Experimental endometriosis: the nude mouse as a xenographic host.

Endometriosis is a complex disease that can develop as a consequence of retrograde menstruation, occurring in association with the cyclic loss of endometrial tissue in primates and humans. In addition, progression of disease parallels a woman's exposure to ovarian steroids, rarely occurring prior to menarche and generally resolving following menopause. Because of the cost of developing primate models to study endometriosis, numerous small animal models have been established to approach various elements related to the pathophysiology of this disease. Our laboratory has developed an experimental endometriosis model using nude mice as a xenographic host for human tissues. Our goal is to approach the basic cellular mechanisms of estrogen and progesterone action that link these hormones to the development or prevention of endometriosis. In our initial studies, we have sought to understand steroid-associated regulation of matrix metalloproteinases (MMPs) with regard to the development of experimental endometriosis. Using both short-term organ cultures and nude mice as xenographic hosts of human tissue, we have demonstrated a critical role of progesterone and progesterone-associated cytokines in preventing the initial establishment of experimental disease. Women with endometriosis appear to lack normal endometrial responsiveness to progesterone, resulting in altered expression of several MMPs and an enhanced ability of these tissues to establish ectopic lesions in nude mice. Developing a better understanding of the impairments in the normal endometrial physiology of women with endometriosis should aid in the development of better treatment or diagnostic strategies.