Dynamic aspects of endometriosis in a mouse model through analysis of implantation and progression.

The aim of this study was to use normal immunocompetent mice to set up a model for endometriosis which allowed to study the dynamic aspects involved in initiation and progression of the disease. Thirty mice were surgically transplanted with autologous endometrium and at 3 weeks showed evidence of endometriosis. Diagnosis of endometriotic lesions was hystologically confimed. Visual inspection using a caliper revealed that, after an initial decrease in size (from 33.44±2.33 mm2 to 24.24±2.37 mm2 (p<0.01)) detected at 3 weeks after transplantation, there was a significant increase of lesion area from 21.30±3.15 mm2 to 43.93±6.29 mm2 (p<0.05) in the following 4 weeks. When we compared these results to those obtained in mice which underwent bilateral annessiectomy, we observed that, when bilateral annessiectomy was performed simultaneously to endometrial transplantation, lesion surfaces were similar between mice which were or were not subjected to bilateral ovariectomy. On the other hand, when bilateral annessiectomy was performed at second laparotomy and then evaluated after 4 weeks, differently from what observed in control mice, surface values decreased from 21.24±2.29 mm2 to 10.58±3.40 mm2 (p<0.01). Finally, progression of lesions in estrogen supplemented mice seems less evident than in control mice since only a slight but not significant increase in size (from 21.32±3.32 mm2 to 26.18±6.98 mm2, p=0.32) was detected. The results presented herein demonstrate that surgically induced endometrial implants in mice are dynamic lesions and that implantation and progression of endometriosis represent different stages in the ethiopathogenesis of the disease. Moreover, we showed that progression, but not implantation, of ectopic endometrium is dependent upon the functionally and structurally integrity of the ovaries. This is a model of endometriosis established in normal immunocompetent mice, and, consequently, may represent a reliable tool for testing new immunological therapeutical approaches and studying the role of different genes using transgenic mice.