Persistent Pelvic Adhesions and Fibrotic Remodeling Following Ectopic Lesion Ablation in a Mouse Model of Endometriosis

ABSTRACT Endometriosis is a chronic, estrogen‐dependent inflammatory disorder characterized by ectopic endometrial‐like lesions, fibrosis, and persistent pelvic pain. Although ectopic lesions are important contributors to pain, symptom severity often correlates poorly with lesion burden, suggesting lesion‐independent mechanisms. Here, we investigated the contribution of ectopic lesion‐derived cells to persistent pelvic adhesions, fibrotic remodeling, and endometriosis‐associated behavioral alterations using a mouse model. A syngeneic model combined with inducible diphtheria toxin receptor (iDTR)‐mediated cell ablation was used to selectively eliminate donor‐derived progesterone receptor‐expressing ectopic cells. Endometriosis was induced by transplantation of uterine tissue from Pgr cre/+ Rosa26 iDTR/mTmG donor mice into recipients, followed by diphtheria toxin‐mediated lesion ablation. Lesion burden, pelvic adhesions, and fibrotic remodeling were assessed by imaging, histology, and molecular analyses, while behavioral outcomes were evaluated using non‐evoked assays. Selective ablation eliminated detectable GFP‐positive ectopic lesions. Histological and molecular analyses demonstrated significantly reduced collagen deposition and α‐SMA‐positive fibrotic remodeling within adhesion‐associated tissues relative to established ectopic lesions, although these measures remained elevated above sham controls. However, despite lesion ablation, no statistically significant differences were detected between DT‐ and vehicle‐treated mice in nesting or marble‐burying performance, although the modest cohort size may have limited detection of partial behavioral effects. These findings indicate that, although fibrosis in adhesion‐associated tissues was reduced relative to established ectopic lesions, residual fibrotic remodeling persisted above sham levels, whereas behavioral outcomes showed variable responses without a significant, uniform reversal, highlighting the potential importance of targeting fibrotic and adhesive remodeling in addition to ectopic lesions.