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The ovaries eventually retire from reproduction, but they also get a career change.
A new study in mice suggests that after ovulation permanently ends, the ovary appears to trade its reproductive role for an immune one, filling with T cells, macrophages, and inflammatory signals that may communicate with the rest of the body. The finding puts menopause into a different perspective, which may change how doctors handle ovarian removal and women’s health in later life.
Until now, the influence of post-reproductive ovaries has been largely overlooked.
The 2nd Job
The new study from Aubrey Converse, Francesca Duncan, and colleagues of Northwestern University tracked the ovary across three points in a mouse’s life: 2 months, when the animals were reproductively young; 18 months, when they were nearing the end of fertility; and 24 months, after ovulation had stopped. By comparing those stages, the team could watch the organ move from egg production into a post-reproductive state—and see that it was still changing.
Each mouse contributed two ovaries. One was examined under a microscope. The other was analyzed with RNA sequencing, a method that shows which genes are active inside tissue.
The expected signs of aging appeared. Older ovaries had lost follicles, the tiny structures that contain eggs. They also showed more collagen, a stiff structural protein that can build up as tissue ages. By 24 months, the ovaries had largely lost the usual markers of reproductive activity.
But the organ had not simply gone dark.
The post-reproductive ovaries showed higher activity in genes tied to immune responses, inflammation, cytokine signaling, and leukocyte activation. Cytokines are chemical messages that immune cells use to communicate. Leukocytes are white blood cells.
The tissue also contained more T cells, macrophages, and multinucleated giant cells—the latter being immune-related cells often seen in chronic inflammation or tissue remodeling.
“We found that ovaries from mice post-oopause completely lost their reproductive cellular identity and instead transitioned to an immune-like inflammatory organ,” the researchers wrote in the study.
A Body-Wide Signal
The ovary ages early. In people, ovarian decline begins long before many other organs show obvious wear. Menopause arrives around the early 50s on average, while life expectancy has stretched far beyond that, leaving many women living decades in a post-reproductive state.
Researchers have known that post-menopausal ovaries are not exactly hormonally silent. They continue to produce testosterone and other androgens, with smaller contributions to estrogen levels. That residual activity has shaped a more cautious approach to removing ovaries for benign conditions in some post-menopausal women.
The new study points to another possible role after fertility ends: immune signaling.
The team found signs that older ovaries may send out different chemical messages than younger ones. Some appeared tied to the immune system, including proteins used to flag trouble, rally immune cells and sustain inflammation.
“These findings challenge the assumption that the post-reproductive ovary is inert, instead indicating that it acquires an immune identity with potential endocrine and paracrine influence on whole-body aging,” the authors wrote.
Endocrine signals are hormones or other chemical messages that travel through the bloodstream. Paracrine signals are shorter-range messages that act on nearby cells and tissues. In menopause, those routes could allow ovarian signals to shape inflammation both inside the pelvis and across the body.
The Mouse Caveat
The study used mice, not people, so the findings need to be interpreted with caution. For instance, one obvious difference between humans and mice is that mice do not menstruate. Their post-reproductive state, called “oopause,” does not match human menopause exactly. They also do not undergo the sharp estrogen drop seen in humans.
Still, mice let researchers follow ovarian aging across a full lifespan in a controlled way. In this study, most molecular changes appeared before the final post-reproductive stage. But the ovaries continued to shift after ovulation had stopped, pushing against the idea that ovarian aging ends in a fixed, inactive state.
For what’s it worth, early human clues point in the same direction. In a separate study still under review, the team examined ovarian tissue from 28 post-menopausal women. The tissue showed age-related differences in protein production, including proteins tied to inflammatory pathways. The samples came from women ages 50 to 75, which limited the comparison, but the pattern echoed the mouse findings.
For now, the ovary’s career shift came clearly into focus. Its new role may help scientists understand aging in women beyond fertility, hormones, and hot flashes — and may open a path to therapies that target inflammation without trying to restore reproduction.
The study was published in the journal Molecular Human Reproduction.
This story originally appeared on ZME Science. Want to get smarter every day? Subscribe to our newsletter and stay ahead with the latest science news.
