Submitted to: American Journal of Reproductive Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2006
Publication Date: 7/1/2006
Citation: Michael, D.D., Ocon, O.M., Talbot, N.C., Rooke, J.A., Ealy, A.D. 2006. Granulocyte-macrophage colony-stimulating factor increases interferon-tau protein secretion without influencing the rate of interferon-tau gene expression in bovine trophectoderm. Domestic Animal Endocrinology. 56:63-67. Interpretive Summary: In ruminants (cattle, sheep, goats, deer, giraffe), the outermost embryo-produced tissue of the placenta, termed the trophectoderm, must proliferate extensively and secrete at least one key factor, termed interferon-tau (IFN-'), in order for pregnancy to succeed. Massive trophectoderm proliferation occurs in ruminants while the early embryo is free-floating in the uterus. In cattle, the embryo transforms from a 3-mm spherical shape to a 250-mm filamentous structure between days 13 to19 of pregnancy. This pre-attachment growth of the early embryo is essential not only to provide extensive surface area for placentation but also to insure that sufficient quantities of IFN-' are secreted so that pregnancy establishment is successful. It is clear that uterine-secretory factors modulate embryo development in ruminants. GM-CSF is produced by the uterine tissue of sheep and cattle, and there is increasing evidence that GM-CSF influences embryo development and IFN-' production in these species. In the present study, GM-CSF was investigated for its ability to stimulate trophectoderm proliferation and IFN-' production in an in vitro model of bovine trophectoderm, the CT-1 cell line. GM-CSF was found to simulate cell growth and IFN-' production of the bovine trophectoderm cells. These findings are important to our understanding of bovine pregnancy establishment and maintenance, and they may foster the development of improved production methods for cattle, sheep, and goats.
Technical Abstract: Uterine-derived factors influence ruminant trophectoderm development and production of the maternal recognition of pregnancy factor, interferon-tau (IFN-'), during peri-attachment conceptus development. Granulocyte macrophage colony stimulating factor (GM-CSF) is known to regulate conceptus development and is suspected to influence IFN-' production. The objective of this study was to examine the effects of GM-CSF on proliferation rates and IFN-' mRNA and protein production in an in vitro model of bovine trophectoderm (CT-1 cell line). Rate of [3H]-Thymidine incorporation into DNA was increased by supplementation of CT-1 medium with 10 or 100 ng/ml porcine (po) GM-CSF when compared with controls. GM-CSF supplementation to CT-1 medium also increased IFN-' protein secretion. When results were normalized to account for differences in number of CT-1 cells, 10 and 100 ng/ml poGM-CSF increased antiviral activity in CT-1 conditioned medium compared to non-treated controls. Lower concentrations of poGM-CSF did not affect antiviral activity of conditioned medium. In a separate study, IFN-' concentrations in conditioned medium were greater for CT-1 cells treated with 100 ng/ml poGM-CSF than non-treated controls when an IFN-'-specific ELISA was used to quantify IFN-'. Interestingly, poGM-CSF supplementation (100 ng/ml) did not affect the abundance of IFN-ô mRNA in CT-1 cells as determined by quantitative real time RT-PCR. These findings indicate that GM-CSF regulates trophectoderm proliferation in ruminant conceptuses. The mechanism by which GM-CSF regulates IFN-' production in the CT-1 cell remains unresolved but is not mediated at the level of transcription.