Expression of AhR and ARNT mRNA in cultured human endometrial explants exposed to TCDD

Endometriosis is a debilitating disease found in 10-15% of reproductive-age women and is characterized by the presence of endometrial tissue outside o f the uterus. The present study characterizes the expression of AhR and ARN T mRNA in a human endometrial explant culture model in the absence and pres ence of TCDD exposure. In a parallel, companion study using this model, TCD D exposure was shown to induce CYP1A1 mRNA, CYP1B1 mRNA, EROD (7-ethoxyreso rufin-O-deethylase) activity, and CYP1B1 protein in human endometrial expla nts. Explants were prepared from specimens obtained at laparoscopy or lapar otomy from women undergoing surgery for tubal ligation, endometriosis, or p elvic pain unrelated to endometriosis. These specimens were a subset of the specimens used in the parallel study. The explants were cultured in medium containing 10 nM estradiol (E-2) or 1 nM estradiol plus 500 nM progesteron e (E-2 + P-4) with or without TCDD (first 24 h). After culture, AhR and ARN T mRNA expression were quantified by RT-PCR. TCDD treatment significantly i ncreased the expression of AhR m-RNA, but not ARNT mRNA. The expression of both genes was similar for all individual explants and the ratio of AhR:ARN T mRNA expression across all samples was 1.7 to 1.8. Constitutive AhR mRNA expression was donor age dependent (increasing with age), while ARNT mRNA e xpression was donor age and tissue phase dependent (increased in older and proliferative phase specimens). Similar to results in the parallel study on expression of CYP1A1 mRNA, CYPlB1 mRNA, EROD activity, and CYP1B1 protein, the presence of endometriosis did not affect the expression of AhR or ARNT mRNA, either constitutively or following TCDD exposure. However, the detec tion of disease-specific change was limited by small sample size and variab ility in tissue cycle phase. The human endometrial explant culture model wi ll be useful for future studies of the effects of dioxin-like compounds on human endometrium in relationship to cycle phase, hormonal exposure, and do nor age.