Endometriosis and Reproductive Disorders

Animal models in endometriosis research

Endometriosis is a common gynaecological disease, defined as the presence of endometrial tissue outside the uterus, causing pelvic pain and subfertility in approximately 10% of women of reproductive age. Current therapies lead to pain relief, however, do not address the causes and entail severe side effects. Still little is known about the pathogenic processes leading to the development and maintenance of endometriosis. Because endometriosis occurs spontaneously only in humans and some non-human primates, animal models of induced endometriosis have been developed and are of high value for the evaluation of pathophysiological mechanisms underlying the development of this disease. These experimental models include the autotransplantation of uterine fragments into the peritoneal cavity of rodents and non-human primates or the heterotransplantation of human endometrial or endometriotic tissue to immunodeficient mice or onto the chicken chorioallantoic membrane (CAM). This review describes the animal models for endometriosis and assesses their different potentials and limitations in regard to endometriosis research, with the aim of developing novel non-invasive diagnostic tools and improved strategies for the treatment of endometriosis in women.

Should endometriomas be treated before IVF–ICSI cycles?

The laparoscopic excision of ovarian endometriomas appears to increase the chances of spontaneous conception, but the value of this treatment in women selected for IVF-ICSI cycles is debated. Studies recruiting women with unilateral disease and comparing ovarian responsiveness in the affected and contralateral intact gonads indicate that excision of endometriomas is associated with a quantitative damage to ovarian reserve. There are no randomized trials comparing laparoscopic excision to expectant management before IVF-ICSI cycles. The idea that surgery increases IVF pregnancy rates is not supported by the available evidence. However, the chance of conception is not the only issue that has to be considered. Some potential drawbacks are associated with both therapeutical strategies. Specifically, costs and hazard of surgical complications support expectant management whereas oocyte retrieval risks, the possibility of missing occult malignancy and endometriosis progression due to ovarian stimulation would favour surgical treatment. Alternative therapeutical options include medical treatment and ultrasound-guided aspiration. Whereas prolonged GnRH agonist down-regulation may be beneficial, data on ultrasound aspiration are more controversial.

Oral contraceptive use, reproductive history, and risk of epithelial ovarian cancer in women with and without endometriosis

OBJECTIVE

Women with endometriosis may be at an increased risk of ovarian cancer. It is not known whether reproductive factors that reduce the risk of ovarian cancer in general also reduce risk in women with endometriosis. We investigated whether the odds ratios for ovarian cancer that were associated with oral contraceptive use, childbearing, hysterectomy, and tubal ligation differ among women with and without endometriosis.

STUDY DESIGN

We pooled information on the self-reported history of endometriosis from 4 population-based case-controlled studies of incident epithelial ovarian cancer, comprising 2098 cases and 2953 control subjects. We obtained data on oral contraceptive use, childbearing, breastfeeding, gynecologic surgical procedures, and other reproductive factors on each woman. Multivariable unconditional logistic regression was used to calculate odds ratios and 95% CI for ovarian cancer among women with endometriosis compared with women without endometriosis. Similar methods were used to assess the frequencies of risk factors among women with and without endometriosis. Adjustments were made for age, parity, oral contraceptive use, tubal ligation, family history of ovarian cancer, and study site.

RESULTS

Women with endometriosis were at an increased risk of ovarian cancer (odds ratio, 1.32; 95% CI, 1.06-1.65). Using oral contraceptives, bearing children, and having a tubal ligation or hysterectomy were associated with a similar reduction in the odds ratios for ovarian cancer among women with and without endometriosis. In particular, the use of oral contraceptives for >10 years was associated with a substantial reduction in risk among women with endometriosis (odds ratio, 0.21; 95% CI, 0.08-0.58).

CONCLUSION

Women with endometriosis are at an increased risk of epithelial ovarian cancer. Long-term oral contraceptive use may provide substantial protection against the disease in this high-risk population.

Role of the nonhuman primate for research related to women's health

This overview of the current status of medical problems that affect women is related to current studies on pathophysiology and therapeutic interventions using nonhuman primates to demonstrate the utility of the primate model for the study of disease processes in women. The current medical literature on women's health is compared with the literature on nonhuman primate research. The findings reviewed in the articles of ILAR Journal Volume 45 Issue 2 of 2004 are evaluated in the context of the scope and problems associated with disease entities in women. Nonhuman primate research with known information regarding women's disease is discussed, and the utility of the animal model for the study of human disease is highlighted, based on its significant relevance due to similarities of nonhuman primate and human subjects' physiology, metabolism, and responses to therapeutic interventions. Additional advantages of the animal model include the ability to control the experimental environment and the capacity to perform chronic study procedures. These findings allow us to utilize the nonhuman primate as the most relevant model in the animal world for the study of human disease processes.