Time course of pelvic endometriotic lesion revascularization in a nude mouse model

Objective: To assess the timing of endometrial lesion revascularization in a murine model. Design: Prospective experimental study. Setting: An academic research environment. Animal(s): Twenty-six nude mice. Intervention(s): Endometriosis was induced in mice by intraperitoneal deposition of human menstrual endometrium. Endometrial implants were recovered on days 1, 3, 5, 8, 10, 15, and 21 after implantation. Main Outcome Measure(s): Sections from the endometrial implants were immunostained with species-specific antiplatelet endothelial cell adhesion molecule-1 (PECAM-1) antibodies and vessels of murine and human origin were counted. Result(s): Endothelial cells of human origin in the implant progressively disappeared between day 3 and day 10. Seventy-eight percent of the vessel sections were positive for human PECAM-1 on day 5, 40.1% on day 8, and only 14.1% on day 10. However, there was a marked increase in murine PECAM-1-expressing vessels in endometrial stroma between day 5 (1.4%) and day 8 (68.0%), 10 (69.5%), and 15 (87.2%). Conclusion(s): Our study demonstrates that PECAM-1 is a reliable endothelial cell marker to evaluate the role of angiogenesis in the nude mouse model. It also indicates that revascularization of human endometrial implants occurs between 5 and 8 days after implantation and involves the disappearance of native graft vessels, coinciding with the invasion of the interface and then the stroma by murine vessels.