Scarred ovaries may cause infertility, say researchers

Excessive scarring and inflammation in women’s ovaries may be responsible for women’s decreasing ability to produce healthy eggs as they become older, according to a new study conducted by the Feinberg School of Medicine at Northwestern University, USA.

The study has shown that the ovarian environment ages and that this affects the quality of eggs produced. This finding could lead to the development of new treatments that preserve fertility by delaying ovarian ageing.

Deteriorating numbers and quality of eggs can contribute to miscarriages, birth defects and infertility.

This new study focused on the reproductive age-related changes that occur in the environment in which the eggs develop, which is known as the ovarian stroma. Until now, little has been known about how the ovarian stroma changes with age.

Lead study author Francesca Duncan, executive director of the Center for Reproductive Science at the Feinberg School of Medicine, explained: "Under the microscope, eggs from reproductively young and old animals may look identical, but the environment in which they are growing is completely different. Ovaries from reproductively old mice are fibrotic and inflamed.”

She added: “There is no way this environment won't impact the eggs growing in it, and it very likely contributes to their decrease in quality."

Scientists analysed ovarian tissue from reproductively young mice (equivalent to women in their early twenties) and old mice (equivalent to women aged 38-45). Fibrosis was consistently discovered in the reproductively old mice. This age period is associated with a decline in reproductive function and egg quality in both humans and mice.

Researchers also found that a type of immune cell (multinucleated macrophage giant cells) was only present in the ovaries of these reproductively old mice. These cells are associated with chronic inflammation in other tissues. They also found ovaries from mice of advanced reproductive age expressed genes and produced proteins that are highly inflammatory.

Duncan said that this work lays the foundation for considering anti-inflammatory treatments to delay the impact of reproductive ageing.