Rethinking Menopause: Ovaries in a New Light
Menopause is often seen as the final chapter for the female reproductive system, a time when the ovaries simply stop releasing eggs and that’s it. But Francesca Duncan, a reproductive biologist, believes there’s much more to the story.
Her research focuses on what happens to ovaries after they cease egg production. Surprisingly, it’s less of a retirement and more akin to a career shift. With life expectancies rising, there are now many post-menopausal individuals out there, and, well, we don’t fully understand the changes their bodies undergo.
A recent study involving mice, published in Molecular Human Reproduction by Duncan and a team from Northwestern University along with collaborators across the U.S., indicates that post-menopausal ovaries are anything but inactive.
This aligns with preliminary findings from Duncan’s earlier research on post-menopausal women, which hasn’t been peer-reviewed yet. It indicated that ovarian tissue from 28 women showed varied protein production based on their age.
If ovaries truly were ‘inactive’ after reproductive years, these differences wouldn’t exist.
Of course, mouse studies don’t provide a complete picture of human biology, but they can offer some clues due to our shared evolutionary background.
In their study, Duncan and her team examined ovaries from mice at different life stages: 2-month, 18-month, and 24-month. Each of these ages reflects a different point in the mouse reproductive timeline.
Typically, mouse ovaries stop functioning around the two-year mark in their relatively short lifespan. While this process doesn’t mirror the drastic estrogen drop that humans experience, certain similarities do exist.
The researchers examined one ovary from each mouse under a microscope to learn about the anatomy of ovarian tissue at various life stages. With the other ovary, they conducted RNA sequencing to identify which genes were active and involved in protein production.
As expected, the samples revealed that reproductive activity decreases with age. Older mice had fewer follicles and noticeable changes in how their tissue and collagen were structured.
However, this doesn’t imply that ovarian activity has entirely ceased. In fact, it seems that ovaries transition into a new role.
“Transcriptomic analyses revealed a shift from reproductive functionality to an immune-dominant signature with age,” the researchers reported.
This means that post-reproductive ovaries displayed increased infiltration of immune cells like T cells and macrophages.
Although the older ovaries appeared and operated quite differently compared to those of younger mice, they also showcased distinct transcriptome profiles, much like the findings in postmenopausal women.
These observations suggest that ovarian tissue continues to change at a molecular level, even after its reproductive purpose diminishes. They seem to take on characteristics of an immune-related organ.
“These findings challenge the assumption that the post-reproductive ovary is inert, instead indicating that it acquires an immune identity with potential impacts on overall aging,” Duncan and her team concluded.
This could have significant implications for how we approach healthcare for individuals in their post-reproductive years, especially for those who have undergone oophorectomy.
The full study can be found in Molecular Human Reproduction.
