DLK1/IGF-2 Axis Promotes the Migration and Adhesion of Ectopic Endometrial Stromal Cells in Endometriosis

Background: Endometriosis affects 5%–10% of fertile women globally. Microarray analysis predicted that Delta-like non-canonical Notch ligand 1 (DLK1) is differentially expressed in normal endometrium tissues (NET) and ectopic endometrial tissues (EET). Insulin-like growth factor 2 (IGF-2) is closely associated with endometriosis. This study aimed to clarify whether the DLK1/IGF-2 axis is involved in the pathogenesis of endometriosis. Methods: DLK1 and IGF-2 expression in endometrial tissues and endometrial stromal cells were measured by quantitative real-time polymerase chain reaction, western blotting, and immunohistochemical assays. After knockdown DLK1 in ectopic endometrial stromal cells (EESCs), cellular behaviors were evaluated using cell counting kit-8, transwell assay, wound healing assay, and western blotting. The interaction between DLK1 and IGF-2 was verified using luciferase reporter assay and RNA-binding protein immunoprecipitation. Finally, an endometriosis mouse model was generated to evaluate the effect of DLK1 on lesion. Results: DLK1 was highly expressed in EET and EESCs. DLK1 silencing inhibited EESC viability, migration, and adhesion. Moreover, IGF-2, which can interact with and is positively regulated by DLK1, was highly expressed in EET and EESCs. IGF-2 overexpression abrogated the biological function of EESCs induced by DLK1 depletion. In addition, DLK1 knockdown suppressed endometrial lesion size and weight and attenuated histopathology. Conclusions: Silencing the DLK1/IGF-2 axis attenuates endometriosis progression by inhibiting EESC viability, migration, and adhesion. These results indicated that the DLK1/IGF-2 axis may be a therapeutic target for the treatment of endometriosis.