“Spot”-ting differences between the ectopic and eutopic endometrium of endometriosis patients

Objective To examine proteins aberrantly expressed in the ectopic endometrium compared with eutopic endometrium from the same patient. Design Experimental study. Setting Research institute and an obstetrics and gynecology clinic (National Institute for Research in Reproductive Health and Sanjeevani Diagnostic Center and Maternity Home, India). Patient(s) Twenty participants with (n = 11) and without (n = 9) endometriosis. Intervention(s) None. Main Outcome Measure(s) Protein identification by two-dimensional (2D) electrophoresis and mass spectrometry as well as validation of the identified proteins by studying protein expression via Western blot and protein localization via immunohistochemical analysis. Result(s) Computer-assisted image analysis detected the presence of 53 protein spots in ectopic 2D gels that were conspicuous by their absence in the 2D maps of eutopic and control endometrium, i.e., these spots were detected only in ectopic gels. Eleven spots were identified by mass spectrometry. The expression of four of these proteins—haptoglobin, Rho-GDIα, SM-22α, and Rab37—have been validated by immunohistochemical and Western blotting analysis. Conclusion(s) This study assumes significance, as there are no reports on the comparison of the global protein profiles of paired eutopic and ectopic endometrium. Furthermore, the study demonstrates a definitive difference in the protein repertoire of the ectopic endometrium compared with its uterine counterpart in the same patient. Such studies are relevant in deciphering the complex biology of the endometriotic lesion.