Role of prostaglandin E2 in bacterial growth in women with endometriosis.

STUDY QUESTION Can prostaglandin E(2) (PGE(2)) in menstrual and peritoneal fluid (PF) promote bacterial growth in women with endometriosis? SUMMARY ANSWER PGE(2) promotes bacterial growth in women with endometriosis. WHAT IS KNOWN ALREADY Menstrual blood of women with endometriosis is highly contaminated with Escherichia coli (E. coli) compared with that of non-endometriotic women: E. coli-derived lipopolysaccharide (LPS) promotes the growth of endometriosis. STUDY DESIGN, SIZE AND DURATION Case-controlled biological research with a prospective collection of body fluids and endometrial tissues from women with and without endometriosis with retrospective evaluation. PARTICIPANTS/MATERIALS, SETTING AND METHODS PF and sera were collected from 58 women with endometriosis and 28 women without endometriosis in an academic research laboratory. Menstrual blood was collected from a proportion of these women. Macrophages (Mφ) from PF and stromal cells from eutopic endometria were isolated in primary culture. The exogenous effect of PGE(2) on the replication of E. coli was examined in a bacterial culture system. Levels of PGE(2) in different body fluids and in the culture media of Mφ and stromal cells were measured by ELISA. The effect of PGE(2) on the growth of peripheral blood lymphocytes (PBLs) was examined. MAIN RESULTS AND THE ROLE OF CHANCE The PGE(2) level was 2-3 times higher in the menstrual fluid (MF) than in either sera or in PF. A significantly higher level of PGE(2) was found in the MF and PF of women with endometriosis than in control women (P < 0.05 for each). Exogenous treatment with PGE(2) dose dependently increased E. coli colony formation when compared with non-treated bacteria. PGE(2)-enriched MF was able to stimulate the growth of E. coli in a dilution-dependent manner; this effect was more significantly enhanced in women with endometriosis than in control women (P < 0.05). PGE(2) levels in the culture media of LPS-treated Mφ/stromal cells were significantly higher in women with endometriosis than in non-endometriosis (P < 0.05 for each). Direct application of PGE(2) and culture media derived from endometrial Mφ or stromal cells significantly suppressed phytohemagglutinin-stimulated growth of PBLs. LIMITATIONS AND REASONS FOR CAUTION Further studies are needed to examine the association between PGE(2)-stimulated growth of E. coli and endotoxin level and to investigate the possible occurrence of sub-clinical infection within vaginal cavity. WIDER IMPLICATIONS OF THE FINDINGS Our findings may provide some new insights to understand the physiopathology or pathogenesis of the mysterious disease endometriosis and may hold new therapeutic potential. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by grants-in-aid for Scientific Research from the Ministry of Education, Sports, Culture, Science and Technology of Japan. There is no conflict of interest related to this study. TRIAL REGISTRATION NUMBER Not applicable.