Interleukin-11 expression: its significance in eutopic and ectopic human implantation U.von Rango1,6, J.Alfer2, S.Kertschanska3, B.Kemp4, G.Müller-Newen5, P.C.Heinrich5,

Embryo implantation and subsequent decidualization, trophoblast invasion and formation of a functional placenta are crucial for establishment and maintenance of pregnancy. Interleukin-11 signalling has been shown to be obligatory for adequate deci-dualization and trophoblast invasion in mice. Defects in IL-11 signalling in mice result in trophoblast over-invasion and fetal loss. The pathological situation of human tubal pregnancy resembles that of IL-11Ra2/2 mice concerning these symptoms. As our interest is focused on the human early pregnancy, we compared IL-11 expression at the implantation site of ectopic tubal pregnancy (EP) to 1st and 2nd trimester of normal intrauterine pregnancies (IP), and to the normal cycling endo-metrium. The mRNA expression of IL-11 and IL-11Ra was analysed by semiquantitative RT–PCR. Protein expression was detected by western blotting and immunohistochemistry. IL-11Ra is expressed constitutively in all tissue specimens analysed. IL-11 is expressed predominantly during follicular and early luteal phase of the menstrual cycle. In IP, IL-11 expression peaks during the 1st trimester and declines from the beginning of the 2nd trimester onwards. In tubal abortions, IL-11 expression is reduced in comparison to vital EP and IP. Cultured primary endometrial and decidual epithelial cells were analysed for hor-monal regulation of IL-11 by enzyme-linked immunosorbent assay and RT–PCR. IL-11 is up-regulated by estrogen and down-regulated by progesterone. Overall, our results indicate that in humans, IL-11 signalling is significantly involved in regulation of trophoblast invasion. In the case of tubal abortion, inadequate IL-11 signalling may therefore result in dysregulation of trophoblast invasion. Key words: decidua/endometrium/IL-11/trophoblast invasion/tubal pregnanc