It is well known that the age of a woman affects how fertile she is. We have all heard of declining fertility already when you reach the age of 3o, and an even more drastic drop at the age of 35. Around 40 we are considered old in terms of becoming mothers and if we are closer to 45, most women will not be able to conceive a child unless she chooses to receive eggs from a younger egg donor.
One of the reasons for the declining fertility is simply that the eggs go bad with time. One of the reasons for the sinking egg quality is based on genetics. Since a woman is born with all her eggs, they will eventually carry a higher frequency of errors (mutations) in their DNA which might lead to problems with her fertility. Recently, a study in mice by Briley et al. has shown that the actual ovarian tissue might play a role in the age-associated decline in egg quality. Here, it was shown that fibrosis was detected in ovarian tissue from reproductively “old” women (equivalent to women at the age of 38-45), meaning that the ovarian tissue was consistently scarred. In some of these reproductively “old” individuals up to 35% of the ovarian tissue was fibrotic. In addition, signs of chronic inflammation in the ovaries from the older individuals were detected, such as multinucleate macrophage giant cells (a type of immune cell) as well as gene expression of highly inflammatory proteins. The young individuals (equivalent to women in their early 20s) however, did not show any signs of fibrosis or inflammation.
These findings establish fibrosis as an early hallmark of the aging ovarian stroma, and the researchers speculate that this altered microenvironment may contribute to the age-associated decline in egg quality. This is the first study that shows how the ovarian environment ages and that this aging may affect the quality of the eggs it produces.
Hopefully this study of how the ovarian microenvironment changes with age, and other studies that might follow, could eventually lead to new treatments that preserve fertility by delaying ovarian aging. In addition, by improving our understanding of ovarian biology in general and ovarian fibrosis in particular these results may give new insight to PCOS (polycystic ovarian syndrome) where ovarian fibrosis and chronic low-grade inflammation are key features.
The study was published in Reproduction in August, 2016
Pictures in this post: Georgia O’Keeffe painting: http://www.gailsibley.com/2012/09/17/emily-carr-georgia-okeeffe-frida-kahlo-and-some-other-gals/
Last picture (Figure 3 from the study): shows highly ordered collagen fibers in mouse ovary)