Fibrosis in Ovaries: Causes, Symptoms, and Treatments

Ovarian fibrosis is the buildup of excess scar-like tissue in the ovary, driven by an overproduction of structural proteins that gradually stiffens the organ and disrupts its normal function. It occurs when damage from ovulation, disease, aging, or medical treatments overwhelms the ovary’s ability to repair itself cleanly, and the body patches things up with dense connective tissue instead. The process is increasingly recognized as a contributor to declining fertility, poor egg quality, and conditions like polycystic ovary syndrome (PCOS) and premature ovarian insufficiency, yet it receives far less attention than fibrosis in the liver or lungs.

How Scar Tissue Forms in the Ovary

Every time you ovulate, the ovary sustains a small wound. The surface breaks open, an egg is released, and the tissue repairs itself. Normally, this cycle of injury and healing proceeds without lasting damage. Fibrosis begins when the repair process goes wrong. When the ovary is damaged beyond the capacity of its own cells to regenerate, the body fills the gap with extracellular matrix, a scaffold of collagen and other structural proteins. A modest amount of this scaffolding is normal. The problem is overproduction: too much matrix gets deposited and never cleared away, leaving stiff, fibrous tissue in place of healthy ovarian tissue.¹

At the cellular level, the key players are myofibroblasts, cells that behave like a cross between a fibroblast and a muscle cell. During normal wound healing, resting fibroblasts transform into myofibroblasts, which contract tissue and lay down new matrix. Once repair is complete, these cells are supposed to stand down. In fibrosis, they persist and keep producing collagen.² A growth factor called TGF-beta is one of the main signals that keeps this process running. When TGF-beta levels stay abnormally high in the ovary, it promotes continued matrix deposition and can interfere with follicle development and ovulation.³

What Causes Ovarian Fibrosis

There is no single cause. Instead, fibrosis develops in response to repeated or severe ovarian injury from several different sources, sometimes acting together.

Aging and Repeated Ovulation

The most universal driver is simply getting older. Each ovulation leaves a tiny wound, and over decades of menstrual cycles the cumulative damage adds up. The ovary’s cleanup systems also slow down with age: old ovaries show reduced cell turnover, impaired wound healing at the surface, and rising collagen accumulation.⁴ On top of ovulation damage, the ovary must constantly clear out follicles that start developing but never ovulate (atretic follicles) and remnants of the corpus luteum. This housekeeping generates chronic low-grade inflammation, which in turn promotes fibrosis.⁵ Proteomic studies confirm that as ovaries age, proteins involved in immune response and matrix remodeling get upregulated while those governing DNA repair and cell growth decline, creating a microenvironment that is both inflamed and fibrotic.⁶

Polycystic Ovary Syndrome

PCOS is one of the most common endocrine disorders in women of reproductive age, and fibrosis appears to be part of its pathology. Ovaries in people with PCOS tend to be stiffer than normal, with increased collagen deposits in the tissue surrounding follicles. Animal models of PCOS consistently show elevated markers of fibrosis in ovarian tissue, including higher levels of TGF-beta and connective tissue growth factor.⁷ Whether fibrosis is a cause of PCOS symptoms, a consequence of them, or both remains an open question, but the stiffened tissue environment clearly makes it harder for follicles to develop and release eggs normally.

Endometriosis

Ovarian endometriomas, the chocolate cysts that form when endometrial tissue implants on the ovary, are strongly associated with fibrosis. The cyst walls show heavy collagen deposition and elevated levels of fibrotic signaling molecules. Endometriotic cyst cells produce TGF-beta, which drives fibrosis in the surrounding ovarian tissue and can cause adhesions.⁸ The damage extends beyond the cyst itself. Fluid from endometriomas increases oxidative stress in nearby granulosa cells and induces fibrotic markers in the tissue layers surrounding developing follicles, which helps explain why endometriomas impair fertility even in ovarian tissue that looks otherwise healthy on imaging.⁹

Chemotherapy and Radiation

Cancer treatments are a well-documented cause. Chemotherapy drugs can accelerate follicle death and directly damage the ovarian stroma, the supportive tissue framework.¹⁰ In ovaries previously exposed to chemotherapy, researchers have found focal areas of fibrosis with complete disappearance of follicles, along with damage to cortical blood vessels and abnormal small-vessel proliferation.¹¹ Cisplatin, a widely used chemotherapy agent, has been specifically shown to induce ovarian fibrosis through the same TGF-beta signaling pathway involved in age-related fibrosis.¹² Pelvic radiation compounds the problem by causing fibrosis not only in the ovary itself but in the surrounding pelvic tissue, which can limit blood supply even to transplanted ovarian tissue used for fertility preservation.¹³

Environmental Exposures

Emerging research points to certain environmental chemicals as potential contributors. Animal studies suggest that exposure to antimony, an estrogenic metal found in some industrial products, can disrupt hormone signaling and promote ovarian fibrosis through the same TGF-beta and related pathways seen in other causes.¹⁴ This is still early-stage research, mostly conducted in zebrafish and rodents, but it hints at a broader story in which endocrine-disrupting chemicals may contribute to ovarian fibrosis in ways we have not yet mapped in humans.

