A mouse model for endometriosis

Endometriosis is a common, benign, estrogen-dependent gynaecological disease characterized by the presence of endometrial tissue outside the uterine cavity. After the Sampson theory one possible pathophysiological cause is retrograde menstruation. Clinical manifestations include dysmenorrhoea, noncyclical pelvic pain, dyspareunia and subfertility. Treatment of endometriosis consists of medical and surgical approaches. Surgical methods are laparotomy and hysterectomy. Medical therapies interrupt the hypothalamic-pituitary-gonadal axis, thus suppressing estrogen action. All of these treatments relieve pain effectively but the recurrence rate is high and severe side effects are quite common. Understanding the processes of endometriosis development, of adherence and survival of the lesions will open up important basic knowledge for the development of new therapeutic approaches. Very valuable information can be gained by animal experiments. The aim of this study was to develop and evaluate a mouse model for endometriosis to gain deeper insights into the pathology with a focus on angiogenetic and immunologic processes. A syngen mouse model with in non-immune compromised mice was established, with the advantage of low host-versus-graft-reaction and an intact immune system. Here, EGFP-positive mouse endometrium was injected into the peritoneal cavity of a sibling acceptor mouse. Established EGFP-positive lesions were easily detectable under UV-light. Histological analysis confirmed characteristics of endometriotic structures. In different experimental settings it was shown, that lesion growth but not lesion establishment in this model is estrogen dependent. Moreover, injection of just endometrium and not whole uterus provided a good mimic of retrograde menstruation. In summary, this model is a very suitable tool to analyse processes involved in establishment and growth of endometriosis. It offers the possibilities to examine angiogenesis and the influence of the immune system in endometriosis and may pave the way to new therapeutic approaches.