Perivascular interleukin-8 messenger ribonucleic acid expression in human endometrium varies across the menstrual cycle and in early pregnancy decidua.

Human endometrium and decidua contain large numbers of different leukocyte populations, the concentration of which fluctuates during the menstrual cycle and pregnancy. There is, for example, a large influx of neutrophils into premenstrual endometrium associated with an increased expression of interleukin (IL)-8 protein, which is chemotactic for neutrophils. Our aim in this study was to localize IL-8 messenger RNA (mRNA) expression in endometrium and decidua using in situ hybridization. In situ hybridization was carried out with a 35S-uridine 5'-triphosphate-labeled riboprobe using standard procedures. Late secretory endometrial and decidual biopsies demonstrated clear perivascular localization of IL-8 mRNA, with additional expression colocalized to activated macrophages. Midluteal endometrium showed minimal IL-8 expression, whereas endometrium obtained from women administered progesterone for 4 days from (LH peak + 8 days), to simulate luteal regression, demonstrated significantly increased localization of IL-8 mRNA, 48 h after withdrawal of progesterone. In conclusion, IL-8 mRNA expression is localized to perivascular cells of late secretory endometrium and decidua.