New Delhi: The primary roles of ovaries in mammals, including humans, are to produce eggs for fertilisation and reproductive hormones. So, after menopause, a woman’s ovaries should effectively become useless. But researchers at the Northwestern University Feinberg School of Medicine suggest otherwise. In a new study, the team observes that ovaries assume a new role once they are no longer needed for menstruation.
For the study, published in the journal Molecular Human Reproduction on 10 June, reproductive biologist Francesca Duncan and her team observed how the functions of ovaries change with age in lab mice. The ovaries of a mouse retire late in the animal’s lifespan of two years, and they also don’t experience the same menopause features as humans. But what’s common in both humans and mice is their ancestors. Hence, a study on mice can offer crucial clues.
The team began by removing ovaries from mice aged two months, 18 months, and 24 months. These helped them observe different phases of a mouse’s reproductive cycle. For each mouse, one ovary was closely examined under a microscope to understand the anatomy of ovarian tissues. The second ovary underwent RNA sequencing, which helps study gene expression.
The results showed that the reproductive functions of ovaries slowed down with age, as expected. However, they didn’t become completely useless. According to the team, the ovaries acquired an “immune identity”.
In postreproductive ovaries, researchers found various kinds of immune cells at higher levels in that they usually are. The older ovaries also produced genes that are linked to inflammation. These genes make immune molecules that can enter the bloodstream and reach different parts of the body.
“Transcriptomic analyses revealed a shift from reproductive functionality to an immune-dominant signature with age. Correspondingly, post-reproductive ovaries exhibited increased infiltration of T cells, macrophages, and multinucleated giant cells,” the researchers said.
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‘Knowledge gap’
The team couldn’t determine if the older ovaries are actually involved in any sort of immune signaling or they are just acting as reservoirs for immune cells. However, one thing the study clarifies is that ovaries don’t become inert after the end of the reproductive cycle.
“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 team said.
Duncan suggested that the findings could help understand why women suffer with more health issues than men as they grow older, adding that the lack of knowledge on how ovaries behave and function after menopause is “a little bit frightening”.
“We really owe it to women’s health to study this period of time,” Duncan said.