Divergent regulation of angiopoietin-1, angiopoietin-2, and vascular endothelial growth factor by hypoxia and female sex steroids in human endometrial stromal cells

Abstract Objective To investigate whether hypoxia or the female sex steroids exert direct effects on angiopoietin-1 (ANGPT1), ANGPT2, and vascular endothelial growth factor (VEGF) in human endometrial stromal cells (ESCs) to clarify the regulatory function of these local angiogenic factors in the endometrium. Study design Human endometrial tissues were obtained from 18 patients aged 34–47 years undergoing hysterectomy for benign reasons. ESCs were cultured under hypoxic condition or treated with 17β-estradiol (E) and/or medroxyprogesterone acetate (MPA). The mRNA levels and production of ANGPT1, ANGPT2, and VEGF were assessed by real-time RT-PCR and ELISA, respectively. Analysis of hypoxia-inducible factor 1α (HIF-1α) and estrogen receptor α (ERα) protein levels were evaluated by Western blot analysis. Result(s) Hypoxia reduced the mRNA expression and protein production of ANGPT-1 in ESCs, whereas those of ANGPT2 were unaffected, resulting in an increase of the ANGPT2/ANGPT1 ratio. Hypoxia induced mRNA expression and protein production of VEGF. E simultaneously induced VEGF production and suppressed ANGPT1 production, resulting in an increase of the ANGPT2/ANGPT1 ratio. MPA or E + MPA reduced ANGPT2 production and sustained the levels of ANGPT1, resulting in a decrease of the ANGPT2/ANGPT1 ratio. With regard to the interaction of E and hypoxia, E did not affect the regulation of angiogenic factors, HIF-1α, and ERα under hypoxic conditions. Conclusions Hypoxia and female sex hormones independently regulate the ANGPT2/ANGPT1 ratio and VEGF expression in human ESCs. These results may indicate a potential mechanism for hypoxia or female sex steroids influencing angiogenesis in the human endometrium.