Creation of a rat model of ovarian endometriosis: a novel and easy approach to simulating chocolate cysts

Ovarian endometriosis(OEM) is the most common type of endometriosis, but there is still a lack of simple and easy-to-promote animal models. Therefore, it is necessary to establish a feasible animal model of OEM and analyze its pathogenesis. In this study, a novel insertional surgical method was used to construct the OEM rat model. The rat model group's morphology and HE staining revealed a close relationship between the transplanted ectopic tissue and the ovary. Compared to the surgery group and the normal group, the bilateral OEM group's level of Anti-mullerian hormone(AMH) was noticeably lower. There was no discernible difference in the unilateral OEM group's AMH level between the normal and sham operation groups. Serum interleukin-1beta(IL-1β) levels in four groups of rats showed bilateral OEM had the greatest level, followed by unilateral OEM. Compared to the normal group, the two model groups had greater serum levels of IL-1β. According to immunohistochemistry, unilateral OEM had higher Intercellular adhesion molecule 1(ICAM1), Matrix metalloproteinase-9(MMP9), Tumor necrosis factor-α(TNF-a), and IL-1β expression levels than the normal rat endometrium. WB revealed that bilateral and unilateral ectopic tissues had higher levels of MMP9, TNF-a, Vascular endothelial growth factor D and IL-1β expression than normal tissues. Transcriptome research revealed that ectopic tissues had higher pro-inflammatory, immunological, and ectopic endometrial proliferation pathways than normal tissues. The ovaries of unilateral OEM have down-regulated immune and inflammation-related pathways and up-regulated steroid hormones compared to normal ovarian tissue. GSEA enrichment analysis comparisons between rat and human endometriotic tissue revealed that Janus kinase-signal transducer and activator of transcription(JAK-STAT), Nuclear factor-kappa B(NFκB), and Toll-like receptors were up-regulated. The intercalation approach of OEM building used in this work is more akin to the human OEM lesion type. It deserves promotion that modeling is more straightforward and has a higher success rate than the suture approach.