary, and the ovaries flushed out the dead eggs every few days.
At that pace, the researchers expected to see the animals’ oocytes depleted in a matter of days or weeks. Yet past work had shown that female mice remain fertile through at least one year of age.
As older eggs die off in juvenile and adult mice, germ stem cells the researchers found in the rodent’s ovaries apparently generate new eggs — a process that had been thought to occur only as female mammals developed in the womb.
“That’s when it really struck us that the dogma must be wrong. That sort of set off the bells and whistles,” said Tilly.
Scientists say they’ve found stem cells in mouse ovaries that apparently generate new eggs well into adulthood, challenging nearly a century of biological dogma about fertility in mammals — including humans.
If similar ovarian stem cells are found in women, researchers say it could lead to improved infertility and menopause treatments and possibly trigger a revolution in research into reproduction and women’s health.
[...] The idea that women are born with a fixed number of eggs, or oocytes, was first suggested nearly a century ago, and Tilly said the subject had not been seriously broached in more than 50 years.
Among humans, mice and other mammals, females gradually lose healthy follicles — the tiny envelopes in which eggs develop and then burst. In older women, eggs often are abnormal, leading to a decline in fertility.
But oocyte research in female fruit flies showed that simpler species remained fertile throughout their adult lives and their ovaries never completely lose their germ stem cells. Despite obvious differences, fruit flies, mice and even humans share many genes and basic biological functions.
Tilly and his colleagues measured the number of healthy and dying eggs in juvenile and adult female mice. Initially, they found that the eggs died at a low but steady rate.
However, once the female mice reached early adulthood, the number of dying eggs accelerated to about one-third of the estimated 3,000 or so total follicles in each ovary, and the ovaries flushed out the dead eggs every few days.
At that pace, the researchers expected to see the animals’ oocytes depleted in a matter of days or weeks. Yet past work had shown that female mice remain fertile through at least one year of age.
As older eggs die off in juvenile and adult mice, germ stem cells the researchers found in the rodent’s ovaries apparently generate new eggs — a process that had been thought to occur only as female mammals developed in the womb.
“That’s when it really struck us that the dogma must be wrong. That sort of set off the bells and whistles,” said Tilly.