Introduction: During ovulation, repeated extracellular matrix remodelling and inflammation occur, disrupting tissue homeostasis over time. This leads to age-associated ovarian fibrosis, the excessive deposition of anisotropic collagen fibres, creating a niche conducive to cancer growth. Preliminary studies have identified that BRCA1/2 mutation carriers, a population at higher risk for the development of ovarian cancer, appear to develop ovarian fibrosis at pre-menopausal ages, whereas this was evident only at post-menopausal ages for non-carriers. The mechanism underlying accelerated fibrosis has yet to be elucidated. We hypothesize that the loss of Brca1 in ovarian fibroblasts facilitates the accumulation of senescent myofibroblasts, thereby accelerating the onset of ovarian fibrosis and creating a niche supportive of cancer growth.

Methods: We optimized primary culture conditions for mouse ovarian fibroblasts (MOFs) from mice bearing loxP sites in the Brca1 gene. MOFs were transduced with adenovirus expressing Cre recombinase to create Brca1-/- (KO) MOFs and cells were analyzed by RNA-seq and western blot.

Results: Using single-cell RNA-sequencing, we discovered that age-associated fibrosis in mice is associated with fibroblasts having a senescence-associated secretory phenotype. Furthermore, core senescence initiators such as Cdkn1α and Cdkn2α were highly expressed in the KO MOFs. Brca1 KO also induced myofibroblast activation as reflected by an increase in Acta2 expression. These findings were confirmed with senescence-associated beta-galactosidase staining. The accumulation of senescent myofibroblasts is being measured by probing western blots for the senescent markers p16, p21, and acetylated p53.

Conclusions: This study will provide insight into the association between BRCA1 mutations and the risk for early onset of ovarian cancer, and will lay the groundwork for future investigations into prophylactic drugs to delay or prevent ovarian fibrosis.