The expression profile of micro-RNA in endometrium and endometriosis and the influence of ovarian steroids on their expression

MicroRNAs (miRNAs), through mRNA degradation or repression, act as key regulator of gene expression. Our aim was to identify specific miRNAs that are expressed in endometrium of women with and without endometriosis. We profiled the expression of 287 miRNAs in paired eutopic and ectopic endometrium and isolated endometrial cells using microarray and validated the expression of selected miRNAs using real-time PCR. On the basis of global normalization, 65 of these miRNAs were identified to be expressed above the threshold levels set during the analysis in the endometrium of women without endometriosis with a progressive decline in expression in paired eutopic and ectopic endometrium. Statistical analysis (ANOVA) identified 48 of these miRNAs as differentially expressed among these tissues and 32 miRNAs between isolated endometrial stromal cell (ESC) and glandular epithelial cell (GEC) (P < 0.05). The expression of hsa-miR20a, hsa-miR21, hsa-miR26a, hsa-miR18a, hsa-miR206, hsa-miR181a and hsa-miR142-5p, predicted to target many genes, including TGF-bR2, ERa, ERb and PR, respectively, was validated in these tissues and cells using real-time PCR. Treatment of ESC and GEC with 17b-estradiol and medroxyprogesterone acetate (10 M) differentially regulated the expression of hsa-miR20a, hsa-miR21 and hsa-miR26a, which in part reversed following co-treatment with ICI-182780 and RU-486 (10 M), respectively (P < 0.05). In conclusion, we provided evidence for the expression of a number of differentially expressed miRNAs in eutopic/ectopic endometrium and isolated endometrial cells, opening up the possibility that aberrant/altered expression of some miRNAs whose expression is regulated by the ovarian steroids may influence the expression of specific target genes with central roles in normal endometrial cellular activities and pathogenesis of endometriosis.