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Background/Aims: Endometriosis is known to be an estrogen-dependent disease. However, only a few studies have analyzed the effect of estrogen treatment in mice xenotransplanted with human endometrium. The objective of this study was to adapt a previously developed heterologous murine model to the study of estrogens and test the impact of estrone treatment on endometriosis development. Methods: Human proliferative endometrium was xenotransplanted into the peritoneal cavity of castrated immunodeficient mice. These mice were treated with estrogens by means of subcutaneous estrone-releasing pellets. The effect of estrone on estradiol level, uterine histology and endometriosis development was evaluated after 21 days. Results: Bioactivity of estrone pellets and their metabolization into estradiol were demonstrated. However, there was no impact on endometriosis development (no difference in lesion number, weight, size or fluorescence). This lack of response was not due to absence of estrogen receptor expression, since strong expression was found in all lesions harvested. Surprisingly, castrated nontreated mice presented with lesions showing high proliferative activity, similar to lesions found in treated mice (around 30%). Conclusion: The high proliferation observed in lesions recovered from ovariectomized nontreated mice questions the utility of using estrogens in heterologous murine models.

Background/Aims: The aim of this study was to induce endometriosis in female rhesus macaques (Macaca mulatta) for research purposes. Methods: Three female monkeys from 4 to 4.5 years of age underwent three consecutive attempts at endometriosis induction over an 8-month period: (i) the first attempt involved intravaginal sampling of endometrial tissue and transplantation into the intrapelvic cavity; (ii) the second entailed surgical removal of endometrium after hysterotomy and intra-abdominal placement, and (iii) the third used endometrial mucosa obtained by scraping the uterus after hysterectomy, placed in a surgical pouch created in the retrovesical space (Retzius). In each case, the pelvic cavity was closely inspected after 7, 9, and 6 weeks respectively for the presence of endometriotic lesions, and peritoneal biopsies were performed. Results: Neither macroscopic observation nor histological analysis revealed any endometriotic lesions. Conclusion: This failure to induce endometriosis in female rhesus macaques suggests that this species is not the most efficient experimental model among primates to investigate endometriosis development or treatment.

Background/Aims: Endometrial cells are chronically exposed to iron due to cyclic menstrual bleeding. Iron induces expression of adhesion molecules in endothelial cells. The purpose of this study was to investigate iron incorporation by human endometrial cells and to test whether iron may stimulate expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1. Methods: Endometrial stromal and epithelial cells were cultured in medium alone or supplemented with INF-γ or transferrin (Tf). Iron incorporation by cells was quantified by densitometry of ferritin immunostaining. ICAM-1 and VCAM-1 expression were evaluated at the transcriptional level by real-time RT-PCR. Membrane-bound and soluble protein levels of ICAM-1 were measured by quantitative immunohistochemistry and ELISA, respectively. Results: Tf induced a significant increase in ferritin immunostaining in both endometrial cell types. Endometrial cells treated with INF-γ expressed more ICAM-1 and VCAM-1 than untreated cells. By contrast, Tf treatment did not alter ICAM-1 and VCAM-1 expression in cultured endometrial cells. Conclusions: Endometrial cells are able to incorporate iron from Tf and to metabolize it to ferritin. Iron, unlike interferon-γ, does not appear to be involved in the regulation of ICAM-1 and VCAM-1 expression in cultured endometrial cells.

This manuscript is a review of new ideas regarding the pathogenesis of peritoneal endometriosis, ovarian endometriosis, and retroperitoneal adenomyosis. Peritoneal endometriosis, the different aspects of which (black, red and white) represent distinctive steps in the evolutionary process, can be explained by the transplantation theory. Red lesions are the most active and most highly vascularized lesions and are considered to be the first stage of peritoneal endometriosis. The retroperitoneal nodule is an adenomyotic nodule whose histopathogenesis is not related to the implantation of regurgitated endometrial cells but to metaplasia of Müllerian remnants located in the rectovaginal septum. Metaplastic changes of Müllerian rests into adenomyotic glands involving the rectovaginal septum and the retroperitoneal space are responsible for the striking proliferation of the smooth muscle, creating an adenomyomatous appearance similar to that of adenomyosis in the endometrium.