The ovary ages earlier than other organs, and it shapes not only fertility but a woman's overall health: early menopause raises the risk of osteoporosis, cardiovascular disease and dementia. Yet the age at menopause has barely shifted over recent decades, even though life expectancy has grown, so women spend more and more years in a state of estrogen deficiency. Fibrosis, that is, the overgrowth of stiff connective tissue, is considered one of the universal mechanisms of aging, and in mice it has long been described in the ovary. In humans, however, there was still no way to assess ovarian fibrosis during life, and histological studies offer only a static picture. This work fills that gap by combining biomechanics, proteomics and transcriptomics in a single cohort of patients.
The study included two groups of women: 32 participants under 33 or over 37 years of age who were undergoing IVF or fertility preservation, and 100 women aged 24 to 45 for independent verification. Ovarian stiffness was measured by transvaginal shear wave elastography (an ultrasound method that assesses tissue elasticity) on days 2-3 of the menstrual cycle. In parallel, neoepitopes of the extracellular matrix, molecular fragments reflecting collagen formation and breakdown, were measured in follicular fluid and blood serum. Single-cell RNA sequencing was performed on cells from follicular fluid to see which cell types change their activity with age. All measurements were taken in the same women, which made it possible to link biomechanical, molecular and cellular changes.
Ovarian stiffness rose significantly in women over 37: mean stiffness increased from 13.3 to 18.8 kPa, maximum stiffness from 23.7 to 40.3 kPa, and the heterogeneity of elasticity from 13.6 to 24.4 kPa. This association held after adjustment for age, AMH level (a hormone that reflects the egg supply) and body mass index. In the independent cohort of 100 women, age also correlated positively with all stiffness parameters. Molecular analysis revealed a shift toward accumulation of collagen VIII (marker PRO-C8) and reduced degradation of collagen VI (marker C6M) in follicular fluid. Single-cell sequencing showed that stromal cells, the connective tissue cells of the ovary, change their gene expression with age more than any other cell type, activating programs of fibrosis and inflammation. Higher ovarian stiffness was linked to fewer eggs retrieved and lower follicular efficiency, regardless of age and reserve.
This work is the first to prove that human ovarian fibrosis can be measured non-invasively and that it is tied to the functional outcome of IVF. Unlike earlier studies that relied on histology of fixed tissues or animal models, this one used a multimodal approach in living women, combining biomechanics, proteomics and transcriptomics. That places ovarian stiffness among the independent biomarkers of aging, complementing the traditional measures of ovarian reserve. The discovery of stromal cells as the main drivers of fibrosis points to a potential therapeutic target.
Looking ahead, transvaginal elastography could become a routine tool for assessing reproductive age and predicting the response to stimulation in IVF programs. Longitudinal studies will help determine whether ovarian stiffness predicts the timing of menopause and pregnancy outcomes. Antifibrotic drugs already tested in animal models could be evaluated in clinical trials, with stiffness serving as a quantitative criterion of efficacy. It may also be possible to create minimally invasive tests based on circulating collagen neoepitopes to monitor ovarian fibrosis.
The results will influence reproductive medicine, gerontology and tissue biomechanics. In clinical practice, they could improve the selection of patients for IVF and the assessment of treatment efficacy. In aging research, they add the ovary to the list of organs where fibrosis serves as a measurable sign of age-related dysfunction.
The next step will be prospective follow-up of women with different ovarian stiffness to assess the link with live birth and age at menopause. Collagen neoepitopes also need to be validated in larger and more diverse populations.
The work addresses a fundamental problem in reproductive biology: why the ovary ages faster than other organs and which mechanisms drive the decline in egg quality. It links stromal fibrosis to functional outcome, but the question remains open whether stiffness is a cause of deteriorating function or merely a marker. It is also unclear whether fibrosis can be reversed and fertility restored in older women.
Ovarian stiffness in women over 37 reaches values comparable to those of a cirrhotic liver (up to 40 kPa), even though the ovary is far smaller. What is more, the spread of stiffness within a single ovary is wider in older women than in younger ones, reflecting the patchy nature of fibrosis.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.