EXPRESSION OF LEUKEMIA INHIBITORY FACTOR IN HUMAN ENDOMETRIUM AND PLACENTA

Leukemia inhibitory factor (LIF), a cytokine that induces macrophage d ifferentiation in the murine M1 myeloid leukemia cell line, is essenti al for blastocyst implantation in mice. However, its expression and th e role it plays in the human uterus are unknown. To clarify these issu es, we examined LIF gene expression in the human uterus by Northern bl ot hybridization and by a quantitative reverse transcription-polymeras e chain reaction (RT-PCR) method. Analysis of LIF mRNA showed two hybr idization bands, with estimated mRNA sizes of about 4.0-kb pairs and 1 .8-kb pairs. LIF mRNA was detected at high levels in endometrial tissu e and decidua, but at low levels in the chorionic villus in first trim ester and term placenta. In the secretory phase, the endometrial tissu e showed higher LIF expression than in the proliferative phase (9.5-fo ld; p < 0.01). The endometrial tissues were separated into a stroma-en riched fraction (SF) and an epithelium-enriched fraction (EF), and the LIF mRNA levels in each fraction were examined by quantitative RT-PCR . These levels were higher in the EF than in the SF (3.3-fold; p < 0.0 5). These findings suggest that, in humans. LIF plays a role in uterin e function during the menstrual cycle, as well as during pregnancy.