Endometrial cell adhesion in an in vitro model using intact amniotic membranes

Objective: To study adhesion between endometrial tissue and peritoneum using intact amniotic membranes as an in vitro model. Design: A cell biologic and immunohistochemical study. Setting: Tertiary-care university medical center. Patients: Ten patients with regular and ovulatory cycles. Interventions: Mechanically dissected tissue fragments from endometrial biopsies were cultured on either side of intact amniotic membranes. Also, the carcinoma cell lines RL95-2 and AN3CA were used. Main Outcome Measures: The adhesion of endometrial fragments and of endometrial carcinoma cell lines to amniotic membrane was studied in vitro and evaluated using frozen sections. The composition of the extracellular matrix and the presence of intermediate filament proteins of amniotic membrane were determined using immunohistochemistry and compared with those of normal peritoneum. Results: Peritoneum and amniotic membrane were similar with respect to expression of cytokeratins in epithelial lining and of extracellular matrix (ECM) components. The endometrial fragments did not adhere to the intact epithelial side of the amniotic membrane. Tn contrast, adhesion did occur to the nonepithelial side of the amnion. The carcinoma cell lines RL95-2 and AN3CA adhered to either side of intact amniotic membranes. Conclusions: An intact epithelial lining prevents adhesion of endometrial fragments to the ECM of amniotic membranes in vitro. An intact epithelium could be an important defense mechanism in preventing initial adhesion of retrogradely shed endometrium fragments to peritoneum.