A novel mouse model of endometriosis: Simulating the recurrent hemorrhagic microenvironment of clinical lesions.

Current models of endometriosis (EMs) still have limitations in replicating the key pathological features of human EMs, particularly the cyclic bleeding associated with ectopic lesions. To address this gap, this study aimed to develop a proof-of-concept mouse model that incorporates repeated retrograde hemorrhagic exposure through the intraperitoneal injection of endometrial fragments, followed by repeated intraperitoneal injections of fresh whole blood. An EMs model was established in female C57BL/6J mice via intraperitoneal injection of endometrial fragments combined with saline or whole blood, respectively. The model was systematically evaluated using ectopic lesion burden, peritoneal adhesion scores, histopathological staining, immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), and quantitative reverse transcription polymerase chain reaction (RT-qPCR). Both models successfully recapitulated the fundamental pathological features of EMs. However, the intraperitoneal injection of whole blood (IPBI) protocol induced a markedly greater lesion burden, together with more pronounced histopathological and molecular alterations, and recapitulated repeated exposure to retrograde menstruation. In addition, the IPBI group exhibited more robust systemic biomarker responses, indicating enhanced clinical relevance. The present study successfully established a proof-of-concept EMs mouse model that introduces repeated retrograde hemorrhagic exposure to create a clinically relevant, blood-stimulated microenvironment. This model provides a reliable tool for investigating the pathogenesis of EMs and developing therapeutic strategies.