How Fibrosis Affects the Ovary and Fertility

Ovarian fibrosis does not always produce obvious symptoms the way, say, a large ovarian cyst might. Many people with early-stage fibrosis have no pain and no outward sign that anything is wrong. The damage tends to be silent and cumulative, revealing itself through declining fertility, irregular cycles, or premature menopause rather than through acute symptoms.

The core problem is mechanical. As fibrotic tissue accumulates, the ovary stiffens. This stiffness is not just a structural inconvenience; it actively interferes with how follicles grow and how eggs mature. Measurements using atomic force microscopy have confirmed that human ovarian tissue gets stiffer with age, and that this stiffening is more pronounced in conditions like chemotherapy-induced premature ovarian insufficiency, PCOS, and ovarian endometriosis.¹⁵

Laboratory experiments show that stiffness alone, even without inflammation or hormonal disruption, can trigger problems that look like ovarian aging. Follicles grown in artificially stiffened environments show reduced growth, lower survival, impaired granulosa cell function, and poorer egg quality.¹⁶ One mechanism appears to involve the tiny cellular bridges (transzonal projections) that connect granulosa cells to the egg. In a stiff environment, fewer of these bridges form, which likely cuts down on the nutrient and signal delivery the egg depends on for proper maturation.¹⁶ So stiffness is not merely a marker of damage; it makes things worse, creating a feedback loop in which fibrosis degrades egg quality, which in turn may trigger more abnormal follicle death and more fibrotic repair.

Detecting Ovarian Fibrosis

There is currently no standard clinical test specifically for ovarian fibrosis. A routine pelvic ultrasound can show enlarged ovaries, increased follicle counts, or cysts, but it cannot directly measure tissue stiffness or collagen content. The most promising tool in development is shear wave elastography, an ultrasound-based technique that quantifies how stiff a tissue is by tracking how quickly sound waves move through it.

In studies of people with PCOS, shear wave elastography has consistently shown that their ovaries are stiffer than those of controls. One study using this technique found that mean stiffness values in the ovarian medulla were significantly higher in PCOS patients, and that stiffness correlated with anti-Müllerian hormone (AMH) levels, a marker of ovarian reserve.¹⁷ Another study using a related technique (real-time elastography) found that a specific stiffness threshold could distinguish PCOS ovaries from healthy ones with about 85% sensitivity and 88% specificity.¹⁸

Researchers have proposed that non-invasive stiffness measurement could eventually serve as a clinical biomarker not just for PCOS but for ovarian reserve, follicle health, egg quality, and possibly even ovarian cancer risk.¹⁹ None of this has entered routine clinical use yet, but the technology is available on many existing ultrasound machines, which makes adoption relatively straightforward if the evidence base continues to grow.

Treatments Under Investigation

No drug is currently approved specifically for ovarian fibrosis in humans. Treatment today focuses on managing the underlying condition, whether that is PCOS, endometriosis, or chemotherapy-related ovarian damage. But several experimental approaches are showing promise in animal models, and some are borrowed from anti-fibrotic therapies already used in other organs.

Pirfenidone

Pirfenidone is an anti-fibrotic drug already approved for a lung condition called idiopathic pulmonary fibrosis. Researchers have started testing it in animal models of ovarian fibrosis, and the early results are striking. In a mouse model of ovarian endometriosis, pirfenidone reduced lesion size and fibrosis while restoring markers of ovarian reserve and follicle development.²⁰ In a separate PCOS rat model, pirfenidone improved estrous cycling, follicular profiles, and the number of corpora lutea (a sign of ovulation) while driving down fibrotic signaling molecules. Interestingly, it did this without significantly altering hormone levels, suggesting its benefits come from targeting the structural tissue damage rather than the hormonal imbalance.²¹ Whether pirfenidone could be repurposed for ovarian fibrosis in humans remains untested, but the animal data have been consistent enough to generate real interest.

Mesenchymal Stem Cells

Stem cell therapy is another active area of investigation. Mesenchymal stem cells (MSCs), which can be harvested from sources like umbilical cord blood, have shown the ability to reduce ovarian fibrosis and improve function in animal models of premature ovarian insufficiency.²² In a lupus mouse model where autoimmune attack causes ovarian fibrosis, MSC transplantation reduced inflammation, suppressed fibrotic markers, and partially restored ovarian function.²³ The cells appear to work partly by tamping down immune-driven inflammation and partly by blocking the signals that keep myofibroblasts active. More recently, researchers have explored using exosomes, tiny vesicles shed by MSCs, as a cell-free alternative. Animal studies suggest these exosomes can restore ovarian function in models of premature ovarian insufficiency by inhibiting granulosa cell death, inflammation, and fibrosis.²⁴ Exosomes are easier to store and standardize than live cells, which could make them more practical if the approach ever moves into clinical trials.

Other Experimental Approaches

Several natural compounds have been explored for anti-fibrotic properties in the ovary. In one study, sinapic acid, a plant-derived compound, reduced atretic and cystic follicle counts and lessened ovarian fibrosis in PCOS rats, with the effect attributed to reduced oxidative stress and metabolic disturbance.⁷ Another study found that indole-3-carbinol, a compound found in cruciferous vegetables, alleviated cisplatin-induced ovarian fibrosis in animal models by blocking TGF-beta signaling.¹² These are not ready for clinical use, but they illustrate a broader trend: researchers are actively searching for ways to interrupt the fibrotic cascade in ovarian tissue, and they have a growing list of molecular targets to aim at.

Why This Research Has Been Slow

Fibrosis in other organs has attracted enormous research investment. Liver fibrosis and lung fibrosis have well-characterized staging systems, approved drugs, and large clinical trial pipelines. Ovarian fibrosis, by comparison, has been understudied for decades. Part of the reason is practical: the ovary is small, sits deep in the pelvis, and is difficult to biopsy without risking the very follicles you are trying to protect. Unlike a liver biopsy, which removes a sliver of a large organ, sampling ovarian tissue can mean sacrificing eggs. This has made it hard to build the kind of large human tissue datasets that drive fibrosis research in other fields.

Another complication is that what counts as “normal” collagen in the ovary changes over the menstrual cycle and with age. The ovary is in constant remodeling, building and tearing down tissue every month, so drawing a clean line between healthy repair and pathological fibrosis is harder than in an organ with a more static architecture. Research has also been hampered by species differences, as discussed below, which limit how directly animal model findings translate to humans.

Mouse Ovaries Are Not Human Ovaries

Most of what we know about ovarian fibrosis comes from mouse studies, and there are important differences between mouse and human ovaries that complicate the translation. A recent comparative analysis using quantitative imaging of collagen architecture found that while both species show increasing collagen with age, the pattern differs. In aging mice, collagen accumulates diffusely throughout both the outer cortex and the inner stroma. In human ovaries, the buildup is confined to the cortex, with no detectable difference between premenopausal and postmenopausal stroma.²⁵ The type of collagen fibers also differs: mice accumulate mostly thin fibers, while humans accumulate thick fibers.

This matters because therapies tested in mice target a diffuse process, while the human version may require a more localized approach. A drug that reduces collagen throughout the ovarian stroma might look great in mice but do little for cortical fibrosis in humans. Researchers studying reproductive aging have started using dog models as well, since dogs share more environmental conditions with humans and also experience age-related fertility loss, though this work is still in its early stages.²⁶ The bottom line for anyone following this field is that animal results, while encouraging, need to be interpreted cautiously until more human tissue data accumulates.

Implications for Fertility Preservation

Ovarian fibrosis adds a layer of complexity to fertility preservation strategies, particularly for cancer patients. Ovarian tissue cryopreservation and later transplantation is an established technique for restoring fertility after cancer treatment. But a multicenter evaluation of ovarian tissue transplantation found that live birth rates were notably lower in women who had received high-dose pelvic radiation, likely because radiation-induced fibrosis in the pelvic tissue compromised blood supply to the transplanted tissue.¹³ This means the problem is not just about preserving healthy ovarian tissue before treatment; it is about whether the body provides a hospitable environment for that tissue when it is transplanted back.

For people with PCOS or endometriosis, fibrosis may also affect outcomes in assisted reproduction. If the ovarian microenvironment is stiffer than normal, developing follicles may produce lower-quality eggs even with hormonal stimulation. If elastography-based stiffness measurements become routine, they could eventually help clinicians tailor stimulation protocols or set more realistic expectations about IVF cycle outcomes. For now, this remains aspirational, but it illustrates why understanding ovarian fibrosis is not just an academic exercise. It sits at the intersection of aging, common gynecological conditions, cancer survivorship, and assisted reproduction, touching millions of people whose fertility depends on ovarian tissue that may be quietly scarring in ways we are only beginning to measure.