Macrophage migration inhibitory factor is expressed by equine conceptuses and endometrium

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine expressed by a wide range of tissues, which has been implicated to be involved in reproduction. Relative abundance of MIF mRNA in conceptus and endometrial tissue was assessed using real-time RT-PCR. Western blot analysis and immunohistochemistry were used to detect MIF protein expression. MIF transcript abundance was lowest in conceptuses obtained 16 days after ovulation, while the remaining stages of conceptus development that were analysed showed relatively constant expression levels. Migration inhibitory factor expression localized to trophectoderm cells, while capsular material was void of MIF immunoreactivity. Throughout the oestrous cycle, no clear statistically significant cycle-dependent expression pattern could be observed. During early pregnancy, the highest mRNA transcript levels were detected 16 days after ovulation. Pregnancy status did not affect MIF mRNA expression. Using immunohistochemistry, MIF protein expression was primarily localized in luminal and glandular epithelial cells, while stromal cells displayed weaker immunoreactivity. Taken together, we suggest that MIF is part of the molecular repertoire that contributes to normal endometrial function. The detailed functional significance of MIF expression in equine endometrium and pre-implantation stages of conceptus development remains to be determined.