Evidence for the presence of macrophage migration inhibitory factor in murine reproductive organs and early embryos

Cytokines appear to play a critical role in the establishment of early pregnancy. In this study, we examined the mRNA expression of murine macrophage migration inhibitory factor (MIF), one of the cytokines activating macrophages, in the murine reproductive system by Northern blot analysis. It revealed that MIF mRNA was expressed in the ovary, the oviduct and the uterus during the pre-implantation period and all stages of the estrus cycle. The histological localization of MIF in the uterus was examined by an immunohistochemical method, which revealed that MIF was mostly present in the tunica muscularis. It was, moreover, demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) that MIF mRNA was expressed in the ovulated oocytes, zygotes, 2-cell embryos, 8-cell embryos and blastocysts. MIF is known to be present in T-lymphocytes and monocytes/macrophages; however, it was revealed by the present study that MIF mRNA is expressed in the reproductive organs and the early stages of embryos. Considering these results, it is suggested that MIF plays an important role in the establishment of pregnancy.