The expression of interleukin-1 alpha, interleukin-1 beta, and interleukin-1 receptor type I mRNA during preimplantation mouse development.

Interleukin-1 (IL-1) plays an important role in implantation of the early embryo since blockade of the IL-1 receptor prevents implantation in the mouse. Whether IL-1 blockade during implantation has a direct effect on the embryo or only the uterus is unknown since reliable data are not available concerning the expression of IL-1 or IL-1 receptor on the preimplantation embryo. Because of the significant role for IL-1 in implantation, we investigated the potential for an embryonic-maternal IL-1 signaling mechanism during mouse preimplantation embryo development. Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed for IL-1 alpha, IL-1 beta and IL-1 receptor type I (IL-1R) on mRNA isolated from mouse preimplantation embryos and uteri collected between the 2-cell to blastocyst stage. Preimplantation embryos have the capability to produce IL-1 beta after the 4-cell stage of development since IL-1 beta mRNA was detected from the 4-cell to blastocyst stage but not at the 2-cell stage. Unlike IL-1 beta, IL-1 alpha was not expressed in preimplantation embryos. It is unlikely that IL-1 has a direct effect on the preimplantation embryo since IL-1R mRNA was not expressed in preimplantation embryos. In contrast, IL-1 could have a direct effect on the uterus since IL-1R mRNA was found to be expressed in uteri at all developmental time points. Our findings suggest that there is a potential embryonic-maternal IL-1 signaling mechanism through the expression of IL-1 beta by the preimplantation embryo and the expression of IL-1R in the uterus.