DNA methylation of HOXA10 in eutopic and ectopic endometrium

Study question: Does the methylation status of the promoter region of the HOXA10 gene differ in eutopic and ectopic endometrium?

Summary answer: The eutopic endometrium in women with endometriosis is significantly more methylated when compared with controls.

What is known already: Expression of the HOXA10 gene, which is important for successful implantation, is reduced in women affected by endometriosis.

Study design, size and duration: A pilot study was carried out including 18 women admitted for surgery for endometriosis-related pain (cases) and 12 women admitted for surgery because of non-endometriotic disease (control). Sample collection and analysis were performed between November 2010 and July 2013.

Participants/materials, setting, methods: Endometrial tissue (eutopic and ectopic) underwent sodium bisulfite DNA modification, PCR amplification of two regions of the HOXA10 promoter and pyrosequencing analysis.

Main results and the role of chance: The eutopic endometrium of women with endometriosis was significantly more methylated compared with endometrium from the control group (sequence 1: 8.68% in cases and 6.25% in the control group: P = 0.037, sequence 2: 11.89% in cases and 9.25% in the control group: P = 0.032). The eutopic endometrium was significantly more methylated than the ectopic tissue in patients with endometriosis (mean difference -3.6 sequence 1: P = 0.001 and -6.0 sequence 2: P = 0.0001).

Limitations, reasons for caution: The study had a limited sample size and the fertility status of the majority of patients in our study was unknown.

Wider implications of the findings: Our data regarding methylation state of the ectopic tissues contribute to a better etiopathologic understanding of endometriosis.

Study funding/competing interests: No external funding was either sought or obtained for this study. The authors have no conflicts of interests to declare.