HOXA10 expression in ectopic endometrial tissue

Objective: To evaluate HOXA10 expression in endometriosis. Design: Laboratory study using human tissue. Setting: Academic research center. Patient(s): Eutopic endometrial tissue was collected from 20 fertile women without endometriosis. Ectopic endometrial tissues from pelvic peritoneum, ovary, and lung parenchyma were collected from 20 women undergoing surgery for endometriosis. Intervention(s): HOXA10 protein expression and localization with immunohistochemistry. Main Outcome Measure(s): Quantitative analysis of HOXA10 expression, according to H score. Results(s): Both eutopic and ectopic endometrial tissue expressed HOXA10. Ectopic endometrial tissue had lower stromal HOXA10 expression compared with eutopic endometrium. The mean H score for stromal expression of HOXA10 was 7.6 in eutopic endometrium and 1.3 in ectopic endometrial tissue. Glandular epithelium from both eutopic and ectopic endometrium had similarly low HOXA10 expression. HOXA10 was also expressed at low levels in lung parenchyma containing endometriosis and in ovarian endometriomas. Conclusion(S): HOXA10 is expressed in endometriosis at locations outside of the normal HOXA10 expression domain, where it is likely necessary to impart endometrial developmental identity on endometriosis. HOXA W might be necessary for de novo endometrial development. However, the diminished expression of HOXA10 in ectopic endometrium might not allow for normal endometrial development and might contribute to the pathogenesis of endometriosis by creating P resistance.