A Comparison of Two Mouse Endometriosis Models using Endometrial Tissue Fragments and Endometrial Isolated Cells

Objectve: Endometriosis is a common disease in which the endometrial stroma and glands grow abnormally outside the uterine cavity. The establishment of animal models can be effective for determining the etiology of endometriosis. In this study we compare two endometriosis models using endometrial fragments and isolated cultured endometrial cells.

We obtained endometrial tissues that were in the proliferative or secretory phases from women who underwent hysteroscopies for benign reasons at Imam Khomeini Hospital (Tehran). Following confirmation of the tissue's normality, we cut the tissues into 2 mm cube pieces. The remainder of endometrial tissues were used for isolation and cultured to the fourth passage. In the first model of endometriosis, the endometrial tissue fragments and in the second model, 2×106 isolated endometrial cells were subcutaneously transplanted into gamma irradiated mice. The mice were kept under controlled, sterile conditions for 20 days. The mice sera were collected before and after transplantation for assessment of 17β estradiol. The ectopic tissues in both models were assessed for morphological staining using hematoxylin and eosin, as well as periodic acid Schiff (PAS) for gland secretion. The gland sections per mm2 were analyzed.

At 20 days after tissue transplantation, we observed endometrial-like glands in the subcutaneous tissue of both endometriosis models. The number of gland sections was 57.55 ± 17.18/mm2 for the first model and 271.57 ± 77.98/mm2 for the second model. This result was significantly higher in the second model when compared to the first model. Gland secretion was positive for PAS. The level of 17β estradiol was higher in both models compared to the control group. This level was significantly higher in the second model compared to the first (P≤0.05).

The endometriosis model that used cultured endometrial cells showed more efficiency in morphology, gland formation and level of17β estradiol.