Indeed, in a study using human endometrial stromal cell (HESCs) gathered from eutopic endometriosis tissue, Xiong et al. (2015) discovered that the β-catenin signaling pathway was activated following estradiol (E2) stimulation; the same stimulation also induced the production of vascular endothelial growth factor (VEGF) and MMP-9, whereas treatment using β-catenin siRNA reversed this effect [17]. Here, MMP9 is linked to endometriosis.