Endometriosis may be generated by mimicking the ontogenetic development of the female genital tract

Objective: To compare the expression of genes playing a decisive role during the embryonic development of the female genital tract (WNT4, WNT5A, WNT7A, PAX8) in the peritoneum of patients with endometriosis and control patients. Design: Experimental study using real-time polymerase chain reaction and in situ hybridization. Setting: University-based laboratory. Patient(s): Patients with and without endometriosis undergoing surgery for benign indications. Intervention(s): None. Main Outcome Measure(s): Percentage of samples positive for gene expression by using real-time polymerase chain reaction, as well as relative expression values compared with housekeeping genes. Confirmation of results by in situ hybridization. Result(s): Expression of WNT7A and PAX8 was found in the normal peritoneum in approximately half of the patients with endometriosis in contrast to the controls. In patients with endometriosis WNT7A and PAX8 in histologically normal peritoneum (with no evidence of endometriosis, endosalpingiosis, or other changes) were confirmed by in situ hybridization. Conclusion(s): The expression of these genes in the normal peritoneum suggests that endometriosis can arise through metaplasia and can in the process make use of the developmental steps involved in the embryonic development of the female genital tract.