Hypoxia and estrogen cooperatively enhance angiogenesis through the GPER/ESR1-HIF-1α/VEGF axis in adenomyosis

Adenomyosis (AM) is a benign gynecological disorder characterized by the presence of endometrial tissue within the myometrium and is commonly associated with dysmenorrhea and menorrhagia. Although angiogenesis is considered a key process in its pathogenesis, the underlying molecular mechanisms remain incompletely understood. In this study, we investigated the role of the hypoxia-inducible factor 1-alpha (HIF-1α)/vascular endothelial growth factor (VEGF) axis in AM. Immunohistochemical analysis revealed that the expression levels of HIF-1α and VEGF, as well as microvessel density (MVD), were significantly increased in the eutopic endometrium of patients with AM, with significant positive correlations among these parameters. Paired analysis further showed that adenomyotic lesion tissues exhibited stronger HIF-1α and VEGF expression and higher MVD than matched eutopic endometrium. In vitro, using adenomyosis-derived eutopic endometrial stromal cells (A-EuESCs) under cobalt chloride (CoCl2)-induced hypoxic conditions, we found that estrogen further enhanced HIF-1α and VEGF expression. Mechanistically, estrogen promoted angiogenesis through two distinct pathways: G protein-coupled estrogen receptor (GPER)-dependent activation of the PI3K/AKT and ERK pathways, which enhanced HIF-1α accumulation, and estrogen receptor alpha (ESR1)-mediated transcriptional upregulation of HIF-1α. These two pathways converged to increase VEGF secretion and ultimately promoted tube formation, migration, and invasion of human umbilical vein endothelial cells (HUVECs). Collectively, these findings demonstrate that under hypoxic conditions, estrogen drives angiogenesis in AM through dual regulation of the HIF-1α/VEGF pathway by GPER and ESR1. This study provides new mechanistic insight into the pathogenesis of AM and supports the GPER/ESR1-HIF-1α-VEGF axis as a potential mechanistic target for further investigation.