Pregnancy-dependent expression of leukaemia inhibitory factor (LIF), LIF receptor-beta and interleukin-6 (IL-6) messenger ribonucleic acids in the porcine female reproductive tract

Leukaemia inhibitory factor (LIF) and interleukin-6 (IL-6) are candidate em bryo-maternal signalling molecules which are present within the uterine lum inal micro-environment. We examined the relative expression of the mRNAs en coding LIF and IL-6, as well as the LIF-binding subunit (LIFR-beta) of the LIF receptor and, as a potential downstream cytokine-responsive gene, beta( 2)-microglobulin (beta(2)m), in porcine peri-implantation conceptuses, and in placenta and endometrium during early and mid-pregnancy. Peri-implantati on spherical and filamentous conceptuses expressed LIFR-beta and beta(2)m m RNAs with no LIF mRNA present. Rapid development in days 11/12 spherical co nceptuses to the filamentous stage was accompanied by transiently increased IL-6 gene expression. The corresponding endometrium, in contrast, expresse d LIF in addition to these other mRNAs. LIFR-beta, IL-6 and beta(2)m, but n ot LIF mRNAs, were expressed in the Jag-1 cell line, an in vitro model for porcine day 14 trophoblast. The greatest steady-state amounts of LIF, LIFR- beta and IL-6 mRNAs in both the endometrium and placenta were evident at th e post-implantation stages (days 30 and 60>day 18 of pregnancy). Treatment of porcine endometrial explants with human recombinant (hr)LIF or hrIL-6 re sulted in no change in, or diminished, the presence of endometrial beta(2)m mRNA, respectively. Addition of LIF to peri-implantation conceptus explant cultures, in contrast, induced beta(2)m mRNA synthesis. These results high light the potential importance of both the endometrium and placenta as sour ces, as well as targets, of these cytokines throughout pregnancy. Cytokine modulation of beta(2)m, a known in vitro mitogen, may constitute one mechan ism for local control of trophoblast and endometrial proliferation. (C) 200 0 Harcourt Publishers Ltd.