LEUKEMIA INHIBITORY FACTOR MESSENGER-RNA CONCENTRATION PEAKS IN HUMANENDOMETRIUM AT THE TIME OF IMPLANTATION AND THE BLASTOCYST CONTAINS MESSENGER-RNA FOR THE RECEPTOR AT THIS TIME

Maternal endometrial leukaemia inhibitory factor (LIF) is required for successful implantation in mice. Mice with homozygous deletions in th is gene fail to support implantation. The localization of immunoreacti ve LIF and the concentration of the mRNA encoding human LIF in normal endometrium during the menstrual cycle were investigated. The amount o f RNA was low or undetectable in the proliferative phase but increased by approximately six times in the mid- to late secretory phase. The p rotein can only be detected by immunocytochemistry in glandular epithe lium in the mid- or late secretory phase. To investigate the possible target for the endometrial LIF, we undertook reverse transcription-PCR analysis of early human embryos to determine whether they contain the mRNA encoding the LIF receptor. This study indicated that at the time of implantation in humans, the maternal endometrium produces LIF and that the blastocyst expresses LIF receptor mRNA and therefore may be c apable of responding to this signal.