When it comes to aging, some people like to say your memory goes first. In reality, it’s the ovaries. Among all the organs in the human body, the ovaries are the earliest to show signs of decline, closing up shop around the age of 52. While scientists long believed they simply became inert after exhausting their egg reserves, that may not be the case. According to new research published in Molecular Human Reproduction, ovaries may take on a second, immune-related job after menopause.
Reproductive biologists led by Francesca Duncan of Northwestern University made the discovery after studying the ovaries of mice. Like humans, mouse ovaries also go quiet, typically around the two-year mark (although they don’t experience the same decline in estrogen humans do). To investigate how their reproductive organs change, the team removed ovaries from young mice, middle-aged mice, and post-reproductive mice. They sequenced the RNA from one ovary of each mouse while examining the other for structural tissue and cell changes.
Read more: “The Evolutionary Mystery of Menopause”
As expected, post-reproductive mouse ovaries showed the typical signs of ovarian senescence (loss of follicles and increased collagen deposition), but they also became infiltrated with new cells (immune cells like T-cells and macrophages). Additionally, as the mouse ovaries aged, they also started transcribing more pro-inflammatory proteins that could be secreted to influence other parts of the body. In other words, they seemed to shed their reproductive function and take on an immune function.
“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.
And it’s not just mice. In a paper currently under review, Duncan and her team studied human ovaries removed from postmenopausal women between the ages of 50 and 75. They found a shift in the production of 177 proteins in the ovaries of women over 70 (compared with those between the ages of 50 and 59), including an increase in proteins involved in inflammation pathways. They were unable to study younger ovaries, but the changing expression patterns in the older cohort points to a potential transition in the ovary’s role over time.
The ovary may be the first organ to start showing its years, but discovering more about its hidden functions could shed light on how the rest of the body ages. 
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Lead image: Alina.Alina / Adobe Stock
