Pathological evaluation of the rat endometriosis model

Objective: To observe in detail the morphology of experimental rat endometriosis, specifically in peritoneum adjacent to uterine transplants attached via autotransplantation. Design: Light and electron microscopic study. Setting: Tochigi Institute of Clinical Pathology, Japan. Animal(s): Female-SD rats maintained on a schedule of 12 hours of light and 12 hours of dark for 2 weeks. Intervention(s): Uterine transplants were attached to rat peritoneum via the surgical autotransplantation technique. The implanted area of peritoneum, including abdominal muscle, were excised from anesthetized rats at four (n = 10), seven (n = 10), and 14 (n = 10) days after uterine autotransplantation. The mesenteries were autotransplanted as a comparative control. Main Outcome Measure(s): We examined the morphologic alterations of uterus-attached peritoneum following the time interval after the implantation. Result(s): In rat endometriosis models, the stromal tissue of uterus-attached peritoneum showed proliferation and infiltration of mast cells, eosinophils, plasma cells, lymphocytes, and macrophages. These lesions increased with time after implantation; however, ultimately these infiltrating cells disappeared and proliferation declined. Conclusion(s): Our findings suggest that uterine autotransplantation induces the infiltration of allergic inflammatory-related cells and proliferative lesions in peritoneal stroma attached endometrium. These data should prove useful for investigations of human endometriosis.