Ovarian Fibrosis Drives Female Infertility and Aging Through Key Molecular Pathways

Ovarian fibrosis is a pathological process in which repeated micro-injury — most notably from repeated ovulation across a woman's reproductive lifespan — triggers a dysregulated wound-healing response. Rather than resolving cleanly, the repair process leads to excessive and permanent accumulation of extracellular matrix (ECM) components, especially collagen types I and III, fibronectin, and hyaluronan. The result is progressive stromal stiffening that architecturally distorts the ovary and impairs its two fundamental functions: folliculogenesis and steroidogenesis. This review from Yeditepe University synthesizes the full cellular and molecular landscape of ovarian fibrosis, drawing on animal models, human tissue studies, and clinical correlates.

At the cellular level, the central effectors of ovarian fibrosis are activated fibroblasts and their differentiated derivatives, myofibroblasts. These cells are driven into a pro-fibrotic state primarily by TGF-β isoforms (TGF-β1, 2, and 3), which signal through TGFBR2 and TGFBR1 receptors to activate Smad2/3/4 transcriptional complexes. Overexpression of TGF-β receptors is sufficient to induce ovarian fibrosis experimentally, and pharmacological inhibition reduces fibrotic markers. Non-Smad pathways — including ERK, p38 MAPK, JNK, ROCK, and AKT — complement canonical Smad signaling. Connective tissue growth factor (CTGF), acting downstream of TGF-β, amplifies collagen and fibronectin production; CTGF knockout models demonstrate altered follicular development, underscoring its dual role in fibrosis and normal ovarian physiology.

Inflammation is both a trigger and a sustaining force for ovarian fibrosis. The NLRP3 inflammasome — activated by oxidative stress, metabolic signals, and elevated androgens — drives maturation of IL-1β and IL-18, creating a pro-inflammatory milieu that perpetuates fibroblast activation. NLRP3 expression is elevated in aged and PCOS ovaries, and its inhibition reduces fibrosis markers in experimental models. The NF-κB pathway mediates inflammatory responses triggered by environmental toxins including heavy metals and herbicides. Conversely, PPAR-γ, a nuclear hormone receptor, exerts anti-fibrotic effects by suppressing TGF-β/Smad signaling and controlling ECM remodeling; PPAR-γ knockout in mice leads to infertility, while its activation by natural compounds reduces fibrosis markers in PCOS models.

Ovarian fibrosis is directly implicated in four major reproductive disorders. In PCOS, stromal fibrosis and androgen-driven NLRP3 activation disrupt folliculogenesis and contribute to anovulation. In premature ovarian insufficiency (POI), accelerated collagen deposition depletes the follicular reserve prematurely. In endometriosis, ectopic endometrial lesions induce local fibrosis that impairs adjacent ovarian tissue. Perhaps most concerning is the potential link to ovarian cancer: repeated ovulatory micro-injury and collagen accumulation may create a tumor-permissive microenvironment, though definitive causal evidence in humans remains elusive. Dysregulated VEGF signaling further complicates matters, driving aberrant angiogenesis that is simultaneously necessary for follicle and corpus luteum development yet pathologically elevated in fibrotic and PCOS ovaries.

Therapeutic strategies remain largely experimental. Pirfenidone, an established anti-fibrotic agent used in pulmonary fibrosis, shows promise in ovarian models by inhibiting TGF-β signaling and reducing collagen deposition. Direct TGF-β inhibitors and modulation of oxidative stress are additional pharmacological avenues under investigation. Stem cell therapies — particularly mesenchymal stem cells — represent an emerging regenerative approach, with early data suggesting they can reduce fibrotic markers and support follicular recovery in animal models. The authors identify critical knowledge gaps: the precise triggers of fibroblast activation in the ovarian microenvironment, the interplay between immune cells and ECM components, and the lack of long-term human intervention data. Future research must prioritize translational studies that bridge mechanistic insights to clinical therapies capable of preventing or reversing ovarian fibrosis.