Fecal transplants from old mice increase fertility in younger ones

Fecal transplants from old mice increase fertility in younger ones

By Claire Cameron edited by Clara Moskowitz

Fecal transplants from old female mice appear to increase fertility and ovarian health in younger ones. The findings are described in a study published on Tuesday in the journal Nature’s agingindicates a direct link between gut health and reproductive health in the animals. They may also have implications for future research into how the microbiome affects ovarian function and fertility in humans.

The results came as a surprise, says Bérénice Benayoun, biologist at the University of Southern California Leonard Davis School of Gerontology and leader of the research. “We went into the study expecting that the old fecal microbiome would prematurely age the young ovaries,” she says. “So we were very intrigued to see that the opposite was true, suggesting that some very interesting biology was happening.”

Scientists already know that the microbiome – a collection of bacteria, organisms and viruses that live both on and inside the body – plays a role in countless aspects of health, including reproduction and fertility.

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Faecal transplants promise to replace “bad” bacteria in a diseased gut with “healthy” bacteria via a donor’s stool. In humans, the benefits of the procedure are still under investigation, but it is used in some cases to treat certain conditions, such as bacterial infections. It may also be useful for treating gastrointestinal and other metabolic problems, and even neurobiological conditions—but the science is preliminary.

The older female mice in the study were all in a life phase called “oestropause,” similar to menopause in humans, and had all stopped ovulating. When the younger mice received fecal transplants from these older animals, genetic markers in the ovarian cells appeared rejuvenated and they were more successful at reproducing.

The effect may be a result of compensation, says Benayoun. In mice, there is a communication pathway between a group of gut microbes called the estrobolome and the ovaries. But as the mice get older, this highway seems to break down, she explains. The younger mice receiving the older fecal transplants can increase the signals between this subset of gut microbes and the ovaries to compensate for the degrading pathway, enhancing their reproductive health.

The study suggests that ovarian function is “plastic,” says Benayoun. Importantly, the findings in mice cannot be applied directly to humans. Researchers need to investigate whether the human gut microbiome has specific organisms that communicate with the ovaries, as the mice do, she says. Still, the discovery suggests that the microbiome may be an entry point for adjusting ovarian function, she adds.

“You can imagine that once such bacteria are identified,” she says, “it would be easy enough to design ovarian-supportive probiotics.”

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