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Aberrant up-regulation of aromatase in eutopic endometrium and implants from women with endometriosis has been reported. Aromatase induction may be mediated by increased cyclooxygenase-2 (COX-2). Recently, we demonstrated that progesterone receptor (PR)-A and PR-B serve an antiinflammatory role in the uterus by antagonizing nuclear factor kappaB activation and COX-2 expression. PR-C, which antagonizes PR-B, is up-regulated by inflammation. Although estrogen receptor alpha (ERalpha) is implicated in endometriosis, an antiinflammatory role of ERbeta has been suggested. We examined stage-specific expression of aromatase, COX-2, ER, and PR isoform expression in eutopic endometrium, implants, peritoneum, and endometrioma samples from endometriosis patients. Endometrial and peritoneal biopsies were obtained from unaffected women and those with fibroids. Aromatase expression in eutopic endometrium from endometriosis patients was significantly increased compared with controls. Aromatase expression in endometriosis implants was markedly increased compared with eutopic endometrium. Aromatase mRNA levels were increased significantly in red implants relative to black implants and endometrioma cyst capsule. Moreover, COX-2 expression was increased in implants and in eutopic endometrium of women with endometriosis as compared with control endometrium. As observed for aromatase mRNA, the highest levels of COX-2 mRNA were found in red implants. The ratio of ERbeta/ERalpha mRNA was significantly elevated in endometriomas compared with endometriosis implants and eutopic endometrium. Expression of PR-C mRNA relative to PR-A and PR-B mRNA was significantly increased in endometriomas compared with eutopic and control endometrium. PR-A protein was barely detectable in endometriomas. Thus, whereas PR-C may enhance disease progression, up-regulation of ERbeta may play an antiinflammatory and opposing role.

It has become apparent that in the ovary, the immune system contributes to the regulation of gonadal function. Leukocytes present within the ovary may constitute potential in-situ modulators of ovarian function that act through local secretion of regulatory soluble factors. These factors include numerous cytokines that largely originate by the action of immune cells within the ovary. Actual rupture of the follicle during ovulation may be dependent on tissue remodelling that is characteristic of an acute inflammatory reaction and includes mobilization of thecal fibroblasts, increased leukocyte migration, release of various mediators and loosening of connective tissue elements in the follicle wall. Both corpus luteum formation and luteal regression also involve progressive infiltration of lymphocytes and macrophages, release of chemokines and cytokines, and communication through cell adhesion molecules. In this review, we examine the evidence for the leukocytes and their products in regulation of ovarian function and relate the potential significance of these cells and substances to some ovarian disorders.

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