**3. PGE2 and its role in the aetiopathogenesis of endometriosis**

COX-2, the crucial enzyme for the production of PGs, has been described to be upregulated in different pathological inflammatory conditions. Endometriosis is characterized by the high proliferation rate of endometrial cells in an ectopic site, inflammation and pain. COX-2 is highly expressed in eutopic endometrium, both in the proliferative and secretory phases, and in ectopic lesions from endometriosis patients compared to disease free women (Ota et al., 2001). Wu and coworkers also described that COX-2 is expressed in stromal and epithelial cells derived from endometriosis patients, and is in agreement with the work from Ota and coworkers, in that this expression is higher in patients (Ota et al., 2001; Wu et al., 2002).
