Fecal transplants from old mice boost fertility in younger ones

Fecal transplants from old mice increase the fertility of younger ones

By Claire Cameron edited by Clara Moskowitz

Fecal transplants from old female mice appear to improve the fertility and ovarian health of younger ones. The results, detailed in a study published Tuesday in the journal Natural agingindicate a direct link between gut health and reproductive health in animals. They could also have implications for future research into how the microbiome influences ovarian function and fertility in humans.

The results were a surprise, says Bérénice Benayoun, a biologist at the Leonard Davis School of Gerentology at the University of Southern California and leader of the research. “We started the study hoping that the old fecal microbiome would prematurely age young ovaries,” she says. “So we were very intrigued to find the opposite, which suggested 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 many aspects of health, including reproduction and fertility.

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Fecal transplants promise to replace “bad” bacteria in a diseased gut with “healthy” bacteria via a donor’s stool. In humans, the benefits of this procedure are still being studied, but it is used in some cases to treat certain conditions, such as bacterial infections. It may also be useful for treating gastrointestinal and metabolic issues, and even neurobiological disorders, but the scientific evidence is still in its early stages.

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

This effect could result from compensation, Benayoun says. In mice, there is a communication pathway between a group of gut microbes called the estrobolome and the ovaries. But as mice age, this highway seems to break down, she explains. Younger mice that receive the older fecal transplants may increase signals between this subset of gut microbes and the ovaries to compensate for this degrading pathway, thereby boosting their reproductive health.

The study suggests that ovarian function is “plastic,” Benayoun says. It is important to note that the results obtained in mice cannot be applied directly to humans. Researchers should determine whether the human gut microbiome contains specific organisms that communicate with the ovaries, as mice do, she says. Still, this finding suggests that the microbiome could be an entry point for modifying ovarian function, she adds.

“One could imagine that once these bacteria were identified,” she says, “it would be quite easy to design ovarian-supportive probiotics.”

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