Genome-wide estrogen receptor-α binding and action in human endometrial stromal cells

Objective: To investigate the gene targets of estradiol (E2)–estrogen receptor-α (ESR1) in human endometrial stromal cells. Design: Basic science. Setting: University research center. Patient(s): Premenopausal women with or without endometriosis. Intervention(s): Primary cultures of human endometrial stromal cells from healthy endometrium, with or without small-interfering RNA (siRNA) knockdown of ESR1 expression, were treated with E2 or vehicle control. Main Outcome Measure(s): Genome-wide RNA expression by RNA sequencing was compared in endometrial stromal cells with or without siRNA knockdown of ESR1 in the presence or absence of E2. Genome-wide recruitment of ESR1 to chromatin was assessed by chromatin immunoprecipitation sequencing. Gene expression by real-time qualitative polymerase chain reaction of a potential E2-ESR1 target gene was determined in endometrial stromal cells and endometriotic stromal cells. Result(s): We identified several important pathways that are dependent on E2-ESR1 signaling in endometrial stromal cells, including progesterone signaling, cell–matrix adhesion, and cytoskeleton rearrangement, as well as paracrine signaling by members of the fibroblast growth factor family. We detected a total of 709 ESR1 target sites on chromatin. By integrating data on genome-wide transcriptomic changes and E2-ESR1 binding sites, we identified inositol polyphosphate phosphatase type II (INPP4B) as a candidate E2-mediated suppressor of proliferation in healthy endometrial cells. INPP4B was downregulated in endometriosis-derived stromal cells. Conclusion(s): E2-ESR1 activates genes involved in human endometrial stromal cell cycle regulation, progesterone response, and production of stromal growth factors. Understanding the direct role of estrogen on the endometrial stroma and identifying downstream targets of E2-ESR1 can inform the development of targeted therapies for endometriosis and diminished endometrial receptivity.