Methods
This laboratory study included 15 patients of reproductive age with endometriosis or normal menstrual cycles. Paired endometrial and endometriotic tissues were collected for assaying the levels of DNMT1, 3a and 3b using quantitative RT-PCR, western blot and immunohistochemical (IHC) staining. Primary cultured endometrial stromal cells maintained in normoxia/hypoxia (1% O2) or treated with hypoxia-mimetic compounds were also assayed. The levels of DNA 5-methylcytosine were assayed by using IHC in clinical specimens and murine tissues, and by ELISA in cultured stromal cells. The 3'-untranslated region reporter assay was used to evaluate the effect of hypoxia, microRNAs (miRNAs) and human antigen R (HuR)/AUF1 on DNMT1 mRNA stability. RNA immunoprecipitation was used to assess the interaction of HuR/AUF1 and miR-148a/DNMT1 mRNA under hypoxia. Finally, a transplant-induced mouse model of endometriosis using 20 mice was used to elucidate the alteration of Dnmt1 levels and DNA methylation in the endometriotic tissues. Main