Marked increase in macrophage migration inhibitory factor synthesis and secretion in human endometrial cells in response to human chorionic gonadotropin hormone

Originally identified for its capacity to inhibit the random migration of macrophages in vitro, macrophage migration inhibitory factor (MIF) is now recognized as a multifunctional cytokine that modulates the immune response and acts as a growth and angiogenic factor. Recent studies showed that MIF is expressed in the human endometrium across the menstrual cycle as well as in chorionic villi from first-trimester human placenta, which suggests an involvement of MIF in reproduction. Herein, we report that human chorionic gonadotropin (hCG), a glycoprotein hormone that plays a critical role in the initiation and maintenance of pregnancy, markedly stimulates MIF expression in endometrial stromal cells. Cell treatment with hCG resulted in a dose-dependent increase in MIF protein secretion and mRNA steady-state levels, as shown by immunocytochemistry, ELISA, and RT-PCR. Assessment of MIF mRNA half-life showed that hCG treatment had no significant effect on MIF mRNA stability ( P = 0.08). However, nuclear transcription assays (run-on) revealed that hCG acts predominantly by up-regulating MIF gene transcription. These data clearly indicate that MIF can mediate hCG effects on the human endometrium and, in view of the immunomodulatory and angiogenic properties of MIF, reveal a new mechanism by which hCG sustains human pregnancy and promotes embryonic growth.