Time series analysis of transmesothelial invasion by endometrial stromal and epithelial cells using three-dimensional confocal microscopy

Objective: To evaluate endometrial adhesion and invasion of peritoneal mesothelium. Design: Descriptive study using confocal laser-scanning microscopy. Setting: University-based laboratory. Patient(s): Women undergoing surgery for benign conditions. Intervention(s): Fluorescence-labeled peritoneal mesothelial cells (PMCs) were grown on coverslips. Fluorescence-labeled endometrial stromal cells (ESCs) and epithelial cells (EECs) and myometrial cells (Myos) were plated on the PMCs. Cultures were examined at 1, 6, 12, and 24-27 hours with differential interference contrast and confocal laser-scanning microscopy. Main Outcome Measure(s): Demonstration of adherence and invasion of endometrial cells through peritoneal mesothelium. Result(s): At 1 hour, there was adherence of the ESCs, EECs, and Myos on the perimeter of PMCs. There was no invasion by the Myos. By 6 hours, ESCs and EECs spread over the surface of the PMCs and extended cell processes through PMC junctions. Extension of pseudopodia under the PMCs followed. By 12 hours, there was vacuolization and lifting of PMCs that had been undermined by endometrial cells. Conclusion(s): This is the first time-phase study to demonstrate adherence and the process of invasion of endometrial cells through the mesothelium. The application of three-dimensional confocal laser-scanning microscopy is a novel technique that can be used to further examine mechanisms involved in the pathogenesis of the early endometriotic lesion.