L26/P-349 Development of a novel mouse model of ovarian endometriosis reproducing cyst formation and peritoneal adhesions

Abstract Study question Can a novel experimental model reliably reproduce ovarian endometriosis with cyst formation and peritoneal adhesions? Summary answer The proposed model consistently induces ovarian cystic lesions associated with peritoneal adhesions, closely reproducing key pathological features of human ovarian endometriosis. What is known already Endometriosis is a chronic inflammatory disease characterized by ectopic endometrial tissue, fibrosis, and adhesion formation, frequently affecting the ovary. Although several animal models exist, none reliably reproduce ovarian endometriomas and their associated inflammatory and adhesive processes, limiting translational relevance. Study design, size, duration This experimental controlled study used a murine model of ovarian endometriosis. 77 female mice were allocated to experimental and control groups according to prior sample size calculation and ethical guidelines. Animals were evaluated 30 days after surgery. Endometriosis was induced using different surgical approaches, including intrabursal suturing or injection of endometrial fragments. Intrabursal suturing enabled controlled lesion placement and assessment of ovarian-specific pathological alterations. Macroscopic evaluation was performed, and endometriosis was confirmed by histological analysis. Participants/materials, setting, methods Female mice underwent surgical induction of ovarian endometriosis using three experimental approaches or sham surgery. The primary outcome was ovarian cystic lesion formation, and secondary outcomes included peritoneal adhesions. Macroscopic evaluation was performed, and endometriosis was confirmed histologically by the presence of endometrial glands and stroma. Statistical analyses were performed using R software (version 4.5.2), with group comparisons conducted using Fisher’s exact test. All procedures were approved by the UFRJ Ethics Committee (protocol no. 177/25). Main results and the role of chance Among the evaluated approaches, the minimally invasive intrabursal suturing method consistently resulted in ovarian cyst formation. Cystic lesions were strongly associated with the development of peritoneal adhesions (p < 0.001), and animals submitted to this method exhibited significantly higher adhesion rates compared with controls (p < 0.001). Other induction techniques failed to reproducibly generate ovarian cysts or adhesions. Histological analysis confirmed the presence of endometrial glands and stroma attached to the ovary, displaying an invasive pattern into the ovarian stroma, consistent with ovarian endometriosis. Cystic lesions were further classified as small, medium, or large. The relationship between cyst size and ovarian laterality (right or left ovary) was also evaluated; however, no statistically significant differences were observed. Adhesion formation was assessed in comparison with control animals to determine whether it resulted from cyst presence or surgical manipulation alone. The results demonstrated a statistically significant association (p < 0.001) between cystic lesion formation and adhesion development, indicating that lesion establishment, rather than surgical manipulation, is essential for adhesion formation. Limitations, reasons for caution Although the model reproduces key morphological and functional features of ovarian endometriosis, it does not recaptulate its etiological origin. Adhesion assessment was semi-quantitative, and further studies should include quantitative fibrosis analysis and long-term reproductive outcomes. Wider implications of the findings This model might represent a reliable and translational platform for studying ovarian endometriosis, enabling investigation of disease mechanisms and preclinical evaluation of therapeutic strategies targeting cyst formation and adhesion development. Trial registration number